Fluorescence lifetimes of drusen in age‐related macular degeneration

Abstract

PURPOSE. The purpose of this study was to characterize fundus autofluorescence lifetimes of retinal drusen in patients with AMD. METHODS.Patients with AMD and retinal drusen and healthy controls of similar age were examined. A fluorescence lifetime imaging ophthalmoscope was used. Retinal autofluorescence was excited using a 473-nm pulsed laser, and fundus autofluorescence lifetimes of the central retina (308) were measured in two distinct spectral channels (short: 498 to 560 nm [SSC]; long: 560 to 720 nm [LSC]). Mean retinal autofluorescence lifetimes, corresponding fundus autofluorescence intensity images, spectral domain optical coherence tomography, color fundus images, and clinical data were investigated. Patients were analyzed in two distinct groups (soft drusen and reticular pseudodrusen) and compared with control subjects.RESULTS. Sixty-four eyes of 64 patients with AMD and retinal drusen (age: mean 6 SD, 78 6 8.5 years; range, 59 to 94 years) were investigated and compared with a control group of 20 age-matched healthy subjects. Mean retinal autofluorescence lifetimes in patients with AMD was significantly prolonged compared with the healthy control eyes (mean 6 SEM: SSC, 486 6 18 vs. 332 6 11 ps, P < 0.0001; LSC: 493 6 9 vs. 382 6 17 ps, P < 0.0001). Areas of drusen featured a wide range of fluorescence lifetime values. Long lifetimes were identified in areas of atrophy and in areas of intraretinal hyperreflective deposits. Short lifetimes corresponded to deposits within the photoreceptor outer segment band.CONCLUSIONS. Mean retinal autofluorescence lifetimes in AMD patients are significantly prolonged. Intraretinal deposits cause prolonged lifetimes, whereas deposits in the area of the outer photoreceptor segments lead to short fluorescence lifetimes.Keywords: fluorescence lifetimes, fundus autofluorescence, retinal imaging, FLIO, age-related macular degeneration, AMD, deposits, drusen A MD is caused by age-related metabolic disorders in the retina, which leads to thickening of the Bruch membrane with calcifications, basal laminar deposits, and appearance of drusen. The predominant symptom is progressive central vision loss. The prevalence of advanced AMD is estimated to increase from 2.2% in 65-year-old patients to more than 21% in patients older than 90 years.1 Various risk factors have been identified, including age, sex, arterial hypertension, arteriosclerosis, elevated serum lipids, smoking, alcohol abuse, exposure to UV light, and various genetic factors. 2-6The hallmark of early AMD is the presence of retinal drusen, which can be classified into soft drusen of various sizes (small, medium, large), hard drusen, cuticular drusen, crystalline drusen, and reticular pseudodrusen. 4,7 In the biomicroscopic fundus examination, drusen are seen as discrete, yellow-white punctuate elevations. Retinal drusen are focal deposits of extracellular debris located between the basal lamina of the RPE and the inner collagenous layer of the Bruch membrane and are mainly concentrated within the posterior pole. The ...