Glaucoma is a group of diseases caused by increased pressure inside the eyeball ( known technically as Intra Ocular Pressure or IOP) resulting either from a malformation or malfunction of the eye’s internal drainage system. Left untreated, elevated IOP can cause irreversible damage to the optic nerve and retinal fibres. This can result in a progressive, permanent loss of vision. However, early detection and treatment can slow, or even halt the progression of the disease.
What causes glaucoma?
The eye constantly produces aqueous, the clear fluid that fills the anterior chamber of the eyeball (the bit between the lens and the retina). The aqueous filters out of the anterior chamber through a complex drainage system. The delicate balance between the production and drainage of aqueous determines the eye’s intraocular pressure (IOP). There is no such thing as a standard IOP, but most people’s IOPs fall between 8 and 21.
Common types of glaucoma
Open angle (also called chronic open angle or primary open angle) is the most common type of glaucoma. With this type of glaucoma, even though the anterior structures of the eye appear normal, aqueous fluid builds within the anterior chamber, causing a higher IOP. Left untreated, this may result in permanent damage of the optic nerve and retina. This increased pressure can be treated with eye drops for most people, but in some extreme cases surgery can be required.
Acute Angle Closure
This is a rare form of glaucoma, representing only 1 in 10 of glaucoma cases. Acute angle closure occurs because of an abnormality of the structures in the front of the eye. Often the space between the iris and cornea is narrower than normal, leaving a smaller channel for the aqueous to drain through. If the flow of aqueous becomes completely blocked, the IOP rises sharply, causing a sudden angle closure attack.
While patients with open angle glaucoma don’t typically have symptoms, those with angle closure glaucoma may experience severe eye pain accompanied by nausea, blurred vision, rainbows around lights, and a red eye. This problem is an emergency and should be treated by an ophthalmologist immediately. If left untreated, severe and permanent loss of vision will occur in a matter of days.
This type of glaucoma occurs as a result of another disease or problem within the eye such as: inflammation, trauma, previous surgery, diabetes, tumor, and certain medications. For this type, both the glaucoma and the underlying problem must be treated.
This is a rare type of glaucoma that is generally seen in infants. In most cases, surgery is required.
Signs and Symptoms
Glaucoma is an insidious disease because it rarely causes symptoms. Detection and prevention are only possible with routine eye examinations.
Detection and Diagnosis
Because glaucoma does not cause symptoms in most cases, anybody aged 40 or older should have an annual examination including a measurement of the intraocular pressure. Patients at higher risk get free NHS eye tests.
The glaucoma evaluation has several components. In addition to measuring the intraocular pressure, the doctor will also evaluate the health of the optic nerve (using an ophthalmoscope), and test the peripheral vision (visual field test) before making a diagnosis.
The progression of glaucoma is monitored with a visual field test. This test maps the peripheral vision, allowing the optician to determine the extent of vision loss from glaucoma and a measure of the effectiveness of the treatment. The visual field test is periodically repeated to verify that the intraocular pressure is being adequately controlled.
Most patients with glaucoma require only medication to control the eye pressure. Sometimes, several medications that complement each other are necessary to reduce the pressure adequately.
In the event that medication doesn’t reduce the IOP, then surgery may be necessary to improve the drainage of aqueous from the eye. There are several types of procedures, some involve laser and can be done as an out patient treatment.