<s>[INST] context: Mixed astigmatism has best visual acuity In the case of mixed astigmatism the circle of least diffusion is nearest to the macula so it has best visual acuity. Simple Myopic Astigmatism One ray focused at Retina Other focused in front Simple Hyperopic Astigmatism One ray focused at Retina Other focused behind Compound Myopic Astigmatism Both rays focused in front Retina Compound Hyperopic Astigmatism Both rays behind the Retina Sturm's Conoid Configuration of rays refracted through toric surface when point Object is focused Curvature of veical plane (V) is more than hirizontal plane (H), hence FHis < Fv.(rays coming in veical plane converge more and earlier in their course as compared to horizontal rays ) POINT in stums's conoid CHRACTESTIC Point A Horizontal oval image is formed as Veical Rays(plane V) converge more than horizonatal rays Point B (Fv) veical rays converge completely ,horizontal line is formed Points C after convergence of veical rays at focal point they sta to diverge , horizontal rays are still converging-horizontal oval image Point D divergence of veical rays = convergence of horizonatl rays hence perfect circular image formed K/a Circle of least Confusion Point E horizonatal rays convrege more than divergence of veical rays ,hence veically oval circle is obtained Point F(FH) horizontal rays converge completely hence we onbtain only vetical straight line Point G both horozonatal and veical rays diverge hence Veically oval circle A/K/A Prolate ellipse [/INST] question: Which of the following type of Astigmatism has best visual quality | options: A: Simple myopic Astigmatism B: Compound myopic Astigmatism C: Mixed astigmatism D: Oblique Astigmatism | answer: C </s>