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Glaucoma Screening and Management
- What is Glaucoma?
Glaucoma is a group of eye disorders often associated with a dangerous increase of internal eye pressure (intraocular pressure or IOP), which can damage the eye's optic nerve that transmits visual information to the brain.
With untreated or uncontrolled glaucoma, you might eventually notice decreased ability to see at the edges of your vision (peripheral vision). Progressive eye damage could then lead to blindness.
- What are the symptoms of Glaucoma?
Glaucoma is often called the "silent thief of sight," because most kinds have no pain nor decreased vision.
Because of this, oftentimes, glaucoma gets worse undetected until the optic nerve damage is irreversible, with various stages of permanent visual loss.
But with acute angle-closure glaucoma, there may be sudden blurred vision, halos, eyepain, nausea and vomiting. When these happen to you, see your eye doctor right away, or go to the emergency room to prevent permanent visual loss.
- What are the Types of Glaucoma?
The two major types of glaucoma are acute angle-closure glaucoma, with angle referring to the portion of the eye that drains fluids, and chronic or primary open-angle glaucoma (POAG). Other variations include congenital glaucoma, pigmentary glaucoma, and secondary glaucoma.
Primary open-angle glaucoma (POAG). In this kind of glaucoma, the drainage system of the eye is open but not working properly. Gradual and painless decrease in vision happens, and by the time it is noticed, there is already permanent damage.
Normal-tension glaucoma. Like POAG, normal-tension glaucoma (also termed normal-pressure glaucoma, low-tension glaucoma or low-pressure glaucoma) is an open-angle type of glaucoma that can cause visual field loss due to optic nerve damage. But in normal-tension glaucoma, the eye's IOP remains in the normal range.
Also, pain is unlikely and permanent damage to the eye's optic nerve may not be noticed until symptoms such as tunnel vision occur.
Pigmentary glaucoma. This rare form of glaucoma is caused by pigment deposited from the iris that clogs the draining angles, preventing aqueous humor from leaving the eye. In time, the inflammation damages the drainage system.
Angle-closure glaucoma. Angle-closure or narrow angle glaucoma produces sudden symptoms such as eye pain, headaches, halos around lights, dilated pupils, vision loss, red eyes, nausea and vomiting. These signs may last for a few hours, then return again for another round. Each attack further damages the eye’s vision.
Secondary glaucoma. Symptoms of chronic glaucoma following an eye injury could indicate secondary glaucoma, which also may develop with presence of infection, inflammation, a tumor or an enlarged cataract.
Congenital glaucoma. This inherited form of glaucoma is present at birth, with 80 percent of cases diagnosed by age one. These children are born with narrow angles or some other defect in the drainage system of the eye. If your child has a cloudy, white, hazy or enlarged eye, consult your eye doctor.
- How is Glaucoma diagnosed, screened and tested?
During routine eye exams, a tonometer is used to measure your intraocular pressure, or IOP. Numbing eyedrops are placed in your eye, and a small probe will gently rest on your eye. An abnormally high IOP indicates that your eye’s fluids are 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 designed to keep IOP low.
Ophthalmoscopy is used to examine the inside of the eye, especially the optic nerve. In a dark room, your doctor will use and ophthalmoscope, an instrument with a small light), to magnify your eye and to check the structures inside, most specially the optic nerve.
Gonioscopy is a painless eye test that checks if the angle where the iris meets the cornea is open or closed, showing if either open angle or closed angle glaucoma is present. Numbing eyedrops will be put in your eyes, and a special lens will gently be placed to examine the angle structures.
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. You will be instructed to stare straight ahead into a machine and click a button when you see a light in your peripheral vision. You doctor will request this test regularly to monitor any visual field losses.
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, Heidelberg Retinal Tomography or HRT, etc.) to establish a baseline and make sure no obvious changes have occurred over a period of time, which might indicate progressive glaucoma damage.
- How is Glaucoma treated?
Treatment can involve glaucoma surgery, lasers or medication, depending on the severity. Eye drops with medication aimed at lowering IOP usually are tried first to control glaucoma.
