Evaluation of Structural and Functional Retinal Changes in the Achromatopsia Spectrum with Multimodal Imaging

Purpose Achromatopsia (ACHM) is a rare hereditary retinal disorder characterized by low vision, photophobia, and nystagmus. Due to its rarity, the relevant literature is limited. This study aimed to evaluate the structural and functional retinal changes observed in the ACHM spectrum using multimodal imaging.Methods In this prospective cross-sectional study, 62 eyes of 31 patients within the ACHM spectrum who applied to the Low Vision Rehabilitation Unit of Ankara University Faculty of Medicine were evaluated. Assessments included macular pigment optical density (MPOD), microperimetry, contrast sensitivity (CS), fundus autofluorescence (FAF), and optical coherence tomography (OCT). Eyes were classified into five stages based on photoreceptor layer damage.Results The mean best-corrected visual acuity (BCVA) was 0.85 ± 0.18 logMAR. Fundus examination showed normal findings in 42%, irregular retinal pigment epithelium (RPE) in 48%, and atrophic RPE in 10%. Mean MPOD was 1.32 ± 2.27 dB, retinal sensitivity 20.85 ± 4.61 dB, and central macular thickness (CMT) 124.88 ± 59.15 µm. Fixation was extrafoveal in 92% and unstable in 83%. Photoreceptor damage was present in 72% of eyes: stage 1 (28%), stage 2 (13%), stage 3 (14%), stage 4 (19%), and stage 5 (26%). The ellipsoid zone was absent in 59%, foveal hypoplasia in 52%, and hypoautofluorescence in 57%. Significant correlations were observed between ellipsoid zone integrity and age, CMT, and FAF pattern (p = 0.044, p = 0.005, p < 0.001).Conclusion This study highlights reduced MPOD, photoreceptor damage (72%), ellipsoid zone loss (59%), and foveal hypoplasia (52%) within the ACHM spectrum. The findings of this study may contribute to the literature on structural and functional retinal changes observed in cases within the ACHM spectrum and may be useful in the design of future clinical studies.