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Kari Viljami Vienola, Min Zhang, Jose Sahel, Ethan A Rossi; Visualizing near-infrared autofluorescence from retinal pigment epithelial cells in AMD using multi-wavelength excitation. Invest. Ophthalmol. Vis. Sci. 2019;60(11):PB0183.
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To visualize determine the efficacy of multi-wavelength excitation for imaging retinal pigmented epithelial cells (RPEs) in vivo using near-infrared autofluorescence (NIRAF) in healthy controls and age-related macular degeneration (AMD) patients.
NIRAF imaging of the RPE was performed in healthy volunteers and patients diagnosed with AMD using a multi-channel adaptive optics scanning laser ophthalmoscope (AOSLO). Two separate superluminescent diodes (centered at 663 nm and 795 nm) were used for NIRAF excitation and confocal reflectance imaging. The time-averaged optical power at pupil plane was 50 µW for 663 nm and 180 µW for 795 nm with a 1.5 deg. field of view. NIRAF signal was collected in an emission band from 814 to 870 nm. A 2.1 Airy disk diameter pinhole was placed in front of the NIRAF detector and an automated algorithm was used for pinhole positioning to maximize the NIRAF signal. The NIRAF images were co-registered using the corresponding reflectance channel(s) as the reference for eye motion.
Individual RPE cells were successfully imaged in the macula of healthy controls and AMD patients with either 663 nm excitation, 795 nm excitation, or simultaneous excitation with both. Shorter wavelength excitation alone produced a slightly noisier image; however, this may be due to different focusing of the two wavelengths due to chromatic aberration. RPE morphology was similar between the two excitation wavelengths with a darker center and hyper autofluorescent border, consistent with the known hexagonal mosaic of RPE cells.
Each excitation wavelength alone was able to produce NIRAF emission capable of resolving individual RPE cells. Combined excitation resulted in a more robust signal. Ongoing work is aimed at determining whether this emission arises from the same structures within the RPE and how NIRAF excited with these different wavelengths may be altered in AMD. Simultaneous excitation of RPE fluorophores with a combination of wavelengths may improve imaging of individual RPE cells.
This abstract was presented at the 2019 ARVO Imaging in the Eye Conference, held in Vancouver, Canada, April 26-27, 2019.
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