Dry eye disease is a common condition in which the eyes are unable to maintain a healthy, stable layer of tears on their surface — either because too few tears are produced, or because the tears that are produced evaporate too quickly. The result is a chronically under-lubricated eye surface, which can cause persistent discomfort, blurred vision, and, if left unaddressed, damage to the surface of the eye over time.
Dry eye is extremely common and becomes more likely with age, but it is increasingly seen in younger adults too, driven by extended screen time, air-conditioned environments, and contact lens use. While rarely dangerous, dry eye disease can meaningfully affect day-to-day comfort, reading, night driving, and quality of life when left untreated — and the good news is that it responds well to treatment once its underlying cause is identified.
How the Tear Film Works and Why It Becomes Unstable
A healthy tear film is made up of three layers working together, each produced by different glands around the eye:
- An outer lipid (oil) layer, produced by the meibomian glands along the eyelid margins, which slows evaporation of the tear film
- A middle aqueous (watery) layer, produced by the lacrimal glands, which provides most of the tear volume and delivers oxygen and nutrients to the eye's surface
- An inner mucin layer, produced by cells on the eye's surface, which helps the tear film spread evenly and adhere to the eye
Dry eye disease develops when this system falls out of balance — either from insufficient tear production, poor tear quality, or tears evaporating too quickly — triggering a cycle of tear film instability, surface irritation, and low-grade inflammation that, left unaddressed, tends to reinforce itself over time.
Types of Dry Eye Disease
- Evaporative Dry Eye: The most common form, caused primarily by meibomian gland dysfunction (MGD) — when the oil-producing glands along the eyelids become blocked or produce poor-quality oil, the protective lipid layer breaks down and tears evaporate too quickly, even when tear production itself is normal.
- Aqueous-Deficient Dry Eye: Caused by insufficient tear production from the lacrimal glands, resulting in a genuinely low volume of tears. Can occur on its own or alongside systemic conditions that affect the lacrimal glands, such as Sjögren's syndrome.
- Mixed Dry Eye: A combination of both evaporative and aqueous-deficient mechanisms, which is common in practice — many patients have some degree of both meibomian gland dysfunction and reduced tear production, particularly as dry eye becomes more longstanding.
Symptoms of Dry Eye Disease
Symptoms typically affect both eyes and often fluctuate depending on the environment and activity — many people notice symptoms worsen on flights, in air-conditioned rooms, or after prolonged screen use.
- Stinging, burning, or scratchy and gritty sensations in the eyes
- A sensation of having something in the eye
- Redness
- Sensitivity to light
- Blurred vision or eye fatigue, particularly with reading or screen use
- Difficulty with night-time driving
- Difficulty wearing contact lenses comfortably
- Stringy mucus in or around the eyes
- Watery eyes — which can seem counterintuitive, but is often the eye's reflex response to the irritation of an unstable tear film
Risk Factors for Dry Eye Disease
- Age: Tear production naturally declines with age, and dry eye is significantly more common in those over 50
- Gender: More common in women, particularly related to hormonal changes from pregnancy, hormonal contraception, or menopause
- Extended screen time: Reduces blink frequency and blink completeness, both of which disrupt the tear film
- Prolonged or improper contact lens wear
- Environmental factors: Air-conditioned or heated indoor environments, wind, and low-humidity settings such as aeroplane cabins
- A diet low in vitamin A or omega-3 fatty acids
- Certain medications: ncluding antihistamines, some antidepressants, decongestants, and certain blood pressure medications, which can reduce tear production as a side effect
- Previous eye surgery, including refractive (laser) surgery
- Underlying autoimmune or systemic conditions, such as Sjögren's syndrome, rheumatoid arthritis, or thyroid eye disease
Why Untreated Dry Eyes Matters
Dry eye disease is rarely dangerous, but it deserves more attention than it often gets, because untreated dry eye tends to be a self-reinforcing cycle rather than a stable, static problem. An unstable tear film triggers low-grade inflammation on the eye's surface, which in turn further destabilises the tear film — meaning symptoms often gradually worsen, rather than plateau, if the underlying cause is not addressed.
Left untreated for a prolonged period, chronic dry eye can lead to punctate damage to the surface of the cornea, an increased risk of eye infection, and in more severe or longstanding cases, corneal scarring that can affect vision. Dry eye can also complicate contact lens wear, interfere with the accuracy of measurements taken before cataract or refractive surgery, and, in a small proportion of cases, point to an underlying systemic autoimmune condition that itself warrants attention.
This is why dry eye that persists despite simple measures such as over-the-counter lubricating drops — rather than resolving — is worth a proper assessment to identify the specific type and driver of the problem, since treatment is far more effective when matched to the underlying cause.
How Dry Eye Disease is Diagnosed
- Comprehensive Eye Examination: Assesses overall eye health, the eyelids, and the ocular surface, and helps rule out other causes of eye irritation.
- Schirmer's Test: A thin strip of paper is placed under the lower eyelid to measure how much moisture is absorbed over several minutes, providing a direct measure of tear production.
- Tear Break-Up Time (TBUT): Measures how quickly the tear film breaks up or becomes unstable after a blink, using a special dye to make the tear film visible under blue light — a shorter break-up time indicates a less stable tear film.
- Ocular Surface Staining: Special dyes are used to highlight areas of damage or dryness on the surface of the cornea and conjunctiva, helping to grade the severity of dry eye.
- Meibomian Gland Assessment: Direct examination or imaging (meibography) of the meibomian glands along the eyelid margins to assess for blockage, dropout, or dysfunction, since this is the most common underlying driver of dry eye.
Living with Dry Eyes: Everyday Self-Care
- Use lubricating drops proactively, not just when symptoms flare, particularly before activities known to trigger symptoms such as flights or long screen sessions
- Follow a consistent lid hygiene routine if you have meibomian gland dysfunction, even once symptoms improve, to maintain gland function
- Take regular breaks during screen use and consciously blink fully and regularly
- Consider a humidifier in air-conditioned bedrooms or offices
- Review contact lens wear time and lens type with your eye care provider if lenses are contributing to discomfort
- Include omega-3-rich foods such as oily fish, walnuts, and flaxseed in your diet
- Seek assessment if symptoms persist despite over-the-counter drops, rather than continuing to self-manage indefinitely — an accurate diagnosis often unlocks more effective, targeted treatment
