title: Perception of Purkinje vessel shadows and foveal granular pattern as a measure of potential visual acuity.
abstract: OBJECTIVE
  To compare perception of 2 entoptic phenomena, the Purkinje vessel shadows and the foveal granular pattern, as measures of retinal visual acuity using a transscleral illumination technique that bypasses the anterior segment.
  
  
  METHODS
  Retinal Vascular Center and General Eye Clinic, Wilmer Ophthalmological Institute, Johns Hopkins Hospital, Baltimore, Maryland, USA.
  
  
  METHODS
  Both eyes of 85 patients with clear ocular media, many with retinal disease, were tested for perception of these entoptic phenomena. Also, retinal 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 Purkinje vessel shadows and 4% perceived the foveal granular pattern.
  
  
  CONCLUSIONS
  Perception of the Purkinje vessel shadows does not distinguish between good and poor retinal acuity, whereas nonperception of the vessel shadows strongly suggests poor acuity. Perception of the foveal granular pattern, on the other hand, provides a positive indication of good retinal acuity and will likely prove to be predictive of good vision after removal of significant media opacity.
authors.affiliation: Wilmer Ophthalmological Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
authors.forename: F
authors.initials: F
authors.lastname: Murillo-Lopez
authors.forename: A E
authors.initials: AE
authors.lastname: Maumenee
authors.forename: D L
authors.initials: DL
authors.lastname: Guyton
mesh_terms: D002386:Cataract / Q000150:complications*; D005584:Fovea Centralis; D006801:Humans; D008027:Light; D011237:Predictive Value of Tests; D012029:Refraction, Ocular; D012160:Retina / Q000502:physiology*; D012680:Sensitivity and Specificity; D014787:Vision Tests / Q000379:methods*; D014788:Vision, Entoptic / Q000502:physiology*; D014792:Visual Acuity / Q000502:physiology*