Insertion of a subretinal prosthesis system for retinitis pigmentosa

In a case series of 9 patients, 75 adverse events occurred within 1 year of prosthesis implantation. These included:

• 'retinal break' without detachment – 2 cases (3% of adverse events): neither resolved (no further details provided)

• conjunctival erosions above the external part of the cable, suture erosions through the conjunctiva, or both – 12 cases (16% of adverse events): all resolved without sequelae (no further details provided)

• conjunctival hyperaemia – 6 cases (8% of adverse events): all resolved without sequelae (no further details provided)

• retinal vascular leakage and neovascularisation – 10 cases (13% of adverse events): 2 occurred before device implantation. Nine did not resolve. In 1 patient, retinal vascular leakage resulted in damage to eye structures and loss of light perception

• retinal haemorrhage – 7 cases (9% of adverse events): all resolved without sequelae (no further details provided)

• ocular hypertension – 8 cases (11% of adverse events): all resolved without sequelae (no further details provided)

• paraesthesia of the skin (location not specified) – 3 cases (4% of adverse events): all resolved without sequelae (no further details provided)

• epistaxis – 2 cases (3% of adverse events): both resolved without sequelae (no further details provided).

In the case series of 9 patients a single occurrence of each of the following was reported within 1 year of prosthesis implantation: intraoperative perforation of the choroid, intraoperative contact of the optic nerve head with the implant, postoperative bleeding, contusion of the eyelid and periocular area, mucopurulent conjunctivitis, a peripheral corneal dent, acute iritis, retinal detachment with a retinal break, ocular pain, dizziness, headache, and chronic pain (unspecified location). Intraoperative perforation of the choroid and intraoperative contact of the optic nerve head with the implant both occurred in the same patient and resulted in loss of residual vision in the study eye. All other adverse events resolved without sequelae.

Device failure was reported in 6 patients in another case series of 9 patients. Cable defects resulted in intraoperative cable breaks in 3 patients: this led to device failure after 3 to 9 months. Corrosion of the periphery of the microchip was reported in 3 patients after 250 days in situ. The chip gradually lost function and the patients opted for explantation of the device.

In addition to safety outcomes reported in the literature, specialist advisers are asked about anecdotal adverse events (events which they have heard about) and about theoretical adverse events (events which they think might possibly occur, even if they have never done so). For this procedure, specialist advisers listed the following anecdotal adverse events: minor intraoperative subretinal bleeding, and the implant malfunctioning, requiring removal and replacement. They considered that the following were theoretical adverse events: intraocular haemorrhage, glaucoma, photopsia, choroidal neovascularisation, thermal injury to neurons, choroidal or retinal circulation abnormalities, and complications associated with vitrectomy.