Characterization of Retinal Structure in CNGA3-associated Achromatopsia

Abstract

Purpose : To investigate retinal structure in CNGA3-associated achromatopsia (ACHM).

Methods : Thirty-five ACHM patients underwent ocular examination, spectral-domain optical coherence tomography (SD-OCT), Adaptive Optics (AO) ophthalmoscopy and colour vision testing. The OCT scans were used for grading the foveal appearance and measuring the outer nuclear thickness (ONL). The interpretable AO images were used to quantify peak foveal cone densities.

Results : The mean (range, ±SD) age was 25.5 years (10-64, ±12.6). Mean (range, ±SD) best-corrected visual acuity (BCVA) was 0.87 LogMAR (0.40-1.30, ±0.17) for 29 of 35 patients. SD-OCT revealed a variable degree of disruption or loss of the foveal inner segment ellipsoid (ISe) layer and was graded as previously published; grade I (continuous ISe): four, II (ISe disrupted): fifteen, III (ISe absent): three and IV (presence of an hyporeflective zone): thirteen patients. The mean (±SD) outer nuclear thickness (ONL) was 75.85μm (± 25.94). AOSLO images were interpretable in 14 of 35 subjects. Mean (range, ±SD) peak foveal cone density was 20,713 cones/mm² (2,191-62,800, ± 16,381).

Conclusions : The cone mosaic in patients harbouring CNGA3 mutations was irregular, variably disrupted and with significantly lower peak foveal densities than normal (Figure). Patients with ACHM should be assessed on an individual basis to determine their potential/remnant cones, for patient selection in upcoming and/or on-going clinical trials.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.

 

Figure: AOSLO imaging in CNGA3-assosiated ACHM.
Split detection AOSLO images depicting the foveal centre in two subjects with CNGA3-ACHM. The foveal cones’ inner segments are visible with substantial variability between the two subjects. The images were acquired using a custom-built AOSLO housed at University College London/Moorfields Eye Hospital, London, UK. Scale bar = 50μm.