Dry eye: symptoms, causes and when it becomes a disease

It usually makes itself felt towards evening. The eyes burn and sting, it feels as though a grain of sand has got under the eyelids; in front of the screen the lines seem less sharp and the eyes tire sooner. Many people call it tiredness, and sometimes it is. At other times it is dry eye, one of the most common eye problems⁹.

For a long time, dry eye was treated as a nuisance to be put up with. Today it is described as a disease in its own right, with precise criteria for recognising it: this is restated by the TFOS DEWS III report, published in 2025 by the Tear Film & Ocular Surface Society, an international scientific society, eight years after the previous one¹.

In this article

1. What dry eye is according to the TFOS DEWS reports
2. Dry eye: the most common symptoms
3. Two mechanisms, often together
4. How common it is
5. Who is most at risk
6. How the diagnosis is made
7. Frequently asked questions
8. Sources

What dry eye is according to the TFOS DEWS reports

On the cornea, the transparent part of the eye, there is a very thin veil: the tear film. It is not just water: the TFOS DEWS III report classifies its possible deficiencies across three components, the oily part, the watery part and the mucus that keeps it attached to the surface¹.

The definition updated in 2025 says that dry eye is a multifactorial disease, always accompanied by symptoms, in which the balance of the tear film or of the ocular surface is lost. Four intertwined causes are involved: unstable tears, tears that are too concentrated (ophthalmologists speak of hyperosmolarity), inflammation and damage of the surface, and alterations of the nerves that regulate its sensitivity¹.

Three words count more than the others. Multifactorial: there is no single cause. Disease, and not simply a syndrome. Symptomatic: without symptoms, one does not speak of dry eye¹. Already in 2017 the nerves had entered the picture for the first time as a cause, together with cases in which there are symptoms, such as pain, without obvious signs on the surface².

Dry eye: the most common symptoms

For the TFOS reports, symptoms include both discomfort and visual disturbances². Among those described by reviews are⁹:

• irritation, which many people describe as burning or as grit in the eyes;
• redness and itching;
• discomfort in light;
• vision that becomes hazy;
• mucus discharge.

These are not minor complaints. An analysis of the Dutch Lifelines study questioned 89,022 adults with two questionnaires, one on dry eye and one on vision-related quality of life. Even after taking into account age, income and 55 other diseases, people with dry eye much more often reported impaired visual quality of life, to a similar or greater extent than people with macular degeneration or glaucoma. The study is observational: it shows an association, it does not measure damage to vision⁷.

Two mechanisms, often together

The TFOS reports distinguish two broad mechanisms. In aqueous-deficient dry eye, the lacrimal glands produce little water; in evaporative dry eye, the tears are there but evaporate too quickly. The 2017 report made it clear that they are not two separate boxes: they are the ends of a single line, and in many people they coexist².

The evaporative form is linked above all to the meibomian glands, a row of small glands that open on the edge of the eyelids and produce the oily part of the tears. In the evaporative forms, malfunction of these glands is the most common feature⁶. Blepharitis, inflammation of the edge of the eyelids, is also among the eye-related risk factors for dry eye⁴.

How common it is

It depends on how you look for it. The epidemiological review of the TFOS DEWS II report, which included a meta-analysis of published data, found values of 5 to 50%; the signs visible on examination are more frequent and more variable than the symptoms reported. The frequency rises with age and is higher in women, although the difference becomes clear only with the years; Asian ancestry is a fairly consistent risk factor³.

A 2024 review, with deliberately cautious estimates, calculates that between 10 and 20% of people over 40 have moderate to severe symptoms or seek medical help for this⁴. In Europe, an important figure comes from the same Lifelines study: among 79,866 adults aged 20 to 94, 9.1% had dry eye according to the questionnaire used by the researchers. Symptoms were particularly frequent between the ages of 20 and 30, a result that the authors consider worrying and in need of further study⁵.

Who is most at risk

Reviews divide the risk factors into those that cannot be changed and those that can, at least in part, be acted upon⁴:

• advanced age, female sex, East Asian ancestry⁴; the role of hormones is one of the chapters of the TFOS DEWS III report⁶ and we describe it in our article on dry eye in menopause;
• general diseases such as migraine, connective tissue diseases, diabetes, mental health disorders and Sjögren’s syndrome, an autoimmune disease⁴;
• contact lenses and eye surgery, including cataract surgery and laser correction of refractive errors, strongly associated with dry eye in the Lifelines study⁵; the TFOS DEWS III report includes them among the causes of iatrogenic dry eye, that is, linked to medical treatment⁶;
• certain medicines, including antidepressants, antihistamines and hormone replacement therapy⁴;
• environment and habits: dry air, prolonged use of screens, poor-quality sleep, diet and eye make-up⁴.

On medicines, the Lifelines study analysed the treatments of 79,606 people: taking each person’s diseases into account, the strongest links with dry eye symptoms involved medicines for ulcers and reflux (in particular proton pump inhibitors), eye drops for glaucoma and anticholinergic medicines⁸. These are associations: none of them, on its own, says that a treatment should be changed, and it is a matter to raise with the doctor who prescribed it.

How the diagnosis is made

The TFOS DEWS III report proposes a precise pathway. First, other conditions that can cause similar complaints are ruled out. Then it uses a six-question questionnaire, the OSDI-6: a score of 4 or more raises the suspicion of dry eye¹.

The suspicion becomes a diagnosis if at least one of these signs is also present¹:

• the tear film breaks up in less than 10 seconds after a blink, measured without touching the eye;
• the tears are too concentrated in at least one eye, or very different between the two eyes;
• after a coloured eye drop, small spots appear on the cornea, the conjunctiva or the edge of the eyelids, a sign that the surface is damaged.

Once the diagnosis has been made, other tests serve to understand which component weighs most: the oily part, the watery part, the mucus, the eyelids, the nerves or the inflammation. It is this distinction that guides the choice of treatments¹, which we discuss in our article on remedies for dry eye.

Frequently asked questions

Is dry eye a disease or just a nuisance?

For the international TFOS DEWS reports it is a disease in every respect, with several causes and always accompanied by symptoms¹. In population studies it weighs on vision-related quality of life as much as other, better-known eye diseases⁷.

Do screens cause dry eye?

Prolonged use of screens is among the lifestyle factors associated with dry eye, along with dry air and poor-quality sleep⁴. These are mostly associations: they do not say how much each factor weighs in an individual person.

Do contact lenses cause dry eye?

Contact lens use is among the factors most strongly associated with dry eye in the Lifelines study⁵, and the TFOS DEWS III report lists it among the causes linked to devices and medical treatment⁶. If you wear lenses and have symptoms, this is information to give your ophthalmologist.

Can you have dry eye without feeling it?

The surface of the eye can show signs of distress even in people who report no complaints: in studies, signs are more frequent than symptoms³. Under the 2025 definition, however, dry eye disease is spoken of only when symptoms are present¹.

Dry eye is common and has many causes, often more than one in the same person. Today, however, there are shared criteria for recognising it and understanding where it comes from¹: the first step in choosing, with your ophthalmologist, what to do.