Non-penetrating surgical options could alter the glaucoma treatment paradigm, making the current gold standard of trabeculectomy one of several possibilities for treating the disease. Landmark studies, including the Collaborative Initial Glaucoma Treatment Study and the Advanced Glaucoma Intervention Study, have shown that filtration surgery has one of the best rates of significant IOP reduction among surgical glaucoma treatments. In addition, certain glaucoma subsets, such as angle-closure glaucoma and secondary glaucoma, are most effectively treated with filtration surgery.