# What Should Eye Pressure Be?

Source page: https://www.kudretgozistanbul.com/en/blog/eye-diseases/what-should-eye-pressure-be

**Author:** Kudret Eye İstanbul | **Medical Approval:** Op. Dr. Mehmet Ali Özdil | **Date:** 2026-09-16

> **Summary:** Eye pressure (intraocular pressure) is the pressure of the aqueous humour inside the eye, kept by the balance between its production and drainage. Normal intraocular pressure lies between 10 and 21 mmHg; high pressure can damage the optic nerve and cause glaucoma, which often advances silently.

## Quick Facts
- **Normal range:** Not lower than 10 mmHg and not higher than 21 mmHg; below 21 mmHg is preferred.
- **High:** Above 21 mmHg calls for a glaucoma assessment.
- **Low:** Readings of 6 mmHg are occasionally seen; below 6 mmHg can point to problems.
- **Screening:** Once a year for people over forty.
- **Measurement:** Painless, usually with numbing drops.

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## What Is Eye Pressure?
Aqueous humour is produced in the front of the eye and drained through small channels. If drainage fails, pressure rises and can press on the optic nerve, causing irreversible sight loss. Glaucoma is insidious: vision is lost gradually and often noticed late.

## Interpreting the Values
- Above 21 mmHg is high and carries a glaucoma risk, but a thicker than normal cornea can make the pressure read high.
- **Ocular hypertension:** High pressure without optic nerve damage.
- **Normal tension glaucoma:** Nerve damage despite pressure in the normal range; optic nerve and visual field tests are also needed.
- Below 10 mmHg is uncommon; a fall to 6 mmHg can mean insufficient fluid production or a problem with the integrity of the eye.

## Causes of High Eye Pressure
- Blockage of the drainage channels
- Family history of glaucoma
- Age forty and over
- Diabetes and high blood pressure
- Long-term corticosteroid use (drops, tablets or injections)
- Eye damage and certain eye conditions

## Effects of High Pressure
Often no symptoms, but over time:
- Optic nerve damage
- Reduced field of vision, lost from the edges towards the centre
- Permanent blindness without treatment

## Low Eye Pressure
Below 6 mmHg may indicate late leakage after an eye injury, insufficient fluid production or side effects of eye surgery. Low pressure can carry as much risk of sight loss as high pressure.

## Measurement Methods
- **Applanation tonometry:** The most important standard method.
- **Non-contact (air puff) tonometry:** Sterile measurement without touching the eye.
- **Portable devices:** For disabled or unwell patients or home measurement.

## Who Should Be Measured?
- People over forty, once a year.
- Those with a family history of glaucoma, more often.
- Patients with diabetes or high blood pressure, at regular intervals.
- People taking corticosteroids, under a doctor's supervision.

## Treatment of High Eye Pressure
- **Eye drops:** The first and easiest option.
- **Laser treatment:** Opens blocked drainage channels or eases drainage.
- **Surgery:** A last resort when drops and laser are not enough.
The aim is to halt optic nerve damage and prevent sight loss; treatment generally continues for life because symptoms can return when stopped.

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## References
- Tonometry, MedlinePlus
- Ocular Hypertension, EyeWiki (AAO)
- Glaucoma: diagnosis and management, NICE