Retinal pigment epithelium thinning is the most significant variable contributing to poor visual acuity in people with advanced choroideremia, according to research results published in Eye. 

In a retrospective, noninterventional image analysis study, researchers sought to assess the structural-functional relationship in people with choroideremia through the correlation of structural changes visible on ocular coherence tomography (OCT) and autofluorescence (AF) images with visual acuity. In particular, the researchers wanted to understand the relationship between retinal layer thickness and choroidal degeneration in people with and without advanced choroideremia. 

After applying inclusion criteria, participants provided a detailed family history and underwent genetic testing. Targeted next-generation sequencing was used to identify CHM, RPGR, and RP2 genes. Participants were divided into 2 groups based on the feature identification via AF. Group 1 included people with choroideremia with the foveal island preserved, while group 2 lacked the foveal island; this group was considered the advanced choroideremia group. 


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The study cohort included 53 eyes from 28 participants (100% men; mean age, 51.7 years ± 13.4 years and 63.6 years ± 11.6 years in each group) who met inclusion criteria (group 1 n=26 eyes in 14 patients; group 2 n=27 eyes in 14 patients). Between the groups, only age and visual acuity were significantly different. 

Investigators identified outer retinal tubulations in 69% and 85% of eyes in group 1 and group 2, respectively. Central retinal thickness and subfoveal choroidal thickness between both groups were significantly different in the right and left eyes. 

Using a Spearman’s correlation test, the researchers found that a decline in visual acuity was associated with increasing age (r=0.483), low central retinal thickness (r=-0.378), thin inner retinal layer thickness (r=-0.512), thin outer retinal layer thickness (r=-0.59), and thin retinal pigment epithelium (r=-0.653). Further multivariate linear regression analysis of these variables found that retinal pigment epithelium thickness was the single most important index that affects visual acuity. 

Study limitations include a lack of availability of molecular choroideremia diagnosis for all participants, potential misdiagnosis of choroideremia in some participants due to the phenotypic overlap of clinical features of choroideremia and X-lined retinitis pigmentosa, and exclusion of women as participants. Additionally, OCT angiography details were not available to assess choriocapillaris damage. 

“[Retinal pigment epithelium] thinning is one of the major contributors to the poor visual acuity in patients with advanced [choroideremia],” according to the researchers. “Larger studies are required to further evaluate the role of the retinal and choroidal thickness and its relationship to visual acuity in [choroideremia] using more sophisticated imaging modalities such as OCT angiography or adaptive optics.” 

Reference

Venkatesh R, Reddy NG, Snehith R, et al. Study of retinal structural-functional relationship in choroideremia using fundus autofluorescence and optical coherence tomography. Eye. Published online February 16, 2021. doi:10.1038/s41433-021-01441-0