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PubMed This is a summary of 21 peer-reviewed journal articles Updated
Ophthalmology · Neurotrophic Keratitis

Why It Happens: Nerve Biology and Common Causes

At a Glance

Neurotrophic keratitis develops when damage to the trigeminal nerve reduces corneal sensation, blinking, tears, and healing signals. Herpes infections, diabetes, surgery, trauma, and other nerve problems can cause a painless eye surface injury that requires careful testing.

Understanding why your eye is struggling to heal requires looking at the “wiring” behind the scenes. Your cornea depends on the trigeminal nerve (specifically the ophthalmic branch, or V1) to stay healthy and clear [1][2]. When this nerve is damaged, the eye loses its most important protection and maintenance systems.

The Biology of an “Invisible” Support System

The trigeminal nerve does much more than just sense pain. It acts as the “manager” of your eye’s health through two main functions:

  1. The Reflex Loop: Normally, when your eye feels a bit of dust or starts to get dry, the trigeminal nerve sends a signal to your brain. Your brain then tells your eye to blink and your tear glands to produce moisture [3][4]. When this nerve is damaged, your eye may not blink or tear up enough, even when it is dangerously dry [5].
  2. Trophic (Healing) Factors: Your nerves actually “feed” your cornea. They release specialized proteins and neuropeptides—such as Nerve Growth Factor (NGF) and Substance P—that act like growth signals for the surface of your eye [6][7]. These signals tell the corneal cells to grow, move, and repair any small scratches [8][9]. Without these signals, the surface of your eye (the epithelium) begins to break down because it simply cannot repair itself efficiently [10].

Common Causes of Nerve Damage

Neurotrophic keratitis (NK) usually results from an underlying injury to the nerve [11]. Common causes include:

  • Viral Infections: This is one of the most frequent causes. Viruses like herpes simplex (affecting the eye itself, not just a distant cold sore) or herpes zoster (the shingles virus) can cause inflammation in the nerve that leads to scarring and loss of sensation [12][13].
  • Systemic Diseases: Long-term diabetes can damage the small nerve endings in the eye, much like it causes “numbness” in the feet (neuropathy) [14]. Other conditions like multiple sclerosis can also affect nerve pathways [11].
  • Surgical and Physical Trauma: Surgeries such as LASIK, cataract surgery, or procedures to remove tumors (like an acoustic neuroma) can temporarily or permanently reduce corneal sensation [5][15]. Chemical burns or severe injuries to the face can also damage these delicate nerve fibers [11].
  • Other Factors: Chronic use of toxic eye drops, facial or skull-base lesions, and even some unknown (idiopathic) reasons can also cause NK. The absence of herpes or surgery does not rule out the disease.

The Challenge of “Look-Alike” Conditions

Because NK doesn’t always hurt, and because its early signs look like many other eye problems, it is often misdiagnosed. Your doctor must carefully distinguish NK from these similar conditions:

  • Severe Dry Eye Disease (DED): Like NK, dry eye causes irritation and surface damage. However, patients with typical dry eye usually feel more pain and grittiness than the appearance of their eye would suggest [16][17]. In NK, the patient feels less than expected [11].
  • Infectious Keratitis: Standard bacterial or fungal infections are usually thought to cause a red, extremely painful eye with discharge [18]. However, an infection in a neurotrophic eye may be completely painless and have very little discharge. A patient should never assume an ulcer is “safe” or uninfected just because it does not hurt [19][20]. An NK defect can easily become secondarily infected.

An important component of telling these apart is a sensitivity test [1]. Your doctor may use a specialized instrument called a Cochet-Bonnet esthesiometer to gently touch the eye and measure exactly how much you can feel [2][21]. Reduced sensation strongly supports a diagnosis of neurotrophic keratitis, especially when combined with a history of nerve damage and a thorough slit-lamp examination [1].

Common questions in this guide

What can lead to neurotrophic keratitis?
Damage to the trigeminal nerve can result from herpes simplex or shingles, diabetes, multiple sclerosis, eye or facial surgery, chemical burns, trauma, toxic eye drops, or lesions near the face or skull base. Some cases have no identified cause.
Why might neurotrophic keratitis cause little or no pain?
The damaged corneal nerves cannot send normal warning signals to the brain, and they may also fail to trigger enough blinking and tearing. As a result, significant surface damage can feel mild or painless, so lack of pain does not mean the eye is safe.
How do doctors measure corneal sensation?
An eye doctor may use a Cochet-Bonnet esthesiometer, a device that gently touches the cornea to measure how much sensation remains. The result is interpreted along with your medical and surgical history and a slit-lamp examination.
How is neurotrophic keratitis different from severe dry eye?
Both conditions can cause surface damage, but severe dry eye often causes more pain and gritty irritation than the eye’s appearance would suggest. Neurotrophic keratitis more often causes reduced sensation and less discomfort than expected, although both conditions can occur together.
Can diabetes or past eye and brain surgery affect corneal nerves?
Yes. Long-term diabetes can damage the small nerve endings in the cornea, and procedures such as LASIK, cataract surgery, or surgery near the brain or ear can reduce corneal sensation. An eye-care professional can consider this history when evaluating a nonhealing eye surface.
Could an old herpes infection be involved even if I do not remember it?
A prior herpes simplex infection involving the eye or shingles affecting the forehead or nose can injure the corneal nerves, even if the infection is not remembered. Old scarring or blood vessel growth may provide clues, but their absence does not rule out neurotrophic keratitis.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Was my corneal sensitivity tested using a specialized tool like a Cochet-Bonnet esthesiometer, or just a cotton swab?
  2. 2.Is there evidence of old scarring or blood vessel growth that suggests a past herpes infection I might not have known about?
  3. 3.Does my history of diabetes (or other systemic conditions) play a direct role in how my corneal nerves are functioning?
  4. 4.How do you distinguish my condition from severe dry eye, and are both present at the same time?
  5. 5.Since I have had neurosurgery (or facial surgery) in the past, how does that change the way we should monitor my eye?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

References (21)
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    Expert consensus on the identification, diagnosis, and treatment of neurotrophic keratopathy.

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    The molecular basis of neurotrophic keratopathy: Diagnostic and therapeutic implications. A review.

    Ruiz-Lozano RE, Hernandez-Camarena JC, Loya-Garcia D, et al.

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This page is for informational purposes only and does not constitute medical advice. An eye-care professional should assess your corneal sensation and interpret your symptoms, history, and test results.

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