Because of circle of least diffusion, the distant vision is comparatively good in
At point D, the divergence of veical rays is exactly equal to the convergence of the horizontal rays from the axis. So here the section is a circle, which is called the circle of least diffusion. Mixed astigmatism: refers to a condition where in the light rays in one meridian are focused in front and in other meridian behind the retina. Thus in one meridian eye is myopic and in another hypermetropic. Such patients have comparatively less symptoms as &;circle of least diffusion&; is formed on the retina. Reference :- A K KHURANA; page:-25,26,37
Compound myopic astigmatism
Mixed astigmatism
Simple myopic astigmatism
Compound hypermetropic astigmatism
Optics and refraction