Does outer retinal thickness represent another clinical biomarker for predicting geographic atrophy growth?

Abstract

Purpose : To determine whether the outer retinal layer (ORL) thickness measurement could serve as a clinical biomarker to predict the annual square root enlargement rate (ER) of geographic atrophy (GA).

Methods : Eyes with GA secondary to age-related macular degeneration (AMD) were imaged over a 12-month span with swept-source OCT (PLEX® Elite 9000 (ZEISS, Dublin, CA)) using a 6 x 6 mm scan pattern. GA lesions were manually identified and measured using the en face sub-retinal pigment epithelium (RPE) OCT images, and GA annual square root ERs were calculated. ORL thickness was measured using segmentation boundaries that extended from the upper boundary of outer plexiform layer to the upper boundary of RPE layer using a validated semi-automatic segmentation software. At baseline visit, the ORL thickness were measured in different sub-regions around the GA (Fig.1).

Results : A total of 38 eyes from 27 subjects were included in this study. The same eyes
were previously used to compute the correlation between GA growth and the measurements of choriocapillaris (CC) flow deficits (FDs) and RPE-Bruch’s membrane (BM) distances^1,2. A negative correlation was observed between the ORL thickness and the annual GA growth in all the sub-regions (Table 1). The ORL thickness immediately around GA showed the strongest correlation with the GA annual square root ERs (r=-0.457, p =0.004 for a 0-300 µm rim around the GA). No correlations were found between ORL thickness and the previously published CC FDs in any sub-regions, whereas a significant correlation was found between the ORL thickness and the RPE-BM distances in the region immediately around GA (r=-0.398, p =0.013).

Conclusions : ORL thickness measurements around the GA showed significant correlations with the annual GA growth, but a significant correlation was also found between the ORL thickness and the RPE-BM distances, suggesting that the ORL thickness and RPE-BM distances do not independently influence the growth of GA. Due to the challenges of segmenting the ORL, RPE-BM distance measurements and CC FDs are sufficient to serve as the clinical biomarkers to predict the annual ERs of GA.
1. Shi Y, et al. Am J Ophthalmol. 2021;224:321-331.
2. Chu Z, et al. Am J Ophthalmol. https://doi.org/10.1016/j.ajo.2021.10.032

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.

 

Figure 1

 

Table 1