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Eye care

Understanding Eye Pressure

What eye pressure (intraocular pressure) is and why it is measured during exams.

Last updated November 3, 2026 · General information only, not medical advice. Please see a licensed eye-care professional for your prescription and eye health.

Woman wearing glasses

Intraocular pressure (IOP) is the fluid pressure inside the eye, measured in millimetres of mercury (mmHg). Eye-care professionals measure it as one part of a routine exam because it is one of several factors considered when assessing eye health.

Many sources describe a commonly cited typical range of roughly 10–21 mmHg, but individual results must be interpreted by a professional together with other findings. A number outside that range does not by itself mean there is a problem, and a number inside it does not rule one out.

How it is measured

  • Non-contact tonometry (a puff of air).
  • Applanation tonometry, using a small probe after numbing drops.

This article is general education, not medical advice. For any change in your vision or eye comfort, see a licensed optometrist or ophthalmologist.

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