William Horatio Bates was an American physician who practiced ophthalmology and developed what became known as the Bates method for better eyesight. The method was based in his theory that the eye does not focus by changing the power of the lens, but rather by elongating the eyeball through use of the extraocular oblique muscles; this model contradicted mainstream ophthalmology and optometry then and now.

The Bates method is an ineffective and potentially dangerous alternative therapy aimed at improving eyesight. Eye-care physician William Horatio Bates (1860–1931) held the erroneous belief that the extraocular muscles effected changes in focus and that "mental strain" caused abnormal action of these muscles; hence he believed that relieving such "strain" would cure defective vision. In 1952, optometry professor Elwin Marg wrote of Bates, "Most of his claims and almost all of his theories have been considered false by practically all visual scientists."