Extended defocus tolerance for image quality in two-photon vision

Two-photon vision represents a novel area of research in vision science. The phenomenon relies on the perception of pulsed infrared light (800-1300 nm) through two-photon absorption in visual pigments, leading to the perception of color corresponding to approximately half of the stimulating wavelength. The potential applications of this effect require a quantitative assessment of the impact of defocus on perceived image quality. Here, we quantify the range of defocus over which image quality in two-photon vision is preserved. We demonstrate that two-photon vision is characterized by a greater tolerance to defocus, enabling high image quality. It may reduce accommodative activation to two-photon stimuli, leading to lower accommodative fatigue in two-photon AR displays.