SLT or "cold" laser is a non-invasive treatment in which short wave lengths are being transduced in short intervals ,through a gonioscopic lens to the area of filtering angle. thec wave length is specific to cells rich in melanin (located in the filtering angle). the mechanism of action is regeneration of cytokine surge -causing macrophages recruitment and breakage of inter-cell connections at the trabecular meshwork (filtering area) and allows rise in fluid shift. the treatment requires several lasering to areas at the surrounding the wave does not cause rise in tissue heat or scaring of tissue and can be repeated.among its disadvantages are reduction in affect during time,causing new elevation of IOP , potential peripheral anterior synechia (PAS), corneal erosion or oedema,requires experience in treating through gonioscopic lense.