An accommodometer: an apparatus for measuring the total accommodation response of the human eye

An apparatus is described that measures automatically the response of the eye to an accommodation stimulus. It enables one to record the change of the lens power, of the pupil size, and of the eye position simultaneously from one eye without impeding that eye from performing its normal visual tasks. The measuring technique is based on the properties of the light beam coming out of the eye from an ir light spot that is projected on the retina. The outcoming beam is split into two parts. The extent of convergence of the beam is a measure for the lens power. The sum of and the difference between the intensities of the two parts of the light beam are measured to determine, respectively, the pupil size and the position of the eye with regard to the axis of symmetry of the apparatus.