What is the treatment for glaucoma?
Although nerve damage and visual loss from glaucoma cannot usually be reversed, glaucoma is a disease that can generally be controlled. That is, treatment can make the intraocular pressure normal and, therefore, prevent or retard further nerve damage and visual loss. Treatment may involve the use of eyedrops, pills (rarely), laser ,or surgery.
In the United States, eyedrops are usually used first in treating most types of open-angle glaucoma. In contrast, in Europe, laser or surgery is sometimes the first choice of treatment. One or more types of eyedrops may have to be taken up to several times a day to lower intraocular pressure. These drops work either by reducing the production of the aqueous fluid (shutting the faucet) or by increasing the drainage of the fluid out of the eye. Each type of therapy has its benefits and potential complications.
Glaucoma surgery or laser
There are several forms of laser therapy for glaucoma. Laser iridotomy (see the section above on angle-closure glaucoma) involves making a hole in the colored part of the eye (iris) to allow fluid to drain normally in eyes with narrow or closed angles. Laser trabeculoplasty is a laser procedure performed only in eyes with open angles. Laser trabeculoplasty does not cure glaucoma but is often done instead of increasing the number of different eyedrops or when a patient’s intraocular pressure is felt to be too high despite the use of multiple eyedrops (maximal medical therapy). In some cases, it is used as the initial or primary therapy for open-angle glaucoma. This procedure is a quick, painless, and relatively safe method of lowering the intraocular pressure. With the eye numbed by anesthetic drops, the laser treatment is applied through a mirrored contact lens to the angle of the eye. Microscopic laser burns to the angle allow fluid to better exit the drainage channels.
Laser trabeculoplasty is often done in two sessions, weeks or months apart. Unfortunately, the improved drainage as a result of the treatment may last only about two years, by which time the drainage channels tend to clog again. There are two types of laser trabeculoplasty: argon laser trabeculoplasty (ALT) and selective laser trabeculoplasty (SLT). ALT is generally not repeated after the second session due to the formation of scar tissue in the angle. SLT is less likely to produce scarring in the angle, so, theoretically, it can be repeated multiple times. However, the likelihood of success with additional treatments when prior attempts have failed is low. Thus, the options for the patient at that time are to increase the use of eyedrops or proceed to surgery.
Laser cyclo-ablation (also known ciliary body destruction, cyclophotocoagulation or cyclocryopexy) is another form of laser treatment generally reserved for patients with severe forms of glaucoma with poor visual potential. This procedure involves applying laser burns or freezing to the part of the eye that makes the aqueous fluid (ciliary body). This therapy destroys the cells that make the fluid, thereby reducing the eye pressure. This type of laser is typically performed after other more traditional therapies have failed.
Trabeculectomy is a delicate microsurgical procedure used to treat glaucoma. In this operation, a small piece of the clogged trabecular meshwork is removed to create an opening and a new drainage pathway is made for the fluid to exit the eye. As part of this new drainage system, a tiny collecting bag is created from conjunctival tissue. (The conjunctiva is the clear covering over the white of the eye.) This bag is called a “filtering bleb” and looks like a cystic raised area that is at the top part of the eye under the upper lid. The new drainage system allows fluid to leave the eye, enter the bag/bleb, and then pass into the capillary blood circulation (thereby lowering the eye pressure). Trabeculectomy is the most commonly performed glaucoma surgery. If successful, it is the most effective means of lowering the eye pressure.
Aqueous shunt devices (glaucoma implants or tubes) are artificial drainage devices used to lower the eye pressure. They are essentiallyplastic microscopic tubes attached to a plastic reservoir. The reservoir (or plate) is placed beneath the conjunctival tissue. The actual tube (which extends from the reservoir) is placed inside the eye to create a new pathway for fluid to exit the eye. This fluid collects within the reservoir beneath the conjunctiva creating a filtering bleb. This procedure may be performed as an alternative to trabeculectomy in patients with certain types of glaucoma.
Viscocanalostomy is an alternative surgical procedure used to lower eye pressure. It involves removing a piece of the sclera (eye wall) to leave only a thin membrane of tissue through which aqueous fluid can more easily drain. While it is less invasive than trabeculectomy and aqueous shunt surgery, it also tends to be less effective.
The surgeon sometimes creates other types of drainage systems. While glaucoma surgery is often effective, complications, such as infection or bleeding, are possible. Accordingly, surgery is usually reserved for cases that cannot otherwise be controlled.
