Optical coherence tomography in patients with Alpha IMS subretinal implant

Purpose: We analyzed optical coherence tomography (OCT) data from a prospective, interventional clinical study to determine changes in retinal thickness after implantation of the RETINA IMPLANT Alpha IMS. Methods: The RETINA IMPLANT Alpha IMS subretinal device (Retina Implant AG, Reutlingen, Germany) carries 1500 photodiodes, amplifiers and electrodes on a 9 mm chip. It has been developed to partially restore vision by stimulating the bipolar cells of the retina in patients suffering from profound photoreceptor loss due to degenerative diseases such as retinitis pigmentosa. Spectral domain OCT scans of 27 patients who received the Alpha IMS in a multi centre trial (ClinicalTrials.gov, NCT01024803) acquired with Spectralis OCT (Heidelberg Engineering, Heidelberg, Germany) or Cirrus OCT (Carl Zeiss Meditec AG, Jena, Germany) were analyzed using the built-in software to assess changes in retinal thickness anterior to the implant between two time points: within 6 weeks and 6 ± 1 months after implantation. Three thickness measurements were performed in each of the 4 quadrants of the retina anterior to the implant for each of the two visits. Statistical analyses were performed with IBM SPSS Statistics for Windows, Version 23.0 using paired samples t-test. The significance level was set at 5%. Results: Due to lack of fixation and common presence of nystagmus, images of a good enough quality to perform quantitative analyses in all 4 quadrants at each of the two time points were available from 15 patients. We observed no statistically significant change in the mean retinal thickness within 6 weeks (288 μm) and 6 ± 1 months (309 μm) after implantation of the Alpha IMS. The results of the detailed analysis for each of the 4 quadrants are shown in Table 1. Epiretinal membranes-if present-remained essentially stable and no proliferative vitreoretinopathy was observed in the areas evaluated. 2 Conclusions: In patients with RETINA IMPLANT Alpha IMS, it is possible to acquire OCT scans and assess the thickness of the retina anterior to the implant. No major changes (e.g. thinning of the retina induced by the implant, induction of epiretinal membranes/proliferative vitreoretinopathy in the analyzed areas) were found during the observation period. With more patients receiving subretinal implants and with advanced OCT technology, the data set will be extended to study possible changes in retinal structure in finer detail.