Glaucoma - Exams and Tests
A doctor evaluating possible glaucoma will take a medical history and do a physical exam. If glaucoma is suspected, you will usually be referred to an eye specialist (ophthalmologist) for further testing and treatment.
Early detection and treatment of open-angle glaucoma (OAG) are important for controlling the condition and preventing blindness. Emergency treatment may be needed for sudden (acute) closed-angle glaucoma (CAG).
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The ophthalmologist will look for signs of damage caused by glaucoma in the back of the eyes to help determine whether the disease is present and to determine its severity. Your medical history and the results of the following tests help determine the severity of glaucoma:
- Ophthalmoscopy . Ophthalmoscopy is used to examine the inside structures of the eye. In glaucoma, it is used to examine the area where the optic nerve leaves the eye (optic disc). Damage to the optic nerve related to glaucoma can be diagnosed by ophthalmoscopy. People who have damage to the optic nerve related to glaucoma will also have loss of side vision.
- Gonioscopy . Gonioscopy uses a special lens to examine the drainage angles of the eyes. This is a very common test in the initial evaluation of suspected glaucoma.
- Tonometry . Tonometry measures the pressure in the eye (intraocular pressure, or IOP). Normal intraocular pressure is usually between 10 and 21 millimeters of mercury (mm Hg). People with glaucoma sometimes have above-normal IOP.
- Slit lamp exam . The slit lamp exam is used to get a magnified view of all parts of the eye. Gonioscopy and tonometry can be done as part of a slit lamp exam.
- Vision tests . Visual acuity testing measures how clearly you are able to see details. Visual field testing (also called perimetry testing) can detect loss of side (peripheral) vision and central vision that may indicate damage to the optic nerve caused by glaucoma. This is the best test for evaluating damage caused by open-angle glaucoma. Perimetry testing is also usually done as part of follow-up exams for glaucoma. Perimetry testing is expensive and time-consuming and thus is not used as a regular screening test or performed as often as other tests for glaucoma.
- Cornea thickness. Tests such as ultrasound pachymetry measure the thickness of the clear front surface of the eye (cornea). Cornea thickness, along with intraocular pressure, helps determine your risk of developing glaucoma.5
After glaucoma is diagnosed, eye exams (including tonometry and ophthalmoscopy) are done on a regular basis to monitor the disease. Perimetry testing is usually done once a year after open-angle glaucoma is diagnosed.
If you have glaucoma and have already experienced a significant loss of vision, your doctor may also perform a low-vision evaluation to help find ways you can make the most of your remaining vision and maintain your quality of life.
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