The first step in understanding glaucoma is to know a few basic facts about the eye and how it works. Once this information is properly explained, it will be better to understand the real condition and treatment of glaucoma. Working together with your ophthalmologist you will be able to act as a team to protect your vision.

Glaucoma …what you should know?
Glaucoma is caused by a number of different eye diseases characterized by increased pressure within the eye. A backup of fluid causes this elevated pressure in the eye. Over time, it causes damage to the optic nerve. Through early detection, diagnosis and management, vision can be preserved.
The aqueous humor is constantly circulating through the anterior chamber. A tiny gland called the ciliary body that is situated behind the iris produces it. It flows between the posterior chamber to anterior and after nourishing the cornea and lens, flows out through
a very tiny spongy tissue called the trabecular meshwork, which is very tiny channel and situated in the angle where the iris and cornea meet and serves as the drain of the eye. When this draining channel becomes blocked aqueous cannot leave the eye as quickly as it is produced, causing the fluid to back up this backed up fluid causes increased pressure within the eye.
As the optic nerve is the part of the eye that carries visual information to the brain. It is made up of over one million nerve cells, and while each cell is several inches long, it is extremely thin -- about one twenty-thousandth of an inch in diameter. When the pressure in the eye builds, the nerve cells become compressed, causing them to become damaged and to eventually die. The death of these cells results in permanent visual loss. Early diagnosis and treatment of glaucoma can help prevent this from happening.

Who is at Risk?
Everyone should be concerned about glaucoma and its effects. It is important for each of us, from infants to senior citizens, to have our eyes checked regularly, because early detection and treatment of glaucoma are the only way to prevent vision impairment and blindness. There are a few conditions related to this disease which tend to put some people at greater risk:

• People over the age of 45.
While glaucoma can develop in younger patients, it occurs more frequently as we get older.

• People who have a family history of glaucoma.
Glaucoma appears to run in families. The tendency for developing glaucoma may be inherited. However, just because someone in your family has glaucoma does not mean that you will necessarily develop the disease.

• People with abnormally high intraocular pressure (IOP).
High IOP is the most important risk factor for glaucomatous damage.

• People of African descent.
African-Americans have a greater tendency for developing primary open-angle glaucoma than do people of other races.

• People who have:
* Diabetes
* Myopia (nearsightedness)
* Regular, long-term Steroid/Cortisone use
* A previous eye injury.

Different types Glaucoma
There are a variety of different types of glaucoma. The most common forms are:
· Normal Tension Glaucoma
· Primary Open-Angle Glaucoma
· Angle-Closure Glaucoma
· Trauma-Related Glaucoma.
· Acute Glaucoma
· Pigmentary Glaucoma
· Exfoliation Syndrome

Lets discuss different forms of glaucoma:
Low or normal Tension Glaucoma.
Normal-tension glaucoma, also known as low-tension glaucoma, is characterized by progressive optic nerve damage and visual field loss with a statistically normal or low intraocular pressure. This form of glaucoma, which is being increasingly recognized, may account for as many as one-third of the cases of open-angle glaucoma.
Normal-tension glaucoma is thought to be related to poor blood flow to the optic nerve, which leads to death of the cells that carry impulses from the retina to the brain. In addition, these eyes appear to be susceptible to pressure-related damage even in the high normal range, and therefore a pressure lower than normal is often necessary to prevent further visual loss.
The optic nerve blood flow and its role in glaucoma is a source of much excitement and hopefully will lead to new methods of treating this disorder. Since the best therapy for normal-tension glaucoma is still unknown,

