Abstract
Purpose :
To assess foveal outer nuclear layer (ONL) thickness over time in participants with congenital achromatopsia (ACHM)
Methods :
Sixty-one participants (31 female, 30 male; mean age at baseline: 22.60 years) with genetically confirmed ACHM (with mutations in CNGA3 (n=8), CNGB3 (n=52), or ATF6 (n=1)) and longitudinal Bioptigen or Cirrus OCT images collected were included in this analysis. Analysis using the measurement tool in ImageJ was completed to extract an average of three measurements of ONL thickness (60 OD; 61 OS). ONL thickness was defined as the distance (in μm) between the external limiting membrane (ELM) to the posterior border of the outer plexiform layer (OPL). For each participant, measurements from the first and last available imaging date were assessed to evaluate changes in ONL thickness over time using paired t-test and Bland-Altman analyses.
Results :
A total of 438 OCT images were utilized to measure ONL thickness (224 OD and 214 OS). Mean ONL thickness at the first imaging date was 66.40 μm (range: 27.06 to 113.19 μm) and 67.37 μm (range: 34.58 to 111.62 μm) for OD and OS, respectively. The mean follow-up period was 3.04 and 2.66 years for OD and OS, respectively (range: 6 months to 10 years). Mean ONL thickness for the last available imaging date was 65.91 μm (range: 39.56 μm to 117.25 μm) and 67.71 μm (range: 39.95 μm to 104.56 μm) for OD and OS, respectively. There was no significant difference in ONL thickness across timepoints measured for both OD (paired t-test; t(59)=0.58, p=0.56) and OS (paired t-test; t(60)=0.41, p=0.68). The mean [95% CI] difference in ONL thickness between the first and last timepoints was -0.49 μm, [-2.19 to 1.20 μm] for OD and 0.36 μm [-1.29 to 1.97 μm] for OS.
Conclusions :
ONL thickness in ACHM did not show significant changes across the follow-up period used here. Any progression that does occur would have to occur at a very slow rate. While continued studies using longer follow-up times, more genetically heterogenous samples, and carefully aligned OCT scans between time points may still be warranted, our results are consistent with relatively stable foveal cone structure in congenital ACHM.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.