title: Cone photoreceptor packing density and the outer nuclear layer thickness in healthy subjects.
abstract: OBJECTIVE
  We evaluated the relationship between cone photoreceptor packing density and outer nuclear layer (ONL) thickness within the central 15 degrees.
  
  
  METHODS
  Individual differences for healthy subjects in cone packing density and ONL thickness were examined in 8 younger and 8 older subjects, mean age 27.2 versus 56.2 years. Cone packing density was obtained using an adaptive optics scanning laser ophthalmoscope (AOSLO). The ONL thickness measurements included the ONL and the Henle fiber layer (ONL + HFL), and were obtained using spectral domain optical coherence tomography (SDOCT) and custom segmentation software.
  
  
  RESULTS
  There were sizeable individual differences in cone packing density and ONL + HFL thickness. Older subjects had on average lower cone packing densities, but thicker ONL + HFL measurements. Cone packing density and ONL + HFL thickness decreased with increasing retinal eccentricity. The ratio of the cone packing density-to-ONL2 was larger for the younger subjects group, and decreased with retinal eccentricity.
  
  
  CONCLUSIONS
  The individual differences in cone packing density and ONL + HFL thickness are consistent with aging changes, indicating that normative aging data are necessary for fine comparisons in the early stages of disease or response to treatment. Our finding of ONL + HFL thickness increasing with aging is inconsistent with the hypothesis that ONL measurements with SDOCT depend only on the number of functioning cones, since in our older group cones were fewer, but thickness was greater.
authors.affiliation: School of Optometry, Indiana University, Bloomington, Indiana 47405-3860, USA.
authors.forename: Toco Y P
authors.initials: TY
authors.lastname: Chui
authors.forename: Hongxin
authors.initials: H
authors.lastname: Song
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Clark
authors.forename: Joel A
authors.initials: JA
authors.lastname: Papay
authors.forename: Stephen A
authors.initials: SA
authors.lastname: Burns
authors.forename: Ann E
authors.initials: AE
authors.lastname: Elsner
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging; D002452:Cell Count; D006801:Humans; D008875:Middle Aged; D009887:Ophthalmoscopy / Q000379:methods; D012016:Reference Values; D017949:Retinal Cone Photoreceptor Cells / Q000166:cytology*; D041623:Tomography, Optical Coherence / Q000379:methods; D055815:Young Adult