Dry eye disease

Dry eye is one of the commonest reasons people come to an eye clinic, and one of the most frustrating conditions to live with. These are the questions that come up most often.

Why do my eyes water if they're dry?

This confuses almost everyone, and it is worth spelling out, because it is the single most common thing people find contradictory.

When the surface of the eye dries out and becomes irritated, the cornea signals distress. The lacrimal gland responds by producing a flood of watery reflex tears — the same mechanism as chopping an onion.

But reflex tears are watery and contain no oil. They arrive too fast, spill over the lid, and evaporate almost instantly. So you end up with a watering eye and a dry surface at the same time.

Wiping it away with a tissue makes it worse, because you remove what little oil is there and irritate the lid margin further.

A watering eye is one of the commonest presentations of dry eye. It is not a contradiction.

What actually is dry eye disease?

The international standard is the TFOS DEWS III report, published in 2025.

It defines dry eye as a multifactorial, symptomatic disease characterised by a loss of homeostasis of the tear film and the ocular surface, in which tear film instability, hyperosmolarity, surface inflammation and damage, and neurosensory abnormalities are all causative factors.

Two changes from the previous definition matter in practice. Symptomatic is now part of the definition, so your symptoms are a prerequisite for the diagnosis rather than an optional extra — signs alone are not enough. And the definition now includes the ocular surface, not just the tear film, which captures a broader range of disease.

Why does it get worse if I leave it?

Because it is a self-reinforcing cycle, and this is the part worth understanding.

Tears become unstable and break up too quickly. What is left becomes more concentrated — hyperosmolar. Hyperosmolarity directly damages the surface cells and triggers inflammation. Inflammation damages the goblet cells that make mucin and the glands that make oil. Less mucin and less oil make the tear film even less stable.

Round it goes. Left alone, dry eye tends to get worse rather than better, which is why treating it properly matters even when symptoms are mild.

How is it diagnosed?

On symptoms first, then signs. A questionnaire is often used to score the symptoms formally.

At the slit lamp we look at how quickly the tear film breaks up, the height of the tear meniscus, the state of the lid margins and the meibomian glands, and we use dyes to show up damage to the surface of the eye. Tear osmolarity and inflammatory markers can be measured where available.

Which drops should I use?

Preservative-free, if you are using them more than about four times a day. Benzalkonium chloride, the standard preservative, is irritating with frequent use and can perpetuate the very problem you are treating.

Oil-based or lipid-containing drops if your dry eye is evaporative, which most is. Plain saline-type drops do less.

A gel or ointment at bedtime if you wake with symptoms. These blur vision, so they are a night-time option.

Use them before symptoms arrive, not only in response to them.

Drops are not a cure. They are comfort while the underlying cause is treated.

Will steroids help?

Sometimes, for a short period, and only under supervision.

A short course of topical steroid can break the inflammatory cycle when disease is moderate or severe, and can settle things enough for other treatments to work. They are used for induction, not maintenance.

Steroids raise eye pressure in a proportion of people and carry other risks with prolonged use, so they are not something to keep repeating from an old prescription.

What is ciclosporin?

A topical immune-modulating treatment used for longer-term control, where steroids are used for short-term rescue.

It reduces inflammation on the ocular surface without the pressure risk of steroids. It is slow — expect to give it at least three months before judging it — and it commonly stings for the first few weeks, which is the main reason people abandon it. If you can get past that period, it is often worth it.

What else is there?

Punctal plugs, which block the tear drainage channels to keep your own tears on the eye for longer. In-clinic treatments aimed at the meibomian glands. Autologous serum drops in severe cases.

And for most people, the foundation is treating the blepharitis underneath, since blocked oil glands are the commonest driver of evaporative dry eye.

Is it my screen use?

Partly. We blink far less, and far less completely, when concentrating on a screen.

Every 20 minutes, look 20 feet away for 20 seconds and blink fully a few times. Position screens below eye level so less of the eye surface is exposed. Neither of these is a cure, but both genuinely help.

Next steps

Patients — contact the clinic to arrange an appointment.

GPs and optometrists — refer directly to Limerick or Ennis, including by Healthmail.