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from the Winter 98 issue
Versión Español de este artículo (Spanish Version)

Retinopathy of Prematurity

by Kate Moss, Family Support Specialist, TSBVI Deafblind Outreach

A disease that occurs in some premature babies, Retinopathy of Prematurity (ROP), also known as Retrolental Fibroplasia, is the growth of abnormal blood vessels in the retina that generally begins during the first few days of life and may progress rapidly to blindness over a period of weeks. This happens because the eye is rapidly developing during gestational weeks 28-40. The blood supply to the retina starts at the optic nerve at about 16 weeks and blood vessels grow out from there toward the edges of the retina until the time of birth. When a baby is born prematurely, this normal vessel growth stops and new abnormal vessels begin to grow. Over time this vessel growth produces a fibrous scar tissue which attaches to the retina and the vitreous gel that gives the eyeball its shape. This ring may extend 360 degrees around the inside of the eye. If enough scar tissue forms, it can begin to pull the retina, detaching it, and, in some cases,causing blindness.

Not all babies who are premature will have ROP. Many of the babies who are born with ROP will improve spontaneously. However, since ROP is "responsible for more blindness among children in this country than all other causes combined" (Watson, 1997), it is important that premature babies are screened for ROP. This examination is done with an indirect ophthalmoscope which allows the doctor to get a wide-angle view of the retina. First a drop of topical anesthetic is applied to the eye to reduce the baby's discomfort. Then the baby's eyelids are held open with a device called a speculum and a special probe holds the eyeball still while the doctor examines it. Because this examination can be stressful to the baby, sometimes the exams are postponed until the baby's medical condition is more stable. Usually only babies that are at high risk for ROP are screened. Those babies are usually the ones with a young gestational age and a low birth weight. Utah NICUs use 2000 grams or less as a weight guideline for screening. (Ophthalmology Associates Homepage, 1997)

Although there has been a correlation made between premies who receive high levels of oxygen and ROP, there appear to be a variety of factors that may account for development of ROP. These include, in addition to birth weight and gestational age: elevated blood carbon dioxide levels, anemia, blood transfusions, intraventricular hemorrhage, respiratory distress syndrome, chronic hypoxia in utero, multiple spells of apnea or bradycardia, mechanical ventilation, and seizures. (Ophthalmology Associates Homepage, 1997) There are some who feel that exposure to bright fluorescent lighting in hospitals contributes to the development of ROP (Prevent Blindness in Premature Babies, 1997), but to date this has not been proven and many ophthalmologists strongly disagree with this theory (Ophthalmology Associates Homepage, 1997). The current thinking is that probably it is a combination of factors, some occurring in utero and some occurring after the baby is born, that lead to this outcome.

There are certain classifications of ROP that are used to describe the progression of the condition. What this classification relates to is the location and degree of retinal scarring that has occured. Chart 1 (below) shows the various stages of ROP (1-5) and what these notations mean. The zone number refers to the International Classification of Retinopahty of Prematurity (ICROP) diagram which designates three zones of the retina. Chart 2 shows the ICROP. For example, stage 3, zone 1 ROP describes ROP which is pretty severe while stage 1, zone 3 ROP describes a condition which is not as progressed. It is important to stress that not every child with ROP will progress to stage 5, and some babies with ROP may recover spontaneously from stage 1 or 2 ROP.

Chart 1 - Stages of retinopathy of prematurity (Vaughan, et al, 1995)

Stage  and Clinical Findings

Stage 1 Demarcation line (line where the normal and abnormal vessels meet)

Stage 2 Intraretinal ridge (ridge that rises up from the retina as a result of the growth of the abnormal vessels)

Stage 3 Ridge with extraretinal fibrovascular proliferation (the ridge grows from the spread of the abnormal vessels and extends into the vitreous)

Stage 4 Subtotal retinal detachment (the partial detachment of the retina)

Stage 5 Total retinal detachment

Chart 2 - ICROP diagram (Ophthalmology Homepage, 1997)

Zone and Area of Retina Affected

Zone I - Area centered on the optic disc and extending from the disc to twice the distance between the disc and the macula.

