Duochrome test is used for: (A) Colour blindness, (B) Cylindrical axis, (C) Spherical axis, (D) Astigmatism
Answer is C. Refining the sphere : The spherical correction is refined after refining the cylinder power and axis . It is done by following tests : Fogging technique Duochrome test Pin-hole test Reference : A.K.Khurana; 6th edition; Page no: 578