Chapter 8 Retinopathy of Prematurity

8.1 Introduction

Definition:

Retinopathy of prematurity (ROP) is a disease affecting the developing retina in a preterm infant that can lead to severe visual impairment and blindness.

Pathophysiology

The vasculature of the retina begins to develop around 16 weeks gestation. The nasal retina becomes completely vascularized by 36 weeks and the temporal retina by term. The incompletely vascularized retina of the preterm infant can be injured by factors such as hypoxia or hyperoxia that can lead to vasoconstriction and reduced blood flow to the retina. After the insult, the retinal vascularization may be abnormal with growth of vessels into the vitreous, retinal edema and/or hemorrhage. In advanced stages, resultant inflammation and fibrosis can lead to retinal detachment and blindness.

Classification

International Classification for ROP includes zone, stage, extent and presence/absence of plus disease. 1) Zone – Denotes the area of the retina affected. Zone 1 is the circular area in the center of the retina including the optic disc and macula. Zone 2 is a circle around zone 1 extending to the nasal retinal edge (ora serrata). Zone 3 is the remaining retina along the temporal retinal edge. 2) Stage – Denotes the severity of the disease. a. Stage 1: vascular and avascular retina demarcated by a flat white line b. Stage 2: vascular and avascular retina demarcated by a fibrous ridge protruding into the vitreous c. Stage 3: blood vessels and fibrous tissue accompany the ridge of stage 2 d. Stage 4: partial retinal detachment e. Stage 5: total retinal detachment 3) Extent – Denotes the amount of retina affected. The retina is divided into 30 segments specified as hours of the clock. Up to 12 hours may be affected. 4) Plus Disease – vessels in the posterior pole of the retina are dilated and tortuous. This condition may rapidly progress to retinal detachment and requires surgical intervention. 5) Threshold Disease – 5 contiguous clock hours or 8 total clock hours of Stage 3 and plus disease in Zone 1 or Zone 2. If untreated, may progress to retinal detachment.

Diagnostic Evaluation

  • Screening eye examinations are performed by the Ophthalmology service on the following infants:
  1. BW <1700 grams
  2. Gestational age <32 weeks
  3. Mechanical ventilation > 24 hours
  4. Supplemental oxygen > 48 hours
  5. ECMO patients
  • The NICU case managers usually schedule the eye exams. For infants < 1250 grams, the initial exam is at 4 weeks of age. For infants > 1250 grams, the initial exam is at 2 weeks of age. Exams should then be repeated Q1-4 weeks as indicated until the retina is fully vascularized.

Management

  • Laser photocoagulation
  • Avastin Injection

Prognosis

Many cases of ROP resolve spontaneously. Treatment for severe ROP is required in approximately 6% of cases. Despite resolution of ROP, preterm infants remain at risk for other ophthalmologic conditions including myopia, amblyopia and strabismus.