OBSERVER SENSITIVITY TO RETINAL VESSEL DIAMETER AND TORTUOSITY IN RETINOPATHY OF PREMATURITY - A MODEL SYSTEM

Background: Abnormally increased diameter and tortuosity of retinal bl ood vessels in the posterior pole, or ''plus disease'' is recognized a s a powerful predictor of poor outcome in eyes with retinopathy of pre maturity (ROP). Although the diagnosis of plus disease depends upon th e examiner's ability to examine retinal blood vessels, the ability of the human observer to identify changes in retinal blood vessel diamete r and tortuosity accurately has not been studied. Methods: Using compu ter-aided analysis of fundus photographs from eyes with a wide range o f ROP severity,we generated tracings of posterior pole blood vessels w hich varied by quintiles of mean vessel diameter and tortuosity. Subje cts (23 naive and 12 expert observers) ranked groups of tracings in or der of increasing mean vessel diameter and tortuosity. These ranking t ests were performed on tracings derived from the same fundus and traci ngs derived from distinct fundi. In a similar fashion, subjects also c ompared one designated standard fundus tracing with 25 distinct fundus tracings. Results: Vessel diameter was assessed correctly more often than vessel tortuosity, both among similar (>99% vs 92% of the time, r espectively, P<0.001), or among distinct (88% vs 78% of the time, resp ectively, P<0.001) fundus images, The mean vessel diameter and tortuos ity of 25 distinct fundus images were correctly ranked versus a standa rd image in 89% of attempts. Assessments of increments in vessel diame ter and tortuosity were independent. Naive and expert subjects perform ed indistinguishably on all tests, Conclusions: Intelligent human obse rvers have considerable ability to discern clinically relevant increme nts in blood vessel diameter and tortuosity, This ability may facilita te standardization in the diagnosis of plus disease in ROP.