Abstract
Purpose :
Choroideremia (CHM) is an X-linked inherited retinal degeneration affecting photoreceptors, retinal pigment epithelium and choriocapillaris. Previous high resolution imaging studies have contributed to the understanding of CHM progression from the mid-periphery toward a retained island of functioning cells at the fovea. Here we describe the phenotypes observable within the retained island in a large cohort of CHM patients using adaptive optics ophthalmoscopy (AOSLO).
Methods :
The foveal region of 104 eyes of 55 individuals clinically diagnosed with CHM were imaged using a custom-built AOSLO. Images were desinusoided, registered, and automatically montaged with manual correction. Montages were qualitatively categorized by consensus of two observers (NW, JIWM). 150 x 150 μm foveal ROIs were selected, inclusive of the region of maximum cone density. Cones were automatically identified with manual correction (Mosaic Analytics, Translational Imaging Innovations) and peak cone density (PCD) was calculated. Optical coherence tomography (OCT) images were acquired (Heidelberg Spectralis OCT+HRA) and best corrected visual acuity (BCVA) was collected. BCVA and PCD were compared using linear regression.
Results :
Participants were aged 10-63 years at the time of imaging. BCVA ranged from 0.1 to 1.5 logMAR. Nearly all eyes (99/104) had foveal cone abnormalities, with only five eyes (4.8%, 4 participants) showing qualitatively normal waveguiding of the residual foveal cone mosaic. 8.7% of eyes (9 eyes, 7 participants) had waveguiding cones at the foveal center, surrounded by parafoveal “spider web” mosaic disruptions that corresponded with inner retinal microcysts on OCT. 85.6% of eyes (89 eyes, 48 participants) showed variable foveal cone reflectivity with patchy regions of hyper and hyporeflectivity; 6 of these eyes (6 participants) had poor visibility of foveal and parafoveal cones despite easily observable cones in the adjacent perifovea. One eye had a full thickness macular hole. PCD measurements (86 eyes) were significantly lower than normal (p<0.0001, t-test, range: 29,382-157,717 cones/mm2). There was a statistically significant relationship between PCD and BCVA (r2=0.22, p<0.0001).
Conclusions :
There are a range of distinct phenotypes observable on AOSLO imaging within the foveal region of individuals with CHM. The reduced PCD in CHM suggests cone loss even within the central island of functioning retina.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.