Abnormal brain function in photophobic patients with dry eye disease: An fMRI study

Photophobia, a frequent and disabling symptom observed in various neurological conditions and eye diseases, is thought to involve maladaptive brain functioning. We assessed this hypothesis, using functional magnetic resonance imaging (fMRI) in photophobic patients with minimal-to-severe dry eye disease (DED), as compared to healthy controls. This prospective, monocentric, comparative, cohort study included eleven photophobic DED patients compared to eight controls. Photophobic patients had a complete evaluation of DED to exclude any other cause of photophobia. All participants were scanned with fMRI under intermittent light stimulation with a LED lamp (27s. ON, 27 s. OFF), and cerebral activations were studied with univariate contrasts between the ON and OFF conditions, and with functional connectivity methods. Firstly, stimulation activated the occipital cortex more strongly in patients than in controls. Moreover, stimulation deactivated the superior temporal cortex in patients less than in controls. Secondly, functional connectivity analysis showed that light stimulation induced lesser decoupling between the occipital cortex and the salience and visual networks in patients than in controls. The current data shows that DED patients with photophobia have maladaptive brain anomalies. There is hyperactivity in the cortical visual system, associated with abnormal functional interactions, both within the visual cortex, and between visual areas and salience control mechanisms. Such anomalies show similarities with other conditions such as tinnitus, hyperacusis, and neuropathic pain. Those findings support novel neurally oriented methods for the care of patients with photophobia.