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Generality/Definition
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Glaucoma is the name for a group of diseases that can destroy the optic nerve, the main nerve of the eye. The word glaucoma means hard eyeball. Any one of the conditions classified as glaucoma can lead to irreversible blindness by damaging the optic nerve. Glaucoma sneaks up on people. Even though glaucoma cannot be cured, it can be treated. If it is spotted in its early stages, before any sight is lost, blindness can almost always be prevented. But the longer glaucoma remains untreated, the more vision can be lost.
Source: What Is Glaucoma? (ehealthmd.com)
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There are several types of glaucoma, however, the two most common are primary open angle glaucoma (POAG), having a slow and insidious onset, and angle closure glaucoma (ACG), which is less common and tends to be more acute.
Source: WHO | VISION 2020 priority eye diseases (who.int)
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Epidemiology
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The number of persons estimated to be blind as a result of primary glaucoma is 4.5 million, accounting for slightly more than twelve per cent of all global blindness. The primary risk factors that are linked to the individual and the onset of the disease are age and genetic predisposition. The incidence of POAG rises with age and its progression is more frequent in people of African origin. ACG is the common form of glaucoma in people of Asian origin.
Source: WHO | VISION 2020 priority eye diseases (who.int)
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Black people are more likely to develop glaucoma than any other race. No one fully understands why this is so. Black people are also more likely to develop glaucoma at a younger age and will experience more damage to their vision because of it. One out of every 100 Black people age 40 and above has glaucoma. This is also true of Caucasians. by age 80, those numbers jump to 11 out of every 100 for Black people, but only 2 in 100 for Caucasians. Black people between the ages of 45 and 65 are much more likely to go blind from glaucoma than are members of other races. People of Asian descent and other races have figures more in line with Caucasians than with Black people.
Source: Who Gets Glaucoma? (ehealthmd.com)
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Prevention
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There is little known about primary prevention of glaucoma; however, there are effective methods of medical and surgical treatment if the disease is diagnosed in its early stage. Through appropriate treatment, sight may be maintained; otherwise the progression of the condition leads eventually to severe restriction of the visual field and irreversible blindness.
Source: WHO | VISION 2020 priority eye diseases (who.int)
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A comprehensive medical history is important in identifying other potential risk factors, such as low blood pressure, that contribute to low-tension glaucoma. If no risk factors are identified, the treatment options for low-tension glaucoma are the same as for open-angle glaucoma. Secondary glaucoma occurs as the result of some other medical problem, such as inflammation, a tumor, or eye injury.
Source: Glaucoma (ahaf.org)
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Symptoms
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- Open-angle glaucoma, the most common form, has no symptoms at first. The pressure in the eye builds up gradually. At some point, side vision (peripheral vision) is lost and without treatment, total blindness will occur.
- Acute closed-angle glaucoma results when the normal flow of eye fluid (aqueous humor) between the iris and the lens becomes suddenly blocked. Symptoms may include severe pain, nausea, vomiting, blurred vision, and seeing a rainbow halo around lights. Acute closed-angle glaucoma is a medical emergency and must be treated immediately or blindness could result in one or two days.
- Chronic closed-angle glaucoma progresses more slowly and can produce damage without symptoms, similar to open-angle glaucoma.
Source: Glaucoma (ahaf.org)
Treatment
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A number of medications are currently in use to treat glaucoma. Your doctor may prescribe a combination of medications or change your prescription over time to reduce side-effects or provide a more effective treatment. Typically medications are intended to reduce elevated intraocular pressure and prevent damage to the optic nerve. Glaucoma medications: Adrenergic, Alpha Agonist Beta Blockers, Carbonic Anhydrase Inhibitors, Cholinergic (Miotic), Cholinesterase Inhibitor, Combined Prostaglandin Analogs.
Source: Glaucoma (glaucoma.org)
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Surgery involves either laser treatment or making a cut in the eye to reduce the intraocular pressure (IOP). The type of surgery your doctor recommends will depend on the type and severity of your glaucoma and the general health of your eye. Surgery can help lower pressure when medication is not sufficient, however it cannot reverse vision loss.
