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Describe exposure keratopathy and neurotrophic keratopathy.

Ophthalmology · 3rd Professional

Exposure keratopathy is corneal damage resulting from failure of the lids to cover and wet the cornea.
The corneal surface is anatomically normal; it is simply not being protected.

Cause	Examples
Lagophthalmos — failure of lid closure	Seventh nerve palsy, which is the classical cause — bell palsy, and particularly leprosy in India, where the combination of lagophthalmos with corneal anaesthesia from fifth nerve involvement is especially dangerous
Proptosis	Thyroid eye disease, orbital tumour, cellulitis and cavernous sinus disease
Lid abnormality	Ectropion, coloboma, symblepharon, scarring after burns or surgery, and over-correction of ptosis
Reduced blinking or loss of consciousness	Parkinsonism; and above all the unconscious, sedated, ventilated or anaesthetised patient, in whom exposure keratopathy is common, entirely preventable, and a recognised cause of avoidable visual loss in intensive care
Nocturnal lagophthalmos	Sleeping with the eyes partly open.

Findings — punctate epithelial erosions in the inferior third of the cornea, in the exposed interpalpebral zone, progressing to a frank epithelial defect, stromal melting, secondary infection and perforation. bell’S phenomenon — the upward rolling of the globe on attempted closure — is protective, and a poor Bell phenomenon greatly increases the risk

Neurotrophic keratopathy is corneal breakdown resulting from loss OF corneal sensation (fifth nerve).
It is not simply a failure of protection: the corneal nerves supply trophic factors (substance P and others) essential for epithelial health.

Cause	Examples
Viral	Herpes simplex and herpes zoster ophthalmicus — the commonest causes
Surgical and traumatic	Trigeminal surgery for neuralgia; acoustic neuroma surgery; and refractive surgery, in which the corneal nerves are divided
Systemic	Diabetes, which is the commonest systemic cause and is widely under-recognised; leprosy; vitamin A deficiency; and familial dysautonomia
Neurological	Cerebellopontine angle tumour, stroke, aneurysm and multiple sclerosis
Toxic	Prolonged topical anaesthetic abuse.

The paradox that defines the condition: the eye has a severe corneal ulcer and the patient has NO pain. They present late, with poor vision or a white eye noticed by someone else, and they are not distressed — which leads to the seriousness being underestimated by everybody, including the doctor

Test corneal sensation before instilling any drop in every corneal presentation; it is the sign that identifies neurotrophic disease and it is easily lost
Protect the eye of every unconscious and ventilated patient with ointment and lid taping; exposure keratopathy in intensive care is common, preventable and indefensible
Do not delay tarsorrhaphy for cosmetic reasons; a temporary suture saves a cornea, and the appearance is a small price that patients accept once it is explained

All questions in Diseases of the Cornea