About Neurotrophic Keratitis

Overview

Neurotrophic keratitis, also known as neurotrophic keratopathy (NK), is a rare degenerative disease that affects the cornea, the clear front part of the eye. It happens when the cornea loses feeling due to nerve damage. This loss of sensitivity leads to instability of the outer layer (epithelium) and damage to the deeper layer (stroma), as well as problems with the tear film that protects the eye. The key symptom of NK is a decrease or absence of corneal sensation. The most common causes of this impairment are related to herpetic keratitis (eye infection caused by the herpes virus), intracranial space-occupying lesions (growths in the brain that can press on nerves affecting the eye), and neurosurgical procedures that damage the trigeminal ophthalmic branch (surgeries that harm the nerve controlling eye sensation). NK is classified by the severity of corneal damage, ranging from minor surface irregularities to deep ulcers that can affect the cornea’s layers and may lead to severe thinning or rupture.

Causes and Risk Factors

The causes of neurotrophic keratitis can vary, but some common ones include congenital problems present at birth, eye conditions like herpes infections, neurological issues or surgeries that affect the nerves, and systemic conditions like diabetes mellitus. Direct damage to the corneal nerves can also occur from chronic use of certain eye drops.

Non-modifiable risk factors for neurotrophic keratitis cannot be changed or controlled. These include:

• Increasing age
• Genetic predispositions, such as a positive family history of the disease or related eye conditions, can also increase the risk.

Modifiable risk factors, factors that can be influenced or changed, for neurotrophic keratits may not be well-documented, meaning there is limited information about lifestyle or environmental changes that could reduce the risk of developing this condition. It is generally recommended to maintain a healthy lifestyle and take care of your overall eye health. This includes practicing good hygiene when it comes to eye care, avoiding excessive eye rubbing or trauma, and managing underlying systemic conditions like diabetes.

It's important to note that while these risk factors may increase the likelihood of developing neurotrophic keratitis, they do not guarantee its occurrence. It's always best to consult with an eye care professional for personalized advice and guidance.

Symptoms

In the early stages of neurotrophic keratitis (NK), it is common for individuals to not experience any symptoms. However, as the disease progresses or reaches a higher severity, several symptoms may occur.

The most common early symptoms of NK include:

• Watery eyes can occur in people whose palpebral fissure (the opening between the eyelids) don’t close completely, leaving the eye exposed and prone to irritation
• Reduced or absent corneal sensitivity, which can lead to a decrease in the lacrimation reflex (reduced tear production)
• Disruption of the corneal epithelium (the outermost layer of the cornea), which can result in impaired healing and the development of corneal opacification (the clear part of the eye becomes cloudy)

With later stages, progression, or higher severity of NK, other common symptoms may occur. These can include:

• Redness of the eye
• Pain or discomfort in the affected eye
• Burning sensation in the eye
• Foreign body sensation (feeling like there is something in the eye)
• Visual impairment or decreased vision due to damage to the corneal epithelium and corneal scarring

It's important to note that NK is often diagnosed in its advanced stages when visual acuity has already worsened. This is because individuals with this condition may have impaired corneal sensory innervation, meaning they may not experience typical symptoms such as redness, pain, or discomfort. Therefore, it's crucial to seek medical attention if you notice any changes in your vision or have concerns about your eye health.

Diagnosis

To diagnose neurotrophic keratitis (NK), healthcare providers commonly perform the following examinations, tests, and procedures:

• Clinical history and physical exam: A diagnosis of NK is suspected based on the patient's history and confirmed through a physical exam. The exam includes a thorough cranial nerve exam to assess sensation in the distribution of cranial nerves V1, V2, and V3. This helps to localize nerve involvement.
• Assessment of eyelids: Healthcare providers inspect the eyelids with a special focus on position and movement. This helps determine if exposure keratopathy (damage to the cornea due to inadequate eyelid closure), degenerative changes, or blepharitis (inflammation of the eyelids) may be exacerbating the disease.
• Corneal examination: Common corneal findings in NK include thinning of the cornea, neovascularization (formation of new blood vessels), ulcers with rounded or rolled edges, severe corneal breakdown (melting) and cloudiness causing by scarring. These findings can progress over time.
• Fluorescein staining: During the examination, healthcare providers utilize fluorescein staining to assess the integrity of the corneal epithelium (the outermost layer of the cornea). The intact epithelium is crucial for preventing infections.
• Cultures: If a corneal ulcer is present, healthcare providers may obtain cultures to identify any infectious causes. This helps rule out infections as the cause of the condition before making a diagnosis of NK.

It is important for healthcare providers to perform a comprehensive evaluation using these diagnostic tools to accurately diagnose NK and determine its severity.

Treatment Options

The goals of treatment for neurotrophic keratitis (NK) are to prevent the progression of corneal damage and promote corneal healing.

There are several treatment options available for NK, depending on the stage of the disease. Here are some of the medication types, therapeutic procedures, lifestyle behavior changes, and other treatments that may be recommended:

• Lubrication: Lubricating the eyes with artificial tears or artificial tear ointment is a common treatment option for all stages of NK. These lubricants help to keep the eyes moist and improve corneal healing.
• Eyelid taping: Eyelid taping involves using special tape to gently close the eyelids during sleep. This helps to protect the cornea and prevent further damage.
• Punctal plugs: Punctal plugs are small devices that are inserted into the tear ducts to block them temporarily. This helps to keep tears on the surface of the eye for a longer period of time, providing additional lubrication.
• Medications: In some cases, medications may be prescribed to help stimulate corneal healing. These medications may include human nerve growth factor or Thymosin 4, which can promote nerve regeneration and improve corneal health.
• Amniotic membrane transplantation: This procedure involves placing a thin piece of amniotic membrane onto the surface of the eye. The membrane contains growth factors that can help promote healing and reduce inflammation.
• Conjunctival flap: A conjunctival flap is a surgical procedure where a piece of tissue from the conjunctiva (the clear tissue that covers the white part of the eye) is used to cover and protect the cornea. This can help to improve corneal healing and prevent further damage.
• Corneal neurotization: Corneal neurotization is a surgical procedure where nerves from other parts of the body are connected to the cornea to provide sensory innervation. This can help restore normal function and promote healing.

In addition to these treatments, it's important to address any underlying conditions that may be causing or contributing to NK. Collaborating with a cornea specialist and oculoplastic surgeon (eyelid repair specialist) can provide patients with a comprehensive approach for their treatment.

Remember, it's essential to consult with a healthcare professional for an accurate diagnosis and personalized treatment plan for NK based on individual circumstances.

Medication dosing may be affected by many factors. Check with your health care professional about dosing for your individual situation. Side effects can occur. Check with your health care professional or read the information provided with your medication for side effect information.

Progression or Complications

Neurotrophic keratitis (NK) can progress over time if left untreated. The natural progression of NK involves the breakdown of the corneal epithelium, which is the outer layer of the cornea. This can lead to corneal ulceration, corneal melting (thinning), and even corneal perforation. As a result, vision loss may occur.

Complications commonly associated with NK include corneal scarring and vision impairment. Corneal scarring happens when the cornea tries to heal itself after damage, leading to an irregular and opaque appearance. This can further affect vision clarity.

It's important to note that the success of treatment depends on early detection and intervention. Therefore, if you suspect you have NK or any concerning eye symptoms, it is essential to seek medical advice from an eye care professional. They will be able to provide a proper diagnosis and recommend appropriate treatment options tailored to your specific needs.