What is astigmatism?
Astigmatism is a refractive error caused by the cornea or lens being curved more in one direction than another, so light is focused unevenly and vision is blurred or distorted rather than simply out of focus.
- Subject
- Vision problems
- Topic
- Astigmatism
- Kind of question
- What is…
- Last reviewed
- 22 September 2026
In more detail
The usual description is that things look smeared or have ghosting at certain angles rather than being uniformly soft, and that is a recognisable difference for many people once it is explained.
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Where this answer sits
It is one of 483 answers in the vision and eye health knowledge base, filed under Vision problems & prescriptions in Astigmatism . The subject page carries the answers either side of it, and the hub is searchable.
Subjects this question touches
The pages that answer the subject behind the question, rather than the question itself.
- Condition Astigmatism
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