Checking eye pressure, also known as intraocular pressure, is an important part of eye health exams. High eye pressure is a major risk factor for glaucoma, which can lead to vision loss and blindness if left untreated. Understanding when and how eye pressure should be checked can help ensure this key measurement is not overlooked.
What is intraocular pressure?
Intraocular pressure, commonly referred to as eye pressure, is a measurement of the fluid pressure inside the eye. This fluid, called aqueous humor, is constantly produced and drained from the eye to nourish the cornea and lens. Normal eye pressure ranges between 10-21 mm Hg. If the drainage channels for aqueous humor become blocked or don’t work properly, pressure can build up inside the eye. Over time, increased eye pressure damages the optic nerve and can lead to vision loss.
High eye pressure is one of the leading risk factors associated with glaucoma. This group of eye diseases affects the optic nerve and is a major cause of irreversible blindness worldwide. However, elevated eye pressure does not necessarily mean someone has glaucoma. Other factors like optic nerve structure also determine an individual’s level of risk.
Why check eye pressure?
Monitoring intraocular pressure is important because high eye pressure often precedes glaucoma and permanent vision loss. Measuring eye pressure is the only way to detect ocular hypertension, which is elevated fluid pressure without optic nerve damage or vision loss. If caught early, steps can be taken to lower pressure and prevent further glaucoma progression.
Checking eye pressure is especially important for people at increased risk for glaucoma. Those over age 60, with a family history of glaucoma, and of African or Hispanic descent are at higher risk. People with health conditions like diabetes and hypertension that affect the eyes are also at greater risk.
Eye pressure measurements also help glaucoma specialists monitor patients already diagnosed with the condition. Tracking pressure over time allows doctors to determine if treatment is effectively lowering pressure and protecting the optic nerve.
How often to check eye pressure
The frequency of eye pressure checks depends on an individual’s personal risk profile and age. In general, the American Academy of Ophthalmology recommends:
- Under 40: Baseline eye pressure measurement
- 40-54: Every 2-4 years
- 55-64: Every 1-3 years
- 65 and older: Every 1-2 years
Those with higher glaucoma risk or an existing diagnosis may need more frequent monitoring, like every 6-12 months. African Americans over age 40, for example, are encouraged to have annual eye pressure checks. Doctors will recommend an appropriate eye pressure recheck schedule based on examination findings and medical history.
Methods of checking eye pressure
There are several different instruments eye doctors use to evaluate intraocular pressure. The most common methods include:
Tonometry
Tonometry uses a tonometer to measure eye pressure. There are several different types of tonometers.
- Goldmann applanation tonometer: This slit lamp device is considered the gold standard tonometer. It uses a small prism to gently flatten (applanate) the cornea. The force required to flatten the corneal surface correlates with eye pressure.
- Non-contact/air puff tonometer: This handheld device puffs a jet of air onto the cornea to flatten it and calculate eye pressure without actually touching the eye.
- Rebound tonometer: A small probe lightly taps the cornea and measures how fast it rebounds to determine eye pressure.
- Handheld tonometer: Portable versions allow patients to measure their own eye pressure at home.
Readings can vary slightly between different measurement methods. Goldmann tonometry is generally considered the most precise.
Ophthalmoscopy
Ophthalmoscopy allows doctors to visually assess the optic nerve at the back of the eye. The appearance of the optic nerve head provides clues about eye pressure levels.
With direct ophthalmoscopy, doctors use an ophthalmoscope held up close to the patient’s pupil. Indirect ophthalmoscopy involves wearing a head-mounted device with a more magnified view.
Subtle changes in the optic nerve over time may indicate chronically elevated eye pressure before actual vision loss occurs.
Pachymetry
Pachymetry measures corneal thickness using an ultrasonic probe. Corneal thickness can influence tonometry readings, so pachymetry allows doctors to factor this in for the most accurate eye pressure measurement.
What does the test involve?
Checking eye pressure is fast, non-invasive, and completely painless. Eye drops are not required. Here’s what you can expect during tonometry to check eye pressure:
- You’ll sit comfortably at a slit lamp microscope while resting your chin on a chin rest.
