to bring it to focus on the retina. Depending on the eyeglasses, they serve many functions. Reading glasses These are general over-the-counter glasses which can be worn for easier reading, especially for defective vision due to aging called presbyopia. Single vision prescription lenses They can correct only one form of defective vision, either far-sightedness or near-sightedness. Multifocal lenses The multifocal lenses can correct defective vision in multiple focus, for example: near-vision as well as far-vision. This are particularly beneficial for presbyobia. Contact lenses Alternatively, many people choose to wear contact lenses. One style is hard contact lenses, which can distort the shape of the cornea to a desired shape. Another style, soft contact lenses, are made of silicone or hydrogel. Depending on the duration they are designed for, they may be worn daily or may be worn for an extended period of time, such as for weeks. There are a number of complication associated with contact lenses. Typically the ones that are used daily. If redness, itching, and difficulty in vision develops, the use of the lenses should be stopped immediately and the consultation of ophthalmologists may be sought. Surgery Laser in situ keratomileusis (LASIK) and photo-refractive keratectomy (PRK) are popular procedures; while use of laser epithelial keratomileusis (LASEK) is increasing. Other surgical treatments for severe myopia include insertion of implants after clear lens extraction (refractive lens exchange). Full thickness corneal graft may be a final option for patients with advanced kerataconus although currently there is interest in new techniques that involve collagen crosslinking. As with any surgical procedure complications may arise post-operatively Post-operative monitoring is normally undertaken by the specialist ophthalmic surgical clinic and optometry services. Patients are usually informed pre-operatively about what to expect and where to go if they suspect complications. Any patient reporting pain and redness after surgery should be referred urgently to their ophthalmic surgeon. Medical treatment Atropine has believed to slow the progression of near-sightedness and is administered in combination with multifocal lenses. These, however, need further research. Prevention Strategies being studied to slow worsening include adjusting working conditions, increasing the time children spend outdoors, and special types of contact lenses. In children special contact lenses appear to slow worsening of nearsightedness. A number of questionnaires exist to determine quality of life impact of refractive errors and their correction. Epidemiology The number of people globally with refractive errors that have not been corrected was