Glaucoma is the name given to a group of conditions caused by increased intraocular (inside the eye) pressure, or IOP, resulting either from a malformation or malfunction of the eye's drainage system. Left untreated, an elevated IOP may cause irreversible damage to the optic nerve and retinal fibers resulting in a progressive, permanent loss of vision. However, early detection and treatment can slow or even halt the progression of the disease.
Most individuals with glaucoma are not aware of problems with their vision. This is because the central vision (for reading and recognizing people) is only affected when glaucoma has advanced to a late stage. Even when central vision is still good, glaucoma may affect the vision needed for driving and other daily functions, including seeing steps or reading.
For most glaucoma sufferers, the main effect of the condition is the inconvenience of taking eye drops daily. Blindness from glaucoma is rare. If blindness does occur, it is usually because the glaucoma is already advanced when it is first diagnosed, because the eye pressure has not responded well to treatment, or because patients have not used their prescription eye drops regularly.
Healthcare professionals recommend that individuals at risk for glaucoma should get eye exams at least every two years. According to the National Eye Health Education Program (NEHEP), higher risk populations include African Americans over age 40, individuals over age 60 (especially Mexican Americans), and individuals with a family history of glaucoma. Inhaled steroids, such as beclomethasone (Beclovent®), fluticosone (Flovent®), and budesonide (Pulmicort®), may also increase the risk of developing glaucoma.
It is estimated that over three million Americans have glaucoma but only half of those know they have it. Approximately 120,000 are blind from glaucoma, accounting for 9-12% of all cases of blindness in the United States. About two percent of the population ages 40-50 years and eight percent over 70 years of age have elevated IOP.
Glaucoma is the second leading cause of blindness in the world, according to the World Health Organization (WHO). Glaucoma is the leading cause of blindness among African-Americans.
Estimates put the total number of suspected cases of glaucoma at around 65 million worldwide.
Without treatment, the loss of vision usually gets worse over the course of many months or several years. Loss of vision in glaucoma is permanent, but with early treatment, the damage to vision can be minimized. Early treatment can help protect the eyes against vision loss. Treatments usually include prescription eye drops and/or surgery. It's best to have routine eye checkups every two to four years after age 40 and every one to two years after age 65. Because African-Americans have a much higher risk of glaucoma, screening should begin every three to five years from age 20-29, and every two to four years after age 30.
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types of glaucoma
Glaucoma can broadly be divided into two main groups including open angle and closed angle glaucoma. Within these groups are primary and secondary conditions with chronic and acute types; each is described as to its type, symptoms, cause, detection, risk factors, and treatment.
Open angle glaucoma: Open angle (also called chronic open angle or primary open angle) is the most common type of glaucoma and usually causes no symptoms at first. With this type, even though the anterior structures of the eye appear normal, aqueous fluid builds within the anterior chamber, causing the intraocular pressure (IOP) to become elevated. Left untreated, this may result in permanent damage of the optic nerve and retina. Prescription eye drops are generally prescribed to lower the eye pressure. In some cases, surgery is performed if the IOP cannot be adequately controlled with medical therapy. Open angle glaucoma accounts for 19% of all blindness among African-Americans compared to six percent in Caucasians. Other high-risk groups include individuals over 60, family members of those already diagnosed, diabetics, and people who are severely nearsighted.
Acute angle closure glaucoma: Acute angle closure glaucoma, or closed-angle glaucoma, occurs because of an abnormality of the trabecular network and the canal of Schlemm in the eye that keeps aqueous humor fluid from draining. In most of these cases, the space between the iris and cornea is narrower than normal, putting pressure on the canal of Schlemm and leaving a smaller channel for the aqueous humor to drain. If the flow of aqueous becomes completely blocked, the IOP rises sharply, causing a sudden angle closure attack. Only about 10% of the population with glaucoma has acute angle closure glaucoma.
While patients with open angle glaucoma do not typically have symptoms, those with angle closure glaucoma may experience severe eye pain accompanied by nausea, blurred vision, seeing rainbows or halos around lights, and a red eye. This problem is an emergency and should be treated by an ophthalmologist immediately. If left untreated, severe and permanent loss of vision can occur in a matter of days.
Chronic closed-angle glaucoma: Closed angle glaucoma progresses more slowly and can produce damage without symptoms, similar to open-angle glaucoma.
Normal tension glaucoma: Normal tension glaucoma (NTG), also known as low tension or normal pressure glaucoma, is a form of glaucoma in which damage occurs to the optic nerve without eye pressure exceeding the normal range of 10-20 millimeters of mercury (mmHg). The causes of NTG are still unknown. For some reason, the optic nerve is susceptible to damage from even the normal amount of eye pressure. Researchers continue to examine why some optic nerves are damaged by these relatively low eye pressure levels. Lowering eye pressure at least 30% through medicines slows the disease in some people.
Neovascular glaucoma: A severe form of glaucoma, called neovascular glaucoma, is linked to diabetes and 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. Blockage of aqueous humor draining may occur, causing a rise in IOP.
Secondary glaucomas: Secondary glaucomas can develop as complications of other medical conditions, such as inflammation, trauma, previous surgery, diabetes, or a tumor. These types of glaucomas are sometimes associated with eye surgery or advanced cataracts, eye injuries, certain eye tumors, uveitis (eye inflammation), and certain medications (including topical steroid creams, cocaine, chlorpromazine or Thorazine®, and phenelzine or Nardil®). Secondary glaucomas include pigmentary glaucoma, pseudoexfoliation syndrome, and irido-corneal-endothelial syndrome (ICE). 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 and canal of Schlemm). 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.
Pediatric glaucomas: The pediatric glaucomas consist of congenital glaucoma (present at birth), infantile glaucoma (appears during the first three years), juvenile glaucoma (age three through the teenage or young adult years), and all the secondary glaucomas occurring in the pediatric age group. Congenital glaucoma is present at birth and most cases are diagnosed during the first year of life. Sometimes symptoms are not recognized until later in infancy or early childhood. The range of treatment is very different from that for adult glaucoma. It is very important to catch pediatric glaucoma early in order to prevent blindness.