The eye consists of three cavities. The “front” two chambers are connected through the pupil. The dividing diaphragm is the mobile iris (the iris is that part of the eye which labels a person black, brown or blue-eyed).
The “front” two cavities are called anterior and posterior chambers respectively. The posterior chamber is separated by the lens from the very large vitreous chamber.
A specialized tissue from which the disc-like lens is suspended (Ciliary body) continuously produces a watery, transparent fluid called aqueous humor. The ciliary body, the lens and the suspensory ligaments, divide the vitreous chamber from the posterior chamber.
To maintain a fairly constant pressure in the eye, (IOP), there must be continuous outflow of fluid from the ciliary body into the posterior chamber and through the papillary opening, into the anterior chamber and thence through the drainage angle to join the general blood circulation.
If the balance of production and outflow is disturbed, the eye becomes softer and harder than normal. (Normal IOP is between 16-20mmHg).
The tissues in the eye may become permanently damaged as a result of the abnormal change in tension.
1. What is glaucoma?
GLAUCOMA is a disease of the eye that results from a sustained increase in fluid pressure inside it, intra-ocular pressure (IOP). If untreated, it causes progressive destruction of the optic nerve head. The damage, in most cases, is directly related to the increased pressure. It is irreversible and leads to blindness.
Fortunately, with early detection and prompt adequate treatment, the visual loss may pass unnoticed by the patient. The disease may be arrested at the point of detection, but vision already lost cannot be regained.
Glaucoma could be PRIMARY (when the cause is unknown) or SECONDARY (when it is due to injury, disease etc).
In primary glaucoma, the cause is unknown and is uncommon before 40 years but heredity could be incriminated.
This is usually due to the under-listed conditions:
1. Raised IOP may occur following injury especially blunt injury chamber like a football or fist in the eye.
2. Chronic (prolonged or longstanding intermitted) eye disease.
3. Side effect of certain drugs e.g. steroids.
Whether primary or secondary, glaucoma could be OPEN ANGLE or CLOSED ANGLE.
Open Angle Glaucoma
Open angle glaucoma, is by far the commonest and it occurs in about 95 percent of all cases of glaucoma in Nigeria. The cause is unknown. It usually lasts as long as the patient lives. The patient therefore needs supervision by an ophthalmologist for life once the condition is diagnosed. Most cases can be controlled with medication in the form of eye – drops or tablets or both.
In advance countries, trials are being carried out to try and administer the drug through special soft contact lenses and also by an implant lodged under the skin. This, if successful, will afford a slow continuous release of the drugs into the eye.
Glaucoma most often develops in people over 40 years of age, but it can develop in the young. In babies, it is referred to as buphthalmos. This is because the eye enlarges and looks like that of a bull. Management of such patient is largely along the same lines as Glaucoma management in the adult.
There is a hereditary tendency to develop the disease, so that it often occurs in more than one member of the same family.
In Open angle glaucoma, the IOP builds slowly, giving the eye time to adjust to the changing pressure. The disease thus develops silently, giving the patient little or no warning at all, until there is considerable loss of visual field.
Without turning your head or eyes, it is possible to see the fingers on both sides. This is your “peripheral” vision. The straight- ahead vision is the “central” vision. The nerves of the eye are usually attacked by the IOP in such a way that the peripheral vision is silently eroded, until the patient becomes very handicapped.
It is quite possible to read down to the bottom line of your doctor’s reading chart, and not be able to cross a road safely.
It is imperative that early diagnosis be made and immediate appropriate treatment be given, before appreciable vision is lost. This is because the damage already done is irreversible, and blindness will follow (with the loss even of the central field) if the eye is not treated.
Closed angle glaucoma
Commoner in the light – skinned race; in these patients, the anterior chamber is very shallow. In the dim light or during stress, prolonged papillary dilatation appears to mechanically close the drainage angle, obstructing the outflow of aqueous humor. IOP builds up rapidly resulting in pressures of up to 60-70 mmHg. The patient suffers very severe pain accompanied by redness and watering of the eyes.
2. What causes glaucoma?
The cause of primary glaucoma is unknown in most cases but heredity plays a role as the condition is more common in some families. Age also plays a role as glaucoma is uncommon before the age of forty years.
However the causes of secondary glaucoma include blunt injury to the eye, long standing eye disease and drugs such as steroids.
3. Can glaucoma spread?
Glaucoma is not an infectious disease and so cannot spread from person to person.
4. When do you suspect you may have glaucoma?
a. Poor night vision; difficulty in adjusting to the dark in a sudden blackout. In the normal person shades of grey may be seen in the dark after usual adjustment period of a few minutes.
People over 40 years may have some difficulty in reading in dim light. Such people need reading glasses. This must not be confused with glaucoma.
b. Patients may trip over furniture or run into people on sidewalks.
c. A halo of colours may be seen around light sources e.g. a light bulb. Most cases are picked up during routine eye examination or eye test for spectacle change.
5. What can put you at risk of glaucoma?
The risk factors include heredity, age (above 40 years), blunt eye injuries, chronic eye diseases and prolong drug use.
6. What are the possible complications of glaucoma?
Complications of glaucoma include irreversible poor vision and blindness.
7. How can you prevent glaucoma?
You can prevent glaucoma by the following ways:
a. regular eye check up especially the eye pressure
b. avoid blunt injuries to the eye
c. see your doctor whenever you have an eye problem
d. use only prescribed drugs
The treatment of the raised IOP is basically the same as in other forms of glaucoma.
The medication used is usually one of two kinds or both if necessary.
Some glaucoma medications increase the outflow of aqueous from the eye.
In some cases surgery may have to be done followed by medication but some do not need further medication.