THERE ARE TWO MAJOR TYPES OF GLAUCOMA WHICH INCLUDES:-
- Primary open angle glaucoma
- Primary closure angle glaucoma
PRIMARY OPEN ANGLE GLAUCOMA
This is a type of glaucoma that is caused by contact between iris and trabecular meshwork, which is turns obstructs outflow of the humor from the eye. This contact between iris and trabecular meshwork may gradually damage the function until it fails to keep pace with aqueous production, and the pressure iris. (Lam. et al., 2007).
Prolonged contact between iris and trabecular meshwork causes the formation of synechial (effectively “scars”). These causes permanent obstruction of aqueous outflow. In some cases, pressure may rapidly build-up in the eye, causing pain and redness (“acute” angle closure). In this situation, the vision may become blurred and halos may be seen around bright lights, and accompanying symptoms may include headache, vomiting, nausea, eye pain, dilated pupils, red eyes and loss of vision.
Diagnosis is made from physical signs and symptoms, however, the majority of cases are asymptomatic. Prior to very severe loss of vision, these cases can only be identified by examination, generally by an eye care professional (Rhee. et al., 2001).
Once any symptoms have been controlled, the first line treatment is laser iridotomy. This may be performed by using argon lasers or in some cases by conventional incisional surging. The goal of treatment is to reverse, and prevent, contact between iris and trabecular meshwork (Mozaffarich and Flammere, 2007).
PRIMARY CLOSURE ANGLE GLAUCOMA
This is a type of glaucoma that occur when there is optic nerve damage, it will result to a progressive loss of the visual field Primary open angle Glaucoma: (Merck, 2011). This is associated with increased pressure in the eye. Not all people with primary open angle glaucoma have eye pressure that is elevated beyond normal, but decreasing the eye pressure further has been shown to stop progression even in these cases. (Rivera. et al., 2008).
The increased pressure as caused by trabecular blockage, because the microscopic passage ways are blocked, the pressure builds up in the eye and causes imperceptible gradual vision loss. Peripheral vision is affected first, but eventually the entire vision will be lost if not treated. (Hatt. et al., 2006).
Diagnosis is made by looking for cupping of the optic nerve. Prostaglandin agonists work by opening uveoscleral passage ways. Beta blockers such as timolol, work by decreasing acqeous formation.
OTHER TYPES OF GLAUCOMA
A. SECONDARY GLAUCOMA
Both open-angle and angle-closure glaucoma can be primary or secondary conditions. They are called primary when the cause is unknown and secondary when the condition can be traced to a known cause, such as eye injury, medications, certain eye conditions, inflammation, tumor, advanced cataract or diabetes.
In secondary glaucoma, the signs and symptoms can include those of the primary condition as well as typical glaucoma symptoms. (Knox. et al., 2007).
B. NORMAL TENSION GLAUCOMA OR LOW TENSION GLAUCOMA
These 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 which will lead to loss of vision.
This type of glaucoma can be diagnosed by repeated examinations by the doctor to detect the nerve damage.
C. CONGENITAL GLAUCOMA
This is an inherited type of open-angle glaucoma, in this condition, the drainage area is not properly developed before birth, this results to the 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 liable than the eye of an adult. Early diagnosis and treatment with medicine or surgery are critical in these infants and children to preserve their sight.(Shabana.2005).
D. PIGMENTARY GLAUCOMA
This 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 their iris, which is the coloured part of the eye. These granules then, may block the trabecular meshwork, is the 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. (Knox. et al.,2007).
- EXFOLIATIVE GLAUCOMA (PSEUDOEXFOLIATION)
This is a type of glaucoma that can occur with either open or closed angles. It is characterized by deposits of flaky material on the front surface of the lens 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.
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.
CAUSES OF GLAUCOMA
CAUSES OF PRIMARY OPEN ANGLE GLAUCOMA
The exact cause of primary open-angle glaucoma is unknown. A number of conditions along or in combination, are needed to trigger the processes leading to increased pressure and then to the nerve damage that destroys sight. The damage done to the optic nerve in glaucoma is triggered in most cases by the excessive pressure on the optic nerve that over time causes damage. Because optic nerve damage occurs in patients with normal as well as high intraocular pressure, however, there are other factors that occur and can damage the optic nerve. (Vass. et al., 2007).
CAUSES OF CLOSED ANGLE GLAUCOMA
People with acute closed-angle glaucoma often have a structural defect that causes a narrow angle between the iris and cornea where the aqueous humor circulates.
Conditions that suddenly dilate the pupils may cause this shallow angle to close and precipitate attacks of acute glaucoma in susceptible people. Such condition includes drugs such as antihistamines, tricyclic antidepressants, some asthenia medications, anti-seizure drugs, darkness and emotional stress.
CAUSES OF SECONDARY GLAUCOMA
When glaucoma is caused by other diseases or conditions, it is known as secondary glaucoma. Both open-angle glaucoma and closed-angle glaucoma can be secondary condition.
Following are the causes of secondary glaucoma.
- Prolonged use of steroids (Steroid-induced glaucoma).
- Severe diabetic retinopathy
- Central retinal vein occlusion (neovascular glaucoma).
- Ocular trauma
- Eye injury
- Advanced case of cataract
OTHER CAUSES OF GLAUCOMA ARE;
Of the several causes of glaucoma, ocular hypertension is the most important risk factor in most glaucoma’s but in some populations only 50% of people with primary open-angle glaucoma actually have elevated ocular pressure. (Sommer. et al., 1991). They includes:-
- DIETARY CAUSE
No clear evidence indicates that vitamin deficiencies causes glaucoma in humans. Therefore, oral vitamin supplementation is not a recommended treatment for glaucoma. Caffeine increases intraocular pressure in those with glaucoma but does not appear to affect normal individuals (Li. et al., 2011).
Many East Asians are prone to develop angle closure glaucoma due to their shallower anterior chamber depths, with the majority of cases of glaucoma in this population consisting of some form of angle closure. (Wang. et al., 2002).
Women are three times more likely than men to develop acute angle closure glaucoma due to their shallower anterior chambers, those of African descent are three times more likely to develop primary open angle glaucoma.
Various genetics eye malformations are associated with glaucoma. Primary open-angle glaucoma has been found to be associated with mutations in genes at Several Loci. Normal tension glaucoma which comprises one third of primary open-angle glaucoma is associated with genetic mutations, people with a family history of glaucoma have about six percent (6%) chance of developing glaucoma.