Oxygen-induced retinopathy in the newborn rat: a scoring system for the evaluation of retinal vascular changes. Scoring system for OIR in the rat.

The authors describe a scoring system they have developed for evaluating damage produced in the retinal vascular network of the newborn rat by exposure to oxygen. India ink-injected retinal flat mounts are used. The scoring system provides for division of the retina into three concentric zones with the optic disk as a center point. Each retinal quadrant is then examined for the presence of the following lesions of progressive severity: vaso-obliteration of the capillary network, loss of the periarteriolar capillary-free zone, newly formed capillary tufts. When more than one type of lesion is present in a quadrant, only the most severe lesion is considered. The numerical score corresponding to that lesion is then multiplied by the factor corresponding to the concentric zone in which the lesion lies to give the quadrant score. The total retinal score is represented by the sum of the four quadrant scores. This type of system, if adopted by other investigators, can facilitate precise and systematic description of the results of different experimental protocols.