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Neuro-Ophthalmology |
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Accommodative Esotropia | Adult Strabismus | Anterior Ischemic Optic Neuropathy (AION) | Amblyopia | Duane Syndrome | Esotropia | Exotropia | Exotropia (Spanish) | Glasses for Children | Congenital Esotropia | Learning Disabilities | Migraine | Myasthenia Gravis | Nystagmus | Optic Neuritis | Papilledema | Pseudo-strabismus | Pseudotumor Cerebri | Ocular Cranial Nerve Palsies(Fourth and Sixth Nerve Palsies) | Strabismus Back to the top of the page Accommodative EsotropiaAccommodative esotropia refers to crossing of the eyes caused by the focusing efforts of the eyes as they try to see clearly. Patients with accomodative esotropia are typically farsighted (hyperopic). This means that the eyes must work harder to see clearly, particularly when looking at objects up close. This focusing effort is called accommodation. The closer an object is to the eye, the greater the amount of accommodation that is required. Because converging, or inward turning of the eyes is connected to accommodation as part of the normal reflexes of the visual system, excessive accommodative effort can cause over convergence, or crossing of the eyes. In general, the more farsighted a person is, the greater the amount of effort they must exert and the more likely they are to cross their eyes. However, not all children have this tendency to cross, and therefore, while two individuals may have the same eye prescription strength, one may cross and the other may have perfectly straight eyes.
It is normal for the eyes to continue crossing without the glasses and in fact the crossing may be even more noticeable than it was before your child started wearing glasses. However, as long as the eyes are straight and controlled with the glasses on, the treatment is working. Your pediatric ophthalmologist will be able to tell whether the eyes are adequately aligned at your follow-up examinations. These follow-up examinations are important not only to monitor the eye crossing, but also to watch for other associated problems such as amblyopia, a developmental vision loss that may affect the eyes in children with esotropia. Surgery is only indicated in these patients if the eyeglasses fail to straighten the eyes adequately while the glasses are on. In this case, eye muscle surgery (strabismus surgery) may be recommended to further help improve the alignment of the eyes. In general, surgery for refractive esotropia does not eliminate the need for glasses but rather fixes the amount of crossing that is “left-over” when the glasses are on, and surgery does not replace the need for eyeglasses. In some cases, children may have particularly excessive amounts of esotropia when reading or looking at objects up close, even while wearing the correct glasses. These children may benefit from either strabismus surgery or the use of bifocal lenses to further reduce the need to focus at near. Back to the top of the page Adult StrabismusAdult strabismus, or mis-alignment of the eyes, can be a significant problem for many patients. Many people find that they are embarrassed by their misaligned eyes and avoid looking people in the eye, or may feel that people are distracted by their wandering eye, causing problems in social situations. Recent studies confirm that misaligned eyes can hinder social interaction, self-confidence and employment opportunities. Recent treatment advances allow most adults with misaligned eyes to have surgical correction. Adult strabismus surgery is not just cosmetic, but can improve eye function in some adults and can have definite social and economic benefits. Because eye muscle surgery is reconstructive rather than cosmetic, most insurance companies will cover this surgery. Your insurance company can tell you if this type of surgery is covered with your specific policy. Eye muscle surgery is not particularly risky for adults, although every surgical procedure has some risks. For strabismus surgery, the most common risks are residual misalignment and double vision (usually temporary). Fortunately, the more serious risks of anesthetic complications, infection, bleeding, retinal detachment, and decreased vision are rare. Health risks vary with the general health of the individual. Eye muscle surgery is generally very successful, although there are a number of individual factors that influence the success of the surgery, including; the starting vision in each eye, the presence or absence of double vision, the amount of crossing or wandering of the eye, and the type of deviation. Although most patients have significant improvement in eye alignment with the surgery, a certain percentage of eyes may drift back inward or outward with time, especially if one or both eyes have poor vision to begin with. Also, occasionally the surgery is only partially successful and additional surgery may be indicated. Eye alignment surgery is usually performed as an outpatient procedure under general anesthesia. Discomfort after eye muscle surgery usually consists of a foreign body sensation in the eye, lasting no more than several days, although the occasional patient may have longer-lasting discomfort. Over-the-counter pain medication usually reduces the discomfort, and stronger medication is rarely prescribed. Most patients return to full activity within several days. Some patients may worry that they are "too old" to have eye muscle surgery, or that they have “missed the boat” by not having this surgery done as a child. While it is true that the often associated problems of amblyopia and decreased stereo vision can not be resolved with adult strabismus surgery, eyes can still be straightened at any age and should be considered as a treatment alternative if it enhances the quality of life. Back to the top of the page Anterior Ischemic Optic Neuropathy (AION)Anterior Ischemic Optic Neuropathy (AION) is a condition where the optic nerve near the back of the eye is damaged due to a loss of blood supply. The optic nerve is unique because it is the only nerve in the body that a physician can directly visualize without surgery. The optic nerve is made up of a million tiny, delicate nerve fibers that carry the visual impulses to the brain, where vision actually takes place. Many blood vessels nourish this important optic nerve with blood rich in oxygen and nutrition. This system may be compared to a video camera (i.e. the eye) taking the picture and transmitting along the cable (the optic nerve) to the television (the brain). If the cable is damaged for any reason, although the video camera and the television may be perfectly normal, a distorted or absent picture is seen on the television. While explaining this disease, a doctor may say that there has been a "stroke” or a “blocked blood vessel” in the back of the eye. A "stroke" is an interruption of the blood supply to the brain or a nerve in the body. When a person has a major stroke in the brain, the blood supply to a part of the brain that controls speech or movement of the arms or legs is often affected. With AION, a loss of blood supply to the optic nerve damages the nerve and leads to loss of vision. A similar event can be caused by closure or blockage of a different blood vessel within the eye, causing damage to the retina itself. This is called a Central Retinal Artery Occlusion (CRAO). How much vision is lost depends on how much the retina or the optic nerve is affected. In this article we are discussing only AION or stroke of the optic nerve and not CRAO. AION is generally divided into two types depending on the cause:
The decision on which type of AION is present is very important, because the treatment and prognosis is very different between the two groups. Most patients with non-arteritic AION have a “choked disc,” also known as a “disc-at-risk.” This is a congenital variant where the optic nerve comes into the eye through an opening in the sclera, (the outer coat of the eye) that is smaller than average. This leaves little room for the nerve itself, and makes it more likely for blood vessels to close off, causing an AION. This congenital variant is exacerbated later in life by hypertension and hardening of the arteries. The prognosis for visual improvement of AION is poor, and although about 50% of patients may have some improvement of the visual field loss, very few regain completely normal vision. Although many treatments have been attempted over the years for AION, none have been conclusively shown to increase the rate of improvement of visual loss in AION. The risk of AION occurring in the opposite eye of a person who has had a single episode of AION is approximately 30% over the next 5 years. Control of systemic hypertension, reducing risk factors for atherosclerotic disease and taking a baby aspirin daily may decrease this risk, but no good controlled studies have ever been done to verify the efficacy of these preventative treatments. Giant cell arteritis (GCA) is a medical emergency because of its complication of visual loss in one or both eyes as well as strokes and heart attacks. These dreaded complications are preventable if these patients are diagnosed early and treated immediately and aggressively with systemic corticosteroids. GCA is a disease of persons aged 50 years or older and is more common among women than men. Most patients with GCA may have one or more of the following symptoms:
A preliminary diagnosis of GCA can be made with two blood tests, the c-reactive protein test (CRP) and the erythrocyte sedimentation rate (ESR). Neither test is conclusive for the disease, but they are very suggestive if high enough. The definitive test is a temporal artery biopsy. The temporal artery lies just under the skin on the side of the forehead, or temple. The area is anesthetized and a small incision is made in the skin to expose the artery. About an inch of the artery is removed for examination and the area is sutured with several stitches, which will be removed in about a week. This sample of the artery is examined under a microscope by a pathologist to determine whether there is inflammation of the artery. The two names of this disease come from the preferential involvement of this disease with the temporal artery, and the characteristic appearance of a finding called giant cells, on the microscopic examination of affected individuals. If the blood tests and clinical findings suggest GCA, immediate treatment with corticosteroid medications is started to prevent further visual loss or other GCA problems, and a temporal artery biopsy is often done within two or three weeks. All of the other risk factors for non-arteritic AION must also be addressed in these cases as well. Back to the top of the page AmblyopiaAmblyopia, or "lazy eye," is a common vision problem in children, and is the reason for more vision loss in children than all other causes put together. Amblyopia is a decrease in vision that occurs from poor development of the nerves that connect the eyes to the brain, and can occur even when there is no problem with the structure of the eye itself. During the developmental years, from birth to about age 9 or 10, the brain must receive visual input from both eyes equally. If this does not occur, the connections between the eye and brain do not develop properly. Amblyopia results when one or both eyes send a blurry image to the brain. The brain then “learns” to only see blurred vision with that eye, even when glasses are used. The underlying problem with all forms of amblyopia is the lack of normal development of the optic nerve. Only children can get amblyopia, and if it is not treated appropriately, it causes permanent loss of vision. [See figure 1] Fortunately, if amblyopia is caught early and treated aggressively, it is usually very correctable.
