Abstract
Purpose:
To characterize disease pathogenesis and correlate retinal structure/function relationships in choroideremia (CHM) through high resolution confocal adaptive optics retinal imaging.
Methods:
60 CHM patients were imaged using adaptive optics scanning light ophthalmoscopy (AOSLO), spectral domain optical coherence tomography (OCT), autofluorescence (AF), and SLO. 15 patients also received microperimetry testing of photopic sensitivity. Images from all modalities were registered and aligned in Photoshop. Cone density was measured in AOSLO images using a semi-automated Matlab script.
Results:
SLO imaging revealed scalloped edges of the retinal pigment epithelial (RPE) atrophy and large intact choroidal vessels. Wide-field SLO imaging showed diffuse peripheral atrophy. AF imaging revealed hypo-AF in areas of degeneration, while central AF remained present. Centrally intact laminar structure and outer retinal tubulation at the edge of atrophy were visible on OCT. AOSLO imaging revealed the cone mosaic in centrally intact retina. Cone density was generally normal at 1.0 and 1.5mm eccentricity but 26% of measurements showed a reduction at 0.5mm. Reductions in cone density were more prevalent in nasal and superior retina. The border of RPE atrophy showed either abrupt loss of the cone mosaic at the same location or continuation of the cone mosaic beyond the atrophic border. Other disease features, including choroidal blood vessels, hyper-reflective cones, and atrophic structures were tabulated to show the frequency of occurrence and model disease progression. Microperimetry testing revealed reduced photopic sensitivity at most retinal locations (mean reduction in intact retina: 10.2dB, standard deviation: 4.7dB), even though many of these same locations exhibited normal cone density. Reduced cone density was always associated with a reduction in sensitivity.
Conclusions:
High resolution imaging, particularly AOSLO in combination with OCT and microperimetry, allows single cell analysis of disease pathogenesis in CHM. RPE is one of the primary sites of degeneration in patients with CHM, and the photoreceptors may also degenerate independently. These imaging techniques to correlate retinal structure and function promise to be useful in studying disease pathogenesis and monitoring disease progression for CHM and other diseases.
Keywords: 648 photoreceptors •
696 retinal degenerations: hereditary •
552 imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)