Abstract
Purpose: :
To study the variation of cone photoreceptor density across retina in healthy subjects of different ages.
Methods: :
A high resolution adaptive optics scanning laser ophthalmoscope (AOSLO) was used to image the cone photoreceptors in the right eyes of 17 healthy subjects (age range 22-65; axial length 22.3-24.6mm). Images were obtained from brief image sequences of an approximately 1.8 deg square field. After each sequence at an individual location, the imaging field was moved, to a new location and images collected and then moved again. The result was an approximately 12 degree by 1.8 degree strips of cone photoreceptor images. Each strip started from fovea and proceeded towards the peripheral retina along four primary meridians. A custom Matlab program (MathWorks, Natick, MA) was used to locate cone photoreceptor positions. Hand editing was performed by the investigator to clean the cone photoreceptor positions located by the program. From these locations, we calculated the average cone density over local regions of 50X50 um along four meridians at 0.5mm, 1mm, 1.5mm and 2mm retinal eccentricity. For comparison purposes the population was segmented into two age groups (group 1: 22-35yo; group 2: 50-65yo).
Results: :
Cone photoreceptor density was highest close to the fovea of each subject and decreased along the retinal eccentricity from 0.5mm to 4mm. No significant differences were measured between superior and inferior or nasal and temporal meridian, but significant differences between the orthogonal meridian (ANOVA, p<0.001). Considerable individual variance with densities varying by 30% or more was found. There was a significant interaction between the meridians measured and age (p<0.01).
Conclusions: :
Our study provides a baseline dataset for how cone photoreceptor density varieties in vivo for healthy subjects.
Keywords: aging • retina • photoreceptors