What is the Connection Between Migraine and Photophobia?
What is the Connection Between Migraine and Photophobia
Migraine headaches come with light sensitivity. Why do persons with migraine get photophobia, or light sensitivity? Migraine affects the senses, such as vision, hearing, and olfaction. Persons with migraine are sensitive to light without headache, but especially sensitive during the time of the migraine.
What is the connection between Migraine and Photophobia? The connection between Migraine and Photophobia is not clearly understood. This is unfortunate and more research needs to be done in this area, but the fact is that the answer is not currently understood.
I am a neurologist, headache doctor, member of the American Academy of Neurology, and the American Headache Society. I have migraine, my wife has migraine, and my 2 daughters have migraine. I have a migraine blog with 113 articles, a Pinterest account, and have written 3 textbooks on migraine.
For over 35 years I have seen headache patients in my office in Dallas. Migraine is a common medical problem. It affects 25% of women and 6% of men. Migraine is a disabling medical condition which causes severe, throbbing, one sided, headache. Migraine is the fifth most common disabling medical condition. It is the tenth most common reason for a visit to the Emergency Room. Migraine is genetic and is part of a person’s genome, and in their DNA. The gene for migraine with and without aura and for hemiplegic migraine is known and has been published in medical journals. A typical article on this would be: (Russell, MB, Iselius, L, Olesen, J. Cephalalgia. 1996 Aug;16(5):305-9. Migraine without aura and migraine with aura are inherited disorders).
The most painful conditions known are: childbirth, a kidney stone, and migraine headache. A single episode of migraine may last 4-72 hours. Chronic migraine is defined as at least 15 headache days per month, 8 of which have migraine features. Chronic migraine is usually due to overtreatment with pain killers, caffeine, triptans, opioid narcotics, or butalbital. Persons with migraine who take triptans, opioid narcotics or butalbital for headache more than ten days per month or over the counter painkillers, like Advil, Tylenol, Aleve, or caffeine more than fifteen days per month may get chronic migraine due to medication overuse headache. This group of patients may have continuous, all day, present for years, sensitivity to light. I meet them in the lobby of my office wearing caps with bills, dark sunglasses, and with all the lights turned off. When I interview these patients, I turn off the lights in the room and close the curtains. When I try to examine their pupils with a bright light or look at their retina with an ophthalmoscope, they are resistant, and blink, and just can’t allow the examination.
Photophobia which means “fear of light.” In the common clinical migraine situation photophobia refers to the abnormal, uncomfortable, pain producing sensitivity to light that migraine patients experience. The International Classification of Headache, the so-called “Bible” of headache disorders, lists photophobia as one of the cardinal diagnostic features of migraine. Just being sensitive to light can indicate a migraine condition. Tension Type Headache, which is more prevalent than migraine, does not have sensitivity to light as a diagnostic symptom. Bright light triggers or makes existing headaches worse in 80% of migraine sufferers, and 98% say they can predict headache onset by light levels. Photophobia is so common among migraine sufferers it’s an important part of diagnostic criteria set out by the International Headache Society.
1. What is the Pathophysiology of Migraine? Part of the reason for the connection between the two is that Migraine is associated with altered processing of sensory stimuli, like light. Migraine patients, called migraineurs, also have altered processing for auditory and olfactory sensory stimuli. Migraine patients are known to be, in general, always sensitive to light even at normal times, in between migraine attacks.
It has been reported (Chong, CD, Starling, AJ, Schwedt, TJ, Cephalalgia, 2016 May;36(6):526-33. Interictal photosensitivity associates with altered brain structure in patients with episodic migraine.) that persons with episodic migraine, which is defined as 14 or less headaches per month, have photosensitivity interictally, or between attacks of migraine. These migraineurs have greater cortical thickness in the right parietal-occipital and left fronto-parietal regions, suggesting that persistent light sensitivity is associated with underlying structural alterations.
Cortical thickness is reported but exactly how that relates to photophobia is uncertain. Between migraine attacks, atypical sensory perception persists, with migraines often demonstrating low discomfort thresholds to various experimentally applied stimuli. Studies are needed to figure out the pathophysiologic mechanisms producing the sensitive migraineur’s brain processing of sensory stimuli, both between and during migraine attacks.
2. What are Other causes of Photophobia?
A. Blepharospasm: an abnormal spasm causing blinking or sudden closure of the eyelids. Light sensitivity occurs with blepharospasm just like it does in migraine. It may come during an attack of migraine or in between attacks. It may be disabling. Migraine and blepharospasm are the 2 most common causes of photophobia.
