Risk Factors to develop retinopathy of Prematurity include Prematurity, Low birth weight, Hyperoxia /Hypoxia, Hypotension, Acidosis, Duration ventilation, Sepsis, Blood transfusions, Antioxidant deficiency, Patent ductus arteriosus, Apnea, Anemia. This is a small list and there are many more that will make the child predisposed to risk of ROP.

Type 2 Retinopathy of Prematurity signifies the ROP disease is not severe enough to require treatment. So the child can be followed up in the routine ROP screening program till either the disease regresses or progresses to type 1 to need treatment.

• Zone I, stage 1-2 without plus
• Zone II, stage 3 without plus

Pre Plus Disease in retinopathy of prematurity signifies dilation and tortuosity of retinal vessels at the posterior pole, which are more than normal and less than Plus disease.

Aggressive Posterior ROP or APROP is a severe form of retinopathy of prematurity which is characterized by fast progression to advances stages. The disease may bypass the early stages 1-3 and progress to stage 5 quickly. The junction is very deceptive and confuses unexperienced doctors easily.  Plus disease is characteristically out of proportion to the lack of severity of disease. It needs prompt treatment.

Threshold Disease signifies stage of retinopathy of prematurity with ROP  inZone II, Stage 3 ROP with Plus disease  (>5 contiguous or 8 interrupted clock hours) OR Zone I, any stage with plus or stage 3 with no plus. It was earlier criteria of treatment, but is no longer followed now.

Plus disease is characterized by abnormal dilation and tortuosity of the retinal arteries and veins at the posterior part of the retina of the eye. This signifies that the disease is active and might progress. Plus disease also causes iris rigidity causing the difficult pupil dilation. Decrease is plus disease is a good sign and might herald disease regression.

Stage 5  retinopathy of prematurity (ROP) signifies that total retinal detachment has occured. This makes the visual prognosis very poor and requires advanced vitreoretinal surgery to repair retinal detachment.

Stage 1 retinopathy of prematurity (ROP) signifies development of a demarcation line between the normal retinal vessel developed retina and avascualr retina, where vessels have not developed.

Immnature retina is incomplete retinal vessel development, but not ROP. The eye goes through a normal vessel development with retinal vessels grow from the optic nerve head towards the retinal periphery. If they grow normally, they reach the nasal retinal peiphery (ora seratta) by 36 weeks post conceptional age and temporal periphery by 40 weeks post conceptional age.

This is a stage of no retinopathy of prematurity. These vessels can grow normally or later get stopped to develop ROP.

International Classification of Retinopathy of Prematurity divided retinopathy of prematurity into 3 zones on the retina of the eye  so as to facilitate clear communication between ROP experts. There are 3 Concentric Zones, wherein each zone is centered on the optic disc (head of the optic nerve) and normal retinal vessel development proceeds outward from the center of the optic disc toward the extreme periphery of the retina.



• Zone 1 – Circle from centre of disc with  radius of twice distance from disc to macula
• Zone 2 – From nasal edge of zone 1 to ora nasally and upto equatot region of retina temporally
• Zone 3 – From temporal crescent of retina anterior to zone II

Retinopathy of Prematurity or ROP is a vasoproliferative disease affecting the retina of premature babies and very low birth weight infants. The eyes of premature babies can be screened and if detected early can be treated in time. Lack of ROP screening and timely laser treatment can lead to advanced ROP and poor prognosis. ROP is an important cause of blindness in developing countries.

Retrolental Fibroplasia is an older terminology and was the first term used for the current retinopathy of prematurity. It was called so because retrolental means behind the lens and fibroplasia means fibrous tissue proliferation. But it was a misnomer and the current terminology of retinopathy of prematurity encompasses a broader scope of the disease.