INTRODUCTION: Photophobia is a common visual symptom following mild traumatic brain injury (mTBI), which can adversely affect the military readiness and performance of service members (SMs). We employed the Defense and Veterans Eye Injury and Vision Registry (DVEIVR) to identify and describe a cohort of SMs diagnosed with photophobia post-mTBI. The objective of this study was to characterize comorbid conditions and symptoms in an mTBI cohort with photophobia, to assess their co-occurrence, to describe the persistence of photophobia, and to assess the effectiveness of utilization of currently available International Statistical Classification of Diseases and Related Health Problems (ICD) codes in reporting photophobia in this cohort.
MATERIALS AND METHODS: The DVEIVR database was searched to identify a cohort of SMs experiencing photophobia after mTBI. Photophobia and other potentially related conditions and symptoms, both coded and descriptive, which were abstracted directly from the medical records of SMs, were found within DVEIVR. The presence of the conditions and symptoms comorbid with photophobia was characterized on both patient and encounter levels. Analysis of co-occurrence of photophobia with these conditions or symptoms was performed on the encounter level using co-occur package in the statistical program R. Persistence of photophobia up to 1 year since the injury was assessed. The utilization of currently available ICD codes for photophobia was analyzed.
RESULTS: A total of 639 SMs exhibiting photophobia after mTBI were identified in DVEIVR. Headaches, including migraines, were the most frequently experienced comorbidity affecting 92% of the SMs in the cohort. The second most frequent complaint was dizziness and/or vertigo (53%) followed by nausea (42%), blurry vision (31%), and irritation and discomfort in the eye (17%). In all, 20% of encounters with photophobia had a complaint of headaches, followed by 8.3% of photophobia encounters co-occurring with dizziness and vertigo, 5.7%-with nausea, 4.5%-with blurred vision, and 2.1%-with subjective sensations in the eye. All comorbidities co-occurred with photophobia at probabilities higher than by chance alone. The percentage of mTBI SMs experiencing photophobia declined to 20% at 30 days after the injury, 17% at 3 months, 12% at 6 months, and 7% at 12  months post-injury, respectively. The use of currently available ICD codes for photophobia was very low-only 27.1% of the cohort had at least 1 ICD code recorded in their medical records.
CONCLUSIONS: The results of this study support the idea that there is a strong relationship between photophobia and headache after an mTBI. Additional research is warranted to better understand this relationship and its causes so that clinical management improves. The results of this study show a precipitous decline in the numbers of cases of photophobia after mTBI over the first 30 days and a longer-term persistence up to a year in a minority of cases, which is consistent with other research in this field. Various ICD codes, which are currently used to code for photophobia, along with other vision conditions, were not widely used to document photophobia symptoms. It is important to adopt a dedicated ICD code for photophobia to improve the surveillance, data collection, and analysis of this condition.