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SLT is used to treat glaucoma, the leading cause of blindness in North America and Europe, and the second leading cause worldwide. It is estimated that over 60.5 million people will be diagnosed with the disease by 2010.
Glaucoma is the name given to a number of conditions in which the optic nerve is damaged at its point of exit from the eyeball. Glaucoma is most often associated with an increase of pressure inside the eye, which, over time, can cause compression damage to some of the sensitive structures that receive and transmit images in the back of the eye.
Although risk factors for glaucoma include heredity, diet, smoking and age, the actual cause is often unclear. Raised IOP, or IOP within the “normal” range associated with other symptoms compounds damage caused by poor blood supply, structural weakness and disordered enzyme systems.
In all cases, the resulting damage is death of retinal nerve cells and irreversible loss of vision.
Primary (chronic) open angle glaucoma (POAG)
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Primary (chronic) open angle glaucoma (POAG), the most common form of glaucoma, effects more than 50 million people worldwide. With POAG, the trabecular meshwork becomes blocked, creating a slow rise in IOP that puts pressure on optic nerve fibers and their supporting tissue, and eventually cuts off the blood supply.
Variants of POAG include “normal tension” glaucoma, which exists in eyes that do not tolerate seemingly normal pressure, and ocular hypertension, a condition in which the IOP is high without loss of visual field.
Treatment for POAG consists of reaching a provisional target level of IOP using SLT, drug therapy or a combination of both. More invasive surgical options include argon laser trabeculoplasty (ALT), cyclocoagulation or trabeculotomy. |
Primary (acute) angle closure glaucoma (PACG)
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Primary (acute) angle closure glaucoma (PACG), most common in Asiatic populations and American Eskimos, occurs when the outer part of the iris bulges forward and touches the back of the cornea, inhibiting the exit of aqueous humour from the eye. Small changes in the iris (lens pushing forward or changes in blood flow) may create a complete blockage, causing the IOP to rise rapidly. With PACG, immediate treatment is required to save the optic nerve.
Treatment consists of creating a hole in the periphery of the iris to allow aqueous to flow through into the anterior chamber and out through the trabecular meshwork. This procedure is called an iridotomy, and is performed using a pulsed YAG laser.
Studies are underway to determine whether treating the TM with SLT after the iridotomy can help prevent recurrence of the problem. To date, the results are promising: at the glaucoma session of the 9th Congress of the Chinese Ophthalmologic Society it was reported that applying SLT to the trabecular meshwork following iridotomy was found to create a 3-4mmHg IOP reduction in Chinese PACG patients.
To view results of the Ellex ‘SLT for PACG’ study please click here.
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