Longitudinal Cone Density Measurements using a Commercially Available Flood-Illuminated Adaptive Optics Camera in Japanese Macaque Monkeys with Dominantly Inherited Drusen

Abstract

Purpose: To study the longitudinal changes in cone density in a line of adult Japanese Macaque monkeys with dominantly inherited drusen using a commercially available flood illuminated adaptive optics camera.

Methods: Twenty male and female Japanese Macaques were sedated and imaged on the RTx1 Adaptive Optics Camera (Imagine Eyes, Orsay, France) at baseline and six months later. In each animal, a series of overlapping AO images were obtained starting at the optic nerve and extending temporally through the fovea. Individual images were montaged using I2k Align (DualAlignTM). Cone profiles were counted using a Matlab algorithm (generously provided by Dr. Joseph Carroll) and axial lengths were measured to correct for magnification. Macular drusen were identified with advanced Weka segmentation (University of Waikato).

Results: Cone density plots revealed an anatomic distribution of cone photoreceptors in the macula, but cones within 1.6° of the foveal center could not be individually identified. The mean cone density across 1.6-3.1° eccentricity was 28843 ± 5284 cones/mm2 after six months. When broken into parafoveal quadrants, cone density was highest in the nasal quadrant and lowest in the superior quadrant for both time points. The mean baseline age for the animals was 10.8 ± 5.5 years. Age was not significantly associated with cone density (p = 0.46), nor was it associated with the change in cone density between the time points (p = 0.75). The fraction of area occupied by drusen was 8.8 ± 12.8 percent. Drusen area also was not significantly associated with cone density (p = 0.55), nor was it associated with the change in cone density between the time points (p = 0.70).

Conclusions: Commercially available flood illuminated adaptive optics allows for longitudinal measurement of cone density in macaques with drusen. Preliminary results indicate that age and drusen load are not associated with a significant change in cone density over the period studied. Further collections are planned every six months to assess long-term changes in cone density.

Keywords: 551 imaging/image analysis: non-clinical • 504 drusen • 412 age-related macular degeneration