Retinopathy of Prematurity
Retinopathy of prematurity (ROP), or retrolental fibroplasia, is a bilateral proliferative retinopathy, occurring in premature infants with low birth weight who often have been exposed to high concentration of oxygen. If a baby is born too early then their retinal blood vessels do not develop completely which can cause problems. Abnormal blood vessels may grow out of the retina and cause scar tissue to form, leading to detachment of the retina. This damage is known as retinopathy of prematurity and if not monitored or not treated at the correct time, can cause vision loss.
Etiopathogenesis
Low birth weight and decreased gestational age are considered the primary causative factors. Supplemental oxygen administration, which was for a long time considered as the important causative factor is now considered only a risk factor.
- Classical theory postulates that owing to exposure to high concentration of oxygen, there occurs obliteration of premature retinal vessels. This is followed by neovascularisation and fibrous tissue proliferation which ultimately forms a retrolental mass.
- Spindle cell theory proposed recently postulates the induction of retinal and vitreal neovascularization by spindle cell insult in a premature retina.
Clinical Features:
ROP mainly affects the retinal blood vessels. When the development of the retinal blood vessels is incomplete, the retina is not receiving enough oxygen so tries to grow new vessels. These new vessels are fragile and cause scarring. Rarely, the most severe forms of ROP, if left untreated, can lead to retinal detachment and blindness. There are a few ways of describing the amount of ROP present, which includes its location, extent and stage.
The location on the retina is divided into three zones where zone 1 is the innermost and zone 3 is the outermost. The zones are not centred around the retina but rather, the optic nerve. This is because the blood vessels tend to grow from the area where the optic nerve leaves the eye called the optic nerve disc.
The extent of ROP is described using clock hours. For example if there is retinopathy present from 6:00 to 9:00 then the extent of ROP is 3 clock hours.
There are five stages of retinopathy of prematurity. These stages describe what the ophthalmologist would see when they looked into a baby's eyes.