What is glaucoma?
Glaucoma is a disease of the major nerve of vision, called the optic nerve. The optic nerve receives light-generated nerve impulses from the retina and transmits these to the brain, where we recognize those electrical signals as vision. Glaucoma is characterized by a particular pattern of progressive damage to the optic nerve that generally begins with a subtle loss of side vision (peripheral vision). If glaucoma is not diagnosed and treated, it can progress to loss of central vision and blindness.
Glaucoma is usually, but not always, associated with elevated pressure in the eye (intraocular pressure). Generally, it is this elevated eye pressure that leads to damage of the eye (optic) nerve. In some cases, glaucoma may occur in the presence of normal eye pressure. This form of glaucoma is believed to be caused by poor regulation of blood flow to the optic nerve.
How common is glaucoma?
Worldwide, glaucoma is the leading cause of irreversible blindness. In fact, as many as 6 million individuals are blind in both eyes from this disease. In the United States alone, according to one estimate, over 3 million people have glaucoma. As many as half of the individuals with glaucoma, however, may not know that they have the disease. The reason they are unaware is that glaucoma initially causes no symptoms, and the subsequent loss of side vision (peripheral vision) is usually not recognized.
Elevated pressure in the eye is the main factor leading to glaucomatous damage to the eye (optic) nerve. Glaucoma with normal intraocular pressure is discussed below in the section on the different types of glaucoma. The optic nerve, which is located in back of the eye, is the main visual nerve for the eye. This nerve transmits the images we see back to the brain for interpretation. The eye is firm and round, like a basketball. Its tone and shape are maintained by a pressure within the eye (the intraocular pressure), which normally ranges between 8 mm and 22 mm (millimeters) of mercury. When the pressure is too low, the eye becomes softer, while an elevated pressure causes the eye to become harder. The optic nerve is the most susceptible part of the eye to high pressure because the delicate fibers in this nerve are easily damaged.
The front of the eye is filled with a clear fluid called the aqueous humor, which provides nourishment to the structures in the front of the eye. This fluid is produced constantly by the ciliary body, which surrounds the lens of the eye. The aqueous humor then flows through the pupil and leaves the eye through tiny channels called the trabecular meshwork. These channels are located at what is called the drainage angle of the eye. This angle is where the clear cornea, which covers the front of the eye, attaches to the base (root or periphery) of the iris, which is the colored part of the eye. The cornea covers the iris and the pupil, which are in front of the lens. The pupil is the small, round, black-appearing opening in the center of the iris. Light passes through the pupil, on through the lens, and to the retina at the back of the eye. Please see the figure, which is a diagram that shows the drainage angle of the eye.
Legend for figure: This diagram of the front part of the eye is in cross section to show the filtering, or drainage, angle. This angle is between the cornea and the iris, which join each other right where the drainage channels (trabecular meshwork) are located. The arrow shows the flow of the aqueous fluid from the ciliary body, through the pupil, and into the drainage channels. This figure is recreated from Understanding and Treating Glaucoma, a human anatomy board book by Tim Peters and Company Inc., Gladstone N.J.
In most people, the drainage angles are wide open, although in some individuals, they can be narrow. For example, the usual angle is about 45 degrees, whereas a narrow angle is about 25 degrees or less. After exiting through the trabecular meshwork in the drainage angle, the aqueous fluid then drains into tiny blood vessels (capillaries) into the main bloodstream. The aqueous humor should not be confused with tears, which are produced by a gland outside of the eyeball itself.
This process of producing and removing the fluid from the eye is similar to that of a sink with the faucet always turned on, producing and draining the water. If the sink’s drain becomes clogged, the water may overflow. If this sink were a closed system, as is the eye, and unable to overflow, the pressure in the sink would rise. Likewise, if the eye’s trabecular meshwork becomes clogged or blocked, the intraocular pressure may become elevated. Also, if the sink’s faucet is on too high, the water may overflow. Again, if this sink were a closed system, the pressure within the sink would increase. Likewise, if too much fluid is being produced within the eye, the intraocular pressure may become too high. In either event, since the eye is a closed system, if it cannot remove the increased fluid, the pressure builds up and optic-nerve damage may result.
What are glaucoma risk factors?
