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Fabio Feroldi, Sanam Mozaffari, Francesco LaRocca, Pavan K. Tiruveedhula, Patrick Gregory, B. Hyle Park, Austin John Roorda; Optoretinography in the human retina using AOOCT and AOSLO-based eye tracking. Invest. Ophthalmol. Vis. Sci. 2021;62(8):28.
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© ARVO (1962-2015); The Authors (2016-present)
Optoretinography is a novel technique that uses light-based measurements to reveal retinal activity. Adaptive optics optical coherence tomography (AOOCT) produces an optoretinogram by resolving individual photoreceptors and recording their physical/physiological responses to light stimuli. However, detecting the nanometer-scale changes measured by AOOCT to obtain optoretinograms is hampered by eye motion. In other laboratories, careful registration of a sequence of volume images is required. Here, we present a system whereby real time eye tracking based on adaptive optics scanning laser ophthalmoscopy (AOSLO) is used to correct the position of the AOOCT beam and compensate eye motion.
The custom AOOCT system is based on a swept source laser centered at 1040 nm with a sweep rate of 100 kHz and an axial resolution of 7 µm in tissue. A dichroic mirror combines the AOSLO and AOOCT beams, which share the AO correction but have independent scanning systems. AOSLO is used to visualize the photoreceptor layer in real time and report eye movement at a 960 Hz rate using strip-based registration. The AOOCT beam was stabilized on the retina by actuating a MEMS mirror in the beam path counter to the eye movement. A 100 ms long flash of narrowband light was deposited on a dark adapted retina to stimulate the photoreceptors. Nanometer-scale changes within a targeted set of cones were obtained by measuring the phase difference between the inner/outer segment junction and the cone outer segment tips as a function of time.
The physiological response of the photoreceptors was revealed as an elongation of the cone outer segment in response to the stimulus. By quantifying the physiological changes, we were able to identify cones belonging to different spectral sub-classes, and we confirmed the result over datasets acquired in separate occasions.
We were able to successfully quantify the response of individual photoreceptors to light stimuli, paving the way to obtain optoretinograms for classifying the cones and measuring other neural activity in the human retina.
This is a 2021 ARVO Annual Meeting abstract.
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