The uneven foreground and background blur that is in an image.
A lens aberration that causes off-axis light bundles to focus to an elliptical, rather than circular, spot.
Astigmatismo
A condition where a misshaped cornea causes light to be focused over a range of distances rather than on a point. this can be corrected by a lens with cylinder power in a certain direction.
A condition in which the eye cannot focus vertical and horizontal lines simultaneously, leading to blurring of vision
