RETINOPATHY OF PREMATURITY
Scott
C. Richards, M.D.
Retinopathy of prematurity (ROP)
is an eye disease that occurs in some premature babies. The last 12
weeks of a full-term delivery, from 28-40 weeks gestation, are
particularly active for the growth of the fetal eye. The blood supply to
the retina starts at the optic nerve at 16 weeks of gestation, and the
vessels gradually grow out over the surface of the retina. The vessels
reach the anterior edge of the retina and stop their progression at
about the time of birth.
In premature infants, the normal
growth of the retinal vessels stops, and abnormal new vessels begin to
grow. There seems to be a barrier to the normal growth of vessels, a
line beyond which the precursors of the vessels cannot pass. The retina
anterior to this line does not have an adequate oxygen supply, and
probably exudes chemical signals that stimulate new vessel growth. As
more new vessels grow in response to the chemical signals, they form
arterio-venous shunts at the location of the barrier on the surface of
the retina. This shunt gradually enlarges, becoming thicker and more
elevated. The new vessels are accompanied by fibroblasts, which produce
fibrous scar tissue. Eventually, a ring of scar tissue is formed which
is attached to the retina and to the vitreous gel, and which may extend
for 360 degrees around the inside of the eye. When this scar tissue
contracts, it pulls on the retina and produces a traction retinal
detachment. If enough scar tissue forms and causes enough traction, the
retina become completely detached, and the infant is blind. An
international classification
of ROP has been developed to standardize evaluation and research in
this disease. This classification is not just a way to pigeonhole
patients; learning about this classification is very helpful in
understanding the disease process and rationale for treatment.
Premature children are at risk for
developing ROP because they have been taken out of the protective
environment of the uterus and are exposed to many things, including
medications, high levels of oxygen, and variations in light and
temperature. Some or all of these factors may have an effect on the
development of ROP. A number of risk
factors for ROP have been identified.
Fortunately, most premature
infants do not develop ROP, and most infants with ROP improve
spontaneously. However, the risk of severe visual loss is high enough to
warrant ROP
screening programs at most newborn intensive care units.
If ROP does develop, it usually
occurs between 34 and 40 weeks after conception, regardless of
gestational age at birth. One might expect an infant born at 23 weeks
gestation to have ROP at a younger age than an infant born at 33 weeks,
since he/she was exposed to extrauterine risk factors at an earlier age.
However, both infants would probably develop their ROP at about the same
gestational age (37 weeks) rather than at the same chronological
(post-natal) age. This implies that pre-natal or intrauterine factors
may have an effect on the development of ROP.
The treatment
of ROP is usually laser treatment. The laser treatment is applied to
the retina anterior to the vascular shunt that does not yet have a blood
supply. The purpose of the treatment is to eliminate the abnormal
vessels before they lay down enough scar tissue to produce a retinal
detachment. Other treatment options include cryopexy, scleral buckle,
and vitrectomy.
Most infants with mild retinopathy
of prematurity that resolves either with or without laser treatment will
have no remaining scar tissue. These infants usually develop normal
central vision. However, some infants who undergo regression may have late
complications of ROP, including strabismus (crossed eyes), amblyopia
("lazy eye"), myopia (near-sightedness), glaucoma and late
onset retinal detachment.
There is an ongoing ROP
Support Group for patients, parents, and others with concerns or
questions about ROP.
There is also an Adult
ROP Support Group specifically to address the concerns of adults
with ROP.
Please join us if you have an interest.
The Country Hills Eye Center Home Page
Dr. Scott C. Richards Main Page
For information regarding the
Country Hills Eye Center phyician
specializing in retinal and diabetic eye diseases
OTHER LINKS OF INTEREST:
ROPARD
- links to resources for parents of visually impaired kids
ComeUnity
- Mailing list for parents of preemies
John
Henry's home page
Ann
Morris Enterprises - Items for sale for visually impaired people
The
American Printing House for the Blind
Kendra's
Story
www.countryhillseyecenter.eyemd.org
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