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Christy K Sheehy, Alexandra Boehm, William S. Tuten, Ethan Bensinger, Brandon J Lujan, Austin Roorda; Multimodal System for Struture/Function Assessments. Invest. Ophthalmol. Vis. Sci. 2016;57(12):1698. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To demonstrate a system for high resolution structure/function assessments in the retina. The system is comprised of an SLO equipped with accurate high-speed eye-tracking to guide an OCT beam. It renders both high-resolution retinal images as well as perform fundus-guided perimetry (microperimetry).
The tracking scanning laser ophthalmoscope (TSLO) was optically combined, via dichroic beamsplitter, with a Bioptigen OCT system. The TSLO was equipped with 840 nm for retinal imaging and 532 nm for functional testing. A 5° scan field was used in order to accommodate fixational eye motion and maintain good image quality for tracking. Eye tracking at 960 Hz was achieved in real-time and eye motion signals were used to control timing of a visible light stimulus to assess cone-mediated sensitivity at targeted retinal locations. Additionally, voltage signals proportional to X-Y motion were generated by the TSLO, scaled, and added directly to X and Y galvo scanners of the OCT system to actively control for eye motion.The multimodal system was used to assess structure and function both within and adjacent to retinal lesions in two patients: P1 with diagnosed toxoplasmosis scarring and P2 with an unknown subclinical lesion. Visual sensitivity was measured using a 40-trial QUEST staircase with a yes/no response paradigm. Each location was tested 2-3 times.
The 532 nm stimulus delivery accuracy matched that previously reported for decrement stimuli with a TSLO system (0.66 arcmin), with the exception of additional error due to transverse chromatic aberration (TCA). TCA was minimized near the fovea using subjective alignment of IR and green light channels, but increased linearly by 0.28 arcmin/degree with increasing eccentricity (Thibos, 1987). While subject P2 showed no statistically significant change in sensitivity, P1 showed clear regions of compromised function. Two areas of absolute scotoma were found experimentally: one immediately adjacent to and one within the toxoplasmosis lesion. Additionally, elevated thresholds were found in areas appearing normal by both OCT and TSLO imaging.
By adding an additional wavelength for stimulus delivery, and combining the system with a Bioptigen OCT, the multimodal system was able to provide information regarding both structure and function in patients with focal retinal lesions. This system could be useful in clinical settings to better understand retinal disease progression.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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