ABSTRACT
Purpose: To determine the interocular symmetry of foveal cone topography in achromatopsia (ACHM) using non-confocal split-detection adaptive optics scanning light ophthalmoscopy (AOSLO).
Methods: Split-detector AOSLO images of the foveal cone mosaic were acquired from both eyes of 26 subjects (mean age 24.3 years; range 8–44 years, 14 females) with genetically confirmed CNGA3- or CNGB3-associated ACHM. Cones were identified within a manually delineated rod-free zone. Peak cone density (PCD) was determined using an 80 × 80 μm sampling window within the rod-free zone. The mean and standard deviation (SD) of inter-cell distance (ICD) were calculated to derive the coefficient of variation (CV). Cone density difference maps were generated to compare cone topography between eyes.
Results: PCD (mean ± SD) was 17,530 ± 9,614 cones/mm2 and 17,638 ± 9,753 cones/mm2 for right and left eyes, respectively (p = .677, Wilcoxon test). The mean (± SD) for ICD was 9.05 ± 2.55 µm and 9.24 ± 2.55 µm for right and left eyes, respectively (p = .410, paired t-test). The mean (± SD) for CV of ICD was 0.16 ± 0.03 µm and 0.16 ± 0.04 µm for right and left eyes, respectively (p = .562, paired t-test). Cone density maps demonstrated that cone topography of the ACHM fovea is non-uniform with local variations in cone density between eyes.
Conclusions: These results demonstrate the interocular symmetry of the foveal cone mosaic (both density and packing) in ACHM. As cone topography can differ between eyes of a subject, PCD does not completely describe the foveal cone mosaic in ACHM. Nonetheless, these findings are of value in longitudinal monitoring of patients during treatment trials and further suggest that both eyes of a given subject may have similar therapeutic potential and non-study eye can be used as a control.
Acknowledgments
The authors would like to thank Alexander Salmon, Erica Woertz, and Jenna Cava for helpful discussions, Phyllis Summerfelt for facilitating subject visits, Brian Higgins for managing data, and Erin Curran for managing human subject protocols.
Presented in part at ARVO Annual Meeting 2018 in Honolulu, HI and FASEB Biology and Chemistry of Vision Conference 2019, in Steamboat Springs, CO.
Disclosure statement
Joseph Carroll has received funding support from Applied Genetic Technologies Corporation, consultant fees from MeiraGTx, and personal financial interest in Translational Imaging Innovations. Michel Michaelides has received consultant fees from MeiraGTx. Mark Pennesi and Byron Lam have received funding support from Applied Genetic Technologies Corporation. Christine Kay has received funding support and consultant fees from Applied Genetic Technologies Corporation. The authors report no other conflicts of interest. The authors alone are responsible for the content and writing of the paper.