GLAUCOMA
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What is Glaucoma?
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Glaucoma is a progessive eye condition charaterised by abnormaly high intra-ocular pressure that can ultimately result in optic nerve damage.
When the pressure in the eye builds, the nerve cells become compressed, damaged, and ultimately destroyed. The death of these cells results in permanent visual loss.
The average intra-ocular pressure(IOP) is about 14-18 millimeters of mercury (mmHg), but upto 20mmHg is regarded as within the normal range for most patients. A presure of 21 to 22 mmHg is defined a the borderline reading for a Glaucoma suspect.
INTRA OCULAR PRESSURE (IOP)
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A typical test method used to measure IOP is called tonometery. The tonometer measures the amount of force neede to indent a small, central portion of the cornea. The Test takes only a short time to complete.
PERIMETERY or VISUAL FILEDS TEST:
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Additional testing is required to accurately diagnose and manage the treatment of glaucoma. Your ophthalmologist may require a perimetery analysis testing of your vision both prior to and during your glaucoma treatment.
HIGH RISK FACTORS:
1 Family history of glaucoma
2 Diabetes
3 Cardiovascular disease LIKE high blood pressure.
4 History of ocular surgery or injury
5 Medications
Types of Glaucoma
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The two major Forms of Glaucoma
A Open-angle Glaucoma
B Narrow- angle Glaucoma
The angle refers to the physiological angle between the iris and the trabecular meshwork.When evaluating a patient for glaucoma, the physician examines this junction between the iris and the trabeclar meshwork. The amount of opening in the junction is referedto as the "angle". An "open angle" means that the junction is wide enough to allow a normal flow of fluid through the trabecular meshwork. A "narrow angle" means that the junction is too narrow for fluid to flow normally, creating a risk of fluid backup which can cause increased eye pressure. As pressure rises, the iris may begin to bow forward, further restricting the flow of fluid.
Open Angle glaucoma:
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Primary open angle glaucoma (POAG)is the most common form of glaucoma. POAG has no symptoms until its late stage, which is why the disease can remain undetected witout regular examinations.
Though the direct cause is yet unknown, it is believed that a defect occurs in the cells within the trabecula meshwork to cary out their normal function.
The damage causes visual field defects(blind spots) in the peripheral vision. These defects appear very faint at first, but gradually darken and increase in size and number. In open angle Glaucoma, pressure from fluid buildup in the eye causes death of the nerve cells in the optic nerve.
Treatment of Open-Angle Glaucoma
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Treatment for glaucoma is trageted at reducing the production of aqueous fluid, or by inducing the outflow of fluid through the trabecular meshwork drainage system. The objective of treatment is to lower the IOP to the normal range between 10-20 mmH. Eye drops are the most common form of treatment; certain oral medication may be used as well.
Laser Trabeculoplasty:
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When Medications become intolerable or ineffective, laser surgery may be considered. The way that laser surgery works is by modyfying the drainage mechanism of the eye. In many cases glaucoma medications will still be required after surgery. Complications may include inflammation and irritation of the eye immediately following the procedure. Overall, The procedure is usually effective and the risks are relatively low.
SURGERY
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When medication and or laser surgery are not effective on lowering pressure inside the eye, then more invasive surgery is required. A small hole is made in the wall of the eye and the fluid then drains through the opening and passes under the conjunctiva into a bleb. In more sever cases of glaucoma, a plastic or silicone shunt may be inserted to redirect the fluid drainage from the eye.
Narrow Angle Glaucoma
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Narrow- angle Glacoma(NAG) accounts for approximately 5-10 percent of all glaucoma. It is more common in far sighted people(hyperopes).Hyperopes tend to have physiologically smaller than average anterior chambers,which causes the iris tissue to bow forward.
This iris bowing causes narrowing of the angle between the iris and the trabecular meshwork. The degree of narrowing determines the amount of pressure increase in the eye. Acute Narrow Angle Closure Glaucoma (ANAG) ia an emergency condition. Unlike POAG, in which the IOP increase slowly,pressure increases suddenly in narrow angle glaucoma patients. It is characheterised by sudden onset of eye pain, halos and lights in vision, blurred vision, and is usually acompanied by nausea and vomiting. If the pressure is not relieved within a few hours, vision can be permanently lost in the affected eye, as damage to the optic nerve may occur quickly.
Peripheral Iridectomy:
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Laser iridectomy also known as iridotomy consists of reestablishing a correct anatomical relationship between the iris & the drainage mechanism.A small hole is made in the iris either with the laser or surgically.This hole allows for excess fluid to drain, relieves the build up of pressure.
Patients who undergo this procedure may experience an increased sensitivity to light, with mild glare noted with night driving
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