B. Ocular causes of photophobia: dry eyes, iritis, uveitis, keratitis, conjunctivitis, cataracts, ocular irritation such as produced by a traumatic scratch or blow to the eye, corneal abrasion, corneal neuropathy, cone dystrophies, retinitis pigmentosa, congenital glaucoma, or inherited degenerative retinal diseases.
C. Central nervous system disorders: subarachnoid hemorrhage from aneurysmal rupture, viral or bacterial meningitis, and pituitary tumors.
D. Functional disorders: persons with underlying psychiatric disorder such as depression, agoraphobia, anxiety, panic disorder, bipolar disorder.
3. How is The Trigeminal nerve involved?
The fifth cranial nerve, the trigeminal nerve, is intimately involved in the pathophysiology of migraine. The first step in the migraine timing cycle (see blog article on the migraine timing cycle at: www.doctormigraine.com) is brain stem activation of pain fibers in the three branches of the trigeminal nerve. The trigeminal nerve lies at the level of the pons in the brain stem and its three branches go to the forehead (V1 division), cheek and nose (V2 division), and lower jaw (V3 division).
The trigeminal nerve carries fibers that go behind the eye and there with arterial branches cause pain behind one eye, a cardinal symptom of migraine. The word “Migraine” comes from the Roman doctor, Galen (131-201), who wrote of a group of Romans who suffered with “Hemicrania,” which means half of head. In later years the term changed to Hemicranium-Hemigranea-Migranea-Migrana-Megrim-and finally to Migraine. The most common clinical feature of migraine is that it occurs on one half of the head and this is present in about 80% of migraine patients. Trigeminal nerve fibers project to the thalamus (the pain center of the brain) in the midbrain.
4. Is the Retina involved with migraine and photophobia? Light comes into the eye via the pupil, impacts the retina, and leaves via the trigeminal nerve fibers. But how light becomes painful in the migraine sensitized retina is the puzzle. The pupil is a circular opening into the eye that varies in size according to the amount of light which illuminates the retina. In a dark room the pupil increases in size, but at the beach on a sunny day the pupil constricts to limit the amount of light it lets in. After entering the eye, light passes through the lens a protein based jelly bean like structure attached above and below by ligaments which affords the ability to focus the eye to see near or far. With ageing the lens loses its flexibility and becomes hard so that it doesn’t move well. That’s when “old age eyes” or presbyopia occurs, the phenomenon in middle age where one must hold the newspaper further out than usual to read the print. This is a humbling experience necessitating a visit to the opthalmologist for an eye exam which results in a prescription for near reading glasses which also can be purchased at a lower price at Walmart and are known as “cheaters.”
Light then reaches the retina where there are rod and cone cells. Rod cells are photoreceptor cells in the retina which work in dim light. Rods are found at the outer edges of the retina and provide peripheral vision. The eye has 92 million rod cells which provide night vision but not much color vision. Cone cells perceive light of different wavelengths and provide color vision. The eye has 6-7 million cone cells which are in the center of the eye. Cone cells detect light and form vision such as reading letters or viewing images. The cones next project through the optic nerve to the center of the brain. Optic nerve signals travel around the pituitary gland and form the optic radiations which pass through the temporal lobes to the back of the brain at the occipital cortex.
Light passing from the retina to the occipital cortex
It has been found (J.Neurosci. 2011 Nov 9;31(45):16094-16101. Melanopsin-positive intrinsically photosensitive retinal ganglion cells: from form to function. Tiffany M. et al) that melanopsin cells (cells in the retina that sense light but don’t provide vision) project to the thalamus and midbrain also. These melanopsin cells are thought to account for light produced pain in blind persons with migraine. The melanopsin system doesn’t provide formed vision but can sense light. There are more cones than melanopsin cells in the eye, but once the melanopsin cells turn on, they don’t turn off. The theory is that these melanopsin cells connect with the trigeminal nervous complex in the deep brain centers and provide a sense of brightness that is related to pain. This may be the explanation for the uncomfortable light producing pain, or photophobia, with migraine, but more research needs to be done.
What is the Treatment of Photophobia?
