Dry Eye Disease (Keratoconjunctivitis Sicca)

Dry eye disease (DED) results from either inadequate tear volume (aqueous-deficient, ADDE) or increased tear evaporation from poor tear film quality (evaporative, predominantly meibomian gland dysfunction — a common cause and common in blepharitis). The 2017 TFOS DEWS II consensus definition frames DED as a multifactorial ocular surface disease with tear film instability, hyperosmolarity, inflammation and neurosensory abnormalities playing a role.

Causes

• Ageing
• Systemic disease — rheumatoid arthritis, SLE, Sjögren syndrome (present in ~50% of patients with severe dry eye)
• Drugs — β-blockers, oral retinoids, sedatives, diuretics, antihypertensives, the combined oral contraceptive pill, anticholinergics
• Menopause
• Meibomian gland dysfunction/blepharitis (evaporative subtype)

History

• Dryness, grittiness, stinging, redness, foreign body sensation
• Photophobia when severe
• Paradoxically, evaporative DED may cause profuse reflex tearing ± foam at the eyelid margin

Worsened by: prolonged visual tasks (screens, driving, TV), dry/windy/dusty environments, dehydration, and the drug classes above.

Investigations

• Schirmer test — filter paper in the lower eyelid fold, blot the closed eye dry first; measure wetting distance at 5 minutes. There’s no single universal cut-off, but <10 mm/5 min is the commonly used abnormal threshold (some sources use <5.5 mm); performed without anaesthesia it estimates stimulated reflex tear flow.
• Tear break-up time (TBUT) — instill fluorescein, ask the patient to blink to refresh the tear film, then time to the first dry spot. <10 seconds is abnormal and indicates the evaporative subtype.

Management

Artificial tears first-line (e.g. Systane, Poly-Tears, Liquifilm):

• Drops: 1 drop every 1–12 hours as required
• Ointment: applied at night as required
• Spray: 1–2 sprays on closed eyelids 3–4 times daily

Switch to preservative-free formulations if irritation occurs with preservative-containing drops (PBS rules require trying preservative-containing drops first).

Dietary: omega-3 fatty acid supplementation (fish/plant oil sources) has evidence for symptom improvement via an anti-inflammatory effect on the ocular surface.

Treat the underlying cause — e.g. blepharitis/meibomian gland dysfunction (see blepharitis.md).

Ophthalmologist-initiated options for more severe/aqueous-deficient disease:

• Topical corticosteroids — effective but increase glaucoma and early cataract risk with long-term use
• Ciclosporin — immune-modulating, reduces symptoms and corneal surface damage in severe ADDE
• Punctal plugs
• Testosterone eye drops, autologous serum eye drops (less commonly used)