Understanding the tear film
Every blink spreads a fresh tear film over the cornea. It has three layers: an oily outer layer (from meibomian glands in the eyelids) that limits evaporation, a watery middle layer for moisture and nutrients, and a mucin inner layer that helps tears stick evenly to the corneal surface. A problem in any one layer breaks the film, causing dry-eye disease.
The corneal nerves constantly sense the tear film’s quality; when it breaks up too quickly, they signal discomfort — burning, grittiness, tiredness — and sometimes reflex watering, which is why watery eyes are often dry eyes.
Symptoms and triggers
Burning, stinging or gritty sensation; dryness that worsens through the day; tired or heavy eyes after screen use; fluctuating blur that clears with blinking; light sensitivity; contact-lens intolerance; stringy mucus; and paradoxically, watering. Triggers include prolonged screens (we blink less), air conditioning and fans, pollution and dust, contact lenses, ageing, hormonal changes, certain medications (antihistamines, some antidepressants, isotretinoin), and systemic conditions such as thyroid disease or Sjögren’s syndrome.
Why dry eye matters before surgery
Refractive surgery (LASIK, SMILE, PRK, ICL) and cataract measurements both depend on a stable corneal surface. An unstable tear film changes the cornea’s shape reading, which can mislead surgical planning, and slows post-operative surface healing. For this reason, ocular-surface optimisation is often the first step before any elective eye procedure — treating it first improves both measurements and comfort.
Evaluation
Assessment reviews symptoms, screen habits, environment, lens wear and systemic health, followed by slit-lamp examination of the lids and tear film. Tests may include tear-film break-up time, staining with diagnostic dyes to reveal surface damage, meibomian gland evaluation, and tear osmolarity or other point-of-care tests where available. The goal is to classify the type — evaporative (oily-layer deficiency, the commonest), aqueous-deficient, or mixed — because treatment differs.
Treatment: a staged approach
Foundations: conscious blinking habits, screen breaks (the 20-20-20 habit), humidifying dry environments, avoiding direct fan/AC flow, eyelid hygiene for gland dysfunction, and preservative-free lubricating drops.
Next steps when foundations are not enough: warm compresses and lid massage; anti-inflammatory drops such as short courses of prescribed medication or ciclosporin/tacrolimus in selected cases; oral omega-3 in appropriate patients; punctal plugs to retain tears; and in-office therapies for meibomian gland dysfunction.
Treating the cause: managing allergy and eyelid inflammation, reviewing culprit medications with the prescribing physician, and coordinating care for systemic associations.
Dry-eye therapy is typically a programme, not a one-off prescription — symptoms respond over weeks as the surface recovers.