Correcting astigmatism.
Measurement of refraction in the principal meridians and off-axis meridians in both directions from the visual axis was undertaken. The extent of disagreement between the sine-squared law and the actual astigmatism of living astigmatic eyes was calculated. The corrected visual acuity correlates with the residual ametropia. The conoid of Sturm is not the same for each eye.
Astigmatism↗