What is it?
The word glaucoma implies that there is an increase (or relative increase) in Intra ocular pressure (IOP) in the globe, in association with functional and structural damage to the optic nerve, with loss of parts of the retinal nerve fibre layer (RNFL) which causes progressive loss of peripheral vision. The words glaucoma and raised intra ocular pressure are therefore not synonymous. The pressure inside the globe is normal when total production of aqueous fluid (aqueous humor) does not exceed the total drainage.
What are the types of glaucoma?
Without going into the most technical of detail about the different forms of glaucoma,
let’s look at the basic types of glaucoma:
Primary Open Angle Glaucoma (POAG): This implies raised IOP (Intra ocular pressure) in the presence of an open irido-corneal angle, and functional / structural damage to the optic nerve. This form of glaucoma can also occur secondary to other causes that cause blockage of the irido-corneal angle.
Angle Closure Glaucoma (ACG): Also implies raised IOP in the presence of a CLOSED irido-corneal angle, with damage to the optic nerve. This can be primary or secondary to mechanisms that causes the angle to close.
What are the symptoms of glaucoma?
Peripheral vision loss is the most common finding. This can be very subtle at first but with sustained raised
IOP (Intra ocular pressure) damage to the optic nerve can cause a severe decrease in the peripheral vision. A slowly progressive
rise in the IOP is usually painless but if there is a sudden high rise in the pressure, this can be very painful and cause a sudden blurring of the vision. This is an emergency and needs to be treated immediately.
How can glaucoma be diagnosed?
It is important for any person with a family history of glaucoma to undergo annual screening.
The most important modifiable risk factor for detecting glaucoma is raised intra ocular pressure. Your eye care professional
can measure the intra ocular pressure through a test called tonometry. If the pressure is raised or there are any changes to
the optic nerve clinically, other tests can be done to detect if there is any damage to the nerve or surrounding nerve fibre layer.
Can it be treated?
Glaucoma can be treated with eye drops, pills, laser surgery, traditional surgery or a combination of these methods.
The goal of any treatment is to prevent loss of vision, as vision loss from glaucoma is irreversible. The good news is that glaucoma
can be managed if detected early, and that with medical and/or surgical treatment, most people with glaucoma will not lose their sight.
Taking medications regularly, as prescribed, is crucial to preventing vision-threatening damage. That is why it is important for you to discuss side effects with your doctor. While every drug has some potential side effects, it is important to note that many patients experience no side effects at all. When medications do not achieve the desired results, or have intolerable side effects, your ophthalmologist may suggest surgery.
Laser surgery has become increasingly popular as an intermediate step between drugs and traditional surgery though the long-term success rates are variable. The most common type performed for open-angle glaucoma is called trabeculoplasty.
This procedure takes between 10 and 15 minutes, is painless, and can be performed in either a doctor's office or an outpatient facility.
The laser beam (a high energy light beam) is focused upon the eye's drain. Contrary to what many people think, the laser does not burn a hole through the eye. Instead, the eye's drainage system is changed in very subtle ways so that aqueous fluid is able to pass more easily out of the drain, thus lowering IOP (Intraocular pressure).
You may go home and resume your normal activities following surgery. After this procedure, many patients respond well enough to be able to avoid or delay surgery. While it may take a few weeks to see the full pressure-lowering effect of this procedure, during which time you may have to continue taking your medications, many patients are eventually able to discontinue some of their medications. Your doctor is the best judge of determining whether or not you will still need medication.
Complications from laser are minimal, which is why this procedure has become increasingly popular and some centres are recommending the use of laser before drops in some patients.
Argon Laser Trabeculoplasty (ALT) -- for open-angle glaucoma
The laser treats the trabecular meshwork of the eye, increasing the drainage outflow, thereby lowering the IOP.
In many cases, medication will still be needed. Usually, half the trabecular meshwork is treated first. If necessary, the other half can be treated as a separate procedure. This method decreases the risk of increased pressure following surgery.
Argon laser trabeculoplasty has successfully lowered eye pressure in up to 75 percent of patients treated.
This type of laser can be performed only two to three times in each eye over a lifetime.
Selective Laser Trabeculoplasty (SLT) -- for open-angle glaucoma
SLT is a newer laser that uses very low levels of energy. It is termed "selective" since it leaves portions of the trabecular meshwork intact. For this reason, it is believed that SLT, unlike other types of laser surgery, may be safely repeated.
Some authors have reported that a second repeat application of SLT or SLT after prior ALT is effective at lowering IOP.
Laser Peripheral Iridotomy (LPI) -- for angle-closure glaucoma
This procedure is used to make an opening through the iris, allowing aqueous fluid to flow from behind the iris directly to the anterior chamber of the eye. This allows the fluid to bypass its normal route. LPI is the preferred method for managing a wide variety of angle-closure glaucoma’s that have some degree of pupillary blockage. This laser is most often used to treat an anatomically narrow angle and prevent angle-closure glaucoma attacks.
Please feel free to contact your eye care professional to make an appointment if you
or a family member are worried about Glaucoma.