Visual Psychophysics and Physiological Optics Experimental Simulation of Simultaneous Vision

METHODS. The instrument provides the eye with two superimposed images, aligned and with the same magnification, but with different defocus states. Subjects looking through the instrument are able to experience pure simultaneous vision, with adjustable refractive correction and addition power. The instrument is used to investigate the impact of the amount of addition of an ideal bifocal simultaneous vision correction, both on image contrast and on visual performance. The instrument is validated through computer simulations of the letter contrast and by equivalent optical experiments with an artificial eye (camera). Visual acuity (VA) was measured in four subjects (age: 34.3 6 3.4 years; spherical error: 2.1 6 2.7 diopters [D]) for low and high contrast letters and different amounts of addition.