Relationship between Delayed RMDA and the Ellipsoid and Interdigitation Zones in Age-related Macular Degeneration (AMD): ALSTAR2 baseline

Abstract

Purpose : To characterize the relationship between integrity of the ellipsoid zone (EZ) and interdigitation zone (IZ) on optical coherence tomography (OCT) and delayed rod-mediated dark adaption (RMDA) in AMD.

Methods : Rod intercept time (RIT) was measured 5° superior to the fovea in patients with early (n=77), intermediate AMD (n=32), and without AMD (n=167) in the Alabama Study on Early Age-related Macular Degeneration 2 (ALSTAR2). Macular OCTs (6x6 mm, 121 B-scans, ART > 9) were acquired (Spectralis HRA+OCT2). A novel deep-learning-derived graph-based algorithm was used to segment the EZ and IZ. Errors were manually corrected by trained, masked graders (Figure 1A). The area of detectable EZ and IZ, and mean thickness of IZ within the entire ETDRS grid (and in inner and outer superior, and central subfields) were computed. Differences in the groups (normal, early, intermediate) were assessed using one-way ANCOVA. The relationship between RIT and the EZ/IZ area and IZ thickness was assessed by Pearson’s correlation coefficient and age-adjusted.

Results : RIT at 5° increased, and area of detectable EZ and IZ decreased, from normal to early to intermediate AMD (Table 1A/1B). A correlation of r = -0.279(p<0.001) was observed between RIT and preserved EZ area and a correlation of r = -0.462(p<0.001) was observed between RIT and preserved IZ area. A correlation of r = -0.445(p<0.001) was observed between RIT and IZ thickness in the superior inner subfield (Table 1C). These correlations were not apparent in normal eyes alone and were similar in each of the measured subfields (Table 1B).

Conclusions : RMDA is moderately correlated with the status of outer retinal bands in early and intermediate AMD eyes. A reduction in detectable IZ area or thickness is associated with a greater delay in RIT measured at 5°. In the central subfield the correlation of IZ with RMDA is stronger than the correlation of EZ with RMDA. These findings provide insight into anatomic and functional changes occurring from aging to early and intermediate AMD.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.

 

Figure 1A. Magnified outer retinal bands of an intermediate AMD eye OCT B-scan
*Indicates preserved EZ

Figure 1B. En face maps of EZ and IZ in normal, early, and intermediate AMD eyes

 

Table 1A. Age-adjusted RIT at 5°

Table 1B. Age-adjusted area of EZ/IZ and correlation with RIT

Table 1C. Age-adjusted thickness of IZ and correlation with RIT