Velocity-based optoretinography for clinical applications using a commercial OCT platform.

Abstract

Purpose : OCT-based optoretinography (ORG) has emerged recently as a promising method for measuring light-evoked responses in photoreceptors. We have previously reported an optoretinographic approach based on a standard, research-grade OCT system without adaptive optics (AO). The approach circumvents the need for adaptive optics (AO) by monitoring phase velocities in the OCT signal rather than its phase. The purpose of this work is to validate the same method using a commercial OCT system. These results further reinforce the conclusions that commercialization of the ORG is practical and that its use in clinical trials and routine ophthalmic care is realistic.

Methods : A commercial SD-OCT system (REVO FC 130; Optopol Technology; Zawiercie, Poland) was used. Key operational specifications were: B-scan rates of 520 Hz; imaging wavelength and bandwidth 850nm @ 50nm; axial and lateral resolutions of 5 μm (in tissue) and 18 μm (typical); serial B-scans subtended 0.75 mm on the retina and consisted of 250 A-scans each. The instrument’s fundus imaging source was used for ORG stimulus with the flash duration set to 23ms and a total photon count of 1.5 e⁷ / μm² (~35% bleaching of L and M photopigment). Data acquisition was synchronized with the flash to allow velocity-based signal processing. 350 B-scans (0.67 s) were acquired in each trial, with the flash delivered after 134 B-scans (0.35 s). Three male subjects without retinal disease were imaged (ages 32 (#1), 43 (#2), and 59 (#3)). Subjects were dark-adapted for 7 minutes before each ORG measurement. Images were acquired 3 deg nasal or temporal to the foveal center.

Results : Results from single trials exhibited OS velocity changes consistent with our previous study. The OS underwent a brief contraction after flash onset, followed by a slower, longer elongation. Examples from all three subjects are shown in Figure 1.

Conclusions : We demonstrated the feasibility of measuring light-evoked photoreceptor responses using a commercial system with a built-in stimulus lamp. Future plans include testing this system to detect functional deficits due to photoreceptor disease and modification of the stimulus source to deliver targeted chromatic stimuli.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.

 

Figure 1. Example, single trial velocity-based ORG signals measured in three healthy subjects. Example B-scans are shown for each subject (top). ORG details are shown for each subject (bottom).