Glaucoma is often called “the sneak thief of sight.” This is because, as already mentioned, in most cases, the intraocular pressure can build up and destroy sight without causing obvious symptoms. Thus, awareness and early detection of glaucoma are extremely important because this disease can be successfully treated when diagnosed early. While everyone is at risk for glaucoma, certain people are at a much higher risk and need to be checked more frequently by their eye doctor. The major risk factors
for glaucoma include the following:
- Age over 45 years
- Family history of glaucoma
- Black racial ancestry
- History of elevated intraocular pressure
- Nearsightedness (high degree of myopia), which is the inability to see distant objects clearly
- History of injury to the eye
- Use of cortisone (steroids), either in the eye or systemically (orally or injected)
- Farsightedness (hyperopia), which is seeing distant objects better than close ones (Farsighted people may have narrow drainage angles, which predispose them to acute
[sudden] attacks of angle-closure glaucoma.)
What are the different types of glaucoma?
There are many different types of glaucoma. Most, however, can be classified as either open-angle glaucomas, which are usually conditions of long duration (chronic), or angle-closure (closed
angle) glaucomas, which include conditions occurring both suddenly (acute) and over a long period of time (chronic). The glaucomas usually affect both eyes, but the disease can progress more rapidly in one eye than in the other. Involvement of just one eye occurs only when the glaucoma is brought on by factors such as a prior injury, inflammation, or the use of steroids only in that eye.
Primary chronic open-angle glaucoma (COAG) is by far the most common type of glaucoma. Moreover, its frequency increases greatly with age. This increase occurs because the drainage mechanism gradually may become clogged with aging, even though the drainage angle is open. As a consequence, the aqueous fluid does not drain from the eye properly. The pressure within the eye, therefore, builds up painlessly and without symptoms. Furthermore, as mentioned previously, since the resulting loss of vision starts on the side (peripherally), people are usually not aware of the problem until the loss encroaches on their central visual area.
Normal tension (pressure) glaucoma or low tension glaucoma are variants of primary chronic open-angle glaucoma that are being recognized more frequently than in the past. This type of glaucoma is thought to be due to decreased blood flow to the optic nerve. This condition is characterized by progressive optic-nerve damage and loss of peripheral vision (visual field) despite intraocular pressures in the normal range or even below normal. This type of glaucoma can be diagnosed by repeated examinations by the eye doctor to detect the nerve damage or the visual field loss.
Congenital (infantile) glaucoma is a relatively rare, inherited type of open-angle glaucoma. In this condition, the drainage area is not properly developed before birth. This results in increased pressure in the eye that can lead to the loss of vision from optic-nerve damage and also to an enlarged eye. The eye of a young child enlarges in response to increased intraocular pressure because it is more pliable than the eye of an adult. Early diagnosis and treatment with medicine and/or surgery are critical in these infants and children to preserve their sight.
Secondary open-angle glaucoma is another type of open-angle glaucoma. It can result from an eye (ocular) injury, even one that occurred many years ago. Other causes of secondary glaucoma are inflammation in the iris of the eye (iritis), diabetes, cataracts, or in steroid-susceptible individuals, the use of topical (drops) or systemic (oral or injected) steroids (cortisone). It can also be associated with a retinal detachment or retinal vein occlusion or blockage. (The retina is the layer that lines the inside of the back of the eye.) The treatments for the secondary
open-angle glaucomas vary, depending on the cause.
Pigmentary glaucoma is a type of secondary glaucoma that is more common in younger men. In this condition, for reasons not yet understood, granules of pigment detach from the iris, which is the colored part of the eye. These granules then may block the trabecular meshwork, which, as noted above, is a key element in the drainage system of the eye. Finally, the blocked drainage system leads to elevated intraocular pressure, which results in damage to the optic nerve.
Exfoliative glaucoma (pseudoexfoliation) is another type of glaucoma that can occur with either open or closed angles. This type of glaucoma is characterized by deposits of flaky material on the front surface of the lens (anterior capsule) and in the angle of the eye. The accumulation of this material in the angle is believed to block the drainage system of the eye and raise the eye pressure. While this type of glaucoma can occur in any population, it is more prevalent in older people and people of Scandinavian descent. It is recently been shown to often be associated with hearing loss in older people.
Angle-closure glaucoma is a less common form of glaucoma in the Western world
but is extremely common in Asia. Angle-closure glaucoma may be acute or chronic.
