Purpose
To explore choriocapillaris (CC) alterations in choroideremia (CHM) with optical coherence tomography (OCT) angiography and to correlate these findings with deficits in retinal structure and visual function.
Methods
This is a prospective study of subjects with CHM, CHM carrier state, and normal controls. Subjects underwent imaging with 70 KHz spectral OCT (RTVue-XR) in 3x3mm and 6x6mm macular areas using the split-spectrum amplitude-decorrelation angiography approach. Segmentation of the CC with en face maximal projection provided a 2 dimensional angiogram. Adaptive optics (AO) images were analyzed with custom cone-counting software to provide a cone density map. Additional structural imaging included fundus autofluorescence and color fundus photography. Visual function was assessed through best corrected visual acuity (BCVA) and microperimetry using a custom 101 point testing grid. Image registration was performed to evaluate the spatial relationship between CC density and structural and functional metrics of the retina and retinal pigment epithelium (RPE).
Results
6 subjects with CHM, 2 carriers, and 7 controls were enrolled. BCVA ranged from 20/20 to 20/30 in affected males and 20/20 to 20/60 in carrier females. Mean age amongst affected males and carriers was 44.5±15.1 years. OCT angiography demonstrated regions nearly devoid of CC amongst affected males, and patchy areas of reduced CC density amongst carriers. In affected males, there was strong spatial correlation between CC density, retinal and RPE anatomy, and visual function. Subtle discrepancies were noted at transition zones. Amongst carrier females, there were greater discrepancies. In some carrier eyes, reduced CC density and visual function coincided in areas with apparently normal retinal structure.
Conclusions
OCT angiography permits in vivo CC assessment not previously possible, and demonstrates a spectrum of CC pathology in CHM. Structure-function correlations provide new insights into the disease pathology. This technology offers promising new endpoints for upcoming clinical trials in CHM.