The Evaluation of Light Sensitivity in Benign Essential Blepharospasm

A Novel Visual Psychometric Test for Light-Induced Discomfort Using Red and Blue Light Stimuli Under Binocular and Monocular Viewing Conditions

“…Our finding is consistent with previous reports indicating that short-wavelength blue light generates more perceptual discomfort in comparison with long or medium wavelengths of light in visually normal 20,22,23 and clinical populations, 21 and correlates with the peak spectral sensitivity of melanopsin. 6 Our results are also consistent with studies that show alleviation of photophobia symptoms when patients with migraine 25 and benign essential blepharospasm 2,24 were fitted with tinted lenses that filter out blue light.…”

“…Third, short-wavelength blue light has been reported to induce the most visual discomfort, [20][21][22][23] whereas blue-filtering lenses have been reported to reduce the symptom in patients with photophobia. 2,24,25 Furthermore, the action spec-trum for visual discomfort and that for ipRGCs (~480 nm, blue light) 6,8 are remarkably similar. 23 Fourth, ipRGCs project directly to pain centers in the posterior thalamus where afferent retinal inputs converge with the trigeminal nociceptive pathway.…”

“…Previous psychophysical studies 2,[21][22][23]28,29,33,34,[36][37][38][39][40][42][43][44] have not used pharmacological mydriasis. Wirtschafter and Bourassa 27 investigated the effect of dilation on discomfort thresholds in a small subset of their participants (6 of 76 participants), but this experimental manipulation was not applied to their entire sample of participants.…”

“…1 A common symptom of several neurological and ophthalmic disorders, including migraine, traumatic brain injury, blepharospasm, and dry eye, photophobia can lead to severe impairment in everyday life. [1][2][3] Visually normal individuals also experience a similar phenomenon when stepping into a brightly lit environment, especially after being in a dark room for a period of time. Because photophobia may present heterogeneously both in visually normal and diverse clinical populations, 4,5 adopting a ''one-size-fits-all'' definition is likely oversimplifying a complex phenomenon, the underlying mechanisms of which remain poorly understood and require further investigation.…”

“…More recent studies have adapted earlier psychophysical protocols and are faced with similar challenges. 2,22,23,33,34,[42][43][44] As a first step in quantifying pathological photophobia, we developed a psychophysical tool to quantify light-induced discomfort in visually normal participants. By incorporating the latest information on the ipRGC pathway characteristics, we examined the effects of stimulus wavelength (blue versus red light) and viewing condition (monocular versus binocular) on light-induced discomfort.…”