Dry eye is defined by the Tear Film and Ocular Surface Society Dry Eye Workshop II (TFOS DEWS II) as a multifactorial disease of the ocular surface characterized by a loss of homeostasis of the tear film, and accompanied by ocular symptoms, in which tear film instability and hyperosmolarity, ocular surface inflammation and neurosensory abnormalities play etiological roles.1
The International Headache Society (IHS) defines migraine as a recurrent headache disorder manifesting in attacks lasting 4 to 72 hours. Migraine episodes can be classified as chronic or episodic and with or without an aura.2
The link between migraines and dry eye
Both dry eyes and migraines are quite common in the general community. Dry eye prevalence ranges from 5% to 50% in the global population, while migraine is up to 9.5% in males and 25% in females in Western nations.3
Dry eye or migraine symptoms can become bothersome and reduce a patient's quality of life. Recent research has revealed that dry eye and migraine share many symptoms, pathogenesis, and possible therapies and treatments.4
Supporting studies on the link between migraines and dry eye
According to the data, people with migraine have more dry eye symptoms versus dry eye signs than those who do not have migraines, and migraine with aura is more related to dry eye than migraine without aura.5,6
Recent studies on the link between migraines and dry eye:
- In a study of 31 South Florida veterans compared to 219 controls, individuals with migraine had significantly higher dry eye symptom scores on the ocular surface disease index (OSDI) but similar tear break-up time (TBUT), corneal staining, and tear production compared to controls.5,7
- A Turkish study comparing 33 migraine patients to 33 controls found that migraine patients had substantially greater dry eye symptoms on the ocular surface disease index (OSDI) and lower TBUT and Schirmer scores than controls.5,6
- A Turkish study of 58 migraine sufferers discovered that those with migraine plus aura were 5.03 times more likely to develop a dry eye condition than those without aura.5,8
- Studies have demonstrated that photophobia is a common feature of both dry eye and migraine.9,10
- A study of 102 South Florida veterans discovered that those with persistent dry eye symptoms were more likely to report photophobia than those without persistent symptoms.9
- Photophobia was identified as the most irritating symptom by 49.1% of 6,045 respondents in the Migraine in America Symptoms and Treatment (MAST) Study, and 80% of 117 patients with chronic migraine ranked their photophobia as severe.10
The pathophysiological relationship between dry eye and migraines
The overlap of dry eye symptoms with migraine symptoms suggests a pathophysiological relationship between them.11 Migraine is assumed to be caused by activation of the trigeminovascular network, whereas dry eye symptoms are thought to be caused by activation of the sensory trigeminal neurons of the cornea.11,12 Both dry eye symptoms and migraine have abnormal peripheral trigeminal nerve activation with subsequent peripheral and central sensitization.
Although the exact pathophysiology is unknown, one explanation is that dry eye symptoms and migraine are caused by aberrant trigeminal nerve activity, which involves the trigeminal nerve and its neuronal projections to the trigeminovascular system.11,12
The neurons of the trigeminal nerve's first division that compose the corneal nerve plexus travel parallel to the ocular surface, and their axons synapse in the brainstem, where the trigeminovascular system occurs. Because the feeling of dry eye activates the trigeminovascular system, changes in corneal innervation from ocular surface inflammation and refractive surgeries may all contribute to migraine.11,12
In people with persistent migraines, abnormal corneal nerves may cause dry eye symptoms.13 According to studies, migraine sufferers were shown to have abnormalities in their corneal nerve structure, such as branching and tortuosity, and considerably more corneal sensitivities when compared to controls, perhaps inducing dry eye symptoms via activation of the trigeminovascular system.13
Research on co-morbidity
Studies have shown that dry eye and migraine can be considered co-morbid.14,15,16 According to a Korean research study of 14,329 individuals, the prevalence of migraine and dry eye diagnosis was identical, with 24.2% reporting migraine, 22.6% reporting a dry eye diagnosis, and 37.1% reporting dry eye symptoms.15
In a hospital-based study of 72,969 people in North Carolina, individuals with migraine and dry eye were identified using the International Classification of Diseases (ICD-9 and ICD-10) codes, and the prevalence of a migraine or dry eye diagnosis was 7.3% and 13.2%, respectively.16
Additionally, the frequency of a dry eye diagnosis was found to be higher in those with migraine.14,17 The presence of a dry eye diagnosis raised the risks of a migraine diagnosis by 1.76-fold in a large Taiwanese research study utilizing ICD-9 codes.17
Treatments to consider for dry eye and migraines
Anti-inflammatory medications are considered to be a first-line treatment in those patients with dry eye and migraine.18,19 Topical corticosteroids are therapies that will decrease ocular surface inflammation.18 Nonsteroidal anti-inflammatory drugs (NSAIDs) can alleviate acute migraines.19
If patients are not responding to the anti-inflammatory treatments initially, then therapies targeting nerve dysfunction should be considered.14,20,21 Tricyclic antidepressants (TCAs) and serotonin and norepinephrine reuptake inhibitors are oral nerve modulators that have been shown to be useful in the treatment of chronic migraine, whereas triptans have been shown to be beneficial in the treatment of acute migraine episodes.14,20
Given the comparable pathophysiology to migraine, patients with dry eyes may benefit from oral nerve modulators as well. Gabapentin, pregabalin, and alpha 2 delta ligands are particular oral nerve modulators that have been studied in dry eye and are hypothesized to work by decreasing excitatory neurotransmission along the trigeminovascular pathways.21 Supportive therapy may be used in people who do not respond to oral nerve modulator medications for dry eye and migraine.
Though these specific treatments are more typically utilized in migraine therapy, they may also help with dry eye care:21,22,23
- Botulinum toxin (BT): Inhibits pain responses by reducing facial muscle contraction and, as a result, trigeminal signaling.22
- Transcutaneous electrical nerve stimulation (TENS): Is thought to alleviate discomfort in dry eyes and migraines by sending pulsed electrical currents over the skin's surface to activate deep sensory afferents, which then suppress nociceptive input in the trigeminovascular system.23
- Blocking occipital nerve afferents: This triggers the trigeminovascular pathway with a local anesthetic, resulting in a considerable reduction in the number and intensity of headaches.
- When administered to trigeminal nerve afferents, this method has the potential to treat individuals suffering from dry eye discomfort.21
In conclusion
Dry eyes and migraines are both prevalent conditions. Clinicians can ask dry eye patients about headaches or vice versa during the case history to better assess both conditions. The occurrence of photophobia in both conditions, as well as the co-morbidity of dry eye and migraine, suggests a pattern of similar etiology and possible therapies.
More studies, along with current data, may be utilized to not only better understand the physiological causes of both disorders, but also to aid in the development of tailored therapeutics for lessening the severe symptoms of migraine and dry eye.
