What Is Normal Eye Pressure?

Eye pressure, also known as intraocular pressure (IOP), is the fluid pressure inside the eye. Used as a measurement for diagnosing eye disease, periodic measurement of your IOP is essential for your eye health. For example, ocular hypertension (increased IOP) is a clinical indicator of glaucoma with the goal of treatment to lower the pressure.

What is Normal Eye Pressure?

Intraocular pressure (IOP), is measurement of the fluid pressure inside the eye that can help diagnosis current eye disorders and give you insight into your eye health. Pressure from aqueous humor fluid drains from the eye and new fluid replaces it as needed. It creates a homeostatic balance that regulates eye pressure.

IOP is not a fixed number but fluctuates in a person but also from person to person. It is impossible to compare your IOP to someone else. Undergoing routine eye exams is crucial to your eye health. This includes a full examination including tonometry, the diagnostic test for measuring IOP.

Some individual fluctuations are normal but also can be a sign of worsening progressive eye disease. Abnormal intraocular eye pressure can be indicative of a serious eye problem.

Ocular hypertension (increased IOP) can be a warning sign of progressive glaucoma and possibly blindness. A decrease in IOP can be an indicator for the progressive detachment of the retina and choroid. Furthermore, differences in the eye pressure between eyes can be a sign of iritis or retinal detachment.

How Is It Measured?

Eye pressure is generally measured during routine or emergency eye exams; however, it is also done after trauma to the eyes in an emergency room or primary care doctor's office.

• Eye drops are put in your eyes to numb them.
• Then the doctor or assistant gently touches the front surface of your eye with a device that glows with a blue light creating a small amount of pressure to the eye.
• The ophthalmologist measures the pressure inside each eye.

The most common type of tonometry test is called the Goldmann applanation tonometry test. Long considered the gold standard of ocular pressure tests it involves the use of a flat-tipped probe that is gently pressed against the surface of your eye.

Other non-contact methods include Tono-Pen and iCare tonometer. Considered less accurate, these diagnostic tests use air pressure that is applied to your eye using an instrument that slightly flattens the cornea.

Interestingly, there is no single correct eye pressure as each individual's eye pressure is different. For this reason, the range for healthy eye pressure is between 10 and 21 mmHg. Ocular pressure above and below this range can cause vision changes.

Most recently, the FDA approved the use of the Diaton Tonometer for measuring IOP through the eyelid and sclera. The Diaton is a pen-like device with a stainless steel tip that allows the user to touch the lid in the area above the corneal margin, at the sclera. This device is very important for patients that are unable to open their eyes and/or have had previous surgery to their eyes.

Eye Pressure and Glaucoma

Glaucoma is a group of chronically progressive eye diseases that can cause vision loss and blindness by damaging a nerve in the back of your eye called the optic nerve. The leading cause of blindness for patients over the age of 60, glaucoma is estimated to affect over 3 million Americans with more than more than 120,000 are blind from glaucoma.

There are three main types of glaucoma including:

• Open-angle glaucoma (most common)
• Angle-closure glaucoma
• Congenital glaucoma

While there is no definitive cause of glaucoma, there is a significant correlation between high ocular pressure and glaucoma. That being said, it does not cause glaucoma but is a significant risk factor.

Over time, high pressure causes the nerve fibers in the retina to die, resulting in decreased vision. Significant vision loss and blindness are extremely common if glaucoma is left untreated.

Unfortunately, there is no way to prevent glaucoma or even heal it but eye medications can lower eye pressure and slow the progression of the disease. Furthermore, any damage from glaucoma cannot be reversed with medications or by lowering the eye pressure.

Treatment for Eye Pressure

Pharmacologic and non-pharmacologic options are available to help lower and normalize eye pressure. All treatment options are determined by your healthcare provider after a comprehensive eye exam and health history.

Medications used to normalize eye pressure have side effects and interact with other medications. For this reason, it is important to take all medication as prescribed and discuss all current medications, vitamins, and supplements with your healthcare provider.

The most common eye drop medications used to normalize eye pressure are:

• Beta blockers (betaxolol)
• Topical carbonic anhydrase inhibitors (dorzolamide, brinzolamide)
• α₂ adrenoceptor agonist (Brimonidine)
• Cholinergic agonists (pilocarpine)
• Prostaglandins (latanoprost, unoprostone isopropyl, travoprost)
• Prostamide (bimatoprost)
• Combination medication drops (Cosopt, Combigan, Simbrinza)

If eye drops are not effective, your healthcare provider may start you on oral medications that will lower the eye pressure by decreasing the amount of fluid production in the eye. These medications are usually carbonic anhydrase inhibitors such as acetazolamide and methazolamide.

Glaucoma surgery is also a common option for these patients. This option will help to normalize IOP but it does not prevent it from rising again. Eye surgery is something that should not be taken lightly and only after thoughtful consideration and open discussion with a qualified eye surgeon.

While non-pharmacologic options will not normalize eye pressure on their own, they are complementary options. Currently, these options are not FDA approved for the treatment of high eye pressure and should only be done after consultation with your healthcare provider.

Complementary therapies should never be used in the replacement of prescribed medications. These options include:

• Homeopathic remedies
• Diet changes including decreasing caffeine intake
• Physical exercise
• Bilberry extract supplements
• Herbal supplements
• Osteopathy
• Vitamin C supplements
• Physiotherapy
• Elevate the head of the bed while sleeping