There are several different types and causes of amblyopia, but the end result of all forms of amblyopia is reduced vision in the affected eye(s). Strabismic amblyopia develops when the eyes are strabismic, or not straight. One eye may turn inward, outward, up or down. When this happens, the brain “turns off” or suppresses the eye that is not straight in order to avoid double vision, and the vision subsequently drops in that eye. Deprivation amblyopia develops when cataracts or similar conditions that physically block vision during the developmental years “deprive” young children’s eyes of visual experience. If not treated very early, these children can have very poor vision. Refractive amblyopia happens when there is a large or unequal amount of refractive error (glasses strength) in a child's eyes. Usually the brain will "turn off" the eye that has more farsightedness or more astigmatism. Parents and pediatricians may not think there is a problem because the child’s eyes may stay straight, and with good vision in the other eye, the child will usually function well visually. For these reasons, this kind of amblyopia in children may not be found until the child has a vision test. This kind of amblyopia can affect one or both eyes and can be helped if the problem is found early. Glasses may partially help a child with amblyopia see better, but will not usually correct the vision all the way to 20/20, because with abnormal development of the optic nerve the brain cannot interpret the clear image that the glasses produce. The glasses, however, are a critical part of the treatment of amblyopia. Over time the glasses will help the brain to re-form the correct connections with the eye, and the vision may improve. If the glasses alone do not help restore vision to the amblyopic eye, treatment of the normal eye with patching or eye drops is used to penalize the good eye and force the amblyopic eye to work harder and become stronger. Bilateral amblyopia is seen when a child has equal high amounts of farsightedness and/or astigmatism which prevents either eye from seeing normally in the developmental years, leading to amblyopia in both eyes. Bilateral amblyopia is usually treated with consistent, early glasses with follow-up over a long period of time. If asymmetric amblyopia (one eye better than the other) occurs, then patching or eye drops may be added. Early treatment of amblyopia is always best. If necessary, children with refractive errors (nearsightedness, farsightedness or astigmatism) can wear glasses when they are as young as one week old. Children with cataracts or other “amblyogenic” conditions are usually treated promptly in order to minimize the development of amblyopia. Some forms of amblyopia, such as those associated with crossed or wandering eyes, may be easily detected by parents. Other types of amblyopia may not be obvious to parents and therefore must be detected by vision screening. Vision screening is strongly recommended by the American Academy of Pediatrics (AAP) over the course of childhood to detect amblyopia early enough to allow successful treatment. Pediatricians check newborns for red reflex to find congenital cataracts, refractive errors or crossed or wandering eyes. Older children can be checked with photoscreening, or by remote autorefraction to identify refractive errors that can cause amblyopia. Once children are old enough to consistently identify objects either by reading or matching, the vision of each eye can be screened with vision charts to identify amblyopia. Patching for amblyopia should only be done if an ophthalmologist recommends it, and only under the ophthalmologist’s direct supervision, since done too much or incorrectly, patching can worsen the eye rather than improve it. Your ophthalmologist will regularly check how the patch is affecting the child’s vision. Although it can be hard to do, patching usually works very well if started early enough and if the parents and child follow the patching instructions carefully. It is important to patch the dominant eye to allow the weak eye to get stronger. [See figure 2]
The classic patch is an adhesive "Band-Aid" which is applied directly to the skin around the eye [See figure 3]. These may be available in different sizes for younger and older children. For children wearing glasses, both cloth and semi-transparent stickers (Bangerter foils) may be placed over or onto the spectacles. "Pirate" patches on elastic bands are especially prone to "peeking" and are therefore only occasionally appropriate. As an alternative to patching, sometimes the stronger (good) eye can be “penalized” or blurred to help the weaker eye get stronger. Blurring the vision in the good eye with dilating drops will penalize the good eye, forcing the child to use the weaker eye. For moderate degrees of amblyopia, studies have shown that patching or eye drops may be similarly effective. The dilating drops take a bit longer to improve the vision than patching, but have the advantage of better compliance, since once the drops are in the patient cannot peek or fight over wearing a patch. Your pediatric ophthalmologist will help you select treatment regimen that is best for your child.
Although vision improvement frequently occurs within weeks of beginning patching treatment, optimal results often take many months. Once vision has been improved, part-time (maintenance) patching or periodic use of dilating eye drops may be required to keep the vision from slipping or deteriorating. This maintenance treatment may be advisable for several months to years. Part-time patching can be done during any waking hours, since as long as the child is conscious and has his or her eyes open, visual input will be processed by the amblyopic eye. On the other hand, the child may be more cooperative or more open to bargaining if patching is performed during certain, desirable activities (such as watching a preferred television program or video). In many instances, school is an excellent time to patch, taking advantage of a non-parental authority figure. While patching is usually well accepted during school, some children may feel self-conscious about the patch and may wish to do patching after school. While in most instances, children may not need to modify their school activities while patching, sometimes adjustments such as sitting in the front row of the classroom will be necessary. On the other hand, frequently a family member may be more vigilant in monitoring patching than is possible in the school setting, so parents should be flexible in choosing when to schedule patching. Many children will resist wearing a patch at first. Successful patching may require persistence, consistent effort and plenty of encouragement from family members and teachers. We have found that if a parent is consistent and firm, most children eventually give up and resign themselves to patching. Some parents find that a system of rewards and punishments help with patching compliance. Surgery on the eye muscles is a treatment for strabismus - it can straighten misaligned eyes. By itself, however, surgery does not usually the problem of amblyopia and, in fact, is generally less successful if the amblyopia has not been resolved before surgery. For this reason, children with strabismic amblyopia still need close monitoring and treatment for the amblyopia, and this treatment is usually performed before strabismus surgery is considered. In all cases of amblyopia, the goal is the best possible vision in each eye. While not every child can be improved to 20/20, most can obtain a substantial improvement in vision. Although there are exceptions, patching does not usually work as well in children who are older than 9 years of age. In some cases, treatment for amblyopia may not succeed in substantially improving vision. It is hard to decide to stop treatment, but sometimes it is best for both the child and the family. Children who have amblyopia in one eye and good vision only in their other eye can wear safety glasses and sports goggles to protect the normal eye from injury. As long as the good eye stays healthy, these children function normally in most aspects of society Back to the top of the page Duane SyndromeWhat is Duane syndrome? Duane syndrome, also called Duane retraction syndrome (DRS), is a group of eye muscle disorders that cause abnormal eye movements. People with Duane syndrome have difficulty rotating one or both eyes outward (abduction) or inward (adduction). Normally, we have six muscles that are attached to the outside of the wall of the eye and control the movement of the eye. In each eye, there are two muscles that move the eye horizontally. The lateral rectus muscle pulls the eye out towards the ear and the medial rectus muscle pulls the eye in towards the nose. There are four other muscles, which move the eye up or down and at an angle. Each eye muscle receives the command for movement from cranial nerves that exit the brain. Duane syndrome is due to miswiring of these eye muscles. The “mistake” probably happens around the 6th week of pregnancy and is due to poor development of tiny parts of the brain stem that control the eye muscles. In Duane syndrome, for reasons we do not understand, the sixth cranial nerve that controls the lateral rectus muscle (the muscle that rotates the eye out towards the ear) does not develop properly. Thus, the problem is not primarily with the eye muscle itself, but with the nerve that transmits the electrical impulses to the muscle. There is also miswiring of the innervation of a branch from the third cranial nerve, which controls the medial rectus muscle (the muscle that rotates the eye toward the nose). This is why abnormalities may be found in both left gaze and right gaze. Duane Syndrome affects girls more often than boys. In addition, the left eye is more likely than the right eye to be affected. The reason for this is not known. Around 20% of Duane syndrome patients have both eyes affected. No particular race or ethnic group is more likely to be affected, and Duane retraction syndrome is present from birth, even if it is not recognized during infancy. An abnormal head posture and strabismus are often visible in old photographs taken in early childhood. Duane syndrome is often characterized by whether the primary abnormality is a reduced ability to turn the affected eye(s) outward (type I), inward (type II), or both (type