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Meghan Marino, Lucy Xu, Aleksandra V Rachitskaya, Alex Yuan; Argus® II array-retina distances correlate with patient thresholds. Invest. Ophthalmol. Vis. Sci. 2017;58(8):4182.
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© ARVO (1962-2015); The Authors (2016-present)
Prior studies have shown the importance of Argus II Retinal Prosthesis array placement. The current retrospective study examined if the gap between the Argus array and the retina correlated to electrical stimulation thresholds in a cohort of Argus II patients implanted at the Cole Eye Institute. We hypothesized that patients with smaller distances will have lower electrical thresholds.
Distance between the array and the retina was measured from spectral domain optical coherence tomography (OCT) macular cube 512x128 scans by three independent graders. The distance between the array and retina at each of the four corner electrodes, and the maximum gap were manually measured with software calipers. Perceptual threshold was previously measured. The average threshold of 4 electrodes at each corner was used for threshold measurement. Average of 9 electrodes in a 3x3 grid was used for the area of maximum gap. The intraclass coefficient (ICC) was used to determine the graders’ inter-rater reliability. Spearman’s rank correlation coefficient was calculated to determine the correlation between array -retina distance (averaged across the graders) and the threshold.
Six patients were included for the study. The ICC between the three graders at the corners was 0.82 (temporal), 0.70 (inferior), 0.94 (superior) and 0.66 (nasal). The ICC for the maximum gap was 0.96. Five patients were included for the Spearman’s rank correlation between array-retina distance (average of graders) and threshold values (1 patient was excluded because thresholds were measured at a different frequency). When the location for the maximum gap was different amongst the three graders, the average for each grid threshold (3x3 grid) at each location was used. The Spearman’s rank coefficient for the corner electrodes was 0.56 (p = 0.01) and the maximum gap was 0.60 (p = 0.28). The overall Spearman’s rank coefficient was 0.48 (p = 0.01), which supports our hypothesis.
Manual measurements of the array-retina distance demonstrated high inter-rater reliability, despite some variation likely due to motion or imaging artifacts. There was a statistically significant correlation between array-retina distance and thresholds. These results suggest minimizing array-retina distance is important for obtaining low thresholds, which could possibly translate to better visual outcomes.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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