Psychophysical Investigation of Human Accommodation and Convergence(Physiology of Vision)

The topics on near reflex, which is composed of ocular convergence, lens accommodation and pupillary constriction, are discussed from a standpoint of visual psychophysics. Each of them has its own controller, and linkage between each other is known. First, recent dual-innervation hypothesis of ciliary muscles by sympathetic and parasympathetic nerves was revivied against the hypothesis of single-innervation by later. For example, it is found that the resting state of accommodation is ordinarily proximal to the far point of the eye by 1～1.5 D, not at the far point. Secondly, the contribution of pupillary constriction to the near response is doubtful because of its slow dynamic properties. Thirdly, although ocular convergence has been classified as slow eye movement, it is found that some of convergence containes rapid components, especially when conjugate eye movement is accompanied. Therefore, eye movement redording method with wide dynamic range and high spacial and temporal resolution, such as the magnetic search coil method, should be used. In keeping with rapid progress in this field, the mechanism of near reflex will be resolved still more in the next decade