Please consult your doctor if you believe you may have Glaucoma
What is Glaucoma?
Glaucoma is a disease of the major nerve of vision, the optic nerve. This nerve receives light-generated nerve impulses from the retina and transmits these to the brain, where we recognise the electrical signals as vision.
It is characterised by a particular pattern of progressive damage to the optic nerve that generally begins with a subtle loss of side vision. If not treated it can progress to loss of central vision and blindness.
It is usually associated with elevated pressure in the eye, though occasionally the pressure is normal and optic nerve damage occurs through poor regulation of blood flow to the nerve.
How common is Glaucoma?
Worldwide, glaucoma is the leading cause of irreversible blindness. As many as half of the individuals with glaucoma may not know that they have the disease. This is due to the fact glaucoma initially causes no symptoms and the loss of peripheral vision goes unnoticed.
What causes Glaucoma?
The front of the eye is filled with a clear fluid called the aqueous humor which provides nourishment to the eye. This is produced by the ciliary body, circulates through the pupil and leaves the eye via tiny channels called the trabecular meshwork.
Theses channels are located at the drainage angle of the eye. An imbalance in fluid production and drainage can lead to elevation of the intraocular pressure and optic nerve damage.
In most people, the drainage angles are wide open, where they are narrow-angle closure glaucoma can occur.
Risk Factors for Glaucoma
- Age over 45 Yrs
- Family history of glaucoma
- Previous history of elevated intraocular pressure
- History of injury to the eye
- Use of cortisone (steroids) either to the eye or systemically)
Different Types Glaucoma
Open Angle Glaucoma:
The most common is open angle glaucoma, this is painless, without symptoms and slowly progressive. Angle closure glaucoma is less common but more acute with severe pain,
Angle closure glaucoma is less common but more acute with severe pain, headache, and a red eye.
Both eyes can be affected but the disease can be asymmetric.
Diagnosis and Treatment of Glaucoma
How is a Glaucoma diagnosed?
An ophthalmologist can usually detect those individuals who are at risk for glaucoma before nerve damage occurs. This is done by measuring the intraocular pressure, a painless, rapid and non-invasive method, in the clinic.
This is supplemented with an assessment of the optic nerve head via direct examination on the slit lamp, optic nerve stereo photography and visual field testing using computerised analysis. Other tests to measure the nerve fibre layer thickness such as the OCT analyser are employed. These tests assist in both diagnosis and ongoing management of the disease.
Screening for Glaucoma
Routine screening eye examinations are mandatory since glaucoma usually causes no symptoms in its early stages. Once damage to the optic nerve has occurred, it cannot be reversed. This is a lifelong disease and in order to preserve vision diagnosis must be early and follow up
This is a lifelong disease and in order to preserve vision diagnosis must be early and follow up regularly. Over 40-year-old individuals should be examined every 2-4 years, more frequently if there is a family history.
What treatment is there for Glaucoma?
Glaucoma is a disease that can generally be controlled and further nerve damage and visual loss can be prevented. This will involve the use of regular eye drops, laser or less commonly surgery. Eye drops are usually used the first choice in treating most open angle glaucoma. They work by either reducing the production of aqueous fluid or by increasing the drainage of fluid out of the eye. Most drops are used either once or twice a day and can be used in combination. They are generally tolerated well and have few general side effects, these will be discussed with you by the ophthalmologist prior to prescribing. Regular lifelong medication is used and compliance essential to adequately control pressure and prevent visual loss.
There are several forms of laser therapy for glaucoma. Laser iridotomy involves making a hole in the coloured part of the eye (iris) to allow fluid to drain normally in eyes with narrow or closed angles. Laser trabeculoplasty is performed in eyes with open angles. This is done to increase the outflow of fluid from the eye if eye drops do not work. It is a quick and relatively painless method of lowering the eye pressure and is done in the clinic. It can be repeated if necessary in the future.
Where the above treatments fail surgical intervention is required. Trabeculectomy is an operation where a piece of the trabecular meshwork is removed to create an opening and a new drainage pathway for the fluid to exit the eye. This is done under local anesthetic in the operating theatre usually as a day case.
Resources on Glaucoma
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