What will be the prescription for spectacles in a patient having simple myopic with the rule astigmatism?
-0.5D at 180 degrees
+0.5D at 180 degrees
-3.0D at 90 degrees
+2.0D at 90 degrees
-0.5D at 180 degrees With the rule astigmatism - two principal meridian are at right angles with the veical meridian being more curved. Correction requires convex(+) cylinder at 90 degrees or concave (-) cylinder at 180 degrees. Myopic astigmatism means the patient has to be given a concave cylindrical lens. Against the rule astigmatism corrected by = convex(+) C at 180 degrees or concave (-) C at 90 degrees Option 4 +2.0D at 90 degrees is also with the rule astigmatism but this patient will have simple hyperopic with the rule astigmatism not simple myopic as expected from the question
Optics and Errors of Refraction