Dry Eye
Disease & Treatment

A healthy eye is kept moist and protected by a thin, balanced layer called the tear film. This film has three layers: an outer oily (lipid) layer that slows evaporation, a middle watery layer that moisturizes, and an inner mucin layer that helps the tears adhere to the surface. A deficiency or disturbance in any of these layers leads to dry eye.

Dry eye develops through two main mechanisms: insufficient tear production (aqueous deficiency) and excessive tear evaporation (usually due to dysfunction of the oil glands at the eyelid margin). Many patients have both. Interestingly, dry eye can present not only with dryness but also paradoxically with watering. When the cornea is affected, an assessment for corneal diseases is also performed.

Dry eye symptoms become more noticeable through the day, especially in the evening and after heavy screen use. The most common are:

• Burning and stinging: Day-long discomfort from a drying ocular surface.
• Redness: Constant or recurrent redness from surface irritation.
• Foreign-body sensation: A gritty feeling as if there is sand or an eyelash in the eye.
• Blurred vision: Fluctuating blur, especially when reading or using screens, that clears on blinking.
• Discomfort with prolonged screen use: Increased dryness and fatigue because blinking decreases.
• Eye fatigue and reflex tearing: Excessive watering as a reaction to dryness.
• Light sensitivity: Increased discomfort and squinting in bright light.

Symptom severity varies between individuals and does not always match the degree of surface damage. Persistent complaints should therefore always be evaluated by an ophthalmologist.

Dry eye usually results from several factors acting together rather than a single cause. The most common include:

• Heavy screen use: Long hours on computers, phones and tablets reduce blink rate and accelerate tear evaporation.
• Environmental factors: Air conditioning, heating, wind, smoke and low-humidity environments dry the surface.
• Ageing and hormonal change: Tear production declines with age and especially during menopause.
• Eyelid-margin (meibomian) dysfunction: Blocked oil glands impair the lipid layer and increase evaporation.
• Contact lens wear: Long-term lens use can disturb the moisture balance of the surface.
• Systemic diseases: Sjögren syndrome, rheumatoid arthritis, thyroid disease and diabetes predispose to dry eye.
• Medications: Some blood-pressure, allergy (antihistamine), antidepressant and contraceptive drugs can reduce tear production.
• Previous eye surgery: Temporary dryness may follow laser and some eyelid procedures.

The right treatment plan starts with a detailed examination that identifies the type and severity of dry eye. After reviewing symptoms, the ocular surface, lid margins and tear film are assessed. Commonly used tests include:

• Slit-lamp examination: The surface, cornea and oil glands at the lid margin are examined under magnification.
• Tear break-up time (TBUT): Measures how quickly the tear film destabilizes, assessing evaporation.
• Ocular surface staining: Dyes such as fluorescein reveal areas of dryness and irritation.
• Schirmer test: A thin paper strip measures the amount of tear production.
• Tear meniscus and lid assessment: Tear reserve and meibomian gland function are evaluated.

These assessments distinguish whether dry eye is due to reduced production or increased evaporation, allowing a personalized treatment plan.