Kathleen Digre, MD, on Eye Pain and Photophobia in Migraine

Kathleen Digre, MD

More and more, clinical endpoints included in migraine treatment trials account for patients' "most bothersome symptom." Among the list is typically photophobia, a sensitivity to light that may drive people with migraine to camp out in a dark room while suffering through their attack.

Despite the common nature of this complaint, there is much to be learned about eye pain and photophobia and its role in migraine care. More pertinent is our ability to address this complaint head on, though this part of the migraine treatment process often goes ignored or avoided. For Kathleen Digre, MD, distinguished professor of neurology and ophthalmology at the John A. Moran Eye Center, chief of the Division of Headache and Neuro-ophthalmology at the University of Utah in Salt Lake City, this is the common story she hears from patients who walk into her clinic. Many have seen multiple neurologists and opthalmologists, yet their eye complaints have not been adequately addressed.

Following her lecture at the 2020 American Headache Society (AHS) Virtual Annual Scientific Meeting, Digre, who is also a past president of the AHS, spoke with NeurologyLive about some of the shortcomings of care for people with eye pain and photophobia, her tips for a thorough exam, and what hurdles still stand in the way of us improving care for these patients. View part 1 of this interview below.

NeurologyLive: Can you share you steps for a thorough exam and diagnosis of patient presenting with eye pain and/or photophobia?

Kathleen Digre, MD: My steps of how to make the diagnosis are first, taking a careful history, asking about underlying migraine, asking about head injuries, chronic pain conditions, other things that could cause this to occur. And then on the examination, I look for findings that could point me to a secondary cause like Horner syndrome or papilledema, or a pupillary defect; something that would say you've got something else going on. And then then once I do that, I also look at the symptom of night blindness and I also look at the symptom of too much light, so when they get into the light they can't see. Those are usually eye complaints and that person probably should see an ophthalmologist and who can look at the retina and macula. The next step is really to figure out whether the cornea or dry eyes are playing a role in the light sensitivity or in the eye pain. By putting a drop of proparacaine into the eye, the physician can see how much of the pain goes away, how much of the light sensitivity goes away, and if a substantial part of it goes away with the proparacaine, that means those corneal nerves on the cornea are perpetuating or making the light sensitivity and the eye pain worse. This is something that an ophthalmologist could partner with a neurologist to do, or a neurologist can do on their own. The next thing I do is a Schirmer's test; this is just a little piece of litmus paper, you put under the lower fornix of the eyelid and then see how far that gets wet, and that tells you whether there's dryness to the eye and if there's a tear production problem that could be occurring. If it's that then you've got something else you can treat to get rid of the light sensitivity, etc. I also look for blepharospasm, which is another neurologic condition with frequent blinking and there's two forms of it; one is where people are blinking all the time, and another form is when light gets in the eye and they clamp down shut and they can't open their eyes. That's a reflex of blepharospasm, and you really have to look for both of them; the frequent blinking or the closure of the eyes inordinately. Finally, if they have migraine, migraine is playing a role in this and whether it's playing a primary role or a secondary role it doesn't matter but the people who have migraine are more prone to photophobia and they are prone to central sensitization, especially if they have chronic migraine, which can keep the pain going. It's also extremely important to look for anxiety and depression. We did a study where we looked at migraine that had just had ictal photophobia versus when they have their migraine with chronic photophobia throughout the migraine but also in between. Those patients had a higher incidence of depression and anxiety. Those are also treatable conditions that neurologists and headache specialists can treat.

How much does our current understanding of the pathophysiology of this pain really play a factor into it not being diagnosed correctly or not being treated correctly?

Pathophysiology is really important and anatomy is really important. When we found out about these melanopsin cells or intrinsically photosensitive retinal ganglion cells, that really changed the landscape for me personally, because I would have patients who are legally blind and yet they were so photophobic. These melanopsin cells are phylogenetically very, very old cells. They live in our retina and they sense light. They don't tell us that there's light, but they sense light. They then anatomically connect to the pain center; the trigeminal pathway. Rami Burstein, PhD, in Boston has shown this eloquently; he and his group have really done some wonderful ground-breaking work in this area of showing how the trigeminal system and the melanopsin system connect. Of course our rods and cones sense light, so that's a second source of light coming in, then there have been some studies done on laboratory animals. These animals are born actually blind for about 7 days, and then during that time, they shine light on these little animals and they squeak and they notice that they're anxious and they can look at the brains and see that their limbic system, their emotional system is impacted. Then they take melanopsin knockout mice, meaning that they take the melanopsin cells out of there and they don't have this same squeaking going on. We know that melanopsin is playing a role in this. How do we control that pathway? That we don't know. There are some big knowledge gaps of what treatments could we use that would help to bring that down. There's lots of knowledge gaps in this area.

Is there anything else you'd like the neurology and ophthalmology communities to know about these symptoms?

Every ophthalmologist needs to know about migraine, and realize that migraine could participate in eye pain and light sensitivity that their patients see. They should recognize it, say yes, this happens and get them to a place that that they can get help. The neurologist may be uncomfortable about the eye pain or photophobia, but once they can partner with an ophthalmologist if they are uncomfortable, then they can start treating the underlying migraine component. It's important to not forget depression and anxiety, because depression can kill people. Migraine doesn't usually kill people, but depression can kill people. So it's really important that we recognize it, and we've got treatments for it, and we take it seriously. I think one of the most powerful things that people can do is say there's an anatomic basis for this and a physiologic basis for this. You're not making this up. It's not all in your head. Let's take care of the eye component, the migraine component, the pain component, and let's take care of the depression anxiety component, and then by doing that we can do a better job of taking care of these people.

Transcript edited for clarity.