Updated: Sep 26, 2021
Click to view article: Ocular Surface Insight, Winter 2021 issue: https://osimag.co.uk/wp-content/uploads/2021/03/OSI-Magazine-Issue-11-Winter-2021.pdf
By Dr. Seema Nanda - Clinical Director: Nanda Dry Eye & Vision Institute
* If the Wi-Fi symbol on a mobile phone shows no bar (indicating a poor signal) the connection is lost and a call cannot be completed.
* Similarly, if the corneal nerves degenerate, the impaired innervation or poor signal, cannot be sent to the trigeminal nerve, the connection is lost so the ocular surface cannot heal adequately.
* This illustration of faulty communication depicts the rare condition known as: Neurotrophic Keratitis (NK).
Neurotrophic keratitis, or neurotrophic keratopathy, is a disease caused by damage to the corneal nerves that affects less than 65,000 people in the USA.1 In a healthy cornea, there are about 7,000 nerve endings per square mm.2,3 These nerves are essential to the health of one’s eyes as they help with reflexes of blinking and tearing to maintain a healthy ocular surface.1 The nerves provide protection and nourishment to the ocular surface due to the avascular nature of the cornea. Akin to an entire electric grid shutting down, when this neural network is injured, moderate neurotrophic keratitis can ensue and become more severe. Consequently, an increased risk of ulcer formation, corneal melt, and subsequent scarring can occur, which contributes to a patient’s permanent loss of vision. 1
Symptoms of neurotrophic keratitis may include: changes in tear viscosity, redness in the eyes, and blurred vision.5,7 Some individuals with neurotrophic keratitis may not have any symptoms at all, since their damaged corneal nerves no longer sense feeling.1,5 The hallmark in diagnosing a neurotrophic cornea is the reduction in corneal sensitivity or complete anesthesia of the ocular surface.4
The clinical diagnosis can be deduced with the patient’s complete medical history and an ocular examination; however, the treatment can be elusive and reasonably challenging until now. Several clinical causes of NK result from (1) common diseases in the herpes family – simplex or zoster, (2) recurrent epithelial erosions from trauma or surgery, or (3) toxicity from prolonged use of topical ocular medications. Hypoesthesia can occur, thus resulting in the neurotrophic condition when the trigeminal ganglion – including the ophthalmic branch – becomes damaged.3 Another cause involves individuals who are known to be poor wound healers who may also suffer from this keratopathy due to sensory loss. Characteristically, inadequately controlled diabetics may develop neuropathies of their extremities in their hands and feet. Comparably, these patients may also develop denervation of nerves in their corneas leading to a neurotrophic keratopathy.
NK can be divided into three stages based on severity, according to the Mackie Classification system. Stage I is characterized by alterations of the corneal epithelium, which are dry and opaque, with superficial punctate keratopathy and mild corneal edema. Stage II is depicted by development of epithelial defects, often near the center of the cornea. Stage III is categorized by ulcers of the cornea, accompanied by stromal edema and/or melting that may result in corneal perforation.3 The key in differentiation from other corneal maladies requires checking a decrease in corneal sensitivity.
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