III). Type I is by far the most common form of Duane syndrome. Because of these miswiring issues, one or both eyes may be unable to look in a particular direction. Unlike patients with amblyopia, where the vision in one eye is suppressed or “turned off,” Duane Syndrome patients usually adapt by turning their heads rather than their eyes in order to avoid double vision or the cosmetic disadvantages of one eye that doesn’t move properly. For this reason, some patients often maintain a head posture or head turn to keep the eyes straight. Rarely, some patient’s with Duane Syndrome may develop amblyopia, or with certain eye movements the eye may occasionally deviate upward or downward. Most patients with Duane Syndrome will have eyelid narrowing on the affected eye on certain gaze directions. Rarely Duane Syndrome may be hereditary, but in 90% of cases, the patient has no family history of Duane syndrome. There is currently no test that can determine whether a patient has a hereditary form. Occasionally, Duane syndrome may be found in association with other eye problems, including disorders of other cranial nerves, nystagmus (an involuntary back-and-forth movement of the eyeball), cataract, optic nerve abnormalities, microphthalmos (abnormally small eye), and crocodile tears. Rarely, some patients with Duane Syndrome have other problems, such as hearing impairment, Goldenhar syndrome, spinal and vertebral abnormalities. There is also an increased frequency of Duane syndrome in patients with thalidomide exposure. For the majority of patients, Duane syndrome does not require surgical treatment. Surgery for Duane syndrome is indicated for one of three reasons: Because the function of the affected nerve and muscle cannot be restored, the other eye muscles are adjusted to compensate and allow for better eye alignment. Surgery cannot fix the problem of nerves that go the wrong way, or re-wire the eye muscles correctly, but by moving the eye muscles surgery can compensate for the miswiring, and usually substantially improves the situation. The full effect of the surgery may take some weeks to become apparent. Back to the top of the page Esotropia
Esotropia means the in-turning or crossing of one or both eyes [See figure 1]. It may be intermittent or constant, and may occur when the child is looking at either distance or near. The crossing may occur predominantly with one eye or may alternate between eyes. Esotropia may occur at any age and is the opposite of exotropia (outward eye turn). Esotropia in infants less than 20 weeks old frequently resolves spontaneously, especially when the misalignment is intermittent and small in magnitude. However, constant eye crossing at any age should be evaluated promptly by a pediatric ophthalmologist. Eye crossing (constant or intermittent) beyond 4 months of age should be evaluated. Esotropia can be classified by age of onset (congenital vs. acquired); by frequency (intermittent vs. constant); or by whether it can be treated with glasses (accommodative vs. non-accommodative). For specific information, see: congenital esotropia and accommodative esotropia. Esotropia can also be secondary to other conditions, including poor vision, neurological conditions such as hydrocephalus, or brain tumor, and other medical conditions such thyroid disease or Duane syndrome, etc. The effect of esotropia on the visual system depends on the frequency and severity of eye crossing and age. Eye crossing affects the ability of the eyes to work together, and can often lead to amblyopia. Older children and adults with a new onset esotropia usually experience diplopia (double vision) and or decreased binocular visual field. Children can lose stereopsis (3-D vision) and binocularity (simultaneous use of the eyes) in addition to loss of vision in the crossing eye (amblyopia). Strabismus, or misalignment of the eyes, often runs in families, although affected family members do not necessarily share the same type and/or severity of strabismus. Any child with a family history of strabismus should be seen at around age 3 ½ by a pediatric ophthalmologist. Prematurity and various neurological and genetic disorders also increase the risk of eye misalignment, as do some systemic disorders such as hyperthyroidism and diabetes. Management of esotropia is based on a number of factors. The overriding principles are: Treatment modalities include spectacles (sometimes with prism or bifocal), strabismus surgery (eye muscle surgery), botulinum toxin (less frequently utilized) and concomitant amblyopia therapy. Back to the top of the page ExotropiaExotropia refers to eyes that turn outward. It is the opposite of crossed eyes, or esotropia. Exotropia may occur from time to time (intermittent exotropia) or may be constant, and is found in every age group [See figures 1 and 2]. Exotropia may be congenital (present at birth) or acquired. The acquired forms of exotropia include intermittent exotropia, sensory exotropia, and consecutive exotropia. Newborn babies commonly have difficulty keeping their eyes straight. While this tendency for the eyes to wander at times is normal until four months of age, any constant eye misalignment during the newborn period should be evaluated by an ophthalmologist. Congenital, or infantile, exotropia, is an outward turning of the eyes from birth or early infancy. Esotropia (crossing of the eyes) is much more common than exotropia in newborns. In fact, constant exotropia is so uncommon in infants that pediatric ophthalmologists generally will investigate the cause to be sure that no additional problem is present.
Many people normally have a tendency for the eyes to drift outward when their eyes are completely relaxed, such as when they are “staring off into space” while daydreaming. This outward drift, which occurs only in those moments when the eyes are not paying attention to each other, is called exophoria, and is controlled effortlessly by refocusing our visual attention. In some patients this tendency to drift outward becomes more frequent and may come even when the patient is alert. This is called intermittent exotropia. At first, the exotropia may occur rarely. Over time, it may become more frequent, even to the point of becoming constant.
Strabismus, or misalignment of the eyes, does run in families. All affected family members will not necessarily share exactly the same type of strabismus, meaning that exotropia may not be the only kind of misalignment possible. In some relatives, the strabismus may be obvious, while others may have a milder form. Many family members will not have any strabismus at all. A family history of strabismus is a good reason to have a child evaluated by a pediatric ophthalmologist.
People with intermittent exotropia may experience that outward drift only occasionally, such as when they are very tired, feeling sick, or after drinking alcohol, despite their efforts to refocus. Children may squint one eye in bright sunlight, or may rub one of their eyes. Their vision may become blurry or they may experience double vision when their eyes are misaligned. Some patients say that they can feel that an eye is misaligned, even though they do not see anything unusual. Others are unaware that an eye is turning unless it is mentioned by another person. Why does my child, who has intermittent exotropia, close one eye frequently? Children with intermittent exotropia commonly close or squint one eye at times, especially when they are exposed to bright sunlight. We used to think that the bright light caused the eye to turn out, and that the child was closing one eye to avoid double vision. Now, we believe that the child is reacting directly to the sunlight itself by closing one eye. In any case, when the eye is closed, the child cannot use both eyes together. Small children who won't wear sunglasses may be offered a hat with a brim, such as a baseball cap, to shield the eyes from the sun, thereby limiting the need to squint. Will my child outgrow the intermittent exotropia? Most exotropia does not resolve spontaneously (without treatment), but occasionally it may be adequately controlled with glasses. How can I keep my child’s intermittent exotropia from getting worse? Common sense approaches to caring for your child will help to control intermittent exotropia as much as possible. For example, be sure that your child gets the recommended amount of sleep for age—many children don’t! Do your best to help her stay healthy, and understand that when she gets sick, the intermittent exotropia is likely to temporarily occur more frequently. See your ophthalmologist as often as recommended, in order to keep your child’s visual system fine-tuned. Otherwise, the progression of intermittent exotropia is not something that we can predictably control. Does watching too much television or playing too many video games make exotropia worse? Or can video games help? Normal visual activities have no effect on exotropia. However, for other health reasons, parents are encouraged to limit the time their children spend watching TV, playing video games, and sitting at their computers. What is sensory exotropia? Exotropia in an eye with very poor vision is called sensory exotropia. In this case, the eye with low vision is unable to work together with the other eye, and therefore, the natural tendency for our eyes to drift outward takes over. Sensory exotropia may occur from an early age in a child with poor vision, or may be acquired later in life due to loss of vision. Of course, if the visual problem is treatable, it should be addressed as soon as possible. In cases of permanent visual loss, surgery to straighten the eye is often an option. What is consecutive exotropia? Exotropia occurring after strabismus surgery to correct esotropia is referred to as consecutive exotropia. This may occur near the time of the original surgery, or may develop many years later. How is exotropia treated? Nonsurgical treatment may include glasses or eye exercises. Occasionally, patching therapy may be recommended. Once the eyes have become misaligned more often than they are straight, surgery on the eye muscles may be recommended in order to realign the eyes. Your pediatric ophthalmologist will discuss the ideal timing of surgery for your situation. When is surgery for exotropia indicated? Criteria for surgery may vary somewhat, but generally surgery is indicated when the exotropia is frequently