From the Guidelines
Normal intraocular pressure (IOP) in the eye is typically considered to be between 10 and 21 mmHg, with an average of around 15-16 mmHg. This definition is supported by a study published in 2021 in the journal Ophthalmology, which defines ocular hypertension as an IOP greater than 21 mmHg 1.
Key Points to Consider
- The study highlights the importance of measuring IOP in all patients over the age of 40 years, as ocular hypertension is a major risk factor for the development of glaucoma 1.
- Elevated IOP can lead to glaucoma, potentially damaging the optic nerve and causing vision loss.
- Abnormally low pressure (below 10 mmHg) can cause the eye to collapse or develop other complications.
- Regular eye examinations that include IOP measurements are crucial for early detection of pressure abnormalities, especially for individuals over 40 or those with a family history of glaucoma.
Clinical Implications
- Clinicians should be aware of the risk factors for glaucoma, including elevated IOP, suspicious visual fields or optic disc appearance, and RNFL abnormalities 1.
- A patient's history of myopia, ethnoracial group, or family history of glaucoma should also be considered when assessing their risk of developing glaucoma 1.
From the Research
Normal Intraocular Pressure (IOP) Range
The normal range of intraocular pressure (IOP) in the eye can vary depending on several factors, including the method of measurement and the individual's overall health.
- According to a study published in 2003 2, the maximum IOP in patients with normal-tension glaucoma was 16.8 +/- 2.0 mmHg, while the minimum IOP was 12.8 +/- 1.7 mmHg.
- A 2018 study 3 suggests that the target IOP range for patients with glaucoma can vary depending on the severity of the disease, with a range of 15-17 mmHg for mild glaucoma, 12-15 mmHg for moderate glaucoma, and 10-12 mmHg for severe glaucoma.
- Another study published in 2021 4 found that the mean IOP measured by the Icare ic200 was 20.8 +/- 9.3 mmHg, while the mean IOP measured by the Goldmann Applanation Tonometer (GAT) was 19.5 +/- 8.8 mmHg.
- A 2016 study 5 reported a mean IOP of 14 +/- 10.3 mmHg in patients with open globe injuries, while a 2022 study 6 found a median IOP of 14 mmHg (range: 37) measured by the Keeler 3000 APT and 12 mmHg (range: 16) measured by GAT.
Factors Affecting IOP Measurement
Several factors can affect the measurement of IOP, including:
- Central corneal thickness (CCT) 4, 6
- Age 4
- Vascular perfusion parameters 3
- Change on perimetry or imaging during follow-up 3
- Method of measurement (e.g. GAT, APT, Icare ic200) 2, 4, 6
Clinical Significance of IOP
Accurate measurement of IOP is crucial for the diagnosis and management of glaucoma and other eye disorders.