High Visual Acuity Retinal Prosthesis: Understanding Limitations and Advancements Toward Functional Prosthetic Vision
Retinal prostheses have been in development for the past 20 years. These devices interface with retinal tissue to restore vision for patients suffering from degenerative retinal diseases such as retinitis pigmentosa (RP) or age-related macular degeneration (AMD). Of the first-generation devices, the Argus II from Second Sight Medical Products has become the first retinal prosthesis to receive FDA approval (2014) and CE mark (2011) to treat retinitis pigmentosa. As an initial attempt at a functioning retinal prosthesis, the Argus II is appropriately hailed as a breakthrough; however, it is approved only for severe advanced retinitis pigmentosa with NLP or bare LP vision1 and the actual vision restoration it accomplishes is subject to debate. While the early results from first-generation prostheses are encouraging, the restored visual acuity results are still well below the 20/200 threshold and average below 20/1,000. To understand the low visual function results from current prosthesis and evaluate the possible improvements in outcomes offered by next generation implants, it is necessary to examine the underlying scientific considerations that constrain their design.