Primary Open-Angle Glaucoma (POAG):
This is most common form of glaucoma and it occurs mainly in between 45 to 55 years of age group. It is a chronic disease and there are no symptoms associated with POAG. Some time it may be hereditary. The intraocular pressure slowly rises and the cornea adapts without swelling. If the cornea were to swell, which is usually a signal that something is wrong, symptoms would be present. But because this is not the case, the POAG often goes undetected. It is painless, and the patient often does not realize that he or she is slowly losing vision until the later stages of the disease. However, by the time the vision is impaired, the damage is irreversible.
In POAG, there is no visible abnormality of the trabecular meshwork. It is believed that
something is wrong with the ability of the cells in the trabecular meshwork to carry out
their normal function, or there may be some cells gets older due to natural result of age. Some time it is due to a structural defect of the eye’s drainage system. Some time it is caused by an enzymatic problem. These theories, as well as others, are currently being studied and tested at numerous research centers across the world.
Glaucoma is really about the problems that occur as a result of increased IOP. The average IOP in a normal population is 16-20 millimeters of mercury (mmHg). In a normal population pressures up to 20 mmHg may be within normal range. A pressure of 22 is considered to be suspicious and possibly abnormal. However, not all patients with elevated IOP develop glaucoma-related eye disease.
As mentioned earlier, this increased pressure can ultimately destroy the optic nerve head. Once a sufficient number of nerve cells are destroyed, `blind spots´ begin to form in the field of vision. These blind spots usually develop first in the peripheral field of vision and then outer sides of the field of vision. In the later stages, the central vision is affected. Once visual loss occurs, it is irreversible because once the nerve cells are dead; nothing can be done to restore them in the original form.
There is no permanent cure for POAG at present, but the disease can be slowed down by treatment. Since there are no symptoms, many patients find it difficult to understand why lifelong treatment with expensive drugs is necessary, especially when these drugs are often bothersome to take and have a variety of side effects.
Taking medications regularly, as prescribed, is crucial to preventing vision threatening
damage. That is why it is important for everybody to discuss these side effects with their ophthalmologist.

Angle-Closure Glaucoma:
Angle-closure glaucoma is also a common form of glaucoma and there is a tendency for this disease to be inherited, and often several members of a family will be affected. It is most common in people of Asian descent and people who are farsighted.
In people with a tendency to angle-closure glaucoma, the anterior chamber is smaller than average. As mentioned earlier, the trabecular meshwork is situated in the angle formed where the cornea and the iris meet. In most people, this angle is about 45 degrees. The narrower the angle, the closer the iris is to the trabecular meshwork. As the people get older and older the lens also slowly grow larger. The ability of aqueous humor to pass between the iris and lens on its way to the anterior chamber becomes decreased, causing fluid pressure to build up behind the iris, which further narrow the angle. If the pressure becomes sufficiently high, the iris is forced against the trabecular meshwork, blocking drainage draining of aqueous. When this space becomes completely blocked, angle closure glaucoma attacks results, which is very severe form of glaucoma.

Acute Glaucoma:
Unlike POAG, where the IOP increases slowly but in acute angle-closure, it increases suddenly. This sudden rise in pressure can occur within a matter of hours and become
very painful. If the pressure rises high enough, the pain may become so intense that it
can cause nausea and vomiting.

The eye becomes red, the cornea become oedematous and the patient may see haloes (rainbow-colored rings around lights) around lights and may experience blurred vision. An acute attack is an emergency condition. If treatment is delayed, eyesight can be permanently destroyed. Scarring of the trabecular meshwork may occur and result in chronic glaucoma, which is much more difficult to control. Cataracts may also develop and damage to the optic nerve may occur quickly and cause permanent impaired of vision.
Many of these sudden attacks occur in darkened rooms where pupil dilate or increase in size. When this happens, there is maximum contact between the lens and the iris. This further narrows the angle and may trigger an attack. But the pupil also dilates when some one is excited or anxious. Consequently, many acute glaucoma attacks occur during periods of stress. A variety of drugs can also cause dilation of the pupil and lead to an attack of
glaucoma. These include anti-depressants, cold medications, antihistamines, and some
medications to treat nausea.

Acute glaucoma attacks are not always full blown. Sometimes a patient may have a series of minor attacks. A slight blurring of vision and haloes may be experienced, but without pain or redness. These attacks may end when the patient enters a well-lit room or goes to sleep, two situations, which naturally cause the pupil to constrict, thereby allowing the iris to pull away from the drain.
An acute attack may be stopped with a combination of drops that constrict the pupil and drugs that help reduce the eye’s fluid production.

Routine examinations using a technique called gonioscopy where a special lens that contains a mirror is placed lightly on the front of the eye and the width of the angle examined visually. Patients with narrow angles can be warned of early symptoms, so that they can seek immediate treatment. In some cases laser treatment is recommended as a preventive measure.
Not all angle-closure glaucoma sufferers will experience an acute attack. Instead, some may develop what is called chronic angle-closure glaucoma. In this case, the iris gradually closes over the drain, causing no symptoms. When this occurs, scars slowly form between the iris and the drain and the IOP will not rise until there is a significant amount of scar tissue formed -- enough to cover the drainage area. If the patient is treated with medication, such as pilocarpine; an acute attack may be prevented, but the chronic form of the disease may still develop.

