ABSTRACT
This chapter examines some optical aspects with major implications for upper disparity, which can help to understand the influence of optical aspects in stereopsis and provides evidence regarding factors that may be important for a better characterization of stereoacuity. The instruments and psychophysical methods used to measure stereoacuity are very diverse. The devices can be classified as real-depth and projected-depth devices, although currently mainly the latter are used. Stereoacuity measured both for real and for projected tests depends largely on the experimental conditions and stimulus parameters. The study of the influence of optical factors in stereoacuity has traditionally been limited to questions concerning interocular differences in low-order aberrations, whether natural interocular differences in ametropia or interocular differences induced by different emmetropization techniques and their effects on visual quality. The numerical relationship that quantifies the deterioration between defocus and stereoacuity depends on the method and experimental device used.
