BackgroundPhotophobia is a potentially debilitating symptom often found in dry eye disease (DE), migraine and traumatic brain injury (TBI).MethodsWe conducted a review of the literature via a PubMed search of English language articles with a focus on how photophobia may relate to a shared pathophysiology across DE, migraine and TBI.ResultsDE, migraine and TBI are common conditions in the general population, are often comorbid, and share photophobia as a symptom. Across the three conditions, neural dysregulation of peripheral and central nervous system components is implicated in photophobia in various animal models and in humans. Enhanced activity of the neuropeptide calcitonin gene-related peptide (CGRP) is closely linked to photophobia. Current therapies for photophobia include glasses which shield the eyes from specific wavelengths, botulinum toxin, and inhibition of CGRP and its receptor. Many individuals have persistent photophobia despite the use of these therapies, and thus, development of new therapies is needed.ConclusionsThe presence of photophobia in DE, migraine and TBI suggests shared trigeminothalamic pathophysiologic mechanisms, as explained by central neuroplasticity and hypersensitivity mediated by neuropeptide CGRP. Treatment strategies which target neural pathways (ie, oral neuromodulators, transcutaneous nerve stimulation) should be considered in patients with persistent photophobia, specifically in individuals with DE whose symptoms are not controlled with traditional therapies.

Background: To evaluate the efficacy of botulinum toxin A (BoNT-A) in reducing photophobia and dry eye symptoms in individuals with chronic migraine. Additionally, we aimed to evaluate tear film volume as a potential contributor to symptoms in these patients. Methods: Retrospective review of seventy-six patients who received BoNT-A for chronic migraine (CM) between August 23, 2017 and December 13, 2017 at the Miami Veterans Affairs Medical Center Neurotoxin Clinic. Demographic data and all co-morbidities were queried via chart review. Standardized validated surveys were administered to assess symptoms prior to and after BoNT-A injection. Pre-injection tear volumes were obtained using the phenol red thread (PRT) test. Results: Pre-injection migraine, photophobia, and dry eye symptom scores were all significantly correlated, p<0.05; and none were associated with pre-injection PRT results. After BoNT-A, improvements in migraine, photophobia, and dry eye symptoms were also significantly correlated, p<0.05; and similarly did not associate with pre-injection PRT results. Photophobia scores significantly improved following BoNT-A, while dry eye symptoms significantly improved in those with severe symptoms at baseline (DEQ-5 score ≥12), p=0.027. In logistic regression analysis of all individuals with dry eye symptoms (DEQ-5≥6), individuals with more severe dry eye symptoms were more likely improve, OR 1.27, 95% confidence interval [1.06, 1.51], p<0.01. Conclusions: BoNT-A significantly improved photophobia in patients being treated for migraine and also improved dry eye symptoms in patients with severe symptoms at baseline, independent of baseline tear film volume. These improvements may be due to modulation of shared trigeminal neural pathways.

Purpose Individuals receiving botulinum toxin A (BoNT-A) injections in the head and neck for migraine treatment have reported decreases in photophobia and sensations of dryness, independent of ocular surface parameters. We hypothesized that patients without migraine but with similar ocular neuropathic-like symptoms would also experience symptomatic improvement with periocular BoNT-A injections, independent of ocular surface changes. Observations We identified four individuals without a history of migraine but with neuropathic ocular pain (symptoms of dryness, burning, and photophobia that were out of proportion to ocular surface findings and unresponsive to ongoing dry eye (DE) therapies). Individuals underwent 1 session of periocular BoNT-A injections. Validated questionnaires (Visual Light Sensitivity Questionnaire-8, Dry Eye Questionnaire-5) assessed photophobia and DE symptoms pre- and 1-month post-injections. All four reported improvements in frequency and severity of photophobia and eye discomfort following BoNT-A injections. Tear film parameters (phenol red thread test, tear break-up time, corneal staining, and Schirmer test) and eyelid (palpebral fissure height and levator palpebrae superioris function) and eyebrow (position) anatomy were also evaluated before and after injections. Despite a unanimous improvement in symptoms, there were no consistent changes in ocular surface parameters with BoNT-A injections across individuals. Conclusions Periocular BoNT-A shows promise in reducing photophobia and sensations of dryness in individuals with neuropathic-like DE symptoms without a history of migraine, independent of tear film, eyelid, or eyebrow parameters.