Glaucoma is often referred to as the “silent thief of sight,” because most types typically cause no pain and produce no symptoms. For this reason, glaucoma often progresses undetected until the optic nerve already has been irreversibly damaged, with varying degrees of permanent vision loss.
But with acute angle-closure glaucoma, symptoms that occur suddenly can include blurry vision, halos around lights, intense eye pain, nausea and vomiting. If you have these symptoms, make sure you immediately see an eye care practitioner or visit the emergency room so steps can be taken to prevent permanent vision loss.
Diagnosis, Screening and Tests for Glaucoma
During routine eye exams, a tonometer is used to measure your intraocular pressure or 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.
An abnormally high IOP reading indicates a problem with the amount of fluid (aqueous humor) in the eye. Either the eye is producing too much fluid, or it’s not draining properly.
Normally, IOP should be below 21 mmHg (millimeters of mercury) – a unit of measurement based on how much force is exerted within a certain defined area. If your IOP is higher than 30 mmHg, your risk of glaucoma damage is 40 times greater than someone with an IOP of 15 mmHG or lower.* This is why glaucoma treatments such as eye drops are aimed at keeping IOP low.
Your eye pressure (intraocular pressure) will be measured with a tonometer. Some tonometers blow a puff of air onto your eye’s surface. Others rest gently against the surface of your eye, which will be numbed with eye drops.
Other methods of monitoring glaucoma involve imaging of the eye’s optic nerve and internal structures (scanning laser polarimetry or SLP, optical coherence tomography or OCT, confocal scanning laser ophthalmoscopy, etc.) to establish a baseline and make sure no obvious changes have occurred over a period of time, which might indicate progressive glaucoma damage.
Visual field testing is another way to monitor whether blind spots are developing in your range of vision, resulting 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 the extent of 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 related angles of the eye’s internal structure. Specialized lenses also may be used (gonioscopy) for better viewing of internal eye structures.