Why early detection of neurotrophic keratitis is crucial
Understanding disease and diagnosis factors
[not actual doctor and patient]
Neurotrophic keratitis is considered a rare disease (1), but it is likely underdiagnosed as there is no routine testing for it (2). Given risk factors include common procedures and behaviors such as laser eye surgery and contact lens wear or over wear (3), the prevalence of NK could be greater than currently understood.
Why Neurotrophic keratitis occurs
This disease of the corneal epithelium (the cornea's outermost layer) occurs when the sensory nerves to the cornea are damaged and stop functioning as they should. Breakdown of the corneal epithelium happens over time due to a loss or abnormality in the sensory nerves which provide trophic support to the cornea and elicit protective blink/tear reflexes in response to touch, pain and temperature (4). If, for example, a particle of dust is blown into a healthy eye, the sensory nerves detect it and elicit a blink reflex as well as create tears to protect the surface of the eye. As sensory innervation is impaired, the cornea becomes vulnerable to injury and when it does sustain an injury, it heals itself slower (5).
Potential outcomes can be devastating, including ulcers, perforation, infection, scarring, and ultimately, sight loss (2). Importantly, it can easily go undetected precisely because the damage to corneal nerve endings means people may not experience symptoms and may delay seeking care.
Catch it quickly
Given neurotrophic keratitis is a degenerative disease, it progresses from mild to moderate to severe – and detecting it as early as possible is crucial. Patients with Stage 1 NK may experience blurred vision, red eyes and photophobia (extreme sensitivity to light) (6).
Even mild neurotrophic keratitis can lead to changes in vision (7); if left undiagnosed or identified late, the disease can progress quickly. Once in the moderate to severe stages, risks include profound vision loss, corneal scarring and perforation. The surface of the eye develops epithelial defect or ulcers and these open wounds are at risk for infection. In later stages, the inner layer can also break down leading to stromal ‘melting’. This can ultimately result in an opening to the inside of the eye, and potentially the loss of the eye (8).
Risk factors and causes
Various factors can lead to neurotrophic keratitis, including conditions like herpetic infections, diabetes and multiple sclerosis or a deficiency in vitamin A (9). The chronic use of topical eye medications, such as IOP-lowering eye drops (10) for glaucoma and certain topical NSAIDS are a known cause due to preservative toxicity that can cause the corneal nerve damage. Ocular surgery, such as laser vision correction procedures or cataract or glaucoma surgery, raises risk (11). Chemical and physical burns can cause neurotrophic keratitis and although less common, some genetic disorders (Riley-Day syndrome (12), Goldenhar-Gorlin syndrome (13), and Mobius syndrome (14), familial corneal hypoesthesia (15) are associated as well. Risk also increases with age (18).
Diagnosis
If there is a suspicion of neurotrophic keratitis based on assessment of medical history and evaluation of corneal staining, a corneal sensitivity test must be performed. Testing corneal sensitivity can reveal decreased corneal nerve function and when done with additional tests, can confirm the diagnosis (2). Additionally, if a patient is being treated for dry eye disease and not seeing an improvement, evaluation of their medical, ocular, and medication history may reveal a raised risk of neurotrophic keratitis which has so far gone undiagnosed (17). Corneal sensitivity testing takes seconds, but can allow early interventions.
Once neurotrophic keratitis is diagnosed, careful monitoring of patients is required, as disease progression can be asymptomatic (2).
Like many other diseases, early detection is fundamental to patients affected by Neurotrophic keratitis.
References
https://karger.com/oph/article/231/4/191/255551/Neurotrophic-Keratitis
https://www.sciencedirect.com/science/article/abs/pii/S1542012420301476?via%3Dihub
https://rarediseases.org/rare-diseases/neurotrophic-keratitis/
Romero-Díaz de León L, Morales-León JE, Ledesma-Gil J, Navas A. Conjunctival and corneal sensitivity in patients under topical antiglaucoma treatment. Int Ophthalmol. 2016;36(3):299-303. doi:10.1007/s10792-015-0115-1
Jaenen N, Baudouin C, Pouliquen P, Manni G, Figueiredo A, Zeyen T. Ocular symptoms and signs with preserved and preservative-free glaucoma medications. Eur J Ophthalmol. 2007;17(3):341-349. doi:10.1177/112067210701700311https://www.aao.org/eyenet/article/diagnosing-treating-neurotrophic-keratopathy
MED-ALL-NA-2400002 03/2024
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