Retinal Anatomy and Electrode Array Position in Retinitis Pigmentosa Patients After Argus II Implantation: An International Study

Purpose: To assess the retinal anatomy and array position in Argus II retinal prosthesis recipients. Design: Prospective, noncomparative cohort study. Methods: SETTING: International multicenter study. PATIENTS: Argus II recipients enrolled in the Post-Market Surveillance Studies. PROCEDURES: Spectral-domain optical coherence tomography images collected for the Surveillance Studies (NCT01860092 and NCT01490827) were reviewed. Baseline and postoperative macular thickness, electrode-retina distance (gap), optic disc–array overlap, and preretinal membrane presence were recorded at 1, 3, 6, and 12 months. MAIN OUTCOME MEASURES: Axial retinal thickness and axial gap along the array's long axis (a line between the tack and handle); maximal retinal thickness and maximal gap along a B-scan near the tack, midline, and handle. Results: Thirty-three patients from 16 surgical sites in the United States and Germany were included. Mean axial retinal thickness increased from month 1 through month 12 at each location, but reached statistical significance only at the array midline (P =.007). The rate of maximal thickness increase was highest near the array midline (slope = 6.02, P =.004), compared to the tack (slope = 3.60, P <.001) or the handle (slope = 1.93, P =.368). The mean axial and maximal gaps decreased over the study period, and the mean maximal gap size decrease was significant at midline (P =.032). Optic disc–array overlap was seen in the minority of patients. Preretinal membranes were common before and after implantation. Conclusions: Progressive macular thickening under the array was common and corresponded to decreased electrode-retina gap over time. By month 12, the array was completely apposed to the macula in approximately half of the eyes.