Define Retinopathy of Prematurity. Describe its pathogenesis, classification and management.

Definition

• Retinopathy of prematurity is a vasoproliferative retinal disorder of premature, low-birth-weight infants, in which abnormal retinal blood-vessel growth can progress to retinal detachment and blindness.
• It is an important preventable cause of childhood blindness, especially in developing countries.

Pathogenesis (two Phases)

• Phase 1 (hyperoxia / vaso-obliteration): premature birth + supplemental oxygen → relative hyperoxia → arrest and obliteration of the developing retinal vessels; ↓ VEGF.
• Phase 2 (hypoxia / vaso-proliferation): as the retina grows, the avascular area becomes hypoxic → ↑ VEGF → abnormal neovascularisation, fibrosis, traction and eventually retinal detachment.

Risk Factors

• Prematurity & low birth weight (the strongest factors).
• Unmonitored / excessive supplemental oxygen and wide oxygen fluctuations.
• Sepsis, apnoea, blood transfusions, poor postnatal weight gain, intraventricular haemorrhage.

Screening (india — High-risk Babies)

• Screen babies ≤ 34 weeks gestation OR ≤ 2000 g birth weight, and larger / older babies with a stormy neonatal course.
• The first examination is by 2–3 weeks of age (within 30 days), using an indirect ophthalmoscope with scleral indentation; repeated as advised until the retina is fully vascularised.

Classification (icrop)

• By zone (I–III, centred on the optic disc) and stage (1–5, from a demarcation line to total retinal detachment).
• 'Plus' disease — dilated, tortuous posterior vessels; indicates activity and the need for urgent treatment.
• Aggressive ROP (A-ROP) — a rapidly progressive, posterior form.

Management

• Laser photocoagulation of the avascular retina — the treatment of choice for threshold / type-1 ROP.
• Intravitreal anti-VEGF (e.g. Bevacizumab / ranibizumab) — for zone-I and aggressive disease.
• Vitreoretinal surgery (scleral buckle / vitrectomy) for retinal detachment (stage 4–5).