Glaucoma is a leading cause of preventable vision loss and blindness in older individuals in the United States and Canada and the second leading cause of blindness in the world, even more than macular degeneration.
Glaucoma causes damage to the optic nerve which can be due to an increase in pressure inside the eye, which is called intraocular pressure (IOP). When detected in the early stages, glaucoma can often be controlled, preventing severe vision loss and blindness. However, symptoms of noticeable vision loss often only occur once the disease has progressed. This is why glaucoma is called “the silent thief of sight”. Unfortunately, once vision is lost from the disease, it cannot be restored.
Treatments include medication or surgery that can regulate the IOP and slow down the progression of the disease to prevent further vision loss. The type of treatment depends on the type and the cause of glaucoma.
Prevention is possible only with early detection and treatment. Since symptoms are often absent, regular eye exams which include a glaucoma screening are essential, particularly for individuals at risk of the disease. While anyone can get glaucoma, the following traits put you at a higher risk:
- Age over 60
- Hispanic or Latino descent, Asian descent
- African Americans over the age of 40 (glaucoma is the leading cause of blindness in African Americans, 6-8 times more common than in Caucasians)
- Family history of glaucoma
- People with nearsightedness (myopia)
- Certain medications (e.g. steroids)
- Significant eye injury (even if it occurred in childhood)
Signs and Symptoms of Glaucoma
Glaucoma can slowly damage the optic nerve, causing a gradual loss of vision. Vision loss begins with peripheral (side) vision, resulting in limited tunnel vision. Over time if left untreated, central vision will also be affected until it eventually causes total blindness. Unfortunately, any vision that is lost from the optic nerve damage cannot be restored.
What are the Symptoms?
Typically, glaucoma occurs without any symptoms. At the early onset of the most common type of glaucoma (primary open angle glaucoma), vision remains normal and there is no pain or discomfort. This is why the disease is nicknamed the “silent thief of sight”.
An acute type of glaucoma, called angle closure glaucoma, can present sudden symptoms such as foggy, blurred vision, halos around lights, eye pain, headache and even nausea. This is a medical emergency and should be assessed immediately as the intraocular pressure can become extremely high and cause permanent damage within hours.
Types of Glaucoma
The primary forms of glaucoma are open angle and narrow angle, with open angle being the most common type.
Primary open-angle glaucoma (POAG)
POAG gradually progresses without pain or noticeable vision loss initially affecting peripheral vision. By the time visual symptoms appear, irreparable damage has usually occurred, however, the sooner treatment starts the more vision loss can be prevented. When untreated, vision loss will eventually result in total loss of side vision (or tunnel vision) and eventually total vision loss.
Normal tension glaucoma or low tension glaucoma
This is another form of open angle glaucoma in which the intraocular pressure remains within the normal level. The cause of this form of glaucoma is not known, but it is believed to have something to do with insufficient blood flow to the optic nerve, causing damage. Individuals of Japanese descent, women and those with a history of vascular disease or low blood pressure are at higher risk.
Angle closure glaucoma
Acute angle closure glaucoma is marked by a sudden increase in eye pressure, which can cause severe pain, blurred vision, halos, nausea, and headaches. The pressure is caused by a blockage in the fluid at the front of the eye which is a medical emergency and should be treated immediately. Without prompt treatment to clear the blockage vision can be permanently lost.
This is an inherited form of the disease that is present at birth. In these cases, babies are born with a defect that slows the normal drainage of fluid out of the eye; they are usually diagnosed by the time they turn one. There are typically some noticeable symptoms such as excessive tearing, cloudiness or haziness of the eyes, large or protruding eyes or light sensitivity. Surgery is usually performed, with a very high success rate, to restore vision.
Glaucoma can develop as a complication of eye surgeries, injuries or other medical conditions such as cataracts, tumors, or a condition called uveitis which causes inflammation. Uncontrolled high blood pressure or diabetes can result in another serious form called neovascular glaucoma.
A rare form of glaucoma, this occurs when pigment from the iris sheds and clogs the drainage of fluid from the eye resulting in inflammation and damage to the eye and drainage system.
Treatment of glaucoma is dependent upon the severity and type of glaucoma present.
Glaucoma Diagnosis and Treatment
During a routine comprehensive eye exam to check for glaucoma, your eye doctor will dilate your eye to examine the optic nerve for signs of glaucoma and will also measure the intraocular pressure (IOP) with an instrument called a tonometer.
Tonometry involves numbing the eye with drops and then gently pressing on the surface of the eye to measure the pressure. Since your IOP can fluctuate throughout the day and glaucoma can exist without elevated IOP this is not enough to rule out the disease. If there are signs of the disease, further testing will be performed.
Visual Field Test
A visual field test is designed to detect any blind spots in your peripheral or side field of vision. You will be asked to place your head in front of a machine while looking ahead and indicate when you see a signal in your peripheral field of view.
Your doctor may also measure the thickness of the cornea with an ultrasonic wave instrument in a test called pachymetry or use imaging techniques such as optical coherence tomography (OCT) to create an image of your optic nerve to look for glaucoma damage.
Treatment for glaucoma depends on the type and severity of the disease and can include medication such as eye drops, pills, laser or traditional surgery.
Medication and drops to lower IOP are often the first resort for controlling pressure-related glaucoma. These drops may have some uncomfortable side effects, but compliance with the treatment plan is essential for preserving vision and halting the progression of the disease.
Surgical procedures are designed to control the flow of fluids through the eye by either decreasing the amount of fluid produced or improving the drainage. Your doctor may decide that a combination of surgery and medication will be the most effective in many cases.
It cannot be stressed enough that the most effective treatment for glaucoma happens when the disease is detected and treated early before significant vision loss occurs. Any vision that is lost cannot be restored. This is why the best prevention is awareness by knowing your risks and taking responsibility by having your eyes examined on a regular basis.
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