Neuropathic Corneal Pain is defined by The National Organization for Rare Disorders (NORD) as "a constellation of persistent ocular pain symptoms (i.e., burning, increased sensitivity to light or wind, shooting pains originating in one or both eyes) that may present with or without ocular surface abnormalities." ¹ The cornea is the most nerve-dense tissue and the most powerful pain generator in the body^2,3.

Neuropathic corneal pain is also referred to as corneal neuralgia, keratoneuralgia, corneal allodynia, corneal neuropathy, or ocular neuropathic pain.

The exact mechanism of NCP is not yet clear, but many specialists believe that it occurs when corneal nerves are damaged or exposed to persistent inflammation. NCP can result from eye surgeries (including laser eye surgery), diseases (such as trigeminal neuralgia , Sjogren's, and diabetes, among a host of others), medications (such as isotretinoin), and other eye conditions (such as chronic dry eyes)^3,4. Covid-19 can also induce NCP, as reported by a recent study⁵. NCP can affect a person of any age, sex, ethnicity, or background.

NCP is frequently misdiagnosed as typical dry eye disease⁷. This is likely because NCP almost always has a dry eye component; the corneal nerve dysfunction in NCP disrupts signals to the lacrimal and meibomian glands that keep eyes moist. Moreover, chronic dry eye disease can be a cause of NCP³.

NCP cannot be detected via a regular slit-lamp examination by an optometrist or ophthalmologist. Clinical signs of common ocular surface disorders or injuries that could result in pain may be lacking in an NCP patient³. As a result, some patients' eyes may look normal at first glance. Many are told that the pain is all “in their head”¹⁰.

To diagnose NCP, imaging of the corneal nerves with an in vivo confocal microscope is often required. Clinical history, symptoms, and results of basic ophthalmologic examination are also considered⁴. As there is no confocal microscope available for physician use in Canada, Canadian eye care providers typically only offer speculative diagnoses of NCP. Even obtaining a speculative diagnosis can be difficult, as patients frequently report that their eye care providers know very little about NCP¹⁰.

A range of evidence-based treatment options exist for NCP. A multi-step approach is usually required to treat NCP^3,4.

First-line treatment involves regenerating corneal nerves using autologous serum drops. These are eye drops containing nerve growth factors made from a patient’s own blood. Anti-inflammatory eye drops (corticosteroids) are typically used in conjunction with serum drops, as inflammation needs to be suppressed to maximize nerve growth⁴. Another option is the use of amniotic membranes, which offer anti-inflammatory and neurotrophic benefits for the ocular surface⁴.

Protective contact lenses (e.g., scleral lenses, bandage contact lenses) and prosthetic ocular surfaces (e.g., PROSE, Eye Print Pro) are effective in mitigating symptoms of NCP. These work by shielding the overactive corneal nerves from external environmental stimuli, thus reducing discomfort and pain⁴.

Managing comorbid dry eye disease is another major component in successfully treating NCP. This includes basic dry eye management, such as the use of lubricating eye drops, and warm compresses followed by lid massage. For moderate and severe cases of dry eye, treatment options include intraductal meibomian gland probing, intense pulse light (IPL) therapy, punctal plugs or punctal cautery, among others ^3,4.

Oral medication has also been shown to be effective in mitigating pain in NCP patients. These medications include nortriptyline⁸, low-dose naltrexone⁹, carbamazepine, tramadol, gabapentin, and pregabalin⁴.