Assessment of a classification of age-related macular degeneration severity from the Northern Ireland Sensory Aging study using a measure of dark adaptation

Purpose To assess differences in rod-mediated dark adaptation (RMDA) between different grades of age-related macular degeneration (AMD) severity using an Optical Coherence Tomography (OCT)-based criterion compared to the Beckman Colour Fundus Photography-based (CFP) classification. To assess association between subretinal drusenoid deposit (SDD) presence and RMDA at different AMD severity grades, using an OCT-based classification. Design Cross-sectional study Participants Participants from the Northern Ireland Sensory Aging study (NISA; Queen's University Belfast). Methods Complete RMDA (rod-intercept time [RIT; AdaptDx; Maculogix, USA]) data, CFP (Canon CX-1 Digital Fundus Camera; Canon, USA) and spectral domain OCT (Heidelberg Spectralis SD-OCT; Heidelberg Engineering, Germany) images were extracted. Participants were stratified into four Beckman groups (omitting late-stage AMD) and three OCT-based groups. OCT grading included: participants with no drusen/retinal pigment epithelium (RPE) abnormalities (OCT0), participants with drusen present but no RPE abnormalities (OCT1) and participants with drusen and RPE abnormalities present (OCT2). SDD presence and stage was identified via OCT. Main Outcome Measure RIT data (age-corrected) assessed across AMD severity groups Results Data from the eye with the worse visual acuity in 459 participants (median [interquartile range[IQR]) age 65[59,71] years) were stratified by both classifications. SDDs were detected in 109 eyes. Median (IQR) RMDA for Beckman classification (Beckman0-3, with 3 being intermediate AMD[iAMD]) groups were 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 (IQR)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 compared to other Beckman groups (p=<0.005 all) with no statistically significant differences between the other Beckman groups. Similarly, after age-correction, eyes in OCT2 had worse RMDA compared to OCT0(p=