Retinal implant provides artificial sight for the blind

Retinal prosthesis systems (RPS) enable patients with retinal dystrophies to identify letters and words, confirms a new study.

A team led by Dr Lyndon da Cruz, NIHR Biomedical Research Centre for Ophthalmology, Moorfields Eye Hospital, London, UK, conducted a prospective, internally controlled, multicentre trial on 28 patients, with light perception vision, who underwent treatment with the Argus II system. Each subject received the retinal implant and underwent forced-choice letter identification and open-choice word identification tests.

Mean ±SD percentage of correct letter identification for 21 of the 28 patients were the letters L, T, E, J, F, H, I, U at 72.3±24.6% with the RPS on and 17.7±12.9% with the RPS off. For letters A, Z, Q, V, N, W, O, C, D, M the rate was 55.0±27.4% with the system on, compared to 11.8%±10.7% with the system off.

Six patients were able to consistently read smaller letters, with a minimum of 0.9 cm at a 30 cm distance and four subjects correctly identified unrehearsed two, three and four letter words.

The results indicated reproducible spatial resolution when patients correctly identified letters and words. With stable, long-term function, the implant represents significant progress in the development of artificial sight.

The abstract can be read in the latest online issue of the British Journal of Ophthalmology.