Wide field topographical choroidal thickness measurement following binocular, eye-tracking mapped, short-term optical defocus
Investigative Ophthalmology & Visual Science
Changes in choroidal thickness observed after short-term optical defocus support the theory that eye growth is optically guided. Most previous studies used a monocular optical appliance to manipulate the potential myogenic factors, which may introduce confounders by disrupting the natural functionality of the visual system. We explored if optical defocus generated by an ecological environment can predict choroidal thickness changes while habitual binocular vision is maintained. A custom 3D eye tracker (Pupil Labs Core, Pupil Labs GmbH, Germany) monitored compliance to fixating the hand-held device (at ~3D, 30min) to estimate dioptric demand over a wide field of view (with magnitudes of ~0.5D up to 4.5D) using a miniature time-of-flight camera (Pico Flexx, PMD Technologies AG, Germany). The spatially diverse peripheral environment around the hand-held device generated an optical defocus at the retinal periphery. Temporal accumulation of dioptric demand was mapped onto a wide field of choroidal locations using gaze direction estimates from the 3D Eye-Tracker. Intra- (3 repeats per participants, pre and post intervention) and inter- participant topographical choroidal maps were landmark matched and subtended a congruent visual field. Local and regional choroidal thickness exposed to different dioptric defocus were evaluated for change with a global, sensitivity enhanced model. The average intra-participant random error of choroidal thickness estimation (1×s.d. at each pixel within the topographical map, n ~100k) could be reduced by ~20% to 5.2 ± 2.1 µm by truncation of outliers. No significant difference in thickness change was found for choroidal regions exposed to different optical defocus (GLM n=21, eye p=0.62, area p=0.21, eye*area p=0.46). Some apparently randomly positioned loci showed significant difference (Fig. 1). A change in topographical choroidal thickness consistent with local relative dioptric defocus was not found. The proposed topographical choroidal thickness model showed a sensitivity comparable to theoretical longitudinal resolution of swept-source OCT (wavelength 1060 nm). The presented methods and device can contribute to a better understanding of the ecologically valid dioptric landscape, and with further development, may provide further insight into short-term myopia models. This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.