What is corneal neuralgia?

What is Corneal Neuralgia?

Corneal neuralgia (also termed neuropathic corneal pain, keratoneuralgia, or corneal neuropathy) is a chronic pain condition caused by injury or dysfunction of corneal nerves, characterized by burning, stinging, or aching ocular pain that is disproportionate to clinical findings on examination. 1, 2

Pathophysiology

Corneal neuralgia develops through two primary mechanisms:

• Peripheral sensitization occurs when corneal nerve injury leads to aberrant nerve regeneration, causing corneal nociceptors to become hyperexcitable and fire spontaneously 1
• Central sensitization develops when chronic inflammation upregulates excitatory neurotransmitters in the trigeminal pathway (thalamus, higher cortical areas), amplifying neuronal responses even after peripheral healing 1, 3

The cornea is the most densely innervated tissue in the human body, supplied by the ophthalmic branch of the trigeminal nerve, making it particularly vulnerable to neuropathic pain states 4, 5

Common Causes and Risk Factors

Corneal neuralgia can develop from multiple triggers:

• Post-surgical: Following refractive surgery (LASIK), cataract extraction 1
• Post-infectious: Herpes zoster ophthalmicus causing post-herpetic neuralgia 1
• Chronic ocular surface disease: Aqueous tear deficiency, meibomian gland dysfunction, chronic inflammation 1
• Trauma: Chemical burns, mechanical injury, traumatic brain injury 1, 6
• Idiopathic: No identifiable cause in some patients 1

Clinical Presentation

The hallmark feature distinguishing corneal neuralgia from nociceptive pain is symptoms that dramatically outweigh observable signs 1, 7:

• Pain descriptors: Burning, stinging, aching, irritation, dryness, grittiness 1
• Photophobia and wind hyperalgesia are characteristic features 1, 7
• Allodynia: Pain triggered by normally non-painful stimuli like light touch or wind 1
• Persistent symptoms despite appropriate treatment and resolution of ocular surface abnormalities 1, 7

Patients often experience comorbid anxiety, depression, and mood disorders due to the chronic, debilitating nature of the pain and neural connections to emotional processing centers (prefrontal cortex, amygdala, insula) 1

Diagnostic Approach

Clinical Examination

Perform thorough ocular surface evaluation to identify nociceptive sources (aqueous tear deficiency, tear film instability, inflammation, epithelial erosions) that may coexist with or trigger neuropathic pain 1

Anesthetic Challenge Test

This test differentiates peripheral from central pain mechanisms 1, 7:

• Pain must be present before testing
• If pain improves after topical anesthetic: Suggests peripheral neuropathic or nociceptive component 1, 7
• If pain persists after topical anesthetic: Suggests central sensitization or non-ocular pain source 1, 7

In Vivo Confocal Microscopy (IVCM)

IVCM provides objective confirmation of nerve damage, serving as an "optical biopsy" 1:

• Decreased corneal nerve density correlates with allodynia and photoallodynia 1
• Microneuromas (sudden swelling of injured nerve terminals) are specific for corneal neuralgia 1
• Increased nerve tortuosity, reflectivity, and beading indicate nerve pathology 1

Distinction from General Neuropathic Pain

While corneal neuralgia is a type of neuropathic pain, it differs from classic neuralgias (like trigeminal neuralgia) 2:

• Classic neuralgias: Brief, electric shock-like paroxysmal attacks triggered by specific stimuli 2
• Corneal neuralgia: More continuous burning or aching pain, though can have paroxysmal components 1, 2

This distinction matters because treatment approaches differ—classic trigeminal neuralgia responds to carbamazepine/oxcarbazepine, while corneal neuralgia requires neuro-regenerative and neuromodulatory approaches 2

Clinical Significance

Corneal neuralgia is frequently misdiagnosed because the disparity between severe symptoms and minimal examination findings leads clinicians to dismiss complaints as "psychological" or "functional," causing diagnostic delays and poor outcomes 3. The condition can persist indefinitely if untreated, significantly impacting quality of life 4. Recognition requires high clinical suspicion when pain severity exceeds observable pathology 1, 7.