This stands for Argon Laser Trabeculoplasty and is a laser procedure designed to lower the eye pressure in people with glaucoma.  This procedure involves using a “hot” laser to burn spots into the trabecular meshwork (the drainage filter of the eye).  By doing this, scar tissue forms that opens up the meshwork and creates better flow. While effective and well tolerated, the pressure improvements of ALT tend to wear off in a couple of years. The procedure can only be done once because of the scar formation. ALT is largely being replaced by a similar procedure called SLT.  With SLT a “cold” YAG laser is used to create similar spots on the trabecular meshwork but instead of creating heat-induced scars, the drainage cells are merely stimulated.  This promotes better flow through the drain without creating permanent tissue damage. This means that SLT can be repeated if it wears off. SLT is slowly becoming first-line therapy for many doctors treating glaucoma.

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:


  1. Even though ALT is preferred over glaucoma surgery (it’s a lot less traumatic) … I was never a huge fan of the procedure. The pressure effect seems to wear off over time and the procedure can’t be repeated. After all, the eye can only suffer so much scarring.

    SLT seems like a better treatment option given the minimal ocular trauma and the ability to be (theoretically) repeated.

    The main downside with both of these lasers is that they don’t work for everyone … I would estimate that 75% of people seem to have a good effect with the remaining having little IOP improvement.


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