Spatial and anatomic parameters from SD-OCT and associations with best corrected visual acuity (BCVA) in ABCA4-associated Stargardt Disease (STGD1)

Abstract

Purpose : To compare retinal layer losses and assess structure function relationship between SD-OCT parameters and BCVA.

Methods : Baseline data collected in the multicenter natural history ProgStar Study were analyzed. From Heidelberg SD-OCT images, retinal pigment epithelium (RPE), outer segment (OS), inner segment (IS), outer nuclear layer (ONL), and inner retina were segmented. ETDRS grid centered at the fovea was overlaid, and thickness of each layer was measured in the center subfield, inner ring, and outer ring. SD-OCT images of 20 normal eyes were also segmented. z-scores measuring the deviation from normal were calculated by layer and region for study eyes. Random effects model was used to compare the z-scores of layers. For the subgroup of eyes with relatively normal RPE thickness, defined as RPE z-score> -1, z-scores were summarized.

Results : There were 259 participants (487 study eyes) aged 7-69 years (54% women). Mean BCVA was 46 (SD=16) letters. Table 1a shows the mean/SD of thicknesses and z-scores by layer/region. All outer retinal layers had significant thinning. The IS showed greatest deviation from normal (mean Z-score -15 in the center and -12 in the inner ring). In both center and inner ring, mean z-scores of the IS and ONL were significantly lower than that of the RPE (p<.001). Mean Z-core of the OS was comparable to that of RPE in the center, but better than RPE in the inner ring. In the subgroups of eyes with relatively normal RPE thickness, all outer retinal layers showed significant thinning (Table 1b). Spearman correlation of BCVA with thicknesses in the center ranged from 0.46 to 0.63; with thickness in the inner ring ranged from 0.34 to 0.38. Figure 1 shows z-scores distributions by BCVA level.

Conclusions : Thinning of outer retinal layers is more pronounced in the center than in the Inner Ring, conforming to the predominantly central involvement known in STGD1. Thinning of the IS exceeds that of the RPE, suggesting that photoreceptor degeneration may occur more rapidly than RPE loss. In subgroups with relatively normal RPE thickness, significant deviations from normal exists in all layers, indicating photoreceptor degeneration may commence early and not necessarily second to RPE loss. Thinning of outer retina layers varied by BCVA level, generally with more thinning associated with more visual impairment.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.

 

Table 1

 

Figure 1