A recent study assessed the relationship between baseline AMD and disease stage, OCT features and dark adaptation changes. The team found that there’s an association between AMD diagnosis and more advanced AMD stage at baseline with more pronounced changes in dark adaptation over time.
The prospective longitudinal study included 27 patients. Of the 42 eyes, 29 had AMD (69%) at baseline. The researchers obtained color fundus photographs, spectral domain OCT scans and rod-mediated dark adaptation (20-minute protocol) to analyze changes in rod intercept time (RIT) at three years.
During the three-year follow-up period, four control eyes developed early AMD and one developed intermediate AMD. Two eyes with early AMD progressed to intermediate and two intermediate eyes progressed to late forms, the researchers reported.
The researchers noted that larger RIT changes at three years were associated with baseline AMD, AMD stage and hyperreflective foci on OCT. When they used area under the dark adaptation curve (AUDAC) as an additional outcome measure, retinal atrophy and drusenoid pigment epithelial detachment (PED) had significant associations. “New subretinal drusenoid deposits at three years was also associated with more pronounced changes in RIT and AUDAC,” they wrote.
Some eyes in the study were unable to reach RIT within 20 minutes (n=11) and were assigned the ceiling value (RIT≥20) by the device, but having a 20-minute baseline made RIT analysis ineffective for tracking longitudinal changes in dark adaptation responses. The researchers calculated the AUDAC as an additional outcome measure to compensate for this limitation. The researchers used the 20-minute time limit for eyes whose curve didn’t reach the 3.0log unit threshold of AUDAC. “There is a large variation in the AUDAC in eyes with RIT≥20 minutes,” they explained.
The same eyes that were unable to reach RIT within 20 minutes of baseline had intermediate AMD as well as subretinal drusenoid deposits and classic drusen visible on OCT. The researchers observed ellipsoid disruption in 90% of these eyes (n=10), hyperreflective foci in 27% (n=3), incomplete RPE and outer retinal atrophy in 19% (n=2) and drusenoid PED in 27% (n=3). They saw similar results with AUDAC.
Eyes able to reach RIT within 20 minutes demonstrated strongly correlated AUDAC and RIT values at both baseline and the three-year follow-up.
The investigators concluded that specific OCT features are associated with dark adaptation changes over time and that structure-function correlations in AMD may have prognostic value. They wrote, “Our results revealed that, accounting for age, presence of AMD and a more advanced AMD stage at baseline were significantly associated with changes in dark adaptation at three years.” They also noted that the presence of hyperreflective foci on baseline OCT scans was “the most consistent predictor of more pronounced changes in dark adaptation over time.”
Lains I, Pundlik SJ, Nigalyue A, et al. Baseline predictors associated with three-year changes in dark adaptation in age-related macular degeneration. Retina. February 17, 2021. [Epub ahead of print].