Glaucoma refers to various eye conditions or disorders that gradually lead to the damage of the optic nerve. The optic nerve is the major nerve of vision and it functions by transmitting electrical impulses from the retina to the brain. These electrical impulses are the visual information received or what we recognize as our vision. Generally, damage to the optic nerve starts with an unnoticeable loss of peripheral vision.
Glaucoma is usually associated with the increase of pressure inside the eye (known as intraocular pressure) which causes damage to the optic nerve. As the intraocular pressure continues to damage the optic nerve, it can lead to vision loss. If left untreated, glaucoma can lead to permanent blindness. Glaucoma ranks second as the leading cause of blindness after cataract.
An individual who has a positive family history of glaucoma is at higher risk of developing glaucoma, particularly primary open-angle glaucoma.
According to studies, glaucoma is much more prevalent in African-Americans than Caucasians. Studies also suggest that those of Japanese, Inuit, Hispanic, Russian or Irish descent are more likely to develop glaucoma.
Most visual problems are gradual and are mostly noticeable at an advanced age. This is the same for glaucoma. African-Americans over the age of 40 and over 60 for others are at higher risk of having glaucoma.
USE OF MEDICATIONS
The prolonged use of certain medications like steroids (e.g. corticosteroids, prednisone) is suggested to make people become at risk of developing secondary glaucoma.
Physical injuries that causes severe trauma to the eyes (i.e. dislocation of the lens) may lead to an increase in eye pressure.
Uveitis, eye inflammation or tumors can induce glaucoma. On the other hand, the anatomy of the eye such as the appearance of the optic nerve and the thickness of the cornea may indicate the risk of getting glaucoma.
There are various classifications of glaucoma and the widely used major classifications are: open-angle glaucoma and angle-closure glaucoma. Glaucoma often affects both eyes although it is very probable that the condition can progress faster in one eye than the other. Usually, glaucoma that affects only an eye is due to factors such as eye inflammation, physical injury or the use of steroids.
Primary open-angle glaucoma is the progressive loss of vision due to the damage of the optic nerve. This type of glaucoma is often associated with aging as the eyes’ drainage mechanism become clogged and less efficient. As a result, the amount of aqueous fluid increases because it isn’t drained properly from the eyes. This would further lead to the gradual build-up of pressure in the eyes (known as intraocular pressure) that ultimately damages the optic nerve over a long period of time.
Secondary open-angle glaucoma can be a result of other factors such as inflammation of the eyes (i.e. uveitis, iritis), other eye problems (i.e. cataracts, retinal detachment, blockage of retinal vein), or even by an injury to the eye that may have recently occurred or have happened in the past. Health conditions like diabetes can also lead to this type of glaucoma.
Congenital or infantile glaucoma is a rare and inherited condition that is already present at birth. In this type of glaucoma, there is an abnormality in the development of the child’s eye, particularly the drainage area. This results in an increase in intraocular pressure and possible damage to the optic nerve which could lead to loss of vision. It is also observed that the child’s eyes may be enlarged as a response to the increase in eye pressure.
Normal tension or Low tension glaucoma involves gradual damage to the optic nerve and therefore loss of side or peripheral vision even when intraocular pressure is at normal or below normal levels. Normal tension glaucoma is a perfusion anomaly whereby there is a decrease in blood flow to the optic nerve.
Angle-closure glaucoma or closed-angle glaucoma is characterized by the clogging of the drainage angle formed by the iris and cornea because the iris has bulged. Therefore, the flow of fluid is obstructed and it can’t exit from the eyes, further increasing eye pressure.
The two main types of angle-closure glaucoma is chronic and acute angle-closure glaucoma.
Chronic angle-closure glaucoma occurs gradually wherein some portions of the drainage angle are closed over long periods of time (months to years). As more areas are affected and closed, eye pressure builds up leading to a progressive loss of vision. On the other hand,
Acute angle-closure glaucoma is when an individual’s eye pressure suddenly increases as the drainage angle is closed whilst blocking off all other drainage areas. This condition causes severe pain in the eye and other accompanying symptoms that would require immediate medical help.
CHRONIC OPEN ANGLE GLAUCOMA
Chronic glaucoma is also known as primary or open-angle glaucoma. It is the most common type of glaucoma (90%). Glaucoma refers to a group of eye conditions characterized by elevated intraocular pressure and damage to the optic nerve. Chronic glaucoma, if left untreated, is one of the leading causes of progressive, painless loss of vision.
The cause of chronic glaucoma is largely unknown but its occurrence runs in families. It develops over time as pressure in the eye builds up. This intraocular pressure elevates when there is slowed or blocked outflow of aqueous humor, the colorless fluid that fills the anterior part of the eye.
Most people with chronic glaucoma are asymptomatic. For those with advanced disease, there may be a complaint of loss of peripheral visual field, also known as tunnel vision. Clinical examination will confirm diagnosis of chronic glaucoma whose medical treatment is aimed at decreasing intraocular pressure using certain eye drops. Other treatment options include laser therapy and eye surgery to correct the impaired drainage meshwork in the eye.
PIGMENT DISPERSION GLAUCOMA
Pigment dispersion syndrome is a condition of the eye that will typically lead to a condition known as pigmentary glaucoma. This usually affects patients at a much earlier age than any other form of glaucoma, with the onset usually occurring between the ages of 40 and 50. The condition is rare.
