The stages of<unk>  disease have been defined by the International Classification of<unk>  (ICROP). In older patients, the appearance of the disease is less well described but includes the residua of the ICROP stages as well as secondary retinal responses. International classification The system used for describing the findings of active<unk>  is entitled The International Classification of<unk>  (ICROP). ICROP uses a number of parameters to describe the disease. They are location (zone) of the disease, the circumferential extent of the disease based on the clock hours, the severity (stage) of the disease and the presence or absence of "Plus Disease". Each aspect of the classification has a technical definition. This classification was used for the major clinical trials. It was revised in 2005. Zones of the retina in<unk> The zones are centered on the optic nerve. ZoneI is the posterior zone of the retina, defined as the circle with a radius extending from the optic nerve to double the distance to the macula. ZoneII is an annulus with the inner border defined by zoneI and the outer border defined by the radius defined as the distance from the optic nerve to the nasal ora serrata. ZoneIII is the residual temporal crescent of the retina. The circumferential extent of the disease is described in segments as if the top of the eye were 12 on the face of an analog clock, e.g. stage1 from 4:00 to 7:00. (The extent is a bit less important since the treatment indications from the Early Treatment for<unk> .) The Stages describe the ophthalmoscopic findings at the junction between the vascularized and avascular retina. * Stage 1 is a faint demarcation line. * Stage 2 is an elevated ridge. * Stage 3 is extraretinal fibrovascular tissue. * Stage 4 is sub-total retinal detachment. * Stage 5 is total retinal detachment. Plus disease Plus disease can be present as a major complicating factor at any stage. It is characterised by: * Significant level of vascular dilation and tortuosity observed at the posterior retinal arterioles. This reflects the increase of blood flow through the retina. * Vitreous haze and anterior chamber haze * Iris vascular engorgement * Persistent tunica vasculosa lentis or immature blood vessels growing over the lens which also restrict the dilatation of the pupils. Differential diagnosis The most difficult aspect of the differential diagnosis may arise from the similarity of two other diseases: * Familial exudative vitreoretinopathy which is a genetic disorder that also disrupts the retinal vascularization in full-term infants. * Persistent fetal vasculature syndrome also known as persistent hyperplastic primary vitreous that can cause a traction retinal detachment difficult to differentiate but typically unilateral.
Retinopathy of prematurity
Vitreoretinopathy
Meningism
Familial exudative vitreoretinopathy
Neonatal jaundice
Neonatal encephalopathy
Neonatal conjunctivitis
Congenital cataract