Do retinal implants provide long-term efficacy and safety and improve implantees' quality of life? A Systematic Literature Review

Abstract

Objective: Severe visual impairment and blindness are considered to be among the most feared disabilities worldwide (Chader et al. 2009). Approximately half of all visual impairments are associated with retinal disorders (Özmert and Arslan 2019). Degenerative retinal conditions such as retinitis pigmentosa (RP) and dry age-related macular degeneration (AMD) can result in severe vision loss and blindness due to a progressive loss of the retinal photoreceptors (Özmert and Arslan 2019; Ayton et al. 2020). Unfortunately, the therapy possibilities and options for patients with advanced stages of these retinal degeneration conditions are limited and any vision restoration is minimal (Chader et al. 2009; Ayton et al. 2020). Retinal implants have been developed and have emerged as novel interventions to restore some degree of vision in patients with severe vision loss due to these retinal degenerative diseases (Özmert and Arslan 2019). This review evaluates the long-term efficacy and safety of various types of retinal implants (epiretinal, subretinal and suprachoroidal) over a follow-up period of at least one year. In addition, the impact that these retinal implants have on the recipient’s quality of life is also assessed. Study design: A systematic search of the Web of Science, PubMed, Medline, Scopus, Cochrane Library and Embase databases was conducted and 222 papers were found. After removing 105 duplicate papers, 117 unique papers remained for eligibility screening, initially by title and abstract and then full-text screening. This process resulted in 13 studies which satisfied the inclusion criteria for the current review and were taken forward to the critical appraisal. Critical appraisal was performed using the Critical Appraisal Skills Programme (CASP) and the Joanna Briggs Institute (JBI) critical appraisal checklists appropriate for the study design. At this stage, one further paper was excluded from the review due to its poor quality. Consequently, 12 studies progressed to the data extraction stage using a tool adapted from a similar review by Hallum and Dakin (2021). Results: All of the included studies were single-arm, prospective, non-randomised clinical trials, except for one which was a retrospective interventional case series. There was considerable heterogeneity in terms of sample size, population, duration of follow-up, and intervention type. Therefore, narrative synthesis was utilised for the purpose of data synthesis. The results were encouraging and indicated that different retinal implant technologies were effective at restoring some degree of vision for blind patients. They improved visual function, functional vision and the quality of life in subjects with substantial vision loss from RP or dry AMD. These improvements appeared to be sustained over time. Furthermore, based on the reported adverse events, these various types of retinal prostheses appeared to have an acceptable risk profile. However, all of the included studies were at risk of bias due to their design, such as how the experiments were conducted or the lack of randomisation, a control group or masking. Conclusion: Although the retinal implants confer some useful vision, the regained vision is still limited and patients remain legally blind. Given the considerable risk of bias in the available literature, better quality evidence is required to evaluate retinal implants’ efficacy, safety and impact on subjects’ quality of life.