1. Treat migraine quickly. Rapid treatment of migraine, usually with a triptan at the onset of headache pain, will treat the headache and photophobia also. Triptans are currently the go to drugs for acute therapy of migraine. The triptans are: Imitrex (sumatriptan), Maxalt (rizatriptan), Axert (almotriptan), Zomig (zolmitriptan), Relpax (eletriptan), Amerge (naratriptan), and Frova (frovatriptan). In general, 80% of patients who treat their migraines at onset with a triptan are headache free in two hours. The fastest triptans are injectable subcutaneous sumatriptan (6,4,3 mg), nasal spray sumatriptan (20 mg), and zolmitriptan nasal spray (2.5, 5 mg). The subcutaneous and nasal spray sumatriptan and zolmitriptan nasal spray all work quickly, in 10 minutes, but nasal spray sumatriptan gives a level of medication in the brain of 10 mg while injectable subcutaneous sumatriptan gives a level of medication in the brain of 100 mg. Therefore, the fastest onset and highest brain dose level of all the triptans is sumatriptan, 6mg, given subcutaneously, the way the drug was first released in 1991.
Dark glasses help Dr. Strangelove with bright fluorescent lighting
2. Do Dark Glasses help? With migraine the brighter the light, the more pain there is. Patients with migraine find extremely dark sunglasses they wear during their migraines. Tinted lenses such as FL-41 lenses, reduce light sensitivity. Blocking blue light seems the most soothing to persons with light sensitivity. Studies done at King’s College Hospital in London and the European Institute of Health and Medical Sciences found migraineurs are especially sensitive to the red and blue light at either end of the spectrum. The greens and yellows in the middle are less problematical. Filtering out the reds and blues through wearing specially developed migraine lenses can have a beneficial effect. Other studies found rose-tinted glasses helped children with migraine.
The problem for chronic migraine patients is they may want to wear dark glasses all the time because they are overtreating with some painkiller and photophobia is there all the time, just like the headache. These patients dim all lights and draw the shades and stay out of the light in their entire environment, a mistake, because chronic dark adaption occurs and then any light exposure is painful, and all light is perceived as “brighter.” The patient shouldn’t always keep themselves in the dark. They should be counseled to not have darkened rooms, darkened windows, and to gradually increase the amount of light in their environment so they become more tolerant of light.
3. Does light avoidance help or hinder?
Migraine patients should not completely avoid light, that is impossible, but prudent exposure is suggested. Migraine patients should limit being out in the bright sun between noon and 4:00 PM. That is the brightest time of day. Migraine patients may wear hats, particularly those with a baseball hat type bill in front that blocks out light. Migraine patients should avoid flickering light. A patient told me years ago that a migraine started after she glanced out the window of her car while driving and saw the sun rising through a picket fence.
The type of light that may bother migraine patients are: flickering lights, glaring light, such as sun light reflected on the ocean or standing water, fluorescent lights used at home or work, low resolution computer screens, TV screens, patterns of light such as high contrast checkered patterns or stripes.
4. Does avoiding aggravating light sources help?
Fluorescent lights, which emit a small flicker or light vibration are notorious for aggravating migraine patients. I have written notes for patients’ work supervisors advising turning down bright lights, removing fluorescent lights, allowing caps with bills, and the use of dark glasses or tinted glasses in work areas. CFL light bulbs save 2,000 times their weight in greenhouse gasses and are an important part of energy efficiency and environmental care. Yet, they may aggravate migraineurs since these compact fluorescents can trigger migraines just as ordinary fluorescent lamps can.
Migraine patients who work on desktop computers all day long often have light brightness or light flicker issues and need to change their work environment, so they are more comfortable. Computer screen flicker can be adjusted by a technician to have static rather than flashing cursors. The computer screen should be placed away from the window to reduce glare. The patient should turn down the brightness of the screen and look away from the screen at regular intervals to give their eyes a rest.
5. How does light sensitivity differ between normal persons and migraineurs?
Migraine patients with photophobia have pain and discomfort at lower light levels than persons without migraine. Research has found that for persons without migraine, light becomes too bright when it reac0hes around 23,000 lux which is equivalent to the amount light on a bright, cloudless sunny day. However, for migraine patients, levels between 500-1,000 lux, such as may be found on a dull overcast day, can be uncomfortable or produce pain.
6. Is Migraine a frequent medical problem?
Migraine is a very frequent medical condition, especially for women. Migraine is The Most Common Medical Condition that women have. Migraine is more prevalent than hypertension, heart disease, arthritis, diabetes, or cancer. Migraine turns on or inflames the thalamus which is the “pain center” deep in the middle of the brain. No other medical condition is known to activate or “turn on” the thalamus. Migraine also causes photophobia or light sensitivity, but the exact way it does it is not currently clear. The graph below shows migraine frequency for 100,000 patients by age. (Lipton RB, Stewart WF. Migraine in the United States: A review of epidemiology and health care use. Neurology 1993;43(suppl3):S6-S10)
Britt Talley Daniel MD