Insertion of a subretinal prosthesis system for retinitis pigmentosa

4 Efficacy

This section describes efficacy outcomes from the published literature that the Committee considered as part of the evidence about this procedure. For more detailed information on the evidence, see the interventional procedure overview.

4.1 In a case series of 6 patients, improvements in visual acuity (measured by the smallest Early Treatment of Diabetic Retinopathy study [ETDRS] letters that could be read) were reported in 3 patients. Visual acuity improved in 1 patient from a Snellen equivalent of 20/800 before the procedure to 20/200 at 6 month follow‑up. In the second patient, visual acuity improved from 20/1600 before the procedure to 20/400 at 6 month follow‑up. The third patient had been unable to read ETDRS letters before the procedure but had a visual acuity of 20/1600 at 18 month follow‑up.

4.2 In a case series of 9 patients, light perception thresholds were considerably better when prosthesis systems were switched on compared against when they were switched off. All patients were able to perceive light when their prosthesis systems were switched on, at maximum follow‑up of 9 months. No further details were provided.

4.3 In a case series of 29 patients, patients were asked to indicate whether they saw light when a black screen was briefly illuminated with 1 or 2 flashes of light: a correct response rate of 75% was considered a pass. At 1 month follow‑up, 78% of patients passed the test when their prosthesis systems were switched on while 10% of patients passed the test when their prosthesis systems were switched off (p<0.05). At 12 month follow‑up, 40% of patients passed the test when their prosthesis systems were switched on while no patients passed the test when their prosthesis systems were switched off (p<0.05).

4.4 In the case series of 29 patients, patients were asked to indicate the direction (up, down, left or right) of the pointed end of a white wedge on a black screen: a correct response rate of 62.5% was considered a pass. At 1 month follow‑up, 38% of patients passed the test when their prosthesis systems were switched on while no patients passed the test when their prosthesis systems were switched off (p<0.05). At 12 month follow‑up, 18% of patients passed the test when their prosthesis systems were switched on while no patients passed the test when their prosthesis systems were switched off (not significant).

4.5 In the case series of 9 patients, patients were asked to indicate the direction (up, down, left or right) of the pointed end of a white wedge on a black screen. Seven patients correctly indicated the direction in which the wedge was pointing when their prosthesis systems were switched on, at maximum follow‑up of 9 months.

4.6 In the case series of 29 patients, patients were asked to indicate the direction of a white polka dot pattern that moved across a black screen: a correct response rate of 62.5% was considered a pass. At 1 month follow‑up, 14% of patients passed the test when their prosthesis systems were switched on while no patients passed the test when their prosthesis systems were switched off (not significant). At 12 month follow‑up, none of the patients passed the test when their prosthesis systems were switched on or off (not significant).

4.7 In the case series of 9 patients, patients were asked to count, locate and identify 4 of 6 possible geometric shapes that were placed on a black table cloth. The mean number of shapes counted was 2.8 when prosthesis systems were switched on, compared against 0.5 when prosthesis systems were switched off, at maximum follow‑up of 9 months (p=0.012). The mean number of shapes located was 2.2 when prosthesis systems were switched on, compared against 0.5 when prosthesis systems were switched off (p=0.012).The mean number of shapes correctly identified was 1 when prosthesis systems were switched on, compared against 0.1 when prosthesis systems were switched off (p=0.018).

4.8 Specialist advisers listed key efficacy outcomes as improvement of visual function (recognition and discrimination of words or objects, as well as perception of light, movement or direction), performance in spatial or motor tasks (including activities of daily living), and improved quality of life.