What is dry eye?
Dry eye is a condition in which the tear film is unstable or insufficient, either because too few tears are produced or because they evaporate too quickly, which leaves the surface of the eye irritated rather than adequately lubricated.
- Subject
- Eye conditions
- Topic
- Dry eye
- Kind of question
- What is…
- Last reviewed
- 22 September 2026
In more detail
It is a surface problem with consequences for vision, not just comfort. A poor tear film makes vision fluctuate, which is why dryness matters so much when measurements are being taken for surgery.
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Where this answer sits
It is one of 483 answers in the vision and eye health knowledge base, filed under Eye conditions & diseases in Dry eye . The subject page carries the answers either side of it, and the hub is searchable.
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The pages that answer the subject behind the question, rather than the question itself.
- Condition Dry eye
This information is for educational purposes and does not replace an examination by a qualified eye-care professional.
General answers cannot tell you what is happening in your own eyes. Only an examination by a qualified ophthalmologist can do that.
Sources & further reading
We prefer primary sources. Where a claim comes from a manufacturer, a single study or a regulator, it is labelled as such below.
- Eye Health Information
Condition-by-condition eye health information from a US government research institute, written for patients rather than for clinicians.
Used for Plain-language explanations of eye conditions and their symptoms; Healthy vision and screening guidance.
Link checked 23 September 2026
- EyeSmart: eye health information for the public
Patient-facing material from the largest ophthalmology professional body, covering conditions, tests and treatments outside refractive surgery.
Used for Cross-checking patient-facing explanations of non-refractive eye conditions; Describing what tests such as dilation and OCT involve.
Link checked 23 September 2026