SN7 SHORT NOTE 5M

Describe conjunctival xerosis and the management of the dry ocular surface.

Ophthalmology · 3rd Professional

Conjunctival xerosis is dryness and keratinisation of the conjunctiva.
It is conventionally divided into parenchymatous xerosis, caused by local destruction of the conjunctiva, and epithelial xerosis, caused by vitamin A deficiency.

Type	Cause and features
Epithelial xerosis	Vitamin A deficiency. The conjunctiva loses its lustre and becomes non-wettable, with BITOT’S spots. It is reversible with systemic vitamin A, and is bilateral.
Parenchymatous xerosis	Local destruction of the conjunctiva and its glands by cicatrising disease — trachoma, chemical burns, stevens-johnson syndrome, ocular cicatricial pemphigoid, and radiation. Irreversible, and usually unilateral or asymmetrical. Vitamin A will not help it.
Exposure-related	From proptosis, seventh nerve palsy, ectropion, symblepharon or lagophthalmos — the surface is anatomically normal but is not being covered

The distinction is entirely practical: epithelial xerosis is a nutritional emergency that reverses within days on vitamin A; parenchymatous xerosis is a structural loss that requires lubrication, surface reconstruction and, ultimately, management of a permanently dry eye

Assessment — schirmer test (which is normal in mucin deficiency, a point worth remembering); tear break-UP time, shortened in mucin and lipid deficiency; staining with fluorescein and lissamine green; assessment of the lids, blink and closure; and impression cytology or conjunctival biopsy to demonstrate goblet cell loss and keratinisation
Treatment principles — a ladder:
1. Treat the cause — systemic vitamin A; control of the cicatrising disease; correction of exposure
2. Preserve the tears — humidified environment, avoidance of fans and air conditioning, moisture chamber spectacles, and punctal occlusion
3. Replace the tears — preservative-free lubricant drops, gels and ointments, used frequently; autologous serum drops in severe surface disease.

Establish whether the xerosis is nutritional or cicatricial; bilateral in a malnourished child means vitamin A, and unilateral after a burn or trachoma means reconstruction
Give vitamin A on suspicion in a child; it is cheap, safe at the recommended dose and reverses the condition within days
Use preservative-free drops when they are needed more than four times daily; benzalkonium chloride damages the very surface being treated
Consider autologous serum drops in severe surface disease; they contain growth factors and vitamin A that no artificial tear provides
Offer a scleral lens in intractable surface disease; it maintains a fluid reservoir over the cornea and often succeeds where everything else has failed

All questions in Diseases of the Conjunctiva