Effectiveness and safety of vision modulation and restoration using noninvasive electrical stimulation: A systematic review and meta-analysis.

Abstract

ABSTRACT Background The number of individuals with irreversible Visual Field Defects (VFD) worldwide is increasing. At current, the damaged visual pathway has more potential for recovery and restoration then recently thought, even long after injury to the visual pathway has occurred due to neuroplasticity. Non-invasive Electrical Stimulation (NES) has been proposed as a possible treatment for irreversible VFD for enhanced vision recovery, and to improve quality of life.

Objective: To determine the effectiveness and safety of NES for the VFD treatment.

Methods: Adhering to PRISMA guidelines, we performed a systematic review to identify all randomized control trials (RCTs) between 2000 and 2022 in which NES was performed and compared with sham stimulation to treat VFD. We search in Cochrane Central Register of Controlled Trials (CENTRAL); MEDLINE, EMBASE, and LILACS. We also checked the literature cited in the included studies and searched gray literature. The main outcomes were visual acuity (VA) and evaluation of the visual field with perimetry, and the secondary outcomes were quality of life and numbers of adverse effects. Paired review authors independently selected studies extracted data and assessed risk of bias of the included trials. We used a random effects model within the meta-analysis, and the GRADE methods were applied to assess the certainty of the evidence. This study was registered with PROSPERO CRD42022329342.

Results We included 13 studies involving 441 participants that met inclusion criteria (12 parallel, and one crossover RCT). Transcorneal, transpalpebral, transorbital, and transcraneal stimulation were evaluated for the treatment of VFD in patients with ischemic or hemorrhagic stroke (15%), amblyopia (23%), proliferative diabetic retinopathy (8%), retinitis pigmentosa (2%), Age-related macular degeneration (AMD) (8%), Retinal Artery Occlusion (RAO) (23%), and optic nerve disease (23%). Regarding our primary outcomes, the evidence suggests that active stimulation results in little to no difference in improving VA at less than one month (MD = -0.03, 95% CI -0.10 to 0.03, N = 290), and more than one month of follow-up (MD = 0.01, 95% CI 0.00 to 0.02, N = 127), detection accuracy (MD = 0.48, 95% CI -0.00 to 0.96, N = 158), foveal threshold ( MD = -0.47, 95% CI -3.03 to 2.08, N = 110), and mean sensitivity (MD = 0.03, 95% CI -0.19 to 0.24, N = 85).

Discussion The data of included studies are unable to suggest NES for the VFD treatment owing to the fact that we did not detect statistical important differences in none of the outcomes evaluated. This review provides moderate and low certainty evidence. Research is required to determine effective protocols of NES, for vision recovery, long term effects and evaluate new alternatives of vision modulation such as more invasive methods.