Insertion of an epiretinal prosthesis for retinitis pigmentosa

# Recommendations
Current evidence on the safety and efficacy of insertion of an epiretinal prosthesis for retinitis pigmentosa is limited in quality and quantity. Therefore, this procedure should only be used in the context of research.
NICE encourages further research on this technology. Outcomes should include the impact on quality of life and activities of daytoday living, and durability of implants. NICE may update the guidance on publication of further evidence.# Indications and current treatments
Retinitis pigmentosa is the encompassing term for a group of degenerative eye conditions that cause progressive loss of retinal photoreceptors. The disease is often inherited. Patients initially experience ring scotoma and night vision problems which, in most cases, slowly progress and lead to the loss of all peripheral vision. Central vision is usually preserved until late stages of the disease, but can be lost earlier with severe disease.
Conservative treatments are aimed at early identification and treatment of complications such as cataract or macular oedema. Some newer treatments aim to slow the progression of the condition. Surgical treatments are being developed, including subretinal and epiretinal prostheses, as well as optic nerve implants to restore basic sight.# The procedure
Retinitis pigmentosa causes loss of retinal photoreceptors but inner retinal cells (ganglion and bipolar cells) remain intact. Insertion of an epiretinal prosthesis aims to restore perception of light, movement and shapes by surgically implanting an array of electrodes onto the retina. The electrodes emit electrical impulses to stimulate the sensory neurons of surviving retinal cells, which send visual information to the brain.
An epiretinal prosthesis system has 2 key components: an eye implant and external camera system. The eye implant consists of an episcleral receiver unit and an epiretinal electrode array. The external camera system comprises an eyeglassmounted video camera and a small patientworn computer (video processing unit ).
Insertion of the eye implant is performed with the patient under general anaesthesia, usually in 1 procedure that may take several hours. The surgeon performs core and peripheral vitrectomies, followed by dissection of any epiretinal membrane in the area where the electrode array will be placed. The electrode array is then inserted through a temporal sclerotomy and secured onto the retina using a retinal tack. It is connected to the receiver unit by a cable that penetrates the sclera in the pars plana.
After surgery, when the implant is set up and fully functional, the video camera records realtime images and sends them to the VPU. The VPU converts the images into data that are wirelessly transmitted to the episcleral receiver unit. The episcleral receiver unit relays the data to the electrode array, which produces electrical impulses that bypass damaged photoreceptors and stimulate the retina's remaining cells. Visual information is then transmitted by the optic nerve to the brain, creating a visual percept.# 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.
The Committee considered evidence from 7 case series that included a total of 129 patients. However, there is likely to have been considerable overlap between studies with patients taking part in more than 1 study.
In a case series of 30 patients implanted with an epiretinal prosthesis, improvements in visual acuity were reported in 23% (7/30) of patients at followup of up to 2.7 years. Visual acuity improved from worse than 2.9 logMAR (logarithm of the minimum angle of resolution) to between 2.9 and 1.6 logMAR (p value not reported).
In the case series of 30 patients, patients were asked to locate a white square that randomly appeared on a black LCD touchscreen. Significantly better square localisation test results were reported in 96% (27/28) of patients when their prosthesis systems were switched on. No further details were provided.
In the case series of 30 patients, patients were asked to indicate the path of a white bar that swept across a black LCD touchscreen. Significantly better direction of motion test results were observed in 57% (16/28) of patients when their prosthesis systems were switched on. No further details were provided.
In the case series of 30 patients, patients were asked to stand in the centre of a room, or offset left of centre by 3 feet, or offset right of centre by 3 feet. They were asked to find a rectangular 'door' 20 feet away and to place their hand on it. The mean success rate was 60% when the prostheses were switched on compared against 5% when the prostheses were switched off, at 24month followup.
In a case series of 6 patients, the mean percentage of successful grasps of a white cube placed on a black surface was 69% when prostheses were switched on compared against 0% when prostheses were switched off, at 3year followup. There was no significant difference between the proportion of successful grasps when patients' eyes were 'patched' (both eyes taped closed) or 'unpatched'.
Specialist advisers listed key efficacy outcomes as improvement in vision (recognition of words or objects, as well as perception of light, movement or direction), performance in spatial or motor tasks and improved quality of life.# Safety
This section describes safety 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.
All the adverse events presented to the Committee came from a single case series of 30 patients; each affected patient may have experienced more than 1 adverse event.
