Perception of Purkinje vessel shadows and foveal granular pattern as a measure of potential visual acuity

Purpose: To compare perception of 2 entoptic phenomena, the Purkinje vessel shadows and the foveal granular pattern, as measures of retinal visual acu ity using a transscleral illumination technique that bypasses the anterior segment. Setting: Retinal Vascular Center and General Eye Clinic, Wilmer Ophthalmolo gical institute, Johns Hopkins Hospital, Baltimore, Maryland, USA. Methods: Both eyes of 85 patients with clear ocular media, many with retina l disease, were tested for perception of these entoptic phenomena. Also, re tinal visual acuity was measured with a Potential Acuity Meter through the current refractive correction. Results: Of 114 eyes with retinal acuity of 20/40 or better, 99% perceived the Purkinje vessel shadows and 86% perceived the foveal granular pattern. Of 45 eyes with retinal acuity of 20/80 or worse, 73% perceived the Purkinj e vessel shadows and 4% perceived the foveal granular pattern. Conclusion: Perception of the Purkinje vessel shadows does not distinguish between good and poor retinal acuity, whereas nonperception of the vessel s hadows strongly suggests poor acuity. Perception of the foveal granular pat tern, on the other hand, provides a positive indication of good retinal acu ity and will likely prove to be predictive of good vision after removal of significant media opacity. (C) 2000 ASCRS and ESCRS.