The pressure inside the eye, or intraocular pressure (IOP), is designed to keep the eye inflated. It comes from a delicate balance of nourishing fluid being continually made and draining from the eye as needed. Measuring this pressure is fundamental to maintaining eye health. If it’s too low or too high, problems can arise. For example, glaucoma can occur when IOP rises above safe levels, leading to vision loss over time.*

Healthy Eye Pressure 

IOP can vary inside a person and between individuals. It can’t be compared between any two people. Because everyone’s eye pressure is different, there is no single correct reading. Instead, a healthy range for IOP is 10-21 mmHg (millimeters of mercury). If IOP rises above or falls below this range, impaired vision can result.

It’s normal for a person to have some fluctuation in eye pressure, but this can also signal serious eye disease. Increased IOP, called ocular hypertension, may indicate advancing glaucoma and potential blindness. On the other hand, decreasing IOP may indicate advancing retinal or choroidal detachment. (The choroid nourishes and oxygenates the outer retina along the back of the eye. It is the vascular layer between the retina and the sclera, or white part of the eye.)

Additionally, differences in pressure between the left and right eye can signal inflammation and swelling of the iris (iritis) or a detached retina.

Glaucoma and Eye Pressure

Glaucoma is an umbrella term for a group of chronic and progressive eye diseases. These diseases can lead to loss of vision and blindness by damaging the optic nerve that transmits visual information to the brain. More than three million Americans have glaucoma, which is the chief cause of blindness in people over 60.

Glaucoma typically occurs in one of several forms:

• Open-angle glaucoma (most cases)
• Angle-closure glaucoma
• Congenital glaucoma (from birth)

Glaucoma doesn’t have a definitive cause, but it is strongly associated with high IOP, which is considered a significant risk factor for the disease. High IOP gradually causes nerve damage in the retina, which can lead to significant vision loss and blindness if left untreated.

Some people have normal-tension glaucoma, however, in which the optic nerve becomes damaged despite the person’s IOP being in the normal range. The treatment for normal-tension glaucoma is generally the same as for other types of glaucoma.

Lowering Eye Pressure

The goal of glaucoma treatment is to bring eye pressure levels back to normal. For patients with normal-tension glaucoma, the goal is to achieve a lower pressure within the normal range. By lowering IOP, further damage can be avoided and vision can be preserved.

After a thorough eye exam, a provider will determine pharmacological and non-pharmacological treatment options for lowering pressure. Note that eye medications have side effects and can have harmful interactions with other medications. It’s important to take these medications as directed, and to disclose all other medications and any dietary supplements being taken.

Examples of the most common eye drops for lowering IOP are:

• Beta blockers, which decrease eye fluid production
• Topical carbonic anhydrase inhibitors, which reduce eye fluid production
• Alpha 2 adrenoceptor agonists, which reduce production while increasing drainage
• Prostaglandins, which increase eye fluid drainage
• Combination medication drops

If eye drops prove ineffective, oral medications may be prescribed to lower IOP. These are usually carbonic anhydrase inhibitors that lower eye fluid production.

When eye drops fail to normalize pressure, common treatment options for glaucoma are laser therapy and surgery. IOP can still rise again after surgery, however. Surgery should only be considered after careful discussion with a qualified surgeon.

*Gaines, K. (2021, February 26). What Is Normal Eye Pressure? Verywell Health. https://www.verywellhealth.com/normal-eye-pressure-5094999