The Yttrium- Aluminum Garnet Crystal is synthetically obtained and represents the active medium of the Nd: YAG, Ho: YAG, Er: YAG lasers. These solid state lasers showed very good results in Ophthalmology, due to their emission in different regimes (continuous wave or giant short pulses), at different wavelengths (near IR and starting from it in UV or visible spectre), the ability to focus the radiation through simple optic systems or the transmission to narrow, hard accessible spaces using flexible optic fibers. The high efficiency of these lasers reported in ophthalmology is obtained by the photo-disruptive or thermic mechanism of the laser beams. This paper introduces the properties of the laser radiation, the structure and the way the YAG laser works and the applications of these lasers in Ophthalmology (such as posterior capsulotomy, iridotomy or trabeculoplasty) as well.