Glaucoma refers to a category of eye disorders often associated with a dangerous buildup of internal eye pressure (intraocular pressure or IOP), which can damage the eye’s optic nerve – the structure that transmits visual information from the eye to the brain.
Glaucoma typically affects your peripheral vision first. This is why it is such a sneaky disease: You can lose a great deal of your vision from glaucoma before you are aware anything is happening. If uncontrolled or left untreated, glaucoma can eventually lead to blindness.
Diagnosis, Screening, and Tests for Glaucoma
During annual eye exams, a tonometer is used to measure your intraocular pressure (IOP). Your eye typically is numbed with eye drops, and a small probe gently rests against your eye’s surface. Other tonometers direct a puff of air onto your eye’s surface to indirectly measure IOP.
An abnormally high IOP reading indicates a problem with the amount of fluid inside the eye. Either the eye is producing too much fluid, or it’s not draining properly.
Another method for detecting or monitoring glaucoma is the use of instruments to create images of the eye’s optic nerve and then repeating this imaging over time to see if changes to the optic nerve are taking place, which might indicate progressive glaucoma damage. Instruments used for this purpose include scanning laser polarimetry (SLP), optical coherence tomography (OCT), and confocal scanning laser ophthalmoscopy.
Visual field testing is another way to monitor whether blind spots are developing in your field of vision from glaucoma damage to the optic nerve. Visual field testing involves staring straight ahead into a machine and clicking a button when you notice a blinking light in your peripheral vision. The visual field test may be repeated at regular intervals so your eye doctor can determine if there is progressive vision loss.
Instruments such as an ophthalmoscope also may be used to help your eye doctor view internal eye structures, to make sure nothing unusual interferes with the outflow and drainage of eye fluids. Ultrasound biomicroscopy also may be used to evaluate how well fluids flow through the eye’s internal structures. Gonioscopy is the use of special lenses that allow your eye doctor to visually inspect internal eye structures that control fluid drainage.