```html

Neurotrophic Keratitis – A Complete Patient Guide

Overview

Neurotrophic keratitis (NK) is a rare, progressive disease of the cornea (the clear front surface of the eye) caused by loss or severe reduction of corneal sensation. The lack of sensation impairs the normal protective reflexes and tear production, making the cornea vulnerable to epithelial breakdown, ulceration, and ultimately scarring.

• Who it affects: Adults of any age, but it is most common in people with a history of eye surgery, facial nerve injury, or systemic conditions that affect nerves (e.g., diabetes).
• Prevalence: Precise global numbers are unknown because NK is often under‑diagnosed. In the United States, an estimated 1–2% of patients seen in tertiary ophthalmology clinics have some form of neurotrophic keratitis [1].
• Classification: The disease is staged by severity (Mackie classification):
  • Stage 1 – Punctate epithelial erosions.
  • Stage 2 – Persistent epithelial defect >2 mm.
  • Stage 3 – Corneal ulceration with stromal melting or perforation.

Symptoms

Because corneal sensation is reduced, classic “pain” may be absent. Patients often present with subtle or atypical complaints:

• Blurred or decreased vision – due to epithelial irregularities or scarring.
• Redness (hyperemia) – an inflammatory response to epithelial breakdown.
• Foreign‑body sensation or feeling that something is “stuck” in the eye, despite reduced pain.
• Dryness or gritty feeling – secondary to impaired tear film.
• Photophobia – especially with ulceration.
• Excessive tearing (epiphora) – reflex tearing in response to ocular surface irritation.
• Recurrent corneal erosions – the epithelium repeatedly sloughs off.
• Visible epithelial defect or ulcer on slit‑lamp examination (often the first objective finding).
• Loss of corneal reflex – clinicians may note a diminished blink response when the cornea is touched with a wisp of cotton.

Causes and Risk Factors

NK results when the trigeminal (ophthalmic) branch that supplies sensation to the cornea is damaged. Common etiologies include:

Ocular causes

• Herpes simplex or herpes zoster keratitis – viral inflammation can destroy nerve endings.
• Eye surgery – especially corneal refractive procedures (LASIK, PRK), cataract extraction, or penetrating keratoplasty that transect corneal nerves.
• Repeated ocular surface trauma – contact‑lens wear, chronic foreign‑body exposure.
• Chemical or thermal burns – direct injury to the corneal nerves.

Systemic or neurological causes

• Diabetes mellitus – peripheral neuropathy may involve the trigeminal nerve.
• Multiple sclerosis – demyelination of cranial nerves.
• Brainstem or cavernous sinus lesions – tumors, stroke, or aneurysms affecting the trigeminal pathway.
• Facial nerve palsy (Bell’s palsy) – reduced blink reflex leads to exposure and nerve insult.
• Neurotrophic drugs – long‑term use of topical anesthetics or certain systemic neurotoxic agents.

Risk factors

• History of ocular viral infection.
• Previous ocular surgery, especially within the last 6 months.
• Uncontrolled diabetes or diabetic neuropathy.
• Chronic dry‑eye disease (e.g., Sjögren’s syndrome).
• Advanced age – corneal nerves naturally decline with age.

Diagnosis

Diagnosis is clinical but relies on a combination of history, examination, and specialized tests.

1. Detailed history and symptom review

Identify prior surgeries, infections, systemic disease, or neurologic events.

2. Slit‑lamp biomicroscopy

Allows visualization of epithelial defects, staining patterns with fluorescein, and assessment of stromal integrity.

3. Corneal sensitivity testing

Using a Cochet‑Bonnet or a newer esthesiometer, the clinician measures the threshold for tactile sensation. Sensitivity <5 g/mm² is highly suggestive of NK.

4. Imaging (optional)

• Anterior segment optical coherence tomography (AS‑OCT) – provides cross‑sectional images of epithelial thickness and ulcer depth.
• In‑vivo confocal microscopy – can visualize sub‑basal nerve plexus loss.

5. Laboratory work‑up (when systemic cause suspected)

Blood glucose, HbA1c, viral serologies, and MRI of the brain/orbits if neurologic lesion is suspected.

Treatment Options

Management is stage‑specific and aims to restore corneal sensation, promote epithelial healing, and prevent further damage.

Stage 1 (early)

• Lubrication – preservative‑free artificial tears q2‑4 h; thicker gels at night.
• Bandage contact lens (BCL) – soft silicone hydrogel lenses protect the epithelium.
• Topical antibiotics prophylactically if risk of infection (e.g., moxifloxacin 0.5% qid).

Stage 2 (persistent epithelial defect)

• Therapeutic contact lenses – extended‑wear BCL or scleral lenses to provide a fluid reservoir.
• Autologous serum eye drops (20‑50%) – contain growth factors that promote healing; typically 4–6 times daily.
• Recombinant human nerve growth factor (rhNGF) – cenegermin – FDA‑approved for NK; 0.1 mg/mL eye drops 6 times/day for 8 weeks (first‑line for stage 2‑3).
• Matrix regenerating agent (RGTA) – Cacicol – a heparan‑sulfate mimic that stabilizes extracellular matrix; used 1‑2 drops daily.

Stage 3 (ulceration, melting, perforation)

• Amniotic membrane transplantation (AMT) – sutured or placed via a ProKera device to provide anti‑inflammatory and healing substrate.
• Tarsorrhaphy – temporary or permanent partial eyelid closure to reduce exposure.
• Corneal gluing (synthetic or autologous fibrin glue) – for small perforations.
• Lamellar or penetrating keratoplasty – surgical corneal transplant when stromal loss is extensive.
• Systemic antibiotics/antivirals as indicated by culture or suspicion of infection.

Adjunctive measures for all stages

• **Punctal plugs** – occlude tear drainage to increase ocular surface moisture.
• **Oral omega‑3 fatty acids** (1 g EPA/DHA daily) – modest benefit for dry‑eye component.
• **Control of systemic disease** – tight glycemic control, antiviral prophylaxis for herpes.

Living with Neurotrophic Keratitis

Daily self‑care and environmental modifications can reduce symptom burden and protect the cornea.

• Lubricate frequently – keep a bottle of preservative‑free tears at work, in your car, and night‑stand.
• Protect the eye – wear sunglasses outdoors to reduce UV exposure and wind‑related dryness.
• Avoid eye rubbing – it can exacerbate epithelial loss.
• Use a humidifier in dry climates or during winter heating.
• Follow medication schedule meticulously – missing doses of cenegermin or serum drops can delay healing.
• Maintain follow‑up appointments – most patients need at least monthly slit‑lamp exams until the defect resolves.
• Contact lens hygiene – if using a therapeutic lens, replace it per the ophthalmologist’s recommendation and clean with hydrogen peroxide systems (no multipurpose solutions).
• Monitor vision changes – use a quick “eye chart” app at home; report any new blurriness promptly.

Prevention

Because NK often follows an inciting event, prevention focuses on minimizing nerve injury and promptly treating risk factors.

• **Pre‑operative counseling** – Discuss nerve‑protective techniques with surgeons (e.g., careful handling during cataract extraction).
• **Prompt treatment of ocular infections** – Early antiviral therapy for herpes keratitis reduces nerve damage.
• **Strict diabetes management** – AHA/ADA goal HbA1c <7% lowers neuropathy risk [2].
• **Avoid chronic topical anesthetic abuse** – Use only under professional supervision.
• **Protective eyewear** during activities that could cause corneal trauma (sports, industrial work).
• **Regular eye examinations** for patients with known risk factors (e.g., longstanding dry‑eye disease, facial nerve palsy).

Complications

If left untreated, neurotrophic keratitis can lead to serious ocular sequelae:

• Corneal scarring – permanent visual axis opacification, often requiring transplant.
• Corneal melting (keratomalacia) – rapid stromal loss that can perforate.
• Corneal perforation – vision‑threatening emergency; may need surgical glue or keratoplasty.
• Secondary infection – bacterial, fungal, or acanthamoeba keratitis can supervene.
• Persistent epithelial defect – can become a chronic ulcerative surface disease.
• Reduced quality of life – chronic discomfort, photophobia, and fear of vision loss.

When to Seek Emergency Care

---

**References**

1. Levy J, et al. Neurotrophic keratitis: current concepts in pathogenesis and management. Cleveland Clinic Journal of Medicine. 2022;89(9):650‑658.
2. American Diabetes Association. Standards of Medical Care in Diabetes—2023. Diabetes Care. 2023;46(Suppl 1):S1‑S350.
3. Mayo Clinic. Neurotrophic keratitis. https://www.mayoclinic.org/. Accessed May 2024.
4. U.S. Food & Drug Administration. Cenegermin (OXERVATE™) Prescribing Information. 2021.
5. World Health Organization. Global report on diabetes. 2021.

```