Effects of an artificial pupil and accomodation on retinal image size.

A very small artificial pupil in front of the eye allows a distinct view of an object when accommodation is incorrect. Helmholtz reported that the retinal image size of the object is changed when the eye is not accommodated for the object. Binocular size matching with an artificial pupil before one eye is used to provide quantitative data relating image-size change to accommodation and distance of the artificial pupil from the eye. Control experiments, including paralysis of accommodation in one eye, establish that the phenomenon is related to accommodation and is not an artifact of other variables.