Neural Changes after Vision Therapy in Convergence Insufficiency: A Systematic Review

Abstract

Objective. To investigate if the use of vision therapy (VT) in convergence insufficiency (CI) has a significant neural impact and how it correlates with the clinical changes occurring with this option of treatment. Methods. A systematic review of the scientific literature was carried out in the PubMed and Scopus databases, where all the scientific literature on the neural impact of VT in CI was analyzed. A total of 17 articles were initially found and a detailed analysis was carried out. After full-text reading, only four studies met the defined inclusion criteria. The following data from them were extracted: CI cases and controls, clinical and neural parameters evaluated, the neural response to VT observed, type of study, and VT performed. The quality of the studies was assessed using the GRADE tool. Results. Some neural changes have been reported after VT in CI with the use of functional magnetic resonance imaging (fMRI). Specifically, a modification of the functional activity of some brain areas (especially front fields, oculomotor vermis, and cerebellum) was found. However, contradictory findings in terms of the change in functional activity (increase or decrease) were found that might be associated to differences in fMRI protocols. In the GRADE analysis, serious concerns were found in the categories of risk of bias, inconsistency, indirectness, and imprecision, so the certainty of evidence for each outcome was very low. Conclusion. The research performed to this date does not allow confirming if there are neural changes occurring after vision therapy in patients with CI because the quality of the research performed on this issue is very low, with several methodological concerns.