- Your doctor will align and gently press a small tonometer prism against the surface of the numbed eye.
- There may be a brief puff of air from the tonometer.
- The tonometer requires only light touch contact with the eye for a few seconds.
- Your doctor will repeat measurements on each eye.
- The whole process takes just a minute or two.
Pachymetry to measure corneal thickness and ophthalmoscopy of the optic nerve are similarly quick, easy exams requiring no eye drops or dilation.
How to prepare for the test
No specific preparation is needed for eye pressure measurement. It’s important not to put any eye drops in your eyes prior to testing.
When visiting an eye doctor:
- Wear your eyeglasses or contact lenses so you can read the eye chart.
- Be prepared to remove eye makeup and contact lenses during the exam.
- Bring a current list of medications.
- Know your family’s history of eye disease.
- Tell your eye doctor if you have any pain, redness, or vision changes.
What do the results mean?
Normal eye pressure is considered between 10-21 mm Hg. Readings above 21 mm Hg are flagged as ocular hypertension.
| Eye Pressure Reading (mm Hg) | Level |
|---|---|
| 10-21 mm Hg | Normal |
| 21-25 mm Hg | Borderline elevated |
| 25-30 mm Hg | Moderately elevated |
| Over 30 mm Hg | Significantly elevated |
Elevated eye pressure alone does not indicate glaucoma if there is no optic nerve damage. But high pressure is a risk factor for developing glaucoma.
If eye pressure is too high, the ophthalmologist may recommend additional tests for glaucoma. Enlarged cupping or thinning of the optic nerve would confirm glaucoma. They will also evaluate factors like corneal thickness and eye anatomy that can influence eye pressure.
Treatment to lower eye pressure is needed for confirmed glaucoma. Repeat testing will monitor if pressure is reduced to a safer level. Even with normal pressure, regular eye exams are still essential to detect any optic nerve changes over time.
How eye pressure is lowered
If confirmed glaucoma or persistently elevated eye pressure requires treatment, ophthalmologists have several options to lower pressure and stabilize vision:
- Eye drops – Prescription medicated eye drops like beta blockers, carbonic anhydrase inhibitors, alpha agonists, or prostaglandins can reduce aqueous production and increase drainage.
- Oral medications – Carbonic anhydrase inhibitor pills may be prescribed.
- Laser therapy – This painless office procedure uses a laser to open up the drainage angle and pathways.
- Surgery – Glaucoma surgery like trabeculectomy and drainage implants allow aqueous humor to exit the eye.
Doctors may recommend a combination of treatments to achieve the best eye pressure control. Any treatment for glaucoma will require lifelong monitoring to ensure eye pressure remains stable.
Who checks eye pressure?
Only trained eye care providers like ophthalmologists and optometrists check intraocular pressure. An ophthalmologist is a medical doctor specializing in the surgical and medical care of eyes. An optometrist diagnoses and manages vision disorders and eye diseases but does not perform eye surgery.
Primary care providers generally do not check eye pressure and will refer patients to an eye specialist if glaucoma screening is needed. Eye pressure assessments require specialized equipment and extensive clinical experience interpreting subtle changes in the optic nerve.
Eye pressure readings done by an experienced eye doctor are more reliable than pressures measured with a home tonometer. Home tonometers can have a wider margin of error and will not evaluate the optic nerve.
Takeaway on checking eye pressure
- Measuring intraocular eye pressure is crucial for evaluating glaucoma risk.
- Eye pressure should be checked every 1-4 years for those over age 40.
- Tonometry, pachymetry, and ophthalmoscopy allow eye doctors to assess eye pressure and nerve damage.
- Repeat testing is needed to monitor pressure control for glaucoma patients.
- Reducing elevated eye pressure can prevent optic nerve injury and vision loss.
Regular eye pressure screenings with an ophthalmologist or optometrist help detect issues like ocular hypertension and glaucoma in the early stages. Early diagnosis and treatment are key to preserving vision and slowing disease progression.