The Retinal Vasculature and Function of the Neural Retina in a Rat Model of Retinopathy of Prematurity

Abstract

In a rat model of retinopathy of prematurity (ROP), the retinal vasculature and function of the neural retina were studied longitudinally. Vascular and neural parameters were evaluated for significant relationships. Retinopathy was induced by exposing newborn rats to alternating 50% and 10% oxygen until age 14 days. To evaluate the function of the neural retina, electroretinographic (ERG) responses to full-field stimuli were recorded from dark-adapted rats at ages 18 and 31 days. Sensitivity and saturated amplitude of photoreceptor and postreceptor activity were derived from ERG a- and b- waves. To evaluate the retinal vasculature, digital fundus photographs were obtained at the same ages, and the tortuosity indices of the arterioles (TIA) and venules (TIV) were calculated. ROP rats and room-air-raised control animals were compared. Vascular and response parameters were evaluated for significant relationships. In ROP rats, TIA was high at 18 days and decreased in every rat to nearly normal levels by 31 days. TIV was less affected by ROP or age. Deficits in all receptor and post-receptor response parameters were present in 18-day-old ROP rats. Post-receptor sensitivity recovered completely by 31 days. Deficits in other response parameters persisted. No significant correlations between vascular and ERG parameters were found in 18-day-old ROP rats. Noninvasive, longitudinal measures in this model of ROP showed significant abnormalities in both the retinal vasculature and function of the neural retina that were most marked at age 18 days. However, vascular and neural abnormalities did not correlate.