Bringing accommodation into focus: the several discoveries of the ciliary muscle.

Since at least the 16th century, many investigators have speculated on the presence of a specialized muscle in the front of the eye designed to somehow alter its disposition to bring about changes in focus. By the 1850s, when Hermann von Helmholtz offered the first plausible theory of accommodation, the anatomy of the ciliary muscle was well known. The credit for this knowledge is generally given to Ernst Brücke and William Bowman, who published their observations on the muscle independently in the 1840s. In fact, not only were Bowman and Brücke wrong about the role of the ciliary muscle in accommodation, and for different reasons, but they shared this distinction with at least 3 investigators who came before them. In the 3 decades before 1840, Philip Crampton, Robert Knox, and William Wallace had all zeroed in on the ciliary muscle, describing its anatomy in varying detail. If none understood its precise role in accommodation--all ignored the work of Thomas Young, who by 1800 had proved that the lens must somehow round up to achieve near vision--each deserves a share of the credit for its discovery.