St. Luke's Hospital
Main Number: 314-434-1500 Emergency Dept: 314-205-6990 Patient Billing: 888-924-9200
Find a Physician Payment Options Locations & Directions
Follow us on: facebook twitter Mobile Email Page Email Page Print Page Print Page Increase Font Size Decrease Font Size Font Size
America's 50 Best Hospitals
Meet the Doctor
Spirit of Women
Community Health Needs Assessment
Home > Health Information

Multimedia Encyclopedia

    Print-Friendly
    Bookmarks

    Tonometry

    Intraocular pressure (IOP) measurement; Glaucoma test; Applanation

    Tonometry is a test to measure the pressure inside your eyes. The test is used to screen for glaucoma.

    How the Test is Performed

    There are several methods of testing for glaucoma.

    The most accurate method measures the force needed to flatten a certain area of the cornea.

    • The surface of the eye is numbed with eye drops. A fine strip of paper stained with orange dye is touched to the side of the eye. The dye stains the front of the eye to help with the examination.
    • The slit-lamp is placed in front of you, and you rest your chin and forehead on a support that keeps your head steady. The lamp is moved forward until the tip of the tonometer just touches the cornea.
    • The health care provider looks through the eyepiece on the lamp and the machine gives a pressure reading. There is no discomfort with the test.

    A slightly different method uses a handheld device similar in shape to a pencil. Again, you are given numbing eye drops to prevent any discomfort. The device touches the outside of the eye and instantly records eye pressure.

    The last method is the noncontact method (air puff). In this method, your chin rests on a padded stand.

    • You stare straight into the examining device. The eye doctor shines a light into your eye to properly line up the instrument, and then delivers a brief puff of air at your eye.
    • The machine measures eye pressure by looking at how the light reflections change as the air hits the eye.

    How to Prepare for the Test

    Remove contact lenses before the examination. The dye can permanently stain contact lenses.

    Tell yourhealth care provider if you have corneal ulcers and eyeinfectionsora history of glaucoma in your family. Always tell your doctor or nurse what medicines you are taking.

    How the Test Will Feel

    If numbing eye drops were used, you should not have any pain. In the noncontact method, you may feel mild pressure on your eye.

    Why the Test is Performed

    Tonometry is a test to measure the pressure inside your eyes. The test is used to screen for glaucoma.

    People over age 40, especially African Americans, have the highest risk for developing glaucoma. Regular eye exams can help detect glaucoma early. If it is detected early, glaucoma can be treated before too much damage is done.

    The test may also be done before and after eye surgery.

    Normal Results

    A normal result means your eye pressure is within the normal range. The normal eye pressure range is 10 - 21 mmHg.

    How thick your cornea is can affect measurements. Normal eyes with thick corneas have higher readings and normal eyes with thin corneas have lower readings.A thin cornea with a high reading may be very abnormal (the actual eye pressure will be higher than shown on the tonometer).

    Currently, a corneal thickness measurement (pachymetry) is needed to get a correct pressure measurement.

    Talk to your doctor about the meaning of your specific test results.

    What Abnormal Results Mean

    Abnormal results may be due to:

    • Glaucoma
    • Hyphema
    • Inflammation in the eye
    • Injury to the eye or head

    Risks

    If the applanation method is used, there is a small chance the cornea may be scratched (corneal abrasion). This will normally heal itself within a few days.

    References

    Stamper RL, Punjabi O, Tanaka G. Intraocular Pressure: Measurement, Regulation, and Flow Relationships. In: Tasman W, Jaeger EA, eds. Foundations of Clinical Ophthalmology. 2012 ed. Philadelphia, Pa: Lippincott Williams & Wilkins; 2012: vol 2, chap 7.

    BACK TO TOP

    • Eye

      illustration

      • Eye

        illustration

      A Closer Look

        Tests for Tonometry

        Review Date: 9/18/2012

        Reviewed By: David Zieve, MD, MHA, Medical Director, A.D.A.M. Health Solutions, Ebix, Inc., and Franklin W. Lusby, MD, Ophthalmologist, Lusby Vision Institute, La Jolla, California.

        The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.
        adam.com

        A.D.A.M. content is best viewed in IE9 or above, Fire Fox and chrome browser.


        Back  |  Top
        About Us
        Contact Us
        History
        Mission
        Locations & Directions
        Quality Reports
        Annual Reports
        Honors & Awards
        Community Health Needs
        Assessment

        Newsroom
        Services
        Brain & Spine
        Cancer
        Heart
        Maternity
        Orthopedics
        Pulmonary
        Sleep Medicine
        Urgent Care
        Women's Services
        All Services
        Patients & Visitors
        Locations & Directions
        Find a Physician
        Tour St. Luke's
        Patient & Visitor Information
        Contact Us
        Payment Options
        Financial Assistance
        Send a Card
        Mammogram Appointments
        Health Tools
        My Personal Health
        mystlukes
        Spirit of Women
        Health Information & Tools
        Clinical Trials
        Health Risk Assessments
        Employer Programs -
        Passport to Wellness

        Classes & Events
        Classes & Events
        Spirit of Women
        Donate & Volunteer
        Giving Opportunities
        Volunteer
        Physicians & Employees
        For Physicians
        Remote Access
        Medical Residency Information
        Pharmacy Residency Information
        Physician CPOE Training
        Careers
        Careers
        St. Luke's Hospital - 232 South Woods Mill Road - Chesterfield, MO 63017 Main Number: 314-434-1500 Emergency Dept: 314-205-6990 Patient Billing: 888-924-9200
        Copyright © St. Luke's Hospital Website Terms and Conditions  |  Privacy Policy  |  Patient Notice of Privacy Policies PDF Sitemap St. Luke's Mobile