Pigment dispersion occurs when the molecules of pigment on the back of the iris begin to flake off into the aqueous humour, which is the clear liquid within the eye. When these flakes of pigment collect in the drainage channels, they can cause a blockage, which raises the pressure inside the eye. This increase in pressure has the potential to cause a considerable amount of damage to the optic nerve, which means that images can no longer be transmitted effectively to the brain. Once this has occurred, the condition is described as pigmentary glaucoma. This progression into the more serious form of the condition appears to be faster in men than in women, although overall, only around 30 percent of cases will develop into glaucoma.
Although it is not possible to reverse the pigment dispersion process, there are a number of treatments that can be used to effectively slow down the release of the pigment. A range of eyedrops are available, and are extremely safe with a very low risk of side effects. Some medications are also available to treat the symptoms. These work by constricting the pupil (making it smaller), which prevents the back of the iris from rubbing on the supporting fibres. This friction can cause pigment to be released. However, eyedrops are preferred because they do not produce side effects such as blurred vision.
If the eyedrops and medications have not been effective in keeping the symptoms under control, it may be necessary to undergo laser surgery. A procedure known as laser trabeculoplasty can help to open up the drainage system, thereby reducing the pressure in the eye and preventing damage to the optic nerve.
It is also thought that exercise can lead to increased amounts of pigment being lost from the back of the eye, so it may be advisable to avoid vigorous forms of activity. Speak to your doctor or eye specialist if you are worried about the effect that your hobbies are having on your eyesight, and for suggestions of how you can minimize your symptoms.
Pseudoexfoliative glaucoma is an eye condition that is known by several different names, including exfoliation glaucoma, exfoliation syndrome and PEX. It is a condition that is considerably more common in older adults, and is an age-related disease. It was first identified in 1917 by John Lindberg, an ophthalmologist in Finland. He noticed that a large number of patients with glaucoma also had grey particles on the lens capsule, and it was seen more frequently in older patients.
The disease may not produce any specific symptoms, and those that are noticed may be associated with the onset of glaucoma rather than the presence of the flakes on the lens. A reduction in visual acuity or in the visual field may indicate that changes have occurred within the eye, but do not show exactly what the condition may be. The condition is therefore diagnosed by an ophthalmologist or optometrist during an eye examination. There will be white or grey flakes of protein in the eye which are likely to be widespread. It is not certain where the protein actually originates from, but it is possible that several different regions produce it.
The causes of pseudoexfoliative glaucoma are unknown, but it has been suggested that it is a disorder of the basement membrane of the eye. The symptoms usually develop in just one eye, and may gradually affect the other eye, but this only occurs in approximately 40 percent of cases. It has been suggested that pseudoexfoliative glaucoma is partially genetic in origin, with specific mutations being identified in some patients who have developed the disease.
Women are much more likely than men to be affected by pseudoexfoliative glaucoma, with approximately three times as many women being diagnosed with the condition. The prevalence increases significantly with age; it is highly unlikely for a person under the age of 50 to develop symptoms. Instead, it usually develops between the ages of 69 and 75, but is relatively uncommon – it is not considered to be part of the normal sight changes that occur with age.
At present, there is no cure for pseudoexfoliative glaucoma, although it is possible to minimize the damage to vision by using the same treatments that are recommended for glaucoma. Eyedrops will normally be the first approach, in an effort to reduce pressure within the eye. This may be followed by laser surgery, which is normally effective at reducing symptoms.
Glaucoma treatment is stability-orientated. Any previous damage to the optic nerve cannot be reversed, however, using a variety of modalities of treatment glaucoma can be stabilized so that loss of vision can be prevented or slowed.
The usual medications prescribed for glaucoma are eye drops. It is vital to follow the doctor’s prescription regarding the application of eye drops because misuse could lead to further damage of the optic nerve. The prescribed eye drops usually are:
Prostaglandin analogs which increase outflow of fluid (aqueous humor) from the eyes. These include:
Lumigan (bimatoprost) 0.03%
Xalatan (latanprost) 0.005%
Travatan (travoprost) 0.004%
Beta-blockers which act to decrease aqueous production. These include:
Betagan 0.25-0.5% (levobunolol)
Timoptic 0.25-0.50% (timolol maleate)
Timoptic-XE (timolol gel) 0.25-0.50%
Alpha-adrenergic agonists which act two-ways by decreasing aqueous production and increase the drainage of aqueous from the eye. These include:
Alphagan-P 0.15% (brimonidine)
Alphagan 0.2% (brimonidine)
Carbonic anhydrase inhibitors which act to decrease aqueous production. These include:
Azopt 1% (brinzolamide)
Trusopt 2% (dorzolamide)
Oral tablets may be prescribed when eye drops alone do not lower pressure to a desired level. These medications include carbonic anhydrase inhibitors such as acetazolamide (Diamox) tablets.
Various forms of laser therapy are available for treating glaucoma:
Laser trabeculoplasty is done to treat open-angle glaucoma. The procedure involves the use of a laser beam to burn the blocked or clogged drainage system to allow the fluid to drain easily from the eye.
Laser iridotomy is done to treat angle-closure glaucoma. The procedure involves creating a hole in the eye’s iris to allow fluid to drain from the eye.
Trabeculectomy is a surgical procedure involving the creation of a drainage flap or opening in the sclera of the eye to facilitate drainage of fluid from the eye. This opening, that allows fluid to freely drain and leave the eye, decreases eye pressure.
Drainage implant surgery is newer technology that involves the use of a drainage implant / device to allow for better flow from the back to the front portion of the eye. The surgery involves the insertion of a small tube in the eye to allow outflow of fluid from the eye.