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.