Burning Eye Syndrome: Do Neuropathic Pain Mechanisms Underlie Chronic Dry Eye?

Abstract

Objective: Dry eye is a multi-factorial disorder that manifests with painful ocular symptoms and visual disturbances, which can only be partly attributed to tear dysfunction. This disorder may also involve neuroplasticity in response to neuronal injury. This review will emphasize the key characteristics of dry eye pain and its pathologic mechanisms, making the argument that a subset of dry eye represents a neuropathic pain disorder of the eye, more appropriately called "burning eye syndrome."

Methods: A literature review was conducted using a PubMed search focusing on dry eye, corneal nociception, and neuropathic pain. Articles were reviewed and those discussing clinical course, pathophysiology, and neuronal regulation of chronic ocular pain as related to dry eye were summarized.

Results: We found that there is a discordance between ocular pain and dryness on the ocular surface. Although tear dysfunction may be one of the initial insults, its persistence may be associated with repeated ocular sensory nerve injury leading to an acute-to-chronic pain transition associated with neuropathologic changes (peripheral and central sensitization), neuronal dysfunction, and spontaneous ocular pain.

Conclusion: Dry eye is becoming a major health concern due to its increasing incidence, significant morbidity, and economic burden. Recent evidence suggests that a subset of dry eye may be better represented as a chronic neuropathic pain disorder due to its features of dysesthesia, spontaneous pain, allodynia, and hyperalgesia. Future therapies targeted at the underlying neuroplasticity may yield improved efficacy for patients with this subset of dry eye, which we term "burning eye syndrome."

Keywords: Cornea; Dry Eye; Hyperalgesia; Neuronal Dysfunction; Neuropathic Pain; Sensitization.

Figure 1

Schirmer strips are used to quantify ocular surface wetness by measuring the amount of moisture (in mm) on a strip after 5 minutes in the eye.

Figure 2

Proposed pathogenesis of Burning Eye Syndrome.

Figure 3

Diffuse corneal staining (white areas on cornea) due to epithelial cell disruption with subsequent exposure and activation of corneal nerves.

Figure 4

Various clinical examples of meibomian gland dysfunction. ( A ) Telangiectasias on the eyelid margin. ( B ) Foaminess on the eyelid margin indicating abnormal meibum quality. ( C ) Abnormal meibum quality detected by manual expression (meibum is thickened and opaque).