Parkinson's disease and convergence insufficiency: A mini-review

Abstract Background: A key manifestation of Parkinson disease (PD) is visual impairment. Cognitive impairment has been found to overlap with convergence insufficiency (CI) in patients with PD and is associated with significantly greater near point convergence (NPC) distance. Difficulty in reading and diplopia were the most common symptoms of CI in PD. The prevalence of CI is greater among patients with PD. Therefore, this study aimed to assess the relationship between PD and CI. Methods: Studies that had included data on CI, NPC, or both were selected by searching PubMed/MEDLINE and clinicaltrails.gov, without any timeline or language limitation. The following terms were used in PubMed/MEDLINE search: Clinical Trials, Parkinson Disease, and Convergence Insufficiency. For clinical trials.gov database, the terms Parkinson Disease, Convergence Insufficiency, and Completed Studies were used. Only those studies with control subjects were included. PubMed/MEDLINE search yielded ۱,۵۶۳ articles, but no article was found in the clinical trails.gov search. Twelve articles met the inclusion criteria, among which nine articles were selected as they had data on CI or NPC distance (cm), and PD. Results: Overall, there were ۱,۵۶۳ articles; among them, ۱۲ articles met the inclusion criteria. Nine articles were selected based on their data concerning CI or NPC distance (cm) and PD. Relative to the control group, the PD group had high CI. In addition, PD group showed increase in NPC distance than the control group. Conclusions: These data suggest that the patients with PD had an increased likelihood of developing CI visual symptoms, and increased NPC distance than healthy controls. These findings indicate that regular eye examination is very important for patients with PD. Keywords: clinical trial convergence insufficiency near point convergence cognitive impairment Parkinson disease