present, when the patient is experiencing significant symptoms (eyestrain, double vision, squinting), or when there is evidence that the patient is losing "binocular vision". Surgery may not be recommended if the exotropia is adequately controlled with nonsurgical means, such as glasses. What is binocular vision? Binocular vision refers to the brain's ability to see objects with both eyes simultaneously. Among other benefits, binocular vision is necessary for normal depth perception, or "3-D vision". What age is best for exotropia surgery? Age is not the main determining factor for exotropia surgery. The surgery is appropriate when exotropia is present for the majority of the time, at any age. Can exotropia be treated with patching? In a small child, part-time patching of the preferred eye is useful, if the child has a preference for one eye over the other, or amblyopia. This helps to protect the vision in the non-preferred eye, but rarely cures the intermittent exotropia. In fact, too much patching can actually make exotropia worse by preventing the eyes from working with each other for prolonged periods of time. Can exotropia be treated with glasses? If a patient is nearsighted, keeping the glasses prescription up-to-date helps control the alignment. Can exotropia be treated with prisms in the glasses? Prisms are not usually used for children with strabismus, at least on a permanent basis. In a minority of adult cases, prisms may play a role in treatment. Prism glasses may occasionally be used on a temporary basis, however. What about exercises or vision therapy for the eyes? Exercises have been proven to help with only one type of exotropia, convergence insufficiency. In other cases of intermittent exotropia, the goal of eye exercises is to teach patients to become aware that they are seeing two images when their eyes are misaligned. Theoretically, once a patient learns to recognize this double vision, he may then learn to realign his eyes. Unfortunately, many patients who are taught this technique accomplish the first goal, recognizing the double vision, but then cannot make it stop, resulting in permanent double vision. For this reason, these exercises are not prescribed by ophthalmologists except for convergence insufficiency.Back to the top of the page Exotropía¿Qué es exotropía? Exotropía se refiere al desvío de los ojos hacia afuera. Es lo opuesto a ojos cruzados, o esotropía. Exotropía puede ocurrir entre tiempo y tiempo (exotropía intermitente) o puede ser constante, y se puede encontrar en cualquier grupo de edad. ¿Cuáles son los diferentes tipos de exotropía? Exotropía puede ser congénita (presente al nacer) o adquirida. Las formas de exotropía adquirida incluyen exotropía intermitente, exotropía sensorial, y exotropía consecutiva. ¿Qué es exotropía congénita? Bebes recién nacidos comúnmente tienen dificultad en mantener sus ojos derechos. Mientras esta tendencia de los ojos en desviarse es normal hasta los 4 meses de edad, cualquier desalineación constante durante el periodo de recién nacido debe ser evaluado por un oftalmólogo. Exotropía congénita o infantil, es el desvío hacia afuera de los ojos desde el nacimiento o desde temprana edad. Esotropía (ojos cruzados) es más común que exotropía en recién nacidos. De hecho, la exotropía constante, como no es tan común en bebes, cuando está presente los oftalmólogos investigan la causa para estar seguros de que no haya otro problema. ¿Qué es exotropía intermitente? Muchas personas tienen la tendencia a que los ojos se les desvíen hacia afuera cuando están completamente relajados, como cuando se mira a lo lejos como dormido con los ojos abiertos. Este desvío hacia afuera, que ocurre durante esos momentos en el cual los ojos no se están prestando atención el uno al otro, se llama exoforia, y es controlado sin esfuerzo al enfocar la visión nuevamente. Al principio, la exotropía puede ocurrir raramente. Con el tiempo, puede volverse más frecuente, hasta el punto de estar constante. Aunque, el tiempo que tome la exotropía intermitente en volverse constante varía desde algunos meses o años hasta durar toda una vida. ¿Puede ser hereditaria la exotropía? Estrabismo, o desalineación de los ojos, si es hereditario. No todos los miembros de la familia van a tener exactamente el mismo tipo de estrabismo, queriendo decir que la exotropía no va a ser el único tipo de desalineación posible. En algunos parientes, el estrabismo puede ser obvio, mientras que otros parientes pueden tener una cantidad mínima. Otros familiares no van a presentar estrabismo. Un historial familiar de estrabismo es una razón bastante fuerte para que lleve a su niño a ser evaluado por un oftalmólogo. ¿Cuáles son los signos de exotropía intermitente? Las personas que tienen exotropía intermitente pueden tener el desvío hacia afuera ocasionalmente, cuando están bien cansados, cuando se sienten enfermos, o luego de tomar alcohol, no importa cuánto traten de reenfocar. Algunos niños cierran un ojo estando bajo la luz brillante del sol, o se frotan uno de sus ojos. La visión la pueden tener borrosa o pueden experimentar visión doble cuando los ojos estén desalineados. Algunos pacientes dicen que pueden sentir que un ojo esta desalineado, aunque no vean algo inusual. Otros no están conscientes que uno de sus ojos se desvía a menos que otra persona lo mencione. ¿Porque mi niño, que tiene exotropía intermitente, cierra uno de sus ojos frecuentemente? Los niños con exotropía intermitente comúnmente cierran o parpadean un ojo, especialmente cuando están expuestos a la luz brillante del sol. Antes pensábamos que la luz del sol causaba que el ojo se desviara, y que el niño cerraba un ojo para evitar visión doble. Ahora, creemos que el niño está reaccionando directamente a la luz del sol al cerrar un ojo. En cualquier caso, cuando el ojo está cerrado, el niño no puede usar ambos ojos juntos. Niños pequeños que no usen gafas oscuras se les puede ofrecer una gorra con visera para proteger los ojos del sol, y así limitar la necesidad de tener que cerrar un ojo. ¿Mi niño podrá superar la exotropía intermitente? La mayoría de las exotropias no se resuelven espontáneamente (sin tratamiento), pero ocasionalmente se puede controlar con anteojos. ¿Qué puedo hacer para evitar que la exotropía intermitente de mi niño empeore? Sentido común en cuidar a su niño le ayudará en controlar la exotropía intermitente lo mejor posible. Por ejemplo, esté seguro de que su niño descanse la cantidad recomendada para su edad – muchos no lo hacen. Haga lo posible para que su niño este saludable, y entienda que cuando se enferme, la exotropía intermitente puede que ocurra más, mientras esté enfermo. Visite a su oftalmólogo como se le ha recomendado, para mantener el sistema visual de su niño bien afinado. En otras palabras, la progresión de la exotropía intermitente no es algo que se pueda predecir. ¿El mirar mucha televisión o jugar muchos juegos de videos pueden causar que la exotropía empeore? ¿O pueden los juegos de video ayudarle? Actividades visuales normales no tienen efecto en la exotropía. Aunque, por motivos de salud, se les recomienda a los padres a que limiten la cantidad de tiempo que su niño pasa mirando la televisión. ¿Qué es la exotropía sensorial? Exotropía en un ojo con visión bien pobre se le conoce como exotropía sensorial. En este caso, el ojo con menos visión no puede trabajar en conjunto con el otro ojo, por eso, la tendencia natural de su ojo en desviarse hacia afuera se apodera. Exotropía sensorial puede ocurrir a una edad temprana en un niño con poca visión, o puede ser adquirida más tarde en la vida a causa de pérdida de visión. Si el problema visual se puede tratar, debe de hacerse lo antes posible. En casos en que hay perdida de visión permanente, cirugía para enderezar el ojo casi siempre es una opción. ¿Qué es la exotropía consecutiva? Exotropía que ocurre luego de cirugía de estrabismo, para corregir esotropía es conocida como exotropía consecutiva. Esta puede ocurrir inmediatamente luego de la cirugía original, o puede desarrollarse muchos años después. ¿Cómo se puede tratar la exotropía? El tratamiento sin cirugía puede incluir anteojos o ejercicios de los ojos. Ocasionalmente, un parche puede ser recomendado. Una vez los ojos se desalinean más de los que se mantienen derechos, se recomienda cirugía en los músculos para poder re alinear los ojos. Su oftalmólogo pediátrico discutirá el momento ideal para practicarla en cada situación. ¿Cuándo se indica la cirugía para exotropía? Los criterios para cirugía pueden variar, pero generalmente esta es indicada cuando la exotropía es frecuente, cuando el paciente tiene síntomas significantes (ojos cansados, visión doble, necesidad en enfocar), o cuando hay evidencia de que el paciente está perdiendo visión binocular. No se recomienda cirugía si la exotropía se puede controlar adecuadamente de otras maneras, como con anteojos. ¿Qué es visión binocular? Visión binocular se refiere a la habilidad del cerebro de ver objetos con ambos ojos a la misma vez. Entre otros beneficios, visión binocular es necesaria para la percepción de profundidad, o “visión 3D”. ¿Cuál es la edad perfecta para tener cirugía de exotropía? La edad no es el factor más importante en determinar cuando se ha de tener la cirugía. Esta será apropiada cuando la exotropía esté presente la mayor parte del tiempo, a cualquier edad. ¿Se puede tratar la exotropía con parche? En un niño pequeño, parchar a tiempo parcial el ojo preferido es útil, si el niño tiene preferencia de un ojo a otro, o ambliopía. Esto ayuda a proteger la visión en el ojo no preferido, pero rara vez cura la exotropía intermitente. De hecho, demasiado parche puede en realidad hacer la exotropía peor al prevenir que los ojos trabajen el uno con el otro por mucho tiempo. ¿Se puede tratar la exotropía con ante ojos? Un paciente que sea miope (visión mejor de cerca), mantener la receta de los anteojos al día ayuda a controlar el alineamiento. ¿Puede ser tratada la exotropía con prismas en los anteojos? Usualmente no se utilizan prismas en niños con estrabismo, por lo menos no permanentemente. En la minoría de los casos en adultos, puede que los prismas se utilicen en el tratamiento. Si se usan prismas en anteojos debe ser temporeramente. ¿Y qué sobre ejercicios o terapia visual para los ojos? Se ha comprobado que los ejercicios ayudan a solo un tipo de exotropía; insuficiencia en convergencia. En