This is the abbreviation for Selective Laser Trabeculoplasty – it is a glaucoma laser procedure designed to lower eye pressure in a non-destructive way.  Most cases of glaucoma involve microscopic blockage of the trabecular meshwork drain inside the eye. If the internal ocular fluid doesn’t drain properly, aqueous fluid pressure builds up and causes gradual damage over time. There are many ways to lower eye pressure.  Glaucoma eye drops work to open the drain chemically and you can think of them like “Drano” for the eye.  Glaucoma surgery is very effective, but it is also a big production and associated with some morbidity. Fortunately, glaucoma laser therapies have come a long way. ALT was the original laser procedure. With ALT, a “hot” laser was directed at the eye’s drain and used to create scars in the trabecular meshwork. These scars helped open drainage tissue to manually get things flowing. This worked really well to lower pressure, but unfortunately the effect is short-lived and tended to wear off after a couple of years.  ALT can’t be repeated as there is only so much scar tissue the eye can suffer. SLT is a newer laser technology that some people have dubbed as a “cold laser.” SLT doesn’t create scaring inside the eye, but instead is used to irritate and stimulate the trabecular drainage cells to flow better.  The benefit to SLT is that no permanent scars are created and the procedure can be repeated if it wears off. The downside to SLT is that is doesn’t work for everyone.  We like to think of SLT as an adjunctive therapy to eye drops … if you are taking a single glaucoma drop, SLT therapy may be able to get you off it.  If you are already on glaucoma drops and your eye pressure is creeping up, an SLT treatment may keep you from needing an additional drop or surgery.  The procedure takes about 5 minutes and is painless with little recovery time.

Dr. Timothy Root is a practicing ophthalmologist and cataract surgeon in Daytona Beach, Florida. His books, video lectures, and training resources can be found at:


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