Assessment of the Classification of Age-Related Macular Degeneration Severity from the Northern Ireland Sensory Ageing Study Using a Measure of Dark Adaptation

Abstract

Purpose: To assess the differences in rod-mediated dark adaptation (RMDA) between different grades of age-related macular degeneration (AMD) severity using an OCT-based criterion compared with those of AMD severity using the Beckman color fundus photography (CFP)-based classification and to assess the association between the presence of subretinal drusenoid deposits (SDDs) and RMDA at different grades of AMD severity using an OCT-based classification.

Design: Cross-sectional study.

Participants: Participants from the Northern Ireland Sensory Ageing study (Queen's University Belfast).

Methods: Complete RMDA (rod-intercept time [RIT]) data, CFP, and spectral-domain OCT images were extracted. Participants were stratified into 4 Beckman groups (omitting late-stage AMD) and 3 OCT-based groups. The presence and stage of SDDs were identified using OCT.

Main outcome measures: Rod-intercept time data (age-corrected).

Results: Data from 459 participants (median [interquartile range] age, 65 [59-71] years) were stratified by both the classifications. Subretinal drusenoid deposits were detected in 109 eyes. The median (interquartile range) RMDA for the Beckman classification (Beckman 0-3, with 3 being intermediate age-related macular degeneration [iAMD]) groups was 6.0 (4.5-8.7), 6.6 (4.7-10.5), 5.7 (4.4-7.4), and 13.2 (6-21.1) minutes, respectively. OCT classifications OCT0-OCT2 yielded different median (interquartile range) values: 5.8 (4.5-8.5), 8.4 (5.2-13.3), and 11.1 (5.3-20.1) minutes, respectively. After correcting for age, eyes in Beckman 3 (iAMD) had statistically significantly worse RMDA than eyes in the other Beckman groups (P ≤ 0.005 for all), with no statistically significant differences between the other Beckman groups. Similarly, after age correction, eyes in OCT2 had worse RMDA than eyes in OCT0 (P ≤ 0.001) and OCT1 (P < 0.01); however, there was no statistically significant difference between eyes in OCT0 and eyes in OCT1 (P = 0.195). The presence of SDDs was associated with worse RMDA in OCT2 (P < 0.01) but not in OCT1 (P = 0.285).

Conclusions: Eyes with a structural definition of iAMD have delayed RMDA, regardless of whether a CFP- or OCT-based criterion is used. In this study, after correcting for age, the RMDA did not differ between groups of eyes defined to have early AMD or normal aging, regardless of the classification. The presence of SDDs has some effect on RMDA at different grades of AMD severity.

Keywords: AMD, age-related macular degeneration; AdaptDx; Age-related macular degeneration; Beckman; CFP, color fundus photography; OCT-based grading; RIT, rod-intercept time; RMDA, rod-mediated dark adaptation; RPE, retinal pigment epithelium; Rod-mediated dark adaptation; SD-OCT, spectral-domain OCT; SDD, subretinal drusenoid deposit; VA, visual acuity; iAMD, intermediate age-related macular degeneration.

Figure 1

Four hundred fifty-nine participants were graded using the Beckman (0–3) and OCT classifications (0–2). A, Participant cohorts in each class. B, Agreement between the 2 classifications. For participants with the greatest discordance between the classifications (n = 8 in OCT 0 and Beckman 3 and n = 11 in OCT 2 and Beckman 0), an additional check of the grading was performed by R.E.H.. The reasons for disagreement were confirmed to be due to the different imaging technologies used, such as vitreous abnormalities detected using OCT looking like soft drusen on color, small drusen visible using OCT but not on color, and poorer-quality images on color in comparison with OCT masking subtle abnormalities on color.

Figure 3

Kaplan–Meier curves illustrating the time taken for participant sensitivity to recover to a value of 5.0 × 10 ^{− 3} scotopic cd/m² (3.0 log units of stimulus attenuation). This time taken is the rod-intercept time. Survival curves shown for the control and age-related macular degeneration groups stratified by the OCT classification and the presence of subretinal drusenoid deposits (SSDs).

Figure 2

A, B, Kaplan–Meier curves illustrating the time taken for participant sensitivity to recover to a value of 5.0 × 10^{− 3} scotopic cd/m² (3.0 log units of stimulus attenuation). This time taken is the rod-intercept time. The 2 plots show survival times for the control and age-related macular degeneration groups stratified by the Beckman (A, C) and OCT classifications (B, D). C, D, Age distribution for each classification. Visually, it seems like there is significant difference in the OCT classification in the rod-intercept time, but after correction for age, this is lost in earlier stages of age-related macular degeneration disease.