title: Variation of cone photoreceptor packing density with retinal eccentricity and age.
abstract: OBJECTIVE
  To study the variation of cone photoreceptor packing density across the retina in healthy subjects of different ages.
  
  
  METHODS
  High-resolution adaptive optics scanning laser ophthalmoscope (AOSLO) systems were used to systematically image the retinas of two groups of subjects of different ages. Ten younger subjects (age range, 22-35 years) and 10 older subjects (age range, 50-65 years) were tested. Strips of cone photoreceptors, approximately 12° × 1.8° long were imaged for each of the four primary retinal meridians: superior, inferior, nasal, and temporal. Cone photoreceptors within the strips were counted, and cone photoreceptor packing density was calculated. Statistical analysis (three-way ANOVA) was used to calculate the interaction for cone photoreceptor packing density between age, meridian, and eccentricity.
  
  
  RESULTS
  As expected, cone photoreceptor packing density was higher close to the fovea and decreased with increasing retinal eccentricity from 0.18 to 3.5 mm (∼0.6-12°). Older subjects had approximately 75% of the cone density at 0.18 mm (∼0.6°), and this difference decreased rapidly with eccentricity, with the two groups having similar cone photoreceptor packing densities beyond 0.5 mm retinal eccentricity on average.
  
  
  CONCLUSIONS
  Cone packing density in the living human retina decreases as a function of age within the foveal center with the largest difference being found at our most central measurement site. At all ages, the retina showed meridional difference in cone densities, with cone photoreceptor packing density decreasing faster with increasing eccentricity in the vertical dimensions than in the horizontal dimensions.
authors: School of Optometry, Indiana University, Bloomington, Indiana 47405, USA.
authors: Hongxin
authors: H
authors: Song
authors: Toco Yuen Ping
authors: TY
authors: Chui
authors: Zhangyi
authors: Z
authors: Zhong
authors: Ann E
authors: AE
authors: Elsner
authors: Stephen A
authors: SA
authors: Burns
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D002452:Cell Count; D005260:Female; D006801:Humans; D007834:Lasers; D008297:Male; D008875:Middle Aged; D019721:Ophthalmoscopes; D012160:Retina / Q000033:anatomy & histology*; D017949:Retinal Cone Photoreceptor Cells / Q000166:cytology*; D014792:Visual Acuity / Q000502:physiology; D055815:Young Adult