The normal range of intraocular pressure is traditionally considered to be between 10 and 21 millimeter of mercury (mmHg) but there are people who have high IOP but no glaucoma. This condition is called as ‘Ocular Hypertension’ (OHT).
On the other hand, there are some people who have normal eye pressure but they still have glaucoma. This condition is called as ‘Normal Pressure Glaucoma’ (NPG).
Eye pressure therefore is just a risk factor for glaucoma. Whether it is normal or high varies from person to person.
In the past, high IOP was thought to be the cause of glaucoma and was even included in the definition of glaucoma. Studies after studies later showed that glaucoma may be present in the absence of high eye pressure and it may not be present even if the eye pressure is consistently high.
In modern ophthalmology, IOP is considered to be the only modifiable factor for the management of glaucoma. It is not included in the definition or diagnostic criteria of glaucoma any more.
So if you have high IOP, you don’t necessarily have glaucoma. At the same time, it’s important to remember that you must have complete eye examination by an ophthalmologist to rule out glaucoma.