Glaucoma patients who are exposed to bright light during the day may have improved sleep and an increased melanopsin-dependent pupil response after just four weeks, a pilot study in Frontiers in Neurology reports.

The multi-international research team suggests the change in pupil response might indicate melanopsin activity in viable intrinsically photosensitive retinal ganglion cells can adapt to different light levels if sustained over a period of time.

Their study enrolled 20 glaucoma patients without severe vision loss and considered how 30 minutes of daily bright light exposure from a table-based light box placed in their homes affected pupil constriction, circadian rest-activity cycles, sleep, relaxation, alertness and mood.

Participants continuously wore an activity monitor and self-assessed sleep quality, well-being and visual comfort for several days before and during the four weeks of daily 10,000 lux polychromatic bright white light exposure.

Individuals underwent pupillometry at baseline and on the last day of the study.

Following light exposure, participants showed a much greater post-illumination pupil response and had better sleep quality. Additionally, researchers found no significant changes in the participants’ 24-hour rhythms or sleep parameters.

The study demonstrated that even a relatively short duration of added light exposure in a room is beneficial and also supports the general advice that the elderly should go outside for half an hour each morning, the researchers suggest.

While glaucoma patients can never recover the vision lost from damaged retinal ganglion cells, they may be able to maintain a robust day–night cycle and concomitant good circadian entrainment which helps maintain high sleep quality, they explain.

Kawasaki A, Udry M, Wardani ME, Mirjam Münch. Can extra daytime light exposure improve well-being and sleep? a pilot study of patients with glaucoma. Front Neurol. 2020;11:584479.