EXPOSURE KERATITIS

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Normally cornea is covered by eyelids during sleep and is constantly kept moist by blinking movements during awaking. When eyes are covered insufficiently by the lids and there is loss of protective mechanism of blinking the condition of exposure
  keratopathy (keratitis lagophthalmos) develops.

Causes
Following factors which produce lagophthalmos may lead to exposure keratitis:
1. Extreme proptosis due to any cause will allow inadequate closure of lids.
2. Bell's palsy or any other cause of facial palsy.
3. Ectropion of severe degree .
4. Symblepharon causing lagophthalmos.
5. Deep coma associated with inadequate closure of lids.
6. Physiological lagophthalmos. Occasionally, lagophthalmos during sleep may occur in healthy individuals.
Pathogenesis
Due to exposure the corneal epithelium dries up
followed by dessication. After the epithelium is cast
off, invasion by infective organisms may occur.

Clinical features
Initial dessication occurs in the interpalpebral area
leading to fine punctate epithelial keratitis which is
followed by necrosis, frank ulceration and
vascularization. Bacterial superinfection may cause
deep suppurative ulceration which may even
perforate.

Treatment
1. Prophylaxis. Once lagophthalmos is diagnosed
following measures should be taken to prevent
exposure keratitis.
Frequent instillation of artificial tear eyedrops.
Instillation of ointment and closure of lids by
a tape or bandage during sleep.
Soft bandage contact lens with frequent
instillation of artificial tears is required in cases
of moderate exposure.
Treatment of cause of exposure: If possible
cause of exposure (proptosis, ectropion, etc)
should be treated.

2. Treatment of corneal ulcer is on the general lines

3. Tarsorrhaphy is invariably required when it is not possible to treat the cause or when recovery of the cause (e.g., facial palsy) is not anticipated.