Zone II - A ring, concentric to Zone I, which extends to the edge of the retina on the side of the eye toward the nose.

Zone III - The remaining crescent area of the retina toward the side and away from the nose.

ROP Zone diagram - discription in text

Treatment for ROP depends on the stage of the condition. Stage 1 and 2 usually require nothing more than observation. (Vaughan, et al, 1995) There are a variety of ways that ROP is treated, but the most common is laser treatment. Laser photocoagulation is used to eliminate the abnormal vessels before they cause the retina to detach. Cryotherapy involves placing a very cold probe on the outside wall of the eye and freezing until an ice ball forms on the retinal surface. These treatment options are usually done with children in Stage 3 ROP. A scleral buckle involves placing a silicone band around the equator of the eye and tightening it to produce a slight indentation on the inside of the eye. This keeps the vitreous gel from pulling on the scar tissue and the retina and allows the retina to flatten back down onto the wall of the eye. Infants who have a sclera buckle done need to have the band removed months or years later since the eye continues to grow. Otherwise they will become nearsighted. Vitrectomy involves making several small incisions into the eye to remove the vitreous and replace it with a saline solution to maintain the shape and pressure of the eyeball. After the vitrous has been removed, the scar tissue on the retina can be peeled back or cut away, allowing the retina to relax and lay back down against the eye wall. Since it may take weeks for the retina to re-attach afterwards, holes or tears can occur which usually prevent the retina from re-attaching. If this happens the lens of the eye has to be removed to be able to remove the scar tissue. Sclera buckles are usually performed on children with Stage 4 and 5 ROP while vitrectomy is performed only at Stage 5. (Ophthalmology Associates Homepage, 1997)

Additionally there are some late complications from ROP which include strabismus (crossed eyes), amblyopia (lazy eye), myopia (near-sightedness), and glaucoma. (Ophthalmology Associates Homepage, 1997) Regular follow-up is needed to monitor and treat these conditions.

Depending on the stage of ROP, a child may have anywhere from near normal vision to light perception to total blindness. Many children will not progress to Stage 5. Usually children will benefit from early intervention and sensory stimulation. Adaptions such as high illumination, magnification for close work, telescopes for distance viewing, and closed-circuit television (CCTV) can be helpful to some students. (Levack, et al, 1991) Students may be braille readers.

Parents of children with ROP may wish to contact some of the following resources for information and support:

ROP Online Support Group - This support group is an attempt to provide a source of information and support for those struggling with these issues about how ROP will affect the future. You can post a message, ask a question, or answer someone else's questions simply by sending e-mail to the group (rop@list.konnections.com). Any messages posted to the group will be forwarded to you as long as you are a member.

Ophthalmology Associates of Ogden, Utah - The purpose of this website is to provide information to the internet public concerning eye diseases and their medical and surgical treatment and has a variety of subjects, with real data in an understandable format. Go to <www.konnections.com/eyedoc/index.html>.

Prevent Blindness in Premature Babies - The major effort of the organization is to work to eliminate the use of bright fluorescent lighting in hospital premie units. Go to <www.brailleplanet.org/pbpb.html>. You may also contact them by phone or mail at P.O. Box 44792, Madison, Wisconsin 53744-4792, (608)845-6500.

References:

Levack, Nancy, et al, 1991. Low vision: a resource guide with adaptations for students with visual impairments. Texas School for the Blind & Visually Impaired, Austin, TX.

Ophthalmology Associates Homepage, 1997. Ogden, Utah.

Prevent Blindness in Premature Babies Homepage, 1997. Madison, Wisconsin.

Vaughan, Daniel G. et al, 1995. General ophthalmology, 14th edition. Appleton & Lange, Stamford, Connecticut.


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