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Durin Yesmin Uddin, Brett Jeffrey, Wai T Wong, Henry Ernest Wiley, Tiarnan D L Keenan, Oliver J Flynn, Emily Y Chew, Catherine A Cukras; Repeatability and Comparison of Dark Adaptation Using the Medmont DAC Perimeter and AdaptDx Dark Adaptometer. Invest. Ophthalmol. Vis. Sci. 2019;60(9):1137.
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© ARVO (1962-2015); The Authors (2016-present)
Functional studies of dark adaptation (DA) using the Medmont Dark-Adapted Chromatic Perimeter and AdaptDx dark adaptometer have demonstrated impairments in rod-mediated kinetics in age-related macular degeneration (AMD). We compared the rod intercept times (RITs) obtained at two retinal loci on the AdaptDx with RITs obtained using the Medmont. We also investigated the repeatability of RIT measures for the Medmont.
Participants >50 years of age, with a range of AMD severity, had dark adaptation testing on the Medmont and AdaptDx within 30 days of each other. DA was measured with the Medmont at 8 loci (4°,6°,8°,12° superior and inferior) along the vertical meridian after a 30% bleach. DA was measured using the AdaptDx protocol either at 5° superior to the fovea or at 12° (using a reduced bleach). Rod intercept time (RIT) defined as the time to detect a -3.1log cd/m2 green stimulus (500/505 nm) was measured. Bland-Altman plots were used to compare RITs measured at 4° and 6° superior on the Medmont to RITs measured at 5° on the AdaptDx; RITs at 12° were also compared.
DA was measured in 45 participants (mean age=76.4±9 years) with a range of AMD severity (no AMD n=18, intermediate AMD n=20, subretinal drusenoid deposits n=7). Longer RITs were observed on the AdaptDx 5° than either the Medmont 4° (n=37, mean difference ±SD = -2.4±4.1 min) or 6° (-3.5±4.2 min). Shorter RITs were observed on the AdaptDx 12° than the Medmont 12° but with similar SD (n=9, 6.9±5.1 min). Ten participants (80.1±8.8 years) repeated Medmont testing within a 30-day period. A Bland-Altman plot of RITs across all retinal eccentricities demonstrated that RIT was reproducible with a mean RIT difference of -0.034±3.5 minutes.
The methods used by Medmont DACP and AdaptDx for measuring DA vary (e.g. bleach and stimulus delivery) yet both devices provide similar measures of DA function with comparable reproducibility. The mean differences in RIT between the instruments indicate a systematic bias which could be attributed to different methodology such as bleach delivery and/or different curve fitting.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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