otros casos como exotropía intermitente, la meta de los ejercicios de ojos es enseñarle a los pacientes a que se den cuenta de que están viendo dos imágenes cuando sus ojos están desalineados. Teóricamente, una vez los pacientes aprenden a reconocer esta visión doble, pueden entonces aprender a alinear los ojos. Desafortunadamente, los pacientes que aprenden esta técnica logran su primera meta, reconocen la visión doble, pero entonces no pueden dejar de ver doble, y resulta en visión doble permanente. Por esta razón, estos ejercicios no son recomendados por oftalmólogos excepto para tratar la insuficiencia en convergencia. Back to the top of the page Glasses for ChildrenChildren may need glasses for several reasons—some of which are different than for adults. Because a child’s vision system is growing and developing, especially during the first 5-6 years of life, glasses may play an important role in insuring normal vision development. The main reasons a child may need glasses are: • To provide better vision, so that a child may function better in his/her environment • To help straighten the eyes when they are crossed or misaligned (strabismus) • To help strengthen the vision of a weak eye (amblyopia or “lazy eye”). This may occur when there is a difference in prescription between the two eyes (anisometropia). For example, one eye may be normal, while the other eye may have a significant need for glasses caused by near-sightedness, far-sightedness or astigmatism. • To provide protection for one eye if the other eye has poor vision An ophthalmologist can detect the need for glasses through a complete eye exam. Typically, the pupils are dilated in order to relax the focusing muscles, so that an accurate measurement can be obtained. By using a special instrument, called a retinoscope, your eye doctor can arrive at an accurate prescription. The ophthalmologist will then advise parents whether there is a need for glasses, or whether the condition can be monitored. There are 4 basic types of refractive errors: • Myopia (near-sighted) – This is a condition where the distance vision is blurred, but a child can usually see well for reading or other near tasks. This occurs most often in school-age children, although occasionally younger children can be affected. The prescription for glasses will indicate a minus sign before the prescription (for example, -2.00). If the myopia is slight, allowing a child to sit a little closer to the front of the classroom may be an alternative. • Hyperopia (far-sighted) – Normally, most children are far-sighted early in life and do not need glasses because they can use their own focusing muscles to provide clear vision for both distant and near vision. Glasses are rarely needed if the far-sightedness is less than +2.00. When an excessive amount of far-sightedness is present, the focusing muscles may not be able to keep the vision clear. As a result of this, problems such as crossing of the eyes, blurred vision, or discomfort may develop. A prescription for hyperopia will be preceded by a plus sign (+3.00). • Astigmatism – Astigmatism is caused by a difference in the surface curve of the eye. Instead of being shaped like a perfect sphere (like a basketball), the eye is shaped with a greater curve in one axis (like a football). If your child has a significant astigmatism, fine details may look blurred or distorted. Glasses that are prescribed for astigmatism have greater strength in one direction of the lens than in the opposite direction. A prescription for astigmatism will have several numbers and will look something like this: -2.00 +2.50 X 90. • Anisometropia – Some children may have a different prescription in each eye. This can create a condition called amblyopia, where the vision in one eye does not develop normally. Glasses (and sometimes patching) are needed to insure that each eye can see clearly. Many parents are concerned as to how they will be able to get their children to wear their glasses, especially when their child is an infant or toddler. Most young children who really need glasses will happily wear them because they make a big difference in their vision. Children with amblyopia or strabismus may be much more resistant to wearing glasses, but if the parents have a positive attitude and are firm and consistent in requiring glasses wear, most children get past this stage fairly quickly. Toddlers often may wear the glasses only when they are in a good mood and reject them (and everything else) when they are not. Getting a good frame fit by an optician who is experienced in pediatric eyewear is also important. The frame should be comfortable with the eye centered in the middle of the lens, and should fit the child well now rather than after they “grow into them” in a year. Lenses made of a material called polycarbonate will provide the best protection for your child because this lens material is shatterproof. Many children’s frames have soft, comfort-cables that fit around the ears. Children rarely need bifocals. Occasionally, children who have crossed eyes (esotropia) may need to have bifocals to help control the crossing. Also, children who have had cataract surgery often need bifocals or reading glasses. Some parents express concern that wearing glasses may make their child’s eyes worse or more dependent on them. In fact, the opposite may be true. If a child does not wear the glasses prescribed, normal vision development can be adversely affected. Back to the top of the page Congenital EsotropiaEsotropia is an inward turning of one or both eyes. Congenital esotropia begins at birth or during the first year of life. Congenital esotropia is also called infantile esotropia Congenital esotropia occurs when the part of the brain that controls the ability to use the eyes together does not form perfectly. If one eye is turned more frequently than the other, there is increased risk for the development of amblyopia which is poor vision in an eye that is structurally normal. It occurs because the brain ignores input from an eye. When an infant looks with either eye an equal amount of time the risk of amblyopia is less. Prematurity, hydrocephalus, seizure disorders, developmental delay, intraventricular hemorrhage and a family history of strabismus are among the risk factors for the development of congenital esotropia. All children with these or other risk factors should be evaluated by an ophthalmologist. Cross fixation is commonly seen in patients with congenital esotropia. Cross fixation is the use of the right eye to view the left visual field and the use of the left eye to view the right visual field. Cross fixation often makes the child appear as if he or she is not looking directly at a target, causing parents to wonder if the vision is reduced. Children with congenital esotropia are usually not more nearsighted or farsighted than those without crossing, although in some cases glasses may be needed. The primary treatment for congenital esotropia, however, is strabismus surgery (eye muscle surgery). Studies have shown that surgery performed prior to 2 years of age gives better long term results, and surgical repair typically occurs during the first year of life. In some cases surgery must be postponed until any associated amblyopia has been treated and the amount of esotropia is stable. The re-operation rate after the first surgery varies, but is usually around 25% of cases. Most children with congenital esotropia demonstrate a deficit of depth perception when old enough to be tested reliably. If esotropia is corrected before 2 years of age, there is a better chance of developing the ability to use the eye at the same time (binocularity). Some of these children also may develop some degree of dissociated vertical divergence (DVD). DVD is an upward drifting of the eyes which is usually more prominent in one eye. Some children become significantly farsighted as they grow and develop accommodative esotropia. Fortunately, accommodative esotropia can usually be treated with glasses. Some children develop a slowly increasing outward drift of the eyes called exotropia. There are surgical and nonsurgical treatments available for exotropia. Latent nystagmus may also be present. This is a small, rhythmic, horizontal movement of the eyes when one eye is closed or covered. Vision may be slightly decreased by the nystagmus but often is not affected. Occasionally a vertical acting eye muscle (inferior oblique) may overact which may cause the eye to move upwards when looking to the side. In certain circumstances eye muscle surgery may be indicated to correct this problem as well. Back to the top of the page Learning DisabilitiesLearning disability (LD) is a lifelong condition which interferes with the ability to learn. There are many types of LD, including: learning to read, reading comprehension, writing and spelling, mathematical operations, learning a foreign language, and organizing written and spoken language. Individuals with LD may be particularly gifted in other skills and are typically of normal intelligence. LD may affect up to 15-20% of the population; of those affected, approximately 85% have dyslexia (language based learning disability). LD affects people of all backgrounds and intelligence, regardless of gender, race, or intelligence. Dyslexia often runs in families. The diagnosis of LD is based on a formal evaluation of intellectual ability, informational processing, and linguistic processing. Recent neurological research in dyslexic patients has shown that there may be reversible neuro-anatomical abnormalities in the language areas of the brain that interfere with both the acquisition and processing of written and spoken language. These anatomic defects have been shown to improve with proper phonemic-based educational techniques. Visual abnormalities have not been found to affect the brain's ability to process visual stimuli and children with LD have no increased incidence of ophthalmologic disease. Ophthalmologic testing should be performed on all children who fail vision screening tests. This allows for diagnosis and therapy of treatable ocular conditions such as refractive errors and eye muscle imbalances, and may help speed the diagnosis and treatment of dyslexia. Treatment for LD involves academic modifications to help the affected child succeed. Often this requires individualized tutoring, multisensory teaching techniques, and