Pigmentary Glaucoma:
Pigmentary glaucoma is a type of inherited open-angle glaucoma that develops more frequently in men than in women. It most often begins in the twenties and thirties, which makes it particularly dangerous to a lifetime of normal vision. Nearsighted patients are more typically affected. The anatomy of the eyes of these patients appears to play a key role in the development of this type of glaucoma.
Myopic (nearsighted) eyes have a concave-shaped iris, which creates an unusually wide angle. This causes the pigment layer of the iris to rub on the lens. This rubbing action causes the iris pigment to shed into the aqueous humor and onto neighboring structures, such as the trabecular meshwork. Pigment may plug the pores of the trabecular meshwork, causing it to block and thereby increasing the IOP.
Miotic therapy is the treatment of choice, but these drugs in drop form can cause disabling visual blurring in younger patients.

Exfoliation Syndrome:
This common cause of glaucoma is found everywhere in the world, but is most common among people of European descent. In about 10% of the population over age 50, a whitish material, which upon slit-lamp examination looks somewhat like tiny flakes of dandruff, builds up on the lens of the eye. This exfoliation material is rubbed off the lens by movement of the iris and at the same time, pigment is rubbed off the iris. Both pigment and exfoliation material clogs the trabecular meshwork, leading to IOP elevation, sometimes to very high levels.
Exfoliation syndrome can lead to both open-angle glaucoma and angle-closure glaucoma, often producing both kinds of glaucoma in the same individual. Not all persons with exfoliation syndrome develop glaucoma. However, if you have exfoliation syndrome, your chances of developing glaucoma are about six times as high than if you don’t have it. It often appears in one eye long before the other, for unknown reasons. If you have glaucoma in one eye only, this is the most likely cause. It can be detected before the glaucoma develops, so that you can be more carefully observed and minimize your chances of vision loss.

Trauma-Related Glaucoma:
A blow to the eye, chemical burn, or penetrating injury may all lead to the development of glaucoma, either acute or chronic. This can be due to a mechanical disruption or physical change within the eye’s drainage system. It is therefore crucial for anyone who has suffered eye trauma to have check-ups at regular intervals.

Diagnosing Glaucoma:
There are varieties of diagnostic tools that aid in determining whether some one has got glaucoma or not? Let us explore these tools and what they do.

The Tonometer:
The Tonometer measures the intraocular pressure in the eye. It’s a simple procedure where eye would be anesthetized with drops. Then, the patient would sit at the slit lamp, and a lastic prism would lightly push against cornea in order to measure IOP. In air tonometry a puff of air is sent onto the cornea to take the measurement.

Visual Field Test:
Testing patient’s visual field lets the doctor know if and how field of vision has been affected by glaucoma. The visual field is an important measure of the extent of damage to optic nerve from increased IOP.
In computerized visual field testing patient will be asked to place their chin on a stand that appears before a computerized screen. Whenever patient see a flash of light appear, he has to press a button. At the end of this test, doctor will receive a printout of patient’s field of vision.
Ophthalmoscope:
Using an instrument called an ophthalmoscope; the eye doctor can look directly through the pupil at the optic nerve. Its color and appearance can indicate whether or not damage from glaucoma is present and if so then how extensive it is.

Managing Glaucoma:
Glaucoma can be managed with eye drops, pills, laser surgery, eye operations, or a combination of methods. The whole purpose of treatment is to prevent further loss of vision. This is imperative as loss of vision due to glaucoma is irreversible. Keeping the IOP under control is the key to preventing loss of vision from glaucoma. The doctor has several options for doing so. They include:

Eye drops:
All eye drops may cause a burning or stinging sensation at first. This is often due to the antibacterial agent present in the drop solution and not due to the drug itself. While it can be uncomfortable, the discomfort lasts for only a few seconds.
Since eye drops are absorbed into the bloodstream, it is important to tell the doctor about all other medications which he or she is currently taking. Some drugs can be dangerous when mixed with other medications. Ask the doctor or pharmacist if the medications are taking together is safe. To minimize absorption into the bloodstream and maximize the amount of drug absorbed into the eye, close the eyes for one to two minutes after administering the drops and press lightly against the nasal corner of the eyelids to close the tear duct that drains into the nose.

