How is the location of retinopathy of prematurity described?

• A. Zones
• B. Clock hours
• C. Stages
• D. Levels

Answer: (A)

The location of retinopathy of prematurity is described using zones. The retina is divided into three concentric zones: Zone I is the posterior retina centered on the optic nerve, Zone II extends outward to the mid-periphery, and Zone III is the temporal peripheral crescent. Knowing which zone is involved helps gauge prognosis and treatment urgency, since involvement of the more posterior Zone I carries a higher risk of progression. While clock hours can describe how much of the retina is affected, the location descriptor most relevant here is the zone system. Stages describe severity, not exact location.