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 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.