Background: Post-implantation visual outcomes in patients with the Argus II Retinal Prosthesis is dependent on a multitude of factors including the positioning of the electrode array on the retina. The purpose of this study is to determine whether the average electrode array-retina gap distance correlates with objective visual function outcomes and sensitivity detection thresholds in patients implanted with the Argus II Retinal Prosthesis.
Methods: 5 patients with implantation of the Argus II Retinal Prosthesis were enrolled in this single-institution retrospective study. Patient demographics were collected from medical records. Visual function data (Square Localization [SL] and Direction of Motion [DOM]) and Optical Coherence Tomography (Cirrus HD-OCT) images were extracted retrospectively from the Argus II Retinal Prosthesis Post-Approval study. Visual function tests were performed with the device OFF and ON at each study visit. Electrode array-retina gap distances were measured at each of the array’s 60 electrodes using the Cirrus HD-OCT software in both the nasotemporal and superoinferior planes. Data was obtained at baseline, and post-operative month 1, month 3, month 6, and year 1. Sensitivity detection thresholds were obtained at the initial programming visit and each reprogramming session.
Results: 1 of 53 patients had a significant average improvementperformed significantly better in the SL visual function test and 0 of 5 had a significant average improvement in the DOM visual when the testing with the device was ON compared to OFF (p < 0.05). Electrode array-retina gap distance did not show a significant correlation with changes in SL . Patients that worsened in visual function (r = 0.20; p = > 0.05) or DOM visual function (r = -0.18; p = > 0.05). In addition,testing with the device ON in both SL and DOM testing had a statistically significant decrease in performance. The electrode array-retina gap distance did not show a significant correlation with was found to effect performance in SL testing in a patient-dependent manner. No effect was found between the electrode-array gap distance and DOM testing or sensitivity detection threshold (r = -0.01; p = 0.98)..
Conclusion: Our results demonstrate that the average electrode array-retina gap distance does not correlate with changes in objectivemay affect visual acuity function or sensitivity detection thresholdsoutcomes in SL testing in a cohort ofcertain patients implanted with the Argus II Retinal Prosthesis. Therefore, and the direction and magnitude of this effect is likely patient-dependent. Furthermore, complete apposition between the electrode array and retina may not always be necessary to achieve optimal visual outcomes.