Neurotrophic keratitis

Neurotrophic Keratitis (NK) is a rare, degenerative disease of the cornea characterized by decreased corneal sensitivity and poor corneal healing. This condition is caused by damage to the trigeminal nerve, which is responsible for providing sensation to the cornea, leading to reduced or absent corneal sensitivity. The lack of normal sensory innervation results in various degrees of corneal epithelial defects, corneal ulceration, and, in severe cases, can progress to corneal perforation.

Etiology

Neurotrophic Keratitis is most commonly caused by any condition that damages the trigeminal nerve or its branches. Causes include herpes simplex virus (HSV) and herpes zoster virus (HZV) infections, surgical interventions to the trigeminal nerve, diabetes mellitus, multiple sclerosis, and chemical burns to the eye. Long-term use of contact lenses can also contribute to the development of NK by causing mechanical damage to the corneal nerves.

Pathophysiology

The pathophysiology of Neurotrophic Keratitis involves the disruption of the normal trophic support provided by the trigeminal nerve to the cornea. This disruption leads to a decrease in corneal sensitivity, impaired healing, and a reduction in tear production and blink reflex, which further exacerbates the condition. The lack of protective sensations can lead to unnoticed injuries to the cornea, increasing the risk of infection and ulceration.

Clinical Presentation

Patients with Neurotrophic Keratitis may present with blurred vision, foreign body sensation, and reduced tear production. In advanced cases, visible signs such as corneal epithelial defects, corneal ulcers, and stromal thinning can be observed. The condition is typically classified into three stages:

• Stage 1: Mild epithelial changes and reduced corneal sensitivity
• Stage 2: Persistent epithelial defects
• Stage 3: Corneal ulceration, stromal melting, and perforation

Diagnosis

Diagnosis of Neurotrophic Keratitis is primarily clinical, based on the patient's history and symptoms, along with a comprehensive eye examination. Specialized tests, such as corneal sensitivity testing using a Cochet-Bonnet esthesiometer, can help confirm the diagnosis. Additional imaging techniques, like corneal topography and confocal microscopy, may be used to assess the extent of nerve damage and corneal changes.

Treatment

The treatment of Neurotrophic Keratitis focuses on promoting corneal healing, preventing further damage, and restoring corneal sensitivity. Management strategies include:

• Lubrication with preservative-free artificial tears and ointments to keep the cornea moist
• Use of autologous serum eye drops to provide essential nutrients and growth factors
• Application of contact lenses to protect the cornea and facilitate healing
• Surgical interventions, such as tarsorrhaphy, amniotic membrane transplantation, or corneal transplantation, in severe cases

Recent advancements have introduced the use of nerve growth factor (NGF) eye drops as a novel treatment for NK, showing promising results in promoting corneal healing and restoring corneal sensitivity.

Prognosis

The prognosis of Neurotrophic Keratitis varies depending on the underlying cause and the stage at which treatment is initiated. Early diagnosis and appropriate management can lead to significant improvement in corneal health and vision. However, advanced stages of the disease may result in permanent vision loss and necessitate corneal transplantation.

NIH genetic and rare disease info

• NIH info on Neurotrophic keratitis

Neurotrophic keratitis is a rare disease.