Retinopathy of Prematurity (ROP) is an abnormality of blood vessels of the developing retina and is a leading cause of childhood blindness in the developed world. This condition typically affects infants born at less than 32 weeks gestation and weighing less than 1500 grams at birth. Many cases of ROP are mild and improve without specific treatment, however severe cases result in retinal scarring and retinal detachment that may lead to blindness or very poor vision that is not correctable with glasses.
For severe cases, diode laser treatment can reduce scar tissue formation, reduce the risk of retinal detachment and reduce the chance of blindness. Research is also ongoing into the use of intraocular anti-VEGF therapies for the treatment of severe retinopathy of prematurity.
ROP is defined and described by its location, stage and extent and prior to the development of ROP in a premature infant, vascularization of the retina is considered incomplete or "immature".
To define the location of ROP, three concentric zones are used, centred on the optic disc.
Zone I is a circle, the radius of which extends from the center of the optic disc to twice the distance from the center of the optic disc to the center of the macula.
Zone II extends centrifugally from the edge of zone I to the nasal ora serrata.
Zone III is the residual crescent of retina anterior to zone II. By convention, zones II and III are considered to be mutually exclusive.
A thin demarcation line is apparent which separates the avascular retina anteriorly from the vascularized retina posteriorly. There is abnormal branching or arcading of vessels leading up to the demarcation line.
Neovascularization extends from the ridge into the vitreous. This extraretinal proliferating tissue is continuous with the posterior aspect of the ridge, causing a ragged appearance as the proliferation becomes more extensive.
Divided into extrafoveal (stage 4A) and foveal (stage 4B) partial retinal detachments. Retinal detachments usually begin at the point of fibrovascular attachment to the vascularized retina and the extent of detachment depends on the amount of neovascularization present.
The presence of Plus disease is used to describe signs of increased venous dilatation and arteriolar tortuosity of the posterior retinal vessels. Pre-Plus disease refers to vascular abnormalities of the posterior pole which are insufficient for the diagnosis of plus disease but demonstrates more arterial tortuosity and more venous dilatation than normal.
Aggressive Posterior ROP (AP-ROP) is a severe, rapidly progressing form of ROP which occurs in a posterior location with plus disease, and if left untreated may progress to retinal detachment.