Abstract
Purpose :
To characterize the effect of varying sampling window size on topographical maps of foveal cone density derived from adaptive optics scanning light ophthalmoscope (AOSLO) images of the cone mosaic.
Methods :
Images of the foveal cone mosaic (300 x 300 μm2), obtained using AOSLO, were used for this study (44 individuals with normal vision, one eye each). Cone photoreceptor coordinates were semi-automatically identified by one experienced grader. From these coordinates, cone density matrices across each foveal image were derived using variable cone sampling window sizes of 5, 10, 15, 20, 40, 60, 80, 100, 150, or 200 cones. For all 440 density matrices (44 mosaics, 10 window sizes each), we extracted the location and value of peak cone density (PCD), the cone density centroid (CDC) location, and cone density at the CDC.
Results :
Across all window sizes, PCD values were larger than those extracted at the CDC location, as expected. The difference between PCD and cone density at the CDC decreased when using larger sampling widows to generate the density matrix (r=0.99, p<0.0001). As window size was increased, the average PCD value decreased (r=0.99, p<0.0001), with a 15.2% lower PCD value on average when using the 200-cone versus the 5-cone window. Density at the CDC also decreased with increasing window size (r=0.99, p<0.0001), though the effect was smaller (only a 3.8% lower density value obtained with the 200-cone versus the 5-cone window, on average). The distance between PCD and CDC locations generally decreased with increasing window size, and the magnitude of the effect was positively correlated with the offset observed with the 5-cone window (r=0.59, p<0.0001). This was driven largely by varying PCD location when using different window sizes; the average per-subject 95% confidence ellipse area across the 10 window sizes was 992.4 μm2 for the PCD location, but only 50.8 μm2 for CDC location.
Conclusions :
As reported previously when using different graders,1 CDC location is more stable across varying sampling window sizes than PCD location. Understanding how density values change according to the method used to sample the cone mosaic may facilitate comparing cone density data across different studies. Further studies are needed to characterize the effect of sampling window size when assessing mosaics over time when there is loss of cones due to disease.
1. PMID: 36032569
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.