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Charles Granger, Hongxin Song, Qiang Yang, Kenichi Saito, Koji Nozato, David R Williams, Mina M Chung, Ethan A Rossi; Contiguous mapping of retinal pigment epithelium (RPE) cell morphometry across the horizontal meridian of the living human eye. Invest. Ophthalmol. Vis. Sci. 2016;57(12):No Pagination Specified.
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© ARVO (1962-2015); The Authors (2016-present)
Lipofuscin autofluorescence (AF) imaging in adaptive optics scanning light ophthalmoscopy (AOSLO) permits single-cell resolution of RPE cells in the human retina, offering potential evaluation of RPE health. However, chromatic aberration and head and eye motion complicate human imaging. We used improved AOSLO methods to image lipofuscin AF across clinically meaningful retinal areas in normal subjects to evaluate this method for mapping RPE cells and provide a dataset of normal in vivo human RPE cell morphometry.
An AOSLO designed for clinical use, capable of eye tracking and image stabilization, was configured for lipofuscin AF imaging. A reduced 532 nm excitation beam diameter (~3 mm) and automated optimization of retinal focus and confocal pinhole placement improved collected signal. Coupled light delivery and data acquisition combined with active stabilization permitted efficient imaging at safe light levels (≤15 µW). A contiguous retinal area was imaged in one eye of 10 normal participants, aged 23–65 yrs, spanning ~2.5°×~30° across the horizontal meridian and foveal center. Post processing removed transverse chromatic aberration blur from pupil motion. RPE cells in 150×150 µm regions of interest (ROIs) positioned at ~250 µm intervals were segmented using automated software with manual correction, permitting evaluation of numerous cell statistics.
The microscopic distribution of lipofuscin AF across the retina varied substantially between subjects. RPE cell densities were mostly consistent with ex vivo data, and were most similar between subjects in the fovea but showed considerable variance at eccentricities greater than 1 mm. The fraction of well-defined cells within ROIs varied from 0 to ~0.8 and was greatest in the temporal periphery for most subjects, possibly due to differences in retinal thickness, vascular topography, or pigment concentration. Apparent RPE cell areas in older eyes were unexpectedly among the smallest.
For the first time, we show lipofuscin AF in AOSLO imaged in vivo over a large retinal area in many normal human subjects. This approach may be limited in some subjects due to pigmentation variability in the fovea and lipofuscin accumulation in aging cells. Combined RPE cell morphometry and photoreceptor topography may be useful for evaluating retinal disease or efficacy of vision restoration methods.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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