maximizing academic strengths. There is no scientific evidence to suggest that vision training, orthoptic exercises, visual perceptual training, or colored spectacle lenses improve academic performance in children with LD. Instead, these treatments are expensive and may distract parents and children form pursuing the treatment modalities that have been scientifically proven to help children with LD. Below are several links to websites with information on learning disabilities: Learning Disabilities, Dyslexia, and Vision The official joint policy statement (1998) for learning disabilities, dyslexia, and vision of the American Academy of Pediatrics, the American Association for Pediatric Ophthalmology and Strabismus, and the American Academy of Ophthalmology; the policy statement (2001) of the American Academy of Ophthalmology regarding vision therapy for learning disabilities. The International Dyslexia Association Great Schools- An information website for parents and children with learning disabilities. Back to the top of the page MigraineMigraine is a complex constellation of neurologic findings that often, but not always, includes recurrent, severe headaches. Migraine headaches may occur with or without a visual prodrome or aura. The aura of a migraine may consist of a variety of neurologic symptoms, such as dizziness, tinnitus, scotomas, photophobia, or visual scintillations (eg, bright zigzag lines). The headache previously described as classic migraine is now known as migraine with aura, and that described as common migraine is now termed migraine without aura. Migraines without aura are the most common, accounting for more than 80% of all migraines. The cause of migraine headaches is not clearly understood. Certainly there is a strong familial predisposition, although many members of the same family can have widely differing migraine symptoms. Initially migraine headaches were felt to be caused by expanding and contracting cerebral arteries. Evidence now supports a neurogenic cause, with neurogenic peptides, such as serotonin and dopamine, triggering the migraines in susceptible patients. These vasoactive neuropeptides stimulate an inflammatory cascade with the release of endothelial cells, mast cells, and platelets. This inflammation causes vasodilation and a perivascular reaction. The serotonin receptor (5-HT) is believed to be the most important receptor in the headache pathway. Some of the symptoms associated with migraine headaches, such as nausea, vomiting, irritability, hypotension, and hyperactivity, can be associated with dopamine receptor activation. Dopamine receptor hypersensitivity has been shown experimentally with dopamine agonists, while dopamine antagonists have been shown clinically to treat migraine headaches effectively. An estimated 10-20% of the US population suffers from migraine headaches, and migraines are found in women three times more often than men. Migraine is the second most common type of headache syndrome in the United States, just behind tension Migraine headaches typically start in childhood or adolescence. More than 80% of patients who develop migraines will have a first attack by age 30. With increased age, attacks usually decrease in severity and frequency. Any patient with the new onset of migraine after the age of 50 years has an increased risk of intracranial pathology. Some patients may have no headache at all, and present with only the visual manifestations of migraine. These visual findings vary from descriptions of zig-zag lines in the vision, kaleidoscope vision, blind spots, “heat-waves” in the vision, “light reflecting off water,” moving or shifting lights or colors, etc. A small percentage of migraine patients, especially children with migraine, may have actual formed visual hallucinations. All of these various visual descriptions seem to last from 10 to 30 minutes on average, and are associated in some cases with headaches. A smaller percentage of patients may have focal neurologic findings that occur with the headache and persist temporarily after the pain resolves. These patterns suggest one of several migraine variants. In hemiplegic migraine, the patient may have one-sided paralysis or weakness. Difficulty speaking, dizziness, and balance problems may be seen in basilar migraines. In ophthalmoplegic migraine, the patient may present with sudden double-vision from temporary ocular muscle paralysis, as well as ptosis, or drooping of the eyelid. These abnormal neurologic findings from migraine variants may at times last for hours to days after the headache. There are a number of known triggers or precipitating causes for migraine, including:
Some members of migraine families are very sensitive to bright lights, even those who do not get migraine themselves. Certain light conditions, such as the large banks of fluorescent lights in grocery or department stores, sun reflecting off water or snow, etc. are very poorly tolerated by many migraine patients. There are special migraine tints for sunglasses that will often help these patients by reducing light sensitivity and, in many cases, reducing the frequency and severity of the headaches themselves. There are many different treatments for migraine. If the headaches are severe, patients presenting in emergency rooms are often treated with narcotic injections, which work quickly but leave patients unable to function well until the narcotic wears off. For acute attacks, tryptan medications (Maxalt, Amerge, etc.) can be used. These medications are usually very effective, but are expensive enough that they become prohibitive if the headaches are coming more than once a week or so. For frequent headaches, prophylactic medications such as Propranalol or Topamax are often used. Caffeine is an important factor in migraine headaches. Caffeine is a very effective treatment for migraine, but only if it is not already being used on a regular basis. This paradoxical reaction occurs because when used regularly in coffee, tea or soft drinks, the caffeine binds to receptors in the brain. If the receptors are all bound, no open receptors are available for additional caffeine to bind, and the caffeine loses its effectiveness. For migraine patients, caffeine should be considered a medication rather than a beverage. Back to the top of the page Myasthenia GravisMyasthenia gravis is an autoimmune disease in which antibodies attack normal skeletal muscle tissue and render it weak. It occurs in both children and adults and can affect different muscle groups in the body. Symptoms include double vision, droopy eyelids, easy muscular fatigue and breathing/swallowing difficulty. The symptoms tend to worsen with increased activity and improve with rest. The eyelid and extra-ocular muscles are commonly involved in myasthenia, either in isolation or in conjunction with other skeletal muscles. Myasthenia gravis develops when auto-antibodies attack normal skeletal muscle tissue. Nerve endings that innervate skeletal muscle typically release a chemical, acetylcholine, to induce the muscles to contract. In myasthenia, antibodies attach themselves to the receptors for the acetylcholine on the skeletal muscle. Thus, when the acetylcholine is released from a nerve and tries to induce contraction in a muscle, the receptors cannot attach to the acetylcholine since they are bound with an abnormal antibody. Myasthenia is an uncommon disease. The incidence is estimated at 1/5,000. There appears to be no racial or sex predilection in myasthenia, and it is not a directly hereditary condition. Approximately 90% of people with myasthenia gravis have ocular involvement and 50% present with ocular symptoms. Double vision from eye misalignment (strabismus) and drooping of the eyelids (ptosis) are the most common symptoms. These symptoms classically vary and worsen throughout the day. The double vision or ptosis may be present in the evening while not present in the morning. Less common symptoms are facial weakness, chewing and swallowing difficulty, respiratory weakness, and arm and leg muscle fatigue. The diagnosis of myasthenia can be challenging. No one test is positive 100% of the time. Examination findings are an important tool to make the diagnosis. Ice testing is another way to diagnose myasthenia. Tensilon and Prostigmin are injectable medications used for testing. Laboratory testing can be helpful in diagnosing myasthenia. The acetylcholine receptor antibody can be detected with a blood test but is only positive in 50% of people with ocular myasthenia. An electromyogram (EMG) can also help detect myasthenia. Myasthenia usually occurs in isolation from other diseases. Rheumatoid arthritis, juvenile-onset diabetes, asthma, thyroid disease and certain cancers (such as breast, uterine, colon and pineal gland) can occur in association with myasthenia. A thymoma in the chest cavity is another association. Myasthenia is rarely cured, but the symptoms can be improved with a number of different medical or surgical interventions. The main goal of treatment from a biochemical perspective is to increase the amount of acetylcholine available to the receptors on the nerve endings in the muscle. This can be done either by increasing the amount of the acetylcholine itself by minimizing its breakdown, or by destroying the antibodies that are attacking the acetylcholine receptors. Mestinon, or pyridostigmine, is a cholinesterase inhibitor which blocks the breakdown of acetylcholine. This is a commonly used medication to treat the symptoms of myasthenia, but studies have shown that this medication is more effective at alleviating the non-ocular symptoms than the ocular ones. Immunosuppressive agents such as prednisone can be effective at blocking the immune response involved in myasthenia. Plasmapheresis is a procedure whereby the offending antibodies are removed directly from the bloodstream. This treatment frequently needs to be repeated as symptoms can return after time. IVIg is an intravenous treatment that affects the production and/or function of the abnormal antibodies. The ptosis and strabismus related to myasthenia can at times be helped with surgery, but not during the acute phases. Surgical intervention is sometimes advised if the ptosis and/or strabismus deviation has been stable for a long time. For more information about myasthenia gravis, contact the Myasthenia Gravis Foundation of America, Inc. Back to the top of the page NystagmusNystagmus is an involuntary, shaking, “to and fro” movement of the eyes. There are many types of nystagmus, typically divided into congenital or acquired categories, with multiple subcategories. Congenital nystagmus is one of the most common types, with an onset typically between 6 weeks and 3 months of age. Congenital motor nystagmus tends to be horizontal, bilateral, idiopathic (cause unknown) and is sometimes inherited. Sensory nystagmus also occurs early in life and is secondary to poor vision caused by a variety of eye conditions such as cataract (cloudiness of the eye’s lens), strabismus (eye misalignment) and optic nerve hypoplasia. Acquired nystagmus occurs later and has many etiologies. Acquired nystagmus can be associated with serious medical conditions such as:
All children and adults with nystagmus should be evaluated by an ophthalmologist (and primary care physician) to determine if any association exists with other conditions. Some types of nystagmus can be inheritable, with dominant, recessive and x-linked patterns being reported. The severity of nystagmus often varies amongst members of an involved family. The visual development of a child with nystagmus is quite variable. Some children with nystagmus have a mild reduction in visual acuity (20/50 or better) while others have severe visual disability (20/200 or worse). It is difficult to predict what the visual acuity will be as an adult; however, most individuals with nystagmus have some reduction of visual function. Children with nystagmus typically see the world similarly to other children, albeit with some blurriness. Their visual world does not appear to “shake”. Individuals with adult onset or acquired nystagmus often report the appearance of movement of the visual world (oscillopsia). Nystagmus severity can vary upon direction of gaze; the eyes oscillate more when looking in certain directions. The gaze position of least eye movement is the “null point” and tends to be where vision is best. Tilting or turning the head can thus optimize vision by keeping the eyes in this null point. Rarely, nystagmus can be unilateral, or occurring in only one eye. Spasmus nutans (nystagmus, head bobbing or nodding, and a head turn or tilt) is often noted to have unilateral nystagmus. However, under close observation the nystagmus is bilateral but highly asymmetric with a high-frequency “shimmering” movement. Eye muscle surgery (strabismus surgery) may be indicated for some individuals with nystagmus. The goal of surgery in most instances is to help alleviate a significantly abnormal head position or to decrease the amplitude of nystagmus. Surgery can sometimes cause vision improvement but does not fully eliminate nystagmus. Other treatments for patients with a significant refractive error include glasses or contact lenses. Contact lenses, in some circumstances, can be more visually beneficial than spectacles. Variable success has been noted with medications used to dampen the severity of nystagmus. Unfortunately, the use of these medications is frequently limited by side effects. Botulinum toxin is helpful for some individuals with severe, intractable oscillopsia. For more information about nystagmus, visit the American Nystagmus Network. Back to the top of the page Optic NeuritisOptic neuritis (ON) can mean any inflammatory condition of the optic nerves, but the term usually refers to an inflammation of the optic nerve caused by demyelination. Demyelination refers to the loss of the myelin sheath, a fatty sheath that surrounds many of the nerves in the body and functions somewhat like insulation around electrical wires. This myelin sheath makes the electrical impulses travel along the nerves more quickly and reliably. Because of this demyelination, many cases of ON are associated with multiple sclerosis (MS) or neuromyelitis optica (NMO), but ON can occur in isolation. In cases associated with MS, ON may be the first manifestation of the chronic demyelinating process. Long-term follow-up studies have indicated that up to 75% of female patients initially presenting with ON ultimately develop MS. Much of our current knowledge regarding the natural history of optic neuritis has been obtained from the Optic Neuritis Treatment Trial (ONTT. Occasionally, ON can be due to an infectious process involving the orbits or paranasal sinuses or occur in the course of a systemic viral infection. Certain optic neuropathies, such as anterior ischemic optic neuropathy (AION) and compressive and hereditary optic neuropathies, can resemble ON. NMO has been recognized as a distinct inflammatory demyelinating disease consisting of ON in combination with other neurologic signs of transverse myelitis. NMO is characterized by ON and myelitis in a close temporal relationship. However, ON can occasionally precede the myelopathy. Some patients with NMO develop relapses limited to the optic nerves and spinal cord. In male patients with bilateral sequential ON with little recovery of vision, a disease called Leber’s Hereditary Optic Neuropathy (LHON) is always a concern. Patients with LHON may have a history of vision loss in maternal uncles. Optic neuritis has an annual incidence of 4-5 per 100,000 for new cases, and patients living in temperate climates seem to be more predisposed to develop it. ON appears to affect Caucasians more commonly than other races, and women are affected twice as often as men. Typically, patients with first time acute ON are young adults aged 20-45 years. Atypical cases of ON may be seen in elderly patients. Bilateral ON in childhood is not uncommon, and it is believed there is less risk of progression to MS. The symptoms of ON vary considerably, but may include any of the following:
The diagnosis of optic neuritis is generally made on clinical examination alone, but all patients with the new onset of ON should have an MRI scan to look for any orbital tumor or other mass lesion that could mimic ON. The MRI is also important to help in determining the prognosis for future development of MS. Back to the top of the page PapilledemaPapilledema is a term referring to optic disc swelling caused by elevated intracranial pressure. In contrast to many other causes of optic disc swelling, the vision usually is initially well preserved with papilledema, although over time if untreated it can have serious visual consequences. Papilledema almost always presents as a bilateral phenomenon and may develop over hours to weeks. The disc swelling in papilledema is the result of stasis or slowing of the flow of fluid through the individual nerve fivers of the optic nerve. Each normal optic nerve (see Fig. 1) has approximately 1 million individual nerve fibers, and each of these fibers has a steady flow of fluid toward and away from the eye, called axoplasmic flow. The sheath that surrounds the brain extends out to surround the optic nerves as well, and the space between the sheath and the nerve itself is bathed with the same cerebrospinal fluid (CSF) that surrounds the brain. If something happens to raise the intra-cranial pressure (ICP) within this space, the pressure is transmitted to the optic nerve, and the optic nerve sheath acts as a tourniquet to impede axoplasmic flow. This leads to a buildup of material at the head of the optic nerve, resulting in the characteristic swelling of the nerve head (see Fig. 2). Papilledema is seen nearly always in cases where the ICP is elevated, although it may be absent in cases of prior optic atrophy. In these cases, the absence of papilledema is most likely secondary to a decrease in the number of physiologically active nerve fibers. Papilledema can present at any age. Most symptoms in a patient with papilledema are secondary to the underlying elevation in intracranial pressure, and can include any of the following:
Although elevation of the ICP for any reason can cause papilledema, there are many causes for the ICP to be elevated, and the exact diagnosis can be difficult at times. The most likely causes for elevated ICP are:
Papilledema can often be hard to distinguish form other causes of optic nerve swelling, and a special test called Optical Coherence Tomography (OCT) can often be helpful in distinguishing the cause. This test is quick and painless, and involves taking a photograph of the back of the eye with a scanning laser. If the examination and OCT show true papilledema, further studies including CT or MRI Scan and a spinal tap are used to determine the cause and possible treatment of the papilledema. Papiledema can be treated in several ways, depending on the cause. In patients with a drug-related papilledema, simply stopping the drug itself usually solves the problem. For patients with Pseudotumor Cerebri, oral medications such as Diamox usually lower the pressure temporarily, while weight loss generally provides the long-term solution. In patients where the pressure cannot be lowered by other means, surgical solutions exist. In one surgery, an opening is made in the sheath surrounding the optic nerve to release the pressure. Other surgical options involve placing an actual tube or shunt to channel the CSF out of the brain or spinal column to other areas of the body where it is harmlessly absorbed. These surgical options are very useful in some patients, but do not replace weight loss or medications in most patients. Back to the top of the page Pseudo-strabismus
Pseudo-strabismus is the false appearance of misaligned eyes. When eyes are truly misaligned, the condition is called strabismus, and it can have serious consequences for long-term vision if left untreated. Some children, however, have the appearance of crossed eyes despite normal ocular alignment. This is usually secondary to the shape of the eyelids and/or nasal bridge, [See figure 2] and is called pseudo-strabismus. Pseudo-strabismus is a fairly common finding in children. Whenever we look at another person, we expect to see sclera or “white of the eye” both on the inside and outside of the eye. If part of the lid covers this sclera, it gives the impression of crossed eyes. Many children, especially those of Asian or Hispanic lineage, have a wide nasal bridge and an extra fold of skin called the epicanthal fold that covers or hides the inner sclera and makes the eyes look crossed. This is usually much more noticeable when the child looks to the right or left and “buries” the inner sclera behind the epicanthal fold.
