Glaucoma is the third leading cause of blindness and affects about 2% of the population over 40, fortunately this disease is easy to detect.
Glaucoma is a result of high eye pressure caused by drainage difficulties in the fluid flowing through the eye. This high pressure gradually damages the retina lining the back of the eye and especially the optic nerve, causing a loss of peripheral vision. Glaucoma is rarely manifested by symptoms. Early detection is therefore important to allow appropriate treatment and avoid serious complications, including blindness.
Since vision loss is permanent, early detection is necessary.
During your complete vision review, the optometrist uses a tonometer to measure intraocular pressure. Then, using specialized equipment, she will explore the quality of your field of vision. She will also examine with a camera intended for this purpose and an ophthalmoscope your fundus and the state of the optic nerve.
These clinical tests must be performed regularly. We advise an annual visit, sometimes more if your optometrist deems it necessary. After the age of 40, it is unwise to wait 2 years or more between visits to your optometrist.
WHAT HAPPENS IN THE EYE?
There are two important chambers (or spaces) in the eye: the anterior chamber (in front of the iris) and the posterior chamber (behind the lens). The anterior chamber is filled with a liquid called the "aqueous humor". This fluid carries nutrients. The aqueous humor is formed behind the lens and must circulate through the pupil and thence through a trellis and subsequently through an evacuation channel to the veins that drain the eye.
The intraocular pressure (for maintaining its round shape) is normally balanced by the production of the aqueous humor and its evacuation. If the production of the latter increases or the evacuation is decreased, then the pressure increases and compresses the structures of the fundus, including the optic nerve and retinal nerve fibers.
The role of the optic nerve is to transmit the visual information captured by the eye (the retina) to the brain. In addition, the optic nerve contains the veins and arteries that enter and exit the eye. Poor drainage is therefore often the common cause of increased intraocular pressure.
EYE HYPERTENSION OR GLAUCOMA?
It is important to distinguish the two conditions. Ocular hypertension is the condition where eye pressure remains too high, but the retina remains healthy and there is no loss of vision in the visual field.
Glaucoma should only really be talked about when the retina starts to be damaged because of the continuous increase in intraocular pressure.
Glaucoma can also be associated with different conditions such as diabetes. It can occur as a result of a trauma or accident, such as a hockey stick, tree branch. It can also be caused by certain medications such as prolonged cortisone intake.
Angle-closure glaucoma (acute glaucoma)
Angle-closure glaucoma is formed in the angle between the iris and the cornea and this glaucoma is very painful. This occurs in about 10% of cases.
Normally, the eye pressure is maintained around 15 to 20 mm of mercury. In the case of acute glaucoma, the pressure could rise to 80 mm of mercury! It's truly an emergency!
THE SIGNS AND SYMPTOMS OF AN ACUTE GLAUCOMA CRISIS (CLOSED ANGLE) ARE AS FOLLOWS:
- Sudden blurred vision
- Redness of the eye
- Pain in and around the eye
- Perception of colored halos around the lights
- Extreme sensitivity to light (photophobia)
- Dilated pupil
- Nausea
- Vomiting
Open angle glaucoma
In this case, the pressure is higher than normal: 22 mm of mercury and more. But in addition, the retina begins to be damaged and losses are visible in the peripheral fields of vision.
(Source : Association des Optométristes du Québec)