title: Relationship between foveal cone structure and clinical measures of visual function in patients with inherited retinal degenerations.
abstract: OBJECTIVE
  To study the relationship between cone spacing and density and clinical measures of visual function near the fovea.
  
  
  METHODS
  High-resolution images of the photoreceptor mosaic were obtained with adaptive optics scanning laser ophthalmoscopy from 26 patients with inherited retinal degenerations. Cone spacing measures were made close to or at the foveal center (mean [SD] eccentricity, 0.02 [0.03] degree; maximum eccentricity, 0.13 degree) and were converted to Z-scores, fraction of cones, and percentage-of-cones-below-average compared with normal values for each location (based on 37 age-similar visually normal eyes). Z-scores and percentage of cones below average were compared with best-corrected visual acuity (VA) and foveal sensitivity.
  
  
  RESULTS
  Visual acuity was significantly correlated with cone spacing (Spearman rank correlation ρ = -0.60, P = 0.003) and was preserved (≥ 80 letters), despite cone density measures that were 52% below normal. Foveal sensitivity showed significant correlation with cone spacing (ρ = -0.47, P = 0.017) and remained normal (≥ 35 decibels), despite density measures that were approximately 52% to 62% below normal.
  
  
  CONCLUSIONS
  Cone density was reduced by up to 62% below normal at or near the fovea in eyes with VA and sensitivity that remained within normal limits. Despite a significant correlation with foveal cone spacing, VA and sensitivity are insensitive indicators of the integrity of the foveal cone mosaic. Direct, objective measures of cone structure may be more sensitive indicators of disease severity than VA or foveal sensitivity in eyes with inherited retinal degenerations.
authors.affiliation: Department of Ophthalmology, University of California, San Francisco, San Francisco, California.
authors.forename: Kavitha
authors.initials: K
authors.lastname: Ratnam
authors.forename: Joseph
authors.initials: J
authors.lastname: Carroll
authors.forename: Travis C
authors.initials: TC
authors.lastname: Porco
authors.forename: Jacque L
authors.initials: JL
authors.lastname: Duncan
authors.forename: Austin
authors.initials: A
authors.lastname: Roorda
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D005584:Fovea Centralis / Q000473:pathology / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D017949:Retinal Cone Photoreceptor Cells / Q000473:pathology*; D012162:Retinal Degeneration / Q000473:pathology / Q000503:physiopathology; D012684:Sensory Thresholds / Q000502:physiology; D014792:Visual Acuity / Q000502:physiology*; D055815:Young Adult
keywords: adaptive optics; cone sensitivity; cone structure; fovea; visual acuity
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