Abstract
Fundus autofluorescence (FAF) imaging is a well-established method in ophthalmology; however, the fluorophores involved need more clarification. The FAF lifetimes of 20 post mortem porcine eyes were measured in two spectral channels using fluorescence lifetime imaging ophthalmoscopy (FLIO) and compared with clinical data from 44 healthy young subjects. The FAF intensity ratio of the short and the long wavelength emission (spectral ratio) was determined. Ex vivo porcine fundus fluorescence emission is generally less intense than that seen in human eyes. The porcine retina showed significantly (p<0.05) longer lifetimes than the retinal pigment epithelium (RPE): 584 ± 128 ps vs. 121 ± 55 ps 498-560 nm, 240 ± 42 ps vs. 125 ± 20 ps at 560-720 nm. Furthermore, the lifetimes of the porcine RPE were significantly shorter (121 ± 55 ps and 125 ± 20 ps) than those measured from human fundus in vivo (162 ± 14 ps and 179 ± 13 ps, respectively). The fluorescence emission of porcine retina was shifted towards a shorter wavelength compared to that of RPE and human FAF. This data shows the considerable contribution of fluorophores in the neural retina to total FAF intensity in porcine eyes.
Highlights
In recent years, fundus autofluorescence (FAF) intensity imaging has been established as diagnostic technique in clinical ophthalmology
We introduced the technique of fluorescence lifetime imaging to the eye by using laser scanning ophthalmoscopy (SLO) [15,16,17]
This study investigates the contribution of non-lipofuscin fluorophores to FAF intensity and lifetimes in porcine eyes
Summary
Fundus autofluorescence (FAF) intensity imaging has been established as diagnostic technique in clinical ophthalmology. Lipofuscin is a mixture of various metabolic byproducts, predominantly all-trans retinal derived compounds as well as lipid peroxidation products, accumulated in the lysosomes of the retinal pigment epithelium (RPE) [2]. Spaide investigated autofluorescent compounds in the outer retina and the sub-retinal space with a fundus camera equipped with a specific filter set to all-trans-retinal-derived compounds, such as the pyridinium bis-retinoid A2E, its precursor products A2-PE and A2-PE-H2, and alltrans retinal dimers. These subretinal accumulations are a result of lacking phagocytosis by the RPE. An investigation of non-lipofuscin compounds that contribute to FAF is of eminent diagnostic interest
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