A cataract is much like a smartie or M&M. It has an outer coating (capsule) and an inner nucleus (the chocolate in the smartie). When an eye surgeon performs cataract/lens surgery the surgeon makes a circular opening in the front facing capsule of the lens and then removes the inner nucleus. The remaining capsular envelope supports the new artificial lens which is typically injected in through the opening in the capsule. Over time the capsule shrinks and wraps around the new lens much like shrink wrap or cling film. As the capsule contains live cells some capsule can develop a layer of new cells that form a frosting on the back surface of the lens. This is called posterior capsular opacification (PCO) or an after-cataract and can occur in up to 10% of patients after lens/cataract surgery. The frosted layer is much like the frosting on a window which can blur the view through the window and similarly through the new lens. PCO can occur at any time after surgery including a few weeks to months later. In some surgeries an adherent plaque may be present on the capsule and a surgeon may prefer to leave this rather than risk tearing the capsule. In these cases early treatment to clear the frosting may be necessary.
The YAG laser is the laser used to clear the frosting from the back surface of an intraocular lens. YAG laser treatment is painless and is completed from outside the eye in a few minutes. During YAG laser treatment your eye doctor may use a magnifying contact lens to help with aiming the YAG laser at the layer of frosting. During the treatment patients will see flashes of light and hear a clicking sound. The pupil needs to be dilated before YAG laser can be performed to allow a good view of the lens surface. After the treatment your doctor will prescribe a short course of anti-inflammatory and pressure drops. Most patients will noticed an improvement in clarity and vision within a day. YAG laser treatments are typically only needed once as the capsule does not regrow after it is vaporised by the YAG.
Complications after YAG laser are very rare but can in rare cases include vitreous floaters, raised eye pressure, retinal swelling, lens damage and very rarely retinal detachment.