The common element in both is that a portion or all of the drainage angle
becomes anatomically closed, so that the aqueous fluid within the eye cannot
even reach all or part of the trabecular meshwork. In acute angle-closure
glaucoma, the patient’s intraocular pressure, which ordinarily is normal, can go
up very suddenly (acutely). This sudden pressure increase occurs because the
drainage angle becomes closed and blocks off all the drainage channels. This
type of glaucoma can occur when the pupil dilates (widens or enlarges). As a
result, the peripheral edge of the iris can become bunched up against its
corneal attachment, thereby causing the drainage angle to close. Thus, the
problem in angle-closure glaucoma is the difficulty with access of the eye fluid
to the drainage system (trabecular meshwork). In contrast, remember that the
problem in open-angle glaucoma is clogging within the drainage system itself. In
chronic open-angle glaucoma, portions of the drainage angle become closed over a
long period of time. As more and more areas become closed, the pressure within
the eye rises, often over a period of months or years.
People with small eyes are predisposed to developing angle-closure glaucoma
because they tend to have narrow drainage angles. Small eyes are not obvious
from their appearance, but they can be measured by an eye doctor. Thus,
individuals who are farsighted or of Asian descent may have small eyes, narrow
drainage angles, and an increased risk of developing angle-closure glaucoma.
Furthermore, this condition may be acutely triggered by medications that can
dilate the pupils. These agents can be found in certain eyedrops, cold
remedies, citalopram (Celexa), topiramate (Topamax), or patches used to prevent seasickness. This
condition can also occur spontaneously in a darkened room or a movie theater,
when the pupil automatically dilates to let in more light. Sometimes, therefore,
people with narrow angles are given eyedrops to keep their pupils small. (See
the section below on parasympathomimetic agents.)
An attack of acute angle-closure glaucoma may be associated with severe eye
pain and headache, a red (inflamed) eye, nausea, vomiting, and blurry vision. In
addition, the high intraocular pressure leads to corneal swelling (edema), which
causes the patient to see haloes around lights. Sometimes, acute glaucoma is
treated with oral carbonic anhydrase inhibitors. (See the section below on these
medications.) An attack of acute glaucoma, however, is usually relieved by eye
surgery. In this operation, the doctor makes a small hole in the iris with a
laser (laser iridotomy) to allow the fluid to resume draining into its normal
What are glaucoma symptoms and signs?
Patients with open-angle glaucoma and chronic angle-closure glaucoma in general have no symptoms early in the course of the disease. Visual field loss (side vision loss) is not a symptom until late in the course of the disease. Rarely patients with fluctuating levels of intra-ocular pressure may have haziness of vision and see haloes around lights, especially in the morning.
On the other hand, the symptoms of acute angle-closure are often extremely dramatic with the rapid onset of severe eye pain,headache, nausea and vomiting, and visual blurring. Occasionally, the nausea and vomiting exceed the ocular symptoms to the extent that an ocular cause is not contemplated.
The eyes of patients with open-angle glaucoma or chronic angle-closure glaucoma may appear normal in the mirror or to family or friends. Some patients get slightly red eyes from the chronic use of eyedrops. The ophthalmologist, on examining the patient, may find elevated intraocular pressure, optic-nerve abnormalities, or visual field loss in addition to other less common signs.
The eyes of patients with acute angle-closure glaucoma will appear red, and the pupil of the eye may be large and nonreactive to light. The cornea may appear cloudy to the naked eye. The ophthalmologist will typically find decreased visual acuity, corneal swelling, highly elevated intraocular pressure, and a closed drainage angle.
How often should someone be checked (screened) for glaucoma?
The following are the American Academy of Ophthalmology’s recommended intervals for eye exams:
- Age 20-29: Individuals of African descent or with a family history of glaucoma should have an eye examination every three to five years. Others should have an eye exam at least once during this period.
- Age 30-39: Individuals of African descent or with a family history of glaucoma should have an eye examination every two to four years. Others should have an eye exam at least twice during this period.
- Age 40-64: Individuals should have an eye examination every two to four years.
- Age 65 or older: Individuals should have an eye examination every one to two years.
These routine screening eye examinations are mandatory since glaucoma usually causes no symptoms (asymptomatic) in its early stages. Once damage to the optic nerve has occurred, it cannot be reversed. Thus, in order to preserve vision, glaucoma must be diagnosed early and followed regularly. Patients with glaucoma need to be aware that it is a lifelong disease. Compliance with scheduled visits to the eye doctor and with prescribed medication regimens offers the best chance for maintaining vision.