Serious retinal complications were reported in 10% (3/30) of patients. A retinal tear was reported in 1 patient (timing not reported and no further details were provided). Rhegmatogenous retinal detachment that needed surgical repair was reported in 1 patient. Tractional retinal detachment was reported in 1 patient at 5month followup: the patient had incurred blunt trauma to the eye with the implant, resulting in proliferative vitreoretinopathy that progressed to retinal detachment. This was repaired by vitrectomy, partial retinectomy and silicone oil.
Replacement of retinal tacks was needed within the first few days of implantation in 7% (2/30) of patients.
Conjunctival dehiscence was reported in 10% (3/30) of patients. Neither the timing nor the clinical significance of these dehiscences was described. They were treated by additional sutures with or without placement of additional tissue.
Conjunctival erosion was reported in 7% (2/30) of patients. Timing of occurrence was not reported.
Presumed endophthalmitis was reported, within 8 weeks of surgery, in 10% (3/30) of patients. This resolved in all cases with antibiotic treatment.
Hypotony was reported in 10% (3/30) of patients within 1 year of surgery. All cases of hypotony needed surgical treatment: 2 patients needed intraocular silicone tamponades and 1 patient had the implant removed.
Severe inflammatory uveitis was reported in 1 patient. Timing of occurrence was not reported and no further details were provided.
Intraocular inflammation, hypotony without choroidal detachment, suture irritation and ocular pain were reported in up to 23% (7/30) of patients. All were reported as nonsevere events. No exact figures were reported, timing of occurrence was not reported, and no further details were provided.
Inflammatory conjunctivitis, corneal filaments, epiretinal membrane, high intraocular pressure (controlled by antiglaucoma medications), epiphora, mild hyphaema, inflammatory uveitis with few keratic precipitates, and mild vitreous haemorrhage were reported in up to 10% (3/30) of patients. All were reported as nonsevere events. No exact figures were reported, timing of occurrence was not reported, and no further details were provided.
A single occurrence was reported of each of the following: limited conjunctival dehiscence, corneal abrasion, mild peripheral corneal vascularisation, cystoid macular oedema, decrease in light perception, dry eye, transient headache, iris vessel engorgement, stable tractional retinal detachment, transient nausea, transient increased nystagmus, scleritis, and transient vertigo. Each occurrence was considered nonsevere.
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 did not highlight any anecdotal adverse events. They considered that the following were theoretical adverse events: loss of residual existing vision, phthisis bulbi, suprachoroidal haemorrhage, secondary neovascularisation, allergic reaction to the implant, failure of the implant, extrusion of the implant, and complications associated with vitrectomies.# Further information
For related NICE guidance, see the NICE website.

# Information for patients
NICE has produced information on this procedure for patients and carers (information for the public). It explains the nature of the procedure and the guidance issued by NICE, and has been written with patient consent in mind.# About this guidance
NICE interventional procedures guidance makes recommendations on the safety and efficacy of the procedure. It does not cover whether or not the NHS should fund a procedure. Funding decisions are taken by local NHS bodies after considering the clinical effectiveness of the procedure and whether it represents value for money for the NHS.
This guidance was developed using the NICE interventional procedures guidance process.
We have produced information for the public explaining this guidance. Information about the evidence the guidance is based on is also available.
NICE produces guidance, standards and information on commissioning and providing highquality healthcare, social care, and public health services. We have agreements to provide certain NICE services to Wales, Scotland and Northern Ireland. Decisions on how NICE guidance and other products apply in those countries are made by ministers in the Welsh government, Scottish government, and Northern Ireland Executive. NICE guidance or other products may include references to organisations or people responsible for commissioning or providing care that may be relevant only to England.
Your responsibility
This guidance represents the views of NICE and was arrived at after careful consideration of the available evidence. Healthcare professionals are expected to take it fully into account when exercising their clinical judgement. This guidance does not, however, override the individual responsibility of healthcare professionals to make appropriate decisions in the circumstances of the individual patient, in consultation with the patient and/or guardian or carer.
Implementation of this guidance is the responsibility of local commissioners and/or providers. Commissioners and providers are reminded that it is their responsibility to implement the guidance, in their local context, in light of their duties to have due regard to the need to eliminate unlawful discrimination, advance equality of opportunity and foster good relations. Nothing in this guidance should be interpreted in a way that would be inconsistent with compliance with those duties.
Copyright
 National Institute for Health and Care Excellence 2015. All rights reserved. NICE copyright material can be downloaded for private research and study, and may be reproduced for educational and not-for-profit purposes. No reproduction by or for commercial organisations, or for commercial purposes, is allowed without the written permission of NICE.
ISBN: 978-1-4731-1141-7