Dr Ben Wild
Overview |
The cornea is the outermost layer of the eye in front of the iris. It is a clear tissue, void of any blood vessels, and is one of the main optical components responsible focusing lights on the retina. The cornea is composed of 5 different layers with the 3 main layers being the epithelium (outermost layer), stroma (providing the focusing power and strength of the cornea) and the endothelium (innermost layer responsible for making sure the cornea doesn’t swell).
A frontal view of a healthy eye (left) and an eye with a whitish/grey neurotrophic ulcer (right).
Interestingly, the entire corneal epithelium gets replaced every 10 days, allowing the cornea to heal itself very quickly. This rapid healing process is largely due to the release of growth factors from corneal nerves that filter through the stroma and into the epithelium. Without growth signals from these nerves the cornea will not heal.
A sagittal view of a healthy cornea (left) and a cornea with a neurotrophic ulcer (right).
Neurotrophic keratopathy occurs due to a variety of conditions where the corneal nerves stop functioning. Without these nerve signals, the epithelium cannot regenerate. This leads to the development of an ulcer. Because the epithelium cannot fully heal, bacterial and fungal infections are more common. Unlike most other ulcers, these ulcers do not typically cause pain, because the nerves that produce pain signals are not functioning.
Signs and Symptoms |
Signs
Non-healing white/grey spot on the cornea, possible red eye.
Symptoms
Blurry vision, slight irritation, numb eye.
Causes and Risk Factors |
Causes
Loss of nerve fiber stimulation of the corneal epithelium.
Risk Factors
Drug toxicity, diabetes, herpes simplex virus (cold sore), herpes zoster (shingles), tumours, facial surgeries, refractive laser eye surgeries, other eye surgeries, stroke, various neuralgias.
Prevention and Treatment |
Prevention
Avoid use of anesthetic eye drops and seek early treatment of herpes zoster or simplex in the eye.
Treatments
· Bandage contact lens.
· Preservative free artificial tears ever hour or 2.
· Tetracycline pills.
· Tape lids shut at night.
· Amniotic membrane implantation.
· Tarsorrhaphy (sow eyelid shut for an extended period of time).
Prognosis |
Mild neurotrophic keratopathy is an easily manageable condition that can usually be successfully treated with either a bandage contact lens or preservative free artificial tears. Severe keratopathy can lead to melting and perforation of the cornea and possible removal of the eye. Usually, amniotic membrane implantation and/or tarsorrhaphy can avert eye removal but at the severe stage, full recovery is usually not possible.