- For patients meeting criteria for anisometropia or combined-mechanism i. Spherical equivalent must be within 0.50 D of fully correcting the anisometropia ii. Hypermetropia must not be undercorrected by more than +1.50 D spherical equivalent, and reduction in plus must be symmetric in the two eyes iii. Cylinder power in both eyes must be within 0.50 D of fully correcting the astigmatism iv. Cylinder axis in the spectacle lenses in both eyes must be within 6 degrees of the axis of the cycloplegic refraction