Assessing Foveal Cone Mosaic in White Dot Syndromes

Abstract

Purpose : To examine the cone-photoreceptor mosaic in patients with white dot syndromes using confocal adaptive optics scanning light ophthalmoscopy (AOSLO).

Methods : Five patients (8 eyes) with white dot syndromes (Table) were imaged using an AOSLO. One healthy female subject (2 eyes) was also included in the study for comparison. Image sequences (150 frames), of 1.0° and 1.5° field of view, spanning the depth of the retina were captured using 790 nm light (54 μW at the pupil). Fifty frames of each sequence were registered and averaged to improve the signal-to-noise ratio. A semi-automatic MATLAB algorithm was used to identify cone-centers in the region of interest (ROI). The number of cones per degree² were calculated for each eye. Subsequently, the number of neighbors for each cone was measured using Voronoi tiling. Percentage of cones with abnormal number (<5 or >7) of neighboring cones were calculated.

Results : The mean age of patients was 41 years (range: 18 to 84 years). The age of the control subject was 31 years. Four (80%) of the patients were females. Number of cone photoreceptors per degree² and the percentage of cones with abnormal number of neighboring cone photoreceptors were tabulated and shown in Table below. Subjects with white dot syndromes had lower cone density (13-70%) and more abnormal neighbors (40-190%) compared to normal eyes (Figure).

Conclusions : Adaptive optics enables detailed visualization of structural integrity of cone photoreceptors in the retina. Patients with birdshot chorioretinopathy and maculopathy demonstrated the least number of cones per degree² compared to normal eyes.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.

 

Table: Comparison of Structural Differences in Cone Photoreceptors

 

Figure: Confocal Foveal Cone Mosaic and Density Measurements of Various White Dot Syndromes