Choriocapillaris changes in myopic macular degeneration

Abstract

Purpose : Myopic macular degeneration (MMD) is rapidly increasing in prevalence worldwide, and severe forms can cause irreversible loss of vision. Recent studies have shown an association between decreased choroidal thickness and increased grade of MMD. Our cross-sectional study aimed to further characterize this choroidal thinning by analyzing choriocapillaris alterations in MMD.

Methods : We recruited controls (n=51 eyes) and high myopes (spherical equivalent ≤ -6 diopters; n=16 eyes) from clinic at the University of California San Francisco. Axial length (AL) from A-scan, best corrected visual acuity (BCVA), fundus photos, and swept-source optical coherence tomography angiography (SS-OCTA) were measured. Fundus photos were graded for stage of MMD by 2 independent ophthalmologists. Inclusion criteria for subjects were those with Grade 2 MMD (diffuse chorioretinal atrophy) and high axial myopia (AL ≥ 26.5 millimeters [mm]). Subjects without MMD, with ages from 19-88 years old (mean=56) and AL from 21.65 to 25.84mm (mean=23.87), were used as controls. Exclusion criterion was BCVA worse than 20/40. 3x3mm SS-OCTA scans were acquired and choriocapillaris (CC) mean thickness was measured by identifying CC peaks in OCTA A-scan intensity profiles. CC flow void percent (CC FV%) was quantified using a fuzzy C-mean thresholding method on enface OCT-A images of an 8-um CC slab below Bruch's membrane. Multivariate regression models were analyzed comparing CC thickness and CC FV% between subjects and controls, with a linear correction for age.

Results : Subjects with diffuse chorioretinal atrophy had both a significantly decreased CC thickness and increased CC FV% compared to controls. CC thickness in subjects with diffuse chorioretinal atrophy measured 5.23 ± 0.68 um (mean ± standard deviation) versus 15.45 ± 1.82 um in controls (p<0.001). CC FV% in subjects with diffuse MMD measured 26.5 ± 0.04 versus 11.6 ± 0.04 in controls (p<0.001).

Conclusions : Patients with diffuse chorioretinal atrophy and good visual acuity had a 66% reduction in CC thickness and a 230% increase in CC FV% compared to controls. Although these patients have essentially normal BCVA and outer retinal landmarks on optical coherence tomography, they demonstrate significant choriocapillaris alterations that are consistent with reduced perfusion to the outer retina. These results point to a potential vascular etiology for MMD.

This is a 2021 ARVO Annual Meeting abstract.