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Teresa Shao Lin Tee, Ian Murray, Tariq Aslam, Ivan Y-F Leung; Detection of peak fundus autofluorescence (FAF) signals and hyperautofluorescent spots using confocal scanning laser ophthalmoscope (cSLO) with 30° and 55° lenses. Invest. Ophthalmol. Vis. Sci. 2014;55(13):3428.
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© ARVO (1962-2015); The Authors (2016-present)
To compare central 30° and 55° FAF signals and to characterise hyperautofluorescent spots in the central retina of normal young subjects.
Eight normal young adults (range: 25-32 years old) were recruited and subjected to FAF imaging using a cSLO (Spectralis, Heidelberg Engineering, Germany) with excitation at 488 nm. Non-normalized images were captured with field of view at 30° and 55° in high-speed automatic real-time (ART) mode by averaging 100 frames. Using Photoshop CS5 (Adobe Systems Incorporated, USA), 3 to 4 repeated images (496x496 pixels) were aligned and superimposed with a grid of 23 (30° images) or 42 (55° images) sampling squares. The squares, each 5x5 pixels in size, were 5 pixels apart and arranged along 8 cardinal meridians (temporal, superior-temporal, superior, superior-nasal, nasal, inferior-nasal, inferior and inferior-temporal). The average gray level (GL) was tabulated for each square to identify the peak FAF along each meridian.
The peak FAF signals along the 8 cardinal meridians were symmetrical between right and left eyes. Peak FAF found in the superior-nasal region was much further from the fovea than the other meridians in 55° images but not in 30° images (P<0.01). Peak FAF positions in the superior and superior-nasal meridians matched well with the highest rod density map in human morphometric data [Curcio et al., J Comp Neurol. 1990]. Hyperautofluorescent spots, which were 28GL to 48GL brighter than background and varied from 62µm to 109µm in size, were found in images from 3 out of 8 subjects.
The presence of the FAF peak at the superior-nasal retina in 55° images suggests that the limited field of view of 30° images obscured the FAF peak at the periphery. Fifty-five degree wide-angle imaging is superior for semi-quantitative analysis of FAF images. Hyperautofluorescent spots in normal retina can be captured with both 30° and 55° lenses. The physiological importance of the hyperautofluorescent spots needs further investigation.
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