Effect of light on blinking in patients with idiopathic isolated blepharospasm. (October 2019)

• Record Type: Journal Article
• Authors: Wu, Yiwen; Cho, Hyun Joo; Panyakaew, Pattamon; Savant, Charulata Sankhla; Wu, Tianxia; Dang, Nguyet; Hallett, Mark
• Is Part Of: Parkinsonism & related disorders. Volume 67(2019)
• Page Start: 66
• Page End: 71
• Publication Date: 2019-10
• Subjects: Blepharospasm -- Dystonia -- Photophobia -- Blink rate; Parkinson's disease -- Periodicals; Movement disorders -- Periodicals; Movement Disorders -- Periodicals; Nerve Degeneration -- Periodicals; Nervous System Diseases -- Periodicals; Parkinson Disease -- Periodicals; Tremor -- Periodicals; Parkinson, Maladie de -- Périodiques; Parkinson's disease; 616.833
• DOI: 10.1016/j.parkreldis.2019.09.010
• Languages: English
• ISSNs: 1353-8020

Abstract

Abstract: Objective: Melanopsin may be involved in the pathophysiology of photophobia in idiopathic isolated blepharospasm. We assessed the efficacy of blocking wavelengths of melanopsin absorption to reduce blinking in blepharospasm as a possible surrogate for photophobia. Methods: Twenty-one participants (11 blepharospasm and 10 healthy controls) were studied. There were three sessions: (1) a baseline condition to measure the blink rate (BR) without intervention; (2) two conditions where the participants received intermittent light stimuli with high or low intensity without wearing study lenses; (3) four conditions in which the participants received intermittent light stimuli with high intensity while wearing one of four different lenses: tinted lenses with neutral gray or FL-41, or coated lenses that block 480-nm or 590-nm wavelength. The primary outcome measure was the BR. Results: The blepharospasm group blinked more frequently than controls in dim room conditions. Patients reported greater photosensitivity compared to controls based on the questionnaire and exhibited a higher BR with intermittent light stimuli. The BR decreased for both groups when using 480-nm and 590-nm blocking lenses. In the patients, 480-nm and 590-nm blocking lenses reduced the mean BR by 9.6 blink/min and 10.3 blink/min, respectively, while in the control group, the mean BR decreased by 4.4 blink/min and 4.3 blink/min, respectively. Conclusions: Blepharospasm patients had increased BR with light stimuli which decreased with 590-nm and 480-nm blocking lenses. The 480-nm- and 590-nm- coated lenses might have therapeutic potential in treating photophobia although BR does not appear to be an optimal biomarker for photophobia. Highlights: Hypersensitivity of melanopsin-mediated pathways may produce photophobia. Blepharospasm patients have a higher blink rate and more photophobia compared to healthy controls. Blocking specific wavelengths that influence melanopsin reduced blink rate.