Optical and visual metrics.

Abstract

The eye is a complex imaging system whose optical components determine the first step of vision. Quantifying and measuring the ocular quality, and how this affects the quality of the retinal images, can allow us to better understand the visual process and to improve diagnostics and correction methods. The optical quality is lowered by aberrations (consequence of the shape of the refracting surfaces), diffraction at the pupil, and scattering (due to particles and nonuniformities localized in the media). The combined effect of these three factors is that light deviates from the ideal trajectory and spreads over a deteriorated retinal image that will limit the visual performance. In general, a system with less aberrations, scattering, and diffraction will produce images with higher quality. Consequently, one expects to have a better vision when images at the retina are fine. However, although the optics, the retinal image stage, and the visual perception are dependent with each other, there is not a direct or obvious relationship between these three levels. In this context, it is necessary to distinguish between optical quality, optical performance (image quality), and visual performance and to be able to define metrics that quantitatively measure each of these matters