The Head Injury-associated Photosensitivity and Pupillary Function (HIPP) Study

The pupils inside the eyes constrict in response to light stimulation. Different classes of cells within the human retina initiate this response. Recent research suggests that one of the ganglion cell types involved in this pupil response also plays a role in the photophobia experienced by migraine sufferers. The main aim of this study is to determine whether this type of ganglion cell becomes 'hypersensitive' after traumatic brain injury, thereby contributing to symptoms of increased photosensitivity experienced by many of these individuals.

In the first session of this study, subjects will be asked questions about their sensitivity to light and the reaction of their eyes' pupils to flashing red and blue lights will be measured. The subjects will be given a full eye examination to rule out other causes of increased photosensitivity.

In some cases, subjects will be asked to attend a second session roughly two weeks later. They will be asked to wear a watch that measures their daily activity/sleep rhythms and light exposure during this inter-session period. During the second session, further testing of the pupil responses to blue and red flickering light will be performed.

Inclusion criteria

• 18+ years old
• reports a previous head injury that occurred at least 6 months ago
• score of 2 or 3 (mild TBI) on OSU-TBI ID Survey
• best-corrected visual acuity of at least 20/30 in both eyes
• reliable visual field

Exclusion criteria

• pregnancy
• significant afferent pupillary defect
• previous history of neurodegenerative disease
• intraocular pressure more than 21 mm Hg
• significant visual field defect
• active corneal pathology
• history of retinal or optic nerve disease
• strabismus (eye turn)