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Zhuolin Liu, Furu Zhang, Daniel Hammer; Impaired cone function in drusen regions revealed by phase-sensitive adaptive optics OCT. Invest. Ophthalmol. Vis. Sci. 2021;62(8):12.
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© ARVO (1962-2015); The Authors (2016-present)
To study how cone photoreceptor function is affected by drusen.
Three subjects with no diagnosed ocular disease were imaged with the FDA adaptive optics (AO) imager . Two subjects were found to have drusen in the macula from previous AO imaging. Brief synchronous flashes of visible stimulus were delivered to the retina with a Maxwellian view illumination channel co-aligned to the AO-OCT beam. Two stimulus sources (centered at 530 nm and 625 nm) were selected to change the relative response of the cones. Seven 1° field of view AO-OCT videos were acquired with each stimulus. The phase difference between cone IS/OS and COST signals was calculated and converted to optical path length change (△OPL). We then analyzed cone response using principal component analysis and classified cone types (L-, M-, and S-) following the methods described by Zhang et al. . To avoid inter subject variability, cone responsivity and outer segment (OS) length were compared between non-drusen and drusen regions.
Despite the presence of drusen, both IS/OS and COST reflections were present above regions of small drusen (Fig.1 A). The responses of the three cone types were distinctly separated in this study (Fig.1 B-C). In S1, the cones above a ~150-µm diameter drusen (drusen 1) have significant weaker response compared to the non-drusen region for both L- (drusen: 639.4; non-drusen: 680.7; p=0.04) and M- (drusen: 309.6; non-drusen: 402.5; p<0.01) cones (Fig.1 C-D). The weaker cell response also prevented separation of the third (S-) cluster from the other two in the drusen region. Intriguingly, the L-cones above drusen 1 had a weaker response to green stimulus compared to the cones in the non-drusen region, suggesting the L- cones spectral sensitivity is affected by drusen. Weaker cone response was also found in the drusen 2 region, with no change in cone spectral sensitivity. Cones in the drusen area also tended to have shorter OS length, suggesting a structure-function correspondence. Similar results were found in S2, but no regional difference in cone functionality was evident in S3, who had no observable drusen.
The presence of drusen results in a weaker cone response to visible stimulation. The ability to measure individual cone function in drusen regions may lead to new functional biomarkers for detection of early age-related macular degeneration.
This is a 2021 ARVO Annual Meeting abstract.
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