Retinopathy of prematurity

Retinopathy of prematurely-born babies is one of the major reasons for child blindness in the developed countries and middle-income countries. With the better care for preterm babies and the high rates of survival of very premature infants the importance of this problem increases. More than 60 000 children in the world are blind because of retinopathy whereas the number of those with monocular blindness and serious visual impairment is unknown. Over 20% of the prematurely born suffer from retinopathy. The frequency rate depends on the low weight of the baby and 50-70% of the infants under 1250g are affected. This issue is of increasing importance in Bulgaria due to its social effect.
The retina of the prematurely born is still developing. This process can complete normally or blood vessels might grow abnormally and lead to retinal detachment and vision loss. This condition is called retinopathy of prematurity. Much research is ongoing in order to find out some of the still unknown causes. Many risk factors and their role in the development of the disease have been analyzed, the major ones are low gestational age and low birth weight. Other important factors are: in vitro fertilization, a multiple pregnancy, recurrent apnea and bradycardia, oxygen level fluctuations during first two weeks of life, diseases, sepsis, anemia, blood transfusion, genetic and other. Oxygen is the first known and most popular factor for the development of retinopathy of prematurity. Initially it was considered that high oxygen level causes the disease. However, lack of oxygen can worsen the condition too. With the development of new technologies this factor is better controlled.
Whom to screen for retinopathy of prematurity?
Prematurely born infants with a birth weight below 2000 g. and gestational age less than 32 weeks are at risk of developing retinopathy of prematurity as well as bigger babies if referred by a neonatologist. Analyses are periodically made in order to revise the screening criteria which vary in different countries and even in different neonatal units. The tendency in recent years is to consider birth weight of less than 1500 g as risky.
Why screening of preterm babies is necessary?
Retinopathy of prematurity has no symptoms. External signs are noticeable only when the disease has developed or progressed to retinal detachment. The only way to find out the disorder is by regular eye fundus examinations of the prematurely born. Neonatologists screen all infants at risk and refer them for examination by a child ophthalmologist in the 4th week after birth.
Frequency of follow-up examination depends on the condition of the eye fundus and the recommendations of the ophthalmologist. Subsequent examinations continue until retinal development finishes. Usually this takes a period of several months.

Who conducts screening?
Not every ophthalmologist is able to give an adequate opinion of the infant’s condition. These examinations are performed by child ophthalmologists with sufficient experience and special knowledge of the disease.

When is treatment of retinopathy of prematurity necessary?
Retinopathy of prematurity is divided into 5 stages. Milder stages need a more frequent observation because changes may spontaneously reverse. If the disease progresses and reaches its full development, according to international standards, vision is at high risk and treatment is performed. Cryotherapy and laser surgery have proven effects in reducing retinal detachments and loss of vision. Another possible treatment, becoming popular in recent years, is an injection of Avastin in the eye. Conclusions about the state of the retina and the type of treatment should be made by an experienced practitioner in retinopathy of prematurity. Unfortunately treatment does not have effect on all infants but this is their only chance for vision.
Prematurely born children with or without retinopathy of prematurity have higher rates of eye disorders: refractive errors (short-sightedness, long-sightedness, astigmatism, anisometropia), strabismus (crossed eyes), amblyopia (lazy eye) and others. In these cases treatment should start as early as possible by prescribing eyeglasses, exercises or surgical treatment. That is why these children should be examined regularly by a child ophthalmologist: at the age of 1, 3 and 5 and more frequently if recommended by the specialist.

Infants with retinopathy of prematurity might have a retinal detachment or a less severe condition. In all cases, however, they should be under long-term observation.