Type of Drug Function Possible Side Effects:

Miotics
Drops, which help to open the aqueous draining system and increase the rate of fluid flowing out of the eye.
These include pilocarpine, carbachol and echothiophate.
These drops may cause pain in and around the eye or brow ache for the first few days of use.
Blurred vision and extreme nearsightedness are most common in younger patients.
As miotics reduce pupil size and prevent normal dilation therefore dim vision, especially at night or in dark rooms, may occur. Stuffy nose, sweating, increased salivation, and occasional gastrointestinal problems may occur with the stronger miotics.

Betablockers.
Timolol:
Have fewer ocular side effects, but may worsen pulmonary disease, cause difficulty breathing, slowing of the pulse, hair loss, decreased blood pressure, and impotence. Central
nervous system side effects include dizziness, fatigue, weakness, hallucination, insomnia, depression, and memory loss.

Betaxolol:
Decrease the rate at which fluid flows into the eye Specific beta-1-blockers, such as betaxolol, are safer for patients who suffer from asthma or emphysema.

Brimonidine:
It is a highly selective alpha2- adrenoceptor agonist. Reduces aqueous humor production and increases uveoscleral outflow. Brimonidine 0.2% instilled twice daily offers long-term IOP control comparable to timolol 0.5%.

Dorzolamide:

This is the first topical carbonic anhydrase inhibitor. It may have side effects similar that of tablet form but of much lower frequency and severity.

Latanoprost:
Increases the rate at which fluid flows out of the eye. This drug acts by a different mechanism from other agents. Only needs to be taken once per day.

While every drug has some potential side effects, it is important to note that some patients experience NO side effects at all.

Oral pills:
Sometimes, drops are not enough to control IOP. When this is the case, pills may be prescribed in addition to drops. These pills, which have more side effects than drops do, also serve to turn down the eye’s faucet and lessen the production of fluid in the eye. The medication is usually taken from two to four times daily.
The following are some commonly prescribed carbonic anhydrase inhibitors and their
more common side effects.

Type of Drug Function Possible Side Effects:
Carbonic anhydrase inhibitors: Acetazolamide
Diamox:
Pills will reduce fluid flow into the eye. These should be taken with meals or milk to reduce
side effects. Bananas or apple juice should be added to the diet to minimize potassium loss.
Symptoms like frequent urination, tingling sensation in the fingers and toes disappear after a few days. Kidney stones may occur. A rare but serious side effect is aplastic anemia. Rashes are not uncommon. Potassium loss may occur when these drugs are taken with digitalis, steroids, or chlorothiazide diuretics. Depression, fatigue, and lethargy are common. Gastrointestinal upset, metallic taste to carbonated beverages, impotence, and weight loss.
Side effects may be more common when using pills.

Surgical Procedures
Surgery is advisable when medication does not achieve the desired results, or when it has intolerable side effects.

Laser Surgery
Laser surgery (a high energy light beam) is also very helpful an intermediate step between drugs and traditional surgery. The most common type performed for open-angle glaucoma is called Laser trabeculoplasty. This procedure is a painless procedure and takes between ten and twenty minutes, and can be performed in an outpatient facility. Laser’s heat causes
some areas of the eye’s drain to shrink, resulting in adjacent areas stretching open and
permitting the fluid to drain more easily.
You may go home and resume normal activities following laser trabeculoplasty surgery. After this procedure, nearly eighty percent of all patients respond well enough to be able to avoid or delay surgery. While it may take a few weeks to see the full pressure-lowering effect of this procedure, during which time patient may have to continue taking the medication. Cataracts do not occur after laser surgery and complications are minimal, which is why this has become increasingly popular.

Traditional Surgery:
Trabeculectomy is the most common procedure, where a small section of the trabecular meshwork (eye’s draining area). This allows the aqueous humor to drain more easily, reducing the pressure in the eye. This procedure is usually done under local anesthesia with a brief hospital stay. It is important to note that the eye may not have their normal visual acuity for several weeks following this procedure.
Although trabeculectomy is a relatively safe surgical procedure, about one-third of patients develop cataracts within five years of surgery. After trabeculectomy, most patients are able to discontinue all anti-glaucoma medications. Perhaps ten to fifteen percent of patients require additional surgery.

Advice to everybody:
Routine eye exams are vital for protecting the vision of eyes. If your optometrist or ophthalmologist detects raised intraocular pressure, early treatment can help prevent the loss of your vision.

Compiled by Dr.Chowdhury; Chief Medical Officer (Ophthalmology); Stanger hospital eye care centre.
(Different internet sources)
 

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