As the child matures, the facial features will gradually change and this appearance of crossing will improve and will usually disappear. To tell the difference between strabismus and pseudo-strabismus, shine a small flashlight on your child’s eyes. When you are certain that your child is looking at the flashlight, observe the light reflection on the front surface of the eye. If both eyes are properly aligned, the light reflection should be in the center of the pupil in both eyes. If the child has true strabismus, the reflection will appear in a different location in one eye. [See fig. 2] Because the light reflectionis not affected by the width of the nose or the folds of the eyelid skin, a child with pseudo-strabismus will have a normal reflection. Flash photos are often very useful in looking for pseudo-strabismus, since you have a stationary image to look at. Also, many flash photos show a prominent red reflex or “red-eye” appearance. In a child with true strabismus, the red reflex will often be different in one eye than another. In pseudo-strabismus the red reflex will look the same in both eyes. Any child suspected of having ocular misalignment should have a thorough examination by a pediatric ophthalmologist. Some children have both pseudostrabismus and actual eye misalignment. Therefore pseudostrabismus (wide nasal bridge/prominent epicanthal eyelid skin folds) does not by itself eliminate the possibility of true eye crossing. Back to the top of the page Pseudotumor CerebriPseudotumor cerebri (PC) is an older term that refers to a condition of high pressure in the fluid around the brain. This name comes from the days prior to CT scans, when a patient would show some of the signs and symptoms of a brain tumor without a brain tumor being present (pseudo meaning false). The newer name for this condition is Idiopathic Intracranial Hypertension (IIH) (idiopathic means unknown cause; intracranial means inside the head; hypertension means the fluid is under high pressure) The space around the brain is filled with cerebrospinal fluid (CSF). If there is too much of this fluid present, (for example, if not enough being absorbed), the pressure around the brain rises. It is this high pressure that causes papilledema, (recommend a hyperlink to papilledema page here) or swelling of the optic nerve, and also produces the symptoms of PC. Although we do not know what causes IIH, or why some people are more susceptible to developing this problem, there are some contributing factors. The condition occurs mostly in moderately obese women in the childbearing years and is rare in thin men. The symptoms often start or worsen during a period of weight gain, and hormonal changes may be a possible cause. Any disorder that blocks the flow of spinal fluid between the brain and its route to the blood, the jugular vein, can cause raised pressure. Damage to the part of the brain that absorb the spinal fluid (the arachnoid granulations) can cause raised pressure. Similarly, blood clots in the veins draining the brain can cause increased intracranial pressure. Withdrawal from oral steroids, large doses of vitamin A or intake of foods containing considerable vitamin A (such as liver), use of body building-type steroids and possibly certain drugs such as tetracycline and lithium can cause raised intracranial pressure. These conditions can mimic IIH. The symptoms most commonly reported by IIH patients, followed by their frequency are:
When the pressure in the CSF increases, that pressure is transmitted along the optic nerves and causes the swelling of the nerves. Untreated, this swelling will almost invariably cause loss of vision because the microcirculation or blood supply to the nerve is also under pressure, which results in decreased blood flow to the optic nerve. Since all of the optic nerve fibers are under pressure, a special test, called a visual field test is necessary to determine whether visual loss is taking place so that the appropriate treatment can be started. The definitive diagnosis of IIH is made by identifying the typical symptoms of the disease along with documentation of papilledema and a high spinal fluid pressure (done during a spinal tap). Lastly, neuroimaging procedures such as CT scans or MRI scanning are done to rule out any tumor and to locate any contributing cause for the IIH. Treatment for patient with IIH can be divided into medical treatment and surgical treatment. The cornerstone of medical treatment is weight loss. It does not appear to be the total number of pounds lost. Some patients are effectively treated by losing one pound every week or two for several months and then maintaining the weight loss. It may be the loss of fluid accompanying weight loss that is the significant factor but this has not been proven. Studies do indicate that if a patient can lose approximately 10% of their initial body weight. Loss of fluid can also be obtained using diuretics (water pills). Diamox (acetazolamide) is the most commonly used medication. It is relatively safe but many patients experience tingling of the fingers and toes while on this medication. Patients also experience that carbonated soft drinks taste metallic. Less commonly, kidney stones can occur and rarely other blood disorders. Another diuretic commonly used that appears to be effective in some patients is Lasix (furosemide). Lasix has fewer side-effects than Dimox, but is less effective in lowering pressure. The surgical treatments currently used are optic nerve sheath fenestration (making slits in the optic nerve sheath or covering) and lumbar shunting procedures (running a tube from the spinal fluid space in the lower spine into the abdominal cavity). These procedures are used when patients do not respond adequately to medical therapy. Back to the top of the page Ocular Cranial Nerve Palsies(Fourth and Sixth Nerve Palsies)A cranial nerve palsy is a weakness of one of the nerves that control one of more of the muscles that move the eye back and forth. There are three cranial nerves that control eye movement, the third, fourth and sixth cranial nerves. Of these, the two most likely nerves to be damaged are the fourth and sixth nerves, which control, respectively, the superior oblique and lateral rectus muscles. The lateral rectus muscle pulls the eye away from the nose and when the lateral rectus muscle is weak, the eye turns inward toward the nose (esotropia). The superior oblique muscle mainly works in vertical gaze, and when damaged it causes a vertical diplopia, or double vision with the images above and below each other. The most common causes of a 4th or 6th cranial nerve palsy are stroke, trauma, viral illness, brain tumor, inflammation, infection, migraine headache and elevated pressure inside the brain. The condition can be present at birth; however, the most common cause in children is trauma. In older persons, a small stroke is the most common cause. Sometimes the cause of the palsy is not determined despite extensive investigation. Both of these cranial nerves have a long course from the brainstem to the muscle, which predisposes the nerve to damage. Depending on the location of the abnormality, other neurologic structures may be involved. Hearing loss, facial weakness, decreased facial sensation, droopy eyelid and/or abnormal eye movement can be associated, depending on the location of the lesion. Both of these nerve palsies may improve spontaneously in many patients, and the amount of resolution primarily depends on the cause. Palsy caused by viral illness or lack of blood supply to the nerve generally resolves completely; whereas palsy caused by trauma is typically associated with incomplete resolution. Maximum improvement usually occurs during the first six months after onset. Double vision (either side by side or above and below) is the most common symptom. The separation between the 2 images is greatest on gaze in one direction than another, depending on which muscle is involved, and there is usually less double vision on near fixation than on distant fixation. Children with either of these palsies typically do not experience persistent double vision, but are more prone to develop amblyopia. Treatment for the double vision, if it does not improve spontaneously, can be problematic. Prism spectacles can realign the images and allow single binocular vision in straight ahead gaze. Because the degree of the misalignment varies in different gaze positions, prism correction does not eliminate double vision in every gaze position. The power of prism can be reduced as the palsy improves. Patching one eye eliminates double vision, however, this treatment must be carefully monitored in children to avoid the development of amblyopia. After observation for improvement (usually six months), strabismus surgery can be performed to maximize eye alignment if prism correction. Back to the top of the page StrabismusStrabismus is any misalignment of the eyes. It is estimated that 4% of the U.S. population has strabismus. Some strabismus is caused by damage to cranial nerves, while other types are congenital or developmental. Special patterns of strabismus can have unique names such as Brown syndrome, and Duane syndrome.
There are many different types of strabismus, as follows: Exotropia is the term used to describe outward turning of the eyes (aka "wall-eyed") [See figures 1 and 2]. The terms hypertropia and hypotropia are used to describe vertical misalignment. Hypertropia is an abnormal eye higher than the normal eye. Hypotropia is when the abnormal eye is lower than the normal eye. The terms can generally be interchanged. Most strabismus is the result of an abnormality of the poorly understood neuromuscular (including brain) control of eye movement. Less commonly, a problem with the actual eye muscle causes strabismus. The result of these abnormalities, however is that eye misalignment can cause amblyopia in children. When the eyes are oriented in different directions, the brain receives 2 different visual images. The brain may ignore the image from the misaligned eye to avoid double vision, resulting in poor vision development of that eye because the connections between the eye and the brain do not develop properly. Strabismus often occurs in children who are otherwise completely normal. However, disorders that affect the brain such as cerebral palsy, Down syndrome, hydrocephalus and brain tumor are more likely to develop strabismus. The goal of strabismus treatment is to improve eye alignment which allows for better work together (binocular vision). Treatment may involve eye glasses, eye exercises, prism, and/ or eye muscle surgery. Problems associated with strabismus (including amblyopia, ptosis, and cataract) are usually treated prior to eye muscle surgery. |
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