• Work has been carried out to determine which techniques for correcting mixed and hyperopic astigmatism conserve tissue optimally. It may be appropriate to use a cross-cylinder technique in this regard, although manufacturers are designing nomograms specifically for hyperopia, which will minimise tissue loss. The greater tissue removal in hyperopic LASIK will lead to greater errors than are inherent in myopic ablations, simply because of the larger standard deviations involved. This may have an effect on predictability of hyperopic ablations, as well as lengthening time to stability of refraction.

Just as placement of the suction ring and choice of microkeratome head are under the control of the surgeon, so the planning of surgical treatment and programming of the laser are under his control. Input errors are not common.
• In order to correct hyperopia, the central zone of the cornea needs to be steepened, whilst avoiding abrupt steps at the edge of the ablation which might encourage significant epithelial remodeling and hence regression. Thus, three curