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It should be noted that no one test can provide the diagnosis. The primary source of suspicion will come from the optic nerve assessment. A combination of many of the tests below will help to provide the necessary pieces of the puzzle to make an accurate and educated diagnosis. These tests will also provide the ability to establish the efficacy of treatment and, ultimately, the stability of the disease.
Dilated Exam and Optic Nerve Assessment: Looks at features of the optic nerve and surrounding nerve fiber tissue for signs of damage from glaucoma. This may include photographs of the optic nerve which allow further analysis and provide documentation for future comparison. This can help the doctor determine if there is deterioration in the nerve at future exams.
Tonometry: Measures the intra-ocular pressure or (IOP), a definite risk factor in the development of glaucoma. In all forms of glaucoma, lowering the IOP is the only available, and FDA approved, treatment for the disease.
Visual Field Analysis: Measures the 'sensitivity' of the retina, and the ability of the optic nerve to send accurate information to the brain. This is performed using various light stimuli presented at different locations in the patient's field of vision. This test requires the full attention and cooperation of the patient for usually up to 4-8 minutes per eye. For some patients, this may be difficult. The reliability of the information obtained in visual field testing can vary greatly, and often results in the need for repeated testing. Visual field tests often show the effects of nerve damage well after it has already occurred, and are therefore not always a good early indicator. They are, however, a standard of care in diagnosing glaucoma and following the disease for signs of worsening. Some of the newer tests like the Matrix, using FDT (Frequency Doubling Technology) analysis, and SWAP (Short Wavelength Automated Perimetry) may provide earlier detection of glaucoma damage.
Pachymetry: Measures the thickness of the central cornea (the clear outer membrane of the eye). This is important for two reasons. Thicker corneas result in higher IOP measurement and thinner corneas result in lower IOP measurement - with this information the doctor is better able to interpret the IOP reading. Secondly, studies show that individuals with thinner corneas may be more vulnerable to developing certain types of glaucoma.
Gonioscopy: Inspection of the structures of the eye located in the angle that are critical to normal function of the eye. The eye produces a fluid called the aqueous which bathes and nourishes the tissues inside the eye. As new aqueous is produced, the old aqueous must drain out of the eye through the trabecular meshwork in the angle . If this area is damaged or becomes plugged, aqueous may back up and result in elevated pressure in the eye.
Imaging Tests: There are several imaging tests which provide newer high-tech ways of looking at the optic nerve and the nerve fiber layer of the eye. Each of these is capable of providing new and different clues to early signs of glaucoma and a means of following the disease for progression. Your doctor may have access to some of these technologies such as GDx, HRT, and OCT.