Binocular visual simulation of a corneal inlay to increase depth of focus.

PURPOSE To investigate binocular visual acuity and depth of focus when one eye forms images through a typical pupil diameter aperture (4 mm) and the other eye through a small pupil of 1.5-mm diameter. METHODS Using a recently developed adaptive optics binocular visual simulator, through focus monocular and binocular visual acuity were measured in three subjects under specially simulated visual conditions: right eyes had "small aperture" vision through a 1.5-mm pupil diameter and left eyes had normal vision through 4-mm pupil diameter. The measurements were performed in photopic and mesopic conditions. RESULTS An increase in binocular and monocular (for the small-aperture eye) depth of focus was measured with respect to the 4-mm pupil diameter eye. It ranged from 1 to 1.5 diopter (D) depending on the threshold requirement and the visibility conditions. For photopic conditions, the J2 visual acuity level was reached at 1 D of defocus for the 4-mm pupil diameter case, while for the 1.5-mm, the J2 level was reached at 2.5 D. Binocular summation occurred only in far vision conditions (no defocus added). For near vision, binocular visual acuity closely followed the values of monocular visual acuity for the eye with the smaller aperture. CONCLUSIONS The small-aperture effect to increase depth of focus in the human eye was successfully implemented in a binocular visual simulator. Although certain limitations exist, the small-aperture approach provided a simple but attractive solution to increase depth of focus in the human eye.