Types of Glaucoma
Glaucoma refers to a group of illnesses that damage the optic nerve of the eyes. This disease affects millions of people, causing pain, vision problems and long-term vision loss. There are several different types of glaucoma that can impact vision.
Primary Open-Angle Glaucoma (POAG)
Primary open-angle glaucoma is often referred to as “the silent thief of sight” because there are few or no warning signs. Unfortunately, approximately half of people with glaucoma do not know they have the disease.
Glaucoma gradually reduces your peripheral vision and by the time you notice the change in your eyesight, permanent damage has already occurred. If your intraocular pressure (IOP) continues to remain high, the damage to the eye can progress until tunnel vision develops, then you will only see objects that are straight ahead.
Normal-Tension Glaucoma (NTG)
Normal tension glaucoma or normal pressure glaucoma also known as low tension glaucoma or low pressure glaucoma in which the intraocular pressure (IOP) is normal but damage to optic nerve and loss of vision still occurs.
Loss of peripheral vision occurs in Normal tension glaucoma just like in open angel glaucoma.
Normal tension glaucoma affects women more commonly. It affects people of around sixty years of age. Low blood pressure is an important risk factor for normal-tension glaucoma.
Raised intraocular pressure is not a factor in normal pressure glaucoma. Possible causes of NTG are nerve irritation, premature nerve cell death, blood flow reduction, excessive glutamate production as well as autoimmune disease.
Primary Angle-Closure Glaucoma (PACG)
Closed-angle glaucoma occurs when the peripheral iris occludes the outflow of intraocular fluid. Closed-angle glaucoma may progress gradually without any symptoms until long after it has begun. Closed-angle glaucoma is rare, accounting for just 15 percent of all glaucoma cases in the US.
This condition is caused by a structural defect within the eye that creates a narrow angle between the iris and cornea. If the iris moves forward, it can block the fluid drainage angle.
This condition can be set off by drugs that cause the dilatation of the pupil, for example tricyclic antidepressants and antihistamines. Pupillary dilatation in low light conditions can also trigger this condition. Farsighted individuals are at an increased risk for developing acute closed-angle glaucoma since their eyes have narrow drainage angles.
Pigmentary glaucoma is often without symptoms, but patients will occasionally notice pain and blurry vision after exercise. Pigmentary glaucoma occurs when the pigment granules that normally adhere to the back of the iris (the colored part of the eye) flake off into the clear fluid produced in the eye.
Additional problems can occur when these granules flow toward the drainage canals of the eye, slowly clogging them and raising eye pressure. The elevated eye pressure then can damage the optic nerve.
Men between the ages of 25-50 are affected more often than women. Studies have found that vigorous exercise seems to cause more pigment to be released from the iris, which may further block eye drainage.
Symptoms of Glaucoma
The greatest danger of glaucoma is that people frequently experience virtually no symptoms at all. The disease slowly progresses until vision is lost. Eventually, permanent blindness can result, so it is essential to diagnose and treat glaucoma as soon as possible. There are several types of glaucoma, including open-angle, normal-tension, closed-angle, congenital and acute glaucoma.
Some general symptoms of open-angle glaucoma (OAG), include: peripheral vision deterioration, excessive blinking, blurred vision, very occasional mild eye pain and only sometimes halos around bright lights.
Open-angle glaucoma often occurs in both eyes at about the same time, but sometimes one eye may be more affected than the other. If open-angle glaucoma is left untreated, the person will continue to lose vision until total blindness develops.
Closed-Angle Glaucoma (CAG)
Closed-angle glaucoma is less common than open-angle glaucoma. It can cause sudden blurred vision with pain and redness, which usually begins in one eye; symptoms may also include nausea and vomiting.
A related form of closed-angle glaucoma called acute glaucoma progresses rapidly, and produces symptoms of severe eye pain, headache, blurred vision, nausea, vomiting and halos.
Congenital glaucoma is often caused by a birth defect that can cause abnormal development of structures in the eye. Infants may be born with a high intraocular pressure (IOP) or develop IOP soon after birth.
Congenital glaucoma is rare and often involves both eyes, with boys being affected slightly more often than girls. While the disease is thought to have a genetic component, there are also cases that are not tied to family history. Infants with congenital glaucoma usually have cloudy eyes that are sensitive to light and have excessive tearing.
Normal-Tension Glaucoma Symptoms
Normal pressure glaucoma results in the peripheral loss of vision. Its symptoms are very similar to those of open angle glaucoma.
Causes of Glaucoma
Glaucoma is a condition in which the pressure within the eye becomes elevated, if left untreated it can damage the optic nerve and lead to blindness. In a normal eye, aqueous fluid is constantly produced and drained from the eye at a balanced rate. The formation and drainage of aqueous fluid determines the eye’s intraocular pressure (IOP). The optic nerve is relatively strong and can often withstand years of elevated eye pressure before damage occurs, however, once damage is done, it is irreversible.
People who are 60-years-old, or older, have an increased risk of developing glaucoma. The eye’s drainage angle become narrower as we age which results in raised intraocular pressure.
Several genetic factors can lead to an occurrence of glaucoma, placing those with a family history of the disease at an increased risk.
Some medical disorders, such as diabetes, hypothyroidism, leukemia, sickle cell anemia and arthritis, could place the patient at a higher risk of developing glaucoma. Increased risk factors are also associated with a previous history of steroid use, ocular injuries, extreme nearsightedness and even nutritional deficiencies. Glaucoma can also develop from the breakdown and flaking off of the colored material (pigment) found in the colored part of the eye.
Certain ethnic backgrounds tend to have a higher risk for glaucoma. African Americans over 40 and Mexican Americans over 60 face an increased risk when compared to Caucasians in the same age group. Among Caucasians, groups at higher risk include people with Russian, Irish and Scandinavian backgrounds.
There are often no obvious signs of glaucoma, so you may not realize that your field of vision is decreasing. Routine eye examinations and special tests of the visual field are key in the detection and treatment of glaucoma at an early stage.
Early diagnosis and treatment can help protect your eyes against vision loss related to glaucoma. People at risk for glaucoma should have a comprehensive dilated eye exam at least once every two years.
Treatment for glaucoma cannot cure it, but but further damage to optic nerve and visual loss can be prevented. An early diagnosis will help to lower the eye pressure in glaucoma’s beginning stages and help to slow the progression of the disease.
Glaucoma is often diagnosed by measuring the pressure of the fluid in the eyeball, known as the intraocular pressure. Sometimes it is necessary to make a series of measurements over time to confirm the diagnosis. The simplest test uses a puff of air blown against the surface of the eye.
For measurements that are more accurate, the eye specialist will numb the eye before performing a quick test. The procedure takes only a moment and is painless.
Glaucoma medications are either topical or oral. Eye drops are usually the first treatment prescribed by eye care professionals. These treatments usually include prescription eye drops, eye ointments or medication inserts for the corner of the eye.
These medications will work to reduce pressure within the eye by increasing the outflow of fluid from the eye, or by reducing the amount of fluid the eye produces. Your ophthalmologist can also prescribe oral medications to treat glaucoma.
Patients will be started on one or a combination of drugs to alleviate glaucoma symptoms, but if drug treatment fails, the ophthalmologist may recommend glaucoma surgery.
There are three types of laser surgeries for glaucoma.
Trabeculoplasty surgery is used to treat patients with open-angle glaucoma. A laser is used to increase the aqueous outflow in the area surrounding the laser spot, relieving pressure within the eye.
Iridotomy surgery is used to treat closed-angle glaucoma. Iridotomy uses a laser to make a small hole in the iris, allowing it to fall away from the fluid channel so that fluid can drain.
Cyclophotocoagulation surgery uses a laser to burn ciliary tissue, which decreases the production of fluid in the eye. This procedure, performed under local anesthesia, is used to treat patients who have failed to respond to other types of glaucoma surgery. Many patients will require more than a single treatment.
In some cases laser surgery will fail to lower intraocular pressure (IOP), and the surgeon may recommend conventional glaucoma surgery, known as trabeculectomy, or filtering surgery.
It is an outpatient procedure and involves the removal of a tiny piece of the eye under the eyelid. This creates a new drainage path that increases the outflow of fluid from the eye.