[Refraction and accommodation].

The main purpose of ophthalmology is to improve the quality of vision by the recovery of visual function. Visual acuity, among the visual functions, is the most important factor. Decreased far vision is caused mainly by refractive errors, while decreased near vision is caused by accommodative insufficiency, especially presbyopia. REFRACTIVE ERRORS: The development of myopia may be influenced by both polygenic and environmental factors. Investigation of the mechanism of myopia has progressed based on the experimental animal models of myopia. The conventional treatments for refractive errors is spectacles or contact lenses, and new treatment includes phakic IOL, orthokeratology, and refractive surgery. There are also newly designed types of equipment to assess refraction and refractive elements. ACCOMMODATIVE INSUFFICIENCY: Presbyopia is mainly corrected using multifocal or progressive power spectacle lenses. Nowadays, bifocal and multifocal contact lenses and sometimes surgical treatment are used for presbyopia. Equipment for asthenopia has also been developed.