Source: Glaucoma Surgery (glaucoma.org)
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Laser trabeculoplasty, a laser surgery procedure that is now a standard treatment for open-angle glaucoma. A safe and fast outpatient procedure that requires almost no recuperation, it normally takes about five minutes per eye and is usually painless. First, the eye is numbed with an anesthetic. The laser is aimed at the drainage channels in the eye, in order to make a tiny hole and let the fluid drain more easily. It normally works for 80 percent of people, and the effects last for five years. Most people will need to continue their medications even after laser treatment. After the operation a person may have slightly blurred vision and some redness in the eyes that lasts a day or so. Trabeculectomyis a traditional surgical procedure. In trabeculectomy, a tiny hole is made in the sclera (the white part of the eye) out of which fluid drains. It may take six to eight weeks for vision to return to the same level as before the operation. This procedure is used to provide long-term relief from high eye pressure without the use of medication. Drain implantation involves placing a microscopic plastic tube, or drain, within the eye to improve drainage and lower eye pressure. Ciliodestructive surgery, sometimes called cyclophotocoagulation, is a procedure in which a laser is used on the surface of the eye. The goal is to disrupt the process within the eye that produces the aqueous fluid. This reduces fluid production.
Source: Surgical Procedures For Glaucoma (ehealthmd.com)
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Illustrations
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Source: What Causes Glaucoma? (ehealthmd.com)
In a normal eye, aqueous humor is produced, circulates through the eye, and then drains out through the trabecular meshwork, which is the eye's filtration system. This is a series of tiny channels near the angle formed by the cornea (the clear portion of the eye), the iris (the colored portion of the eye), and the sclera (the white of the eye). If there is any sort of blockage in these channels, pressure builds up inside the eyeball.
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Information for specialists
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- Secondary glaucoma occurs as the result of some other medical problem, such as inflammation, a tumor, or eye injury.
- Congenital glaucoma is a condition where babies are born with defects that prevent the normal drainage of fluid from the eye. - Juvenile glaucoma has been used to describe open-angle glaucoma in children, adolescents and young adults.
- Pigmentary glaucoma is a rare form of the disease where pigment granules from the iris flake off into the aqueous humor (eye fluid) and then clog the eye drainage system (trabecular meshwork).
- Pseudoexfoliation syndrome occurs when outer layers of the lens flake off and block normal flow of the aqueous humor.
- Irido-corneal-endothelial syndrome (ICE) consists of a number of features, including the loss of cells from the cornea, which break off and block the drainage channels in the eye, resulting in increased eye pressure. There also may be scarring that connects the iris to the cornea.
- Neovascular glaucoma results from abnormal blood vessel growth that blocks the fluid drainage channels of the eye, resulting in increased eye pressure. Low blood supply to the eye as a result of diabetes, insufficient flow of blood to the head due to blocked arteries in the neck, or blockage of blood vessels in the back of the eye can cause the abnormal blood vessel growth.
Source: Glaucoma (ahaf.org)
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Eye drops are used to reduce eye pressure by either increasing the eye's ability to drain or by decreasing the amount of fluid it produces. Beta-blockers cause little discomfort and work by decreasing the production of aqueous fluid. However, they can make breathing and heart problems worse in people with heart or lung conditions. Prostaglandins increase drainage. They can cause blue and green eyes to become darker. Alpha-stimulators are used with other medications to lower eye pressure. These can cause allergic reactions in and around the eyes. Carbonic anhydrase inhibitors decrease fluid production. Because they are sulfa based, they should not be used by people allergic to sulfa. Miotics increase fluid drainage. They can, however, cause headaches when first used. They also cause the pupil to constrict-shrink-which can cause blurred vision. Epinephrine increases fluid drainage. Although there are not usually any major complications, it can cause temporary redness of the eye and blurred vision. Oral Medication Pills are usually used to decrease fluid production. They can be very effective in lowering eye pressure, but they also cause side effects in about half of the people who take them. For this reason, your doctor may want to try other options first.
Source: How Is Glaucoma Treated? (ehealthmd.com)
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Doctors often recommend laser surgery before filtering microsurgery, unless the eye pressure is very high or the optic nerve is badly damaged. During laser surgery, a tiny but powerful beam of light is used to make several small scars in the eye's trabecular meshwork (the eye's drainage system). The scars help increase the flow of fluid out of the eye.
In contrast, filtering microsurgery involves creating a drainage hole with the use of a small surgical tool. When laser surgery does not successfully lower eye pressure, or the pressure begins to rise again, the doctor may recommend filtering microsurgery.
Source: Glaucoma Surgery (glaucoma.org)
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