Longitudinal Imaging of the Foveal Cone Mosaic in CNGA3-Associated Achromatopsia

Abstract

Purpose The purpose of this study was to assess the natural history of the foveal cone mosaic in CNGA3 -associated achromatopsia (ACHM). Methods Thirteen eyes from 10 genetically confirmed patients underwent longitudinal imaging with optical coherence tomography (OCT) and non-confocal split detection adaptive optics scanning light ophthalmoscopy (AOSLO). OCT scans assessed outer nuclear layer (ONL) thickness, foveal ellipsoid zone (EZ) disruption, and foveal hypoplasia. AOSLO images were analyzed to calculate peak foveal cone density (PCD) and mean inter-cell distance (ICD) between cones. Mixed effects models were used to analyze the rate of annual change of PCD and ICD. Results Mean (±SD) age at visits was 29 ± 10 years, with a follow-up of 2.6 ± 1 years. There was no change in ONL thickness, degree of EZ disruption, or foveal hypoplasia over the follow-up period. We also observed a stable foveal cone mosaic using AOSLO imaging, with no significant change in PCD or ICD. Mean PCD was 15,346 cones/mm² at the mean age of 29 years old (cf. 64,000–324,000 cones/mm² in previously reported healthy controls), with a mean rate of change of –117.79 cones/mm² (0.8%) per year, P = 0.130. Mean ICD at the mean age was 13.82 µm, with a rate of change of 0.17 µm per year, P = 0.83. Conclusions CNGA3 -associated ACHM displays stable foveal cone structure over time with a similar rate of change to CNGB3 -associated ACHM (2% decline per year). The stable PCD, small cohort, and large variability within the cohort means significant age associations were not detected.