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Michael J. Byrnes, Patrick Johnston, Sunita Saigal, Gail Torkildsen, Avner Ingerman; Progression Of Early To Intermediate Dry AMD Eyes Measured By L-cone Dark Adaptation After Photostress At Baseline And After One Year. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5738.
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© ARVO (1962-2015); The Authors (2016-present)
Due to the slow progression of dry AMD and its initial presentation outside the fovea, visual acuity is typically not affected until advanced AMD has developed. There is an unmet need for visual function tests that can be used to monitor the progression of dry AMD. We have previously developed a highly reproducible method for L-Cone Dark Adaptation after photostress and shown that recovery time is significantly elevated in older subjects relative to younger and in some AMD eyes. In this study, we assessed L-Cone Dark Adaptation at baseline and after 1 year in AMD patients, older controls, and younger controls.
L-Cone Dark Adaptation was assessed in 12 eyes of 12 subjects, including 2 young controls (aged 20-22; BCVA ≥ 20/20 in better eye), 2 old controls (aged 60-74; BCVA ≥ 20/40 in better eye), and 8 patients with early-to-intermediate dry AMD (aged 60-81; BCVA ≥ 20/40 in better eye). Subjects with vision loss secondary to other conditions were excluded. At baseline and 1 year, L-cone dark adaptation each subject was assessed 3 times within 2 weeks to assess reliability. For each trial, recovery half-lives were estimated using exponential models. The effects of age and disease status on baseline cone threshold, and recovery half-life were assessed via an exponential model with fixed effects for age and AMD status and random effects for subjects, and each subject’s change from baseline was measured.
Mean ages of younger controls, older controls, and AMD patients were 21.0, 67.0, and 70.3. Mean logMAR BCVA at baseline was -0.12, 0.2, and 0.23 in young, old, and AMD eyes. Mean change in BCVA from baseline to 1 year was < 0.1. Baseline mean half-lives of younger subjects (61, 72 s) were shorter than mean half-lives of older subjects (73, 124 s). Mean half-lives of AMD eyes fit a bimodal pattern with 4 eyes similar to older controls (76, 88, 98, 120 s) and 4 eyes with prolonged recovery (164, 179, 189, 226 s).
L-Cone Dark Adaptation after photostress is a reliable assessment of cone function that can discriminate between young, old, and dry AMD eyes. This technique may be a useful way to monitor progression of early-to-intermediate dry AMD.
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