Abstract
Purpose: We assessed the safety and efficacy of a technically advanced subretinal electronic implant, RETINA IMPLANT Alpha AMS, in end stage retinal degeneration in an interim analysis of two ongoing prospective clinical trials. The purpose of this article is to describe the interim functional results (efficacy).Methods: The subretinal visual prosthesis RETINA IMPLANT Alpha AMS (Retina Implant AG, Reutlingen, Germany) was implanted in 15 blind patients with hereditary retinal degenerations at four study sites with a follow-up period of 12 months (www.clinicaltrials.gov NCT01024803 and NCT02720640). Functional outcome measures included (1) screen-based standardized 2- or 4-alternative forced-choice (AFC) tests of light perception, light localization, grating detection (basic grating acuity (BaGA) test), and Landolt C-rings; (2) gray level discrimination; (3) performance during activities of daily living (ADL-table tasks).Results: Implant-mediated light perception was observed in 13/15 patients. During the observation period implant mediated localization of visual targets was possible in 13/15 patients. Correct grating detection was achieved for spatial frequencies of 0.1 cpd (cycles per degree) in 4/15; 0.33 cpd in 3/15; 0.66 cpd in 2/15; 1.0 cpd in 2/15 and 3.3 cpd in 1/15 patients. In two patients visual acuity (VA) assessed with Landolt C- rings was 20/546 and 20/1111. Of 6 possible gray levels on average 4.6 ± 0.8 (mean ± SD, n = 10) were discerned. Improvements (power ON vs. OFF) of ADL table tasks were measured in 13/15 patients. Overall, results were stable during the observation period. Serious adverse events (SAEs) were reported in 4 patients: 2 movements of the implant, readjusted in a second surgery; 4 conjunctival erosion/dehiscence, successfully treated; 1 pain event around the coil, successfully treated; 1 partial reduction of silicone oil tamponade leading to distorted vision (silicon oil successfully refilled). The majority of adverse events (AEs) were transient and mostly of mild to moderate intensity.Conclusions: Psychophysical and subjective data show that RETINA IMPLANT Alpha AMS is reliable, well tolerated and can restore limited visual functions in blind patients with degenerations of the outer retina. Compared with the previous implant Alpha IMS, longevity of the new implant Alpha AMS has been considerably improved. Alpha AMS has meanwhile been certified as a commercially available medical device, reimbursed in Germany by the public health system.
Highlights
Inherited retina degenerations (IRD) are a broad group of genetic retinal disorders of varying severity with retinitis pigmentosa being the most common form
The results showed that the earlier version of the implant, the RETINA IMPLANT Alpha IMS is able to restore low but useful vision in patients blind from hereditary degenerations of the photoreceptors with visual acuities up to 20/546, as measured by standardized Landolt C-rings, and 45% of patients could recognize object shapes or rough details in everyday life
21 patients were screened for RETINA IMPLANT Alpha AMS
Summary
Inherited retina degenerations (IRD) are a broad group of genetic retinal disorders of varying severity with retinitis pigmentosa being the most common form. Its estimated prevalence is between 1 in 3,000–7,000 (Ferrari et al, 2011) Most of these retinal degenerations lead to a progressive visual loss and eventually to blindness caused by photoreceptor degeneration and atrophy. As these diseases are genetically heterogeneous, a causative cure is not yet available. Several approaches tested in clinical trials in the last 10 years are close to, or have reached, the state of approval in the USA or Europe. Further alternative approaches are being tested clinically and preclinically worldwide such as pharmacotherapy, stem cell research or optogenetics (Busskamp et al, 2012; Singh et al, 2013; Scholl et al, 2015)
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