Table 1.

Common features between dry eye and neuropathic pain

Epidemiology	Both are common conditions, affecting a large proportion of the older population. More common in females than males.
Shared clinical features	Frequent disconnect between symptoms and signs; spontaneous dysesthesias and evoked pain common to both entities, even in the absence of ongoing nerve damage.
Shared co-morbidities	Dry eye and other chronic neuropathic pain conditions often co-exist, including co-morbid conditions associated with pain amplification and psychological distress (e.g., pain, fatigue, sleep disorders, depression, anxiety, etc.).
Abnormal somatosensory testing	Hypoesthesia, hypo- or hyperalgesia, or allodynia commonly seen on somatosensory testing. Dynamic testing has revealed increased wind up, a surrogate metric of central sensitization in both conditions.
Nerve injury implicated	Anatomical abnormalities observed in corneal nerves consistent with nerve injury (confocal microscopy), similar to neuropathic pain elsewhere in the body (magnetic resonance imaging)
Shared pathophysiology	Somatosensory nerve sensitization, inflammation and supporting cell abnormalities are common to both entities.
Heritability	Both conditions appear to be heritable and shared genetic factors have been demonstrated in large twin studies.
Overlapping therapeutic response	Nerve modulators, such as calcium channel alpha 2 delta ligands (e.g., gabapentinoids), improve symptoms in some individuals.