Study explores the role of light sensitivity in blepharospasm

By John Battiston 

Light sensitivity, or photophobia, affects the vast majority of people living with blepharospasm, a neurological disorder that causes involuntary contractions of the muscles around the eyes. But while as many as 94% of patients report sensitivity to light, researchers worldwide still don’t fully understand why. 

Now, a new study led by Brian Berman, M.D., director of the VCU Parkinson’s and Movement Disorders Center (PMDC), aims to shed light – literally – on the relationship between certain retinal cells and the disabling symptom of photophobia. The study, funded by a research grant from the nonprofit Benign Essential Blepharospasm Research Foundation (BEBRF), seeks to identify how specific wavelengths of light trigger discomfort and spasms.  

Berman says the project grew out of both collaboration and curiosity. A former VCU neurology resident interested in neuro-ophthalmology approached him about working with him on a research study that was related to visual function. “I mentioned a study from the National Institutes of Health that had looked at different lenses filtering out frequencies of light in patients with blepharospasm, and I always thought about potentially building and improving on that early study,” Berman says. After proposing this to the resident, the pair developed the current study over roughly a year. 

Based in Beaumont, Texas, the BEBRF is committed to finding a cause and cure for blepharospasm and similar disorders. It was critical to bringing the project to life, especially since blepharospasm-centric studies rarely receive federal funding. “Blepharospasm overall is an uncommon disorder, but it is very disabling,” Berman says. “The BEBRF is always seeking to find research that's dedicated to finding out what causes blepharospasm and to help develop better treatments and, eventually, a cure for the condition. We’re really excited to be partnering with them.” 

At the heart of the study is a set of retinal cells called melanopsin-containing intrinsically photosensitive retinal ganglion cells, or mRGCs. These light-sensitive cells differ from better-known receptors like cones and rods in that they do not participate in visual imagery, but rather detect the intensity of light. 

mRGCs help regulate circadian rhythms and control the pupillary reflex — how the eye adjusts to changing brightness. “They also let the brain know when the light is so intense that you need to close or avert your eyes,” Berman says. He compares them to the exposure meter in a camera, which indicates whether a photo will be too bright or dark. 

These cells are most reactive to light at a wavelength of 480 nanometers, a blue light close to the sun’s peak wavelength. By filtering out that specific wavelength and measuring participants’ responses, the team hopes to better understand the mechanism behind photophobia and its connection to blinking and eyelid spasms. 

Project coordinator Jaclyn Raper oversees the study’s day-to-day operations. “We wanted to see if blocking specific wavelengths helped reduce the activity of melanopsin cells and perhaps this in turn could help reduce symptoms,” she says. “So if we could block the wavelengths that are associated with photophobia, then hopefully we could reduce the symptoms that patients experience, such as spasming their eyes shut.” 

Raper says the study involves participants with blepharospasm and healthy controls, each fitted with four sets of randomized lenses: three that block out distinct wavelengths of light and one that doesn’t block any at all. The participants are placed in a dark room so their retinal cells return to their baseline. After five minutes, they put on the lenses, and Berman and Raper start measuring their pupils with a recently acquired pupillometer. 

This pupil measurement continues as the participants are exposed to a bright light. Berman and Raper also observe participants’ blink rate and the severity of their spasms before asking them how bad and controllable their photophobia symptoms were. 

The pupillometer, funded through the BEBRF grant, has been key to capturing precise data. “It gives us a lot of information down to the millisecond on how the pupil is acting,” Raper says. “We are running it through Excel programming to get these really cool graphs.” 

While data collection is ongoing, both Berman and Raper believe the findings could have immediate, real-world implications. If they find blocking specific frequencies makes a significant difference, it could lead to the design of specialized glasses that are highly effective for treating blepharospasm patients. 

Berman says even a “minor intervention” such as this “could make the difference between someone being disabled or not from one of the conditions that we treat.” For patients who often give up driving or daily activities because of uncontrollable eye spasms, that could be life-changing. 

“Our hope is to get a lens that gives patients back a little bit more freedom,” Raper says.