Update on Neurotrophic Keratopathy

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Neurotrophic Keratopathy: A Comprehensive Update for Ophthalmologists and Trainees

Neurotrophic keratopathy (NK) is a rare, potentially sight-threatening corneal disease characterized by impaired corneal innervation leading to decreased or absent corneal sensation and subsequent impaired corneal healing. This condition results primarily from damage to the ophthalmic branch of the trigeminal nerve, which is responsible for sensory innervation of the cornea. The loss of trophic support from these nerves compromises corneal epithelial integrity, resulting in progressive epithelial breakdown, persistent epithelial defects, stromal ulceration, and in severe cases, corneal perforation and vision loss.​

Pathophysiology and Causes

The cornea is one of the most densely innervated tissues in the body, with corneal nerves playing a critical role not only in sensation but also in maintaining the health and homeostasis of the ocular surface through neurotrophic factors. Damage to these sensory nerves disrupts this neurotrophic support, impairing epithelial cell proliferation, differentiation, and wound healing.

Common causes of NK include infectious etiologies such as herpes simplex and herpes zoster keratitis, surgical trauma (e.g., trigeminal nerve or ocular surgery), chemical and thermal injuries, chronic use of topical medications, systemic diseases like diabetes mellitus, multiple sclerosis, and intracranial pathologies affecting the trigeminal nerve such as tumors or aneurysms.​

Clinical Presentation and Staging

Despite the severity of underlying corneal damage, patients with NK often present with minimal or no symptoms due to the diminished corneal sensation. This silent progression makes early diagnosis and vigilance crucial.

The disease progression is classically categorized into three stages according to the Mackie classification:

• Stage 1: Characterized by mild epithelial changes including punctate epithelial erosions and irregularities without frank epithelial defect. Patients may have decreased tear film stability and subtle corneal haze.​

• Stage 2: Presence of persistent or recurrent epithelial defects (PEDs) typically oval-shaped with smooth, rolled edges due to impaired epithelial migration and healing. There is no stromal involvement at this stage but Descemet’s folds and mild anterior chamber reactions may be seen.​

• Stage 3: The most severe stage marked by stromal ulceration, melting, and often corneal perforation. This stage carries a high risk of permanent vision loss and significant ocular morbidity.​

Diagnosis

A high index of suspicion is required to diagnose NK, especially in patients with known risk factors. Clinical evaluation includes:

• Corneal Sensation Testing: Using a cotton wisp, Cochet-Bonnet esthesiometer, or specialized devices to quantitatively measure corneal sensitivity.​

• Slit-lamp Examination: To assess epithelial integrity, presence of epithelial defects, stromal changes, tear film quality, and associated conjunctival inflammation.

• Fluorescein and Rose Bengal Staining: To detect epithelial damage and conjunctival involvement.

• Tear Film Assessment: Schirmer’s test and tear breakup time (TBUT) to evaluate tear quantity and quality.

• Imaging: Anterior segment optical coherence tomography (AS-OCT) and in vivo confocal microscopy (IVCM) can visualize the subbasal nerve plexus and assess nerve density, epithelial thickness, and stromal changes.​

Histopathology and Cellular Changes

Histological studies reveal thinning of the corneal epithelium from the normal 5-7 layers to as few as 1-2 layers. Basal epithelial cells show loss of polarity, vacuolization, abnormal basement membrane synthesis, and reduced mitotic activity. These changes impair epithelial regeneration and contribute to persistent defects.​

Management Strategies

The management of NK is challenging and requires a multimodal approach tailored to disease severity.

Conservative Medical Treatment

• Preservative-free Artificial Tears and Lubricants: To maintain ocular surface hydration and protect the epithelium.​

• Therapeutic Contact Lenses: Silicone hydrogel or scleral lenses to protect the corneal surface and promote healing.

• Autologous Serum Eye Drops: High in growth factors and essential nutrients, they enhance epithelial regeneration and improve symptoms.​

• Matrix Regenerating Therapy: Agents such as ReGeneraTing Agent (RGTA) (Cacicol®) have shown promise in promoting corneal healing by mimicking extracellular matrix components.​

Advanced and Surgical Treatments

• Recombinant Human Nerve Growth Factor (rhNGF): Cenegermin (Oxervate™) is a topical biological therapy that has revolutionized treatment by stimulating corneal nerve regeneration and accelerating epithelial healing. It is approved for stage 2 and 3 NK and administered as eye drops over an 8-week course.​

• Amniotic Membrane Transplantation (AMT): Provides trophic support, reduces inflammation, and promotes epithelialization, used particularly in non-healing epithelial defects and ulcers.​

• Tarsorrhaphy: Surgical or temporary botulinum toxin-induced ptosis to protect the cornea by reducing exposure in refractory or severe cases.

• Corneal Neurotization: A novel surgical technique involving transfer of healthy nerves to restore corneal sensation in select patients.

• Management of Corneal Perforation: Small perforations can be treated with cyanoacrylate glue and bandage contact lenses or AMT; larger perforations may require tectonic keratoplasty.​

Prognosis and Follow-up

Early diagnosis and prompt treatment significantly improve visual outcomes. Stages 1 and 2 are more amenable to medical therapy, while stage 3 requires aggressive surgical intervention. Regular follow-up with assessment of corneal healing and nerve recovery is essential to prevent progression and complications such as secondary infections and scarring.​

Take-home message

Neurotrophic keratopathy remains a diagnostically challenging but increasingly treatable corneal disease. Advances in biologic therapies like rhNGF have expanded therapeutic options beyond supportive care to potentially reverse nerve damage. Ophthalmologists must maintain vigilance in at-risk populations and employ a comprehensive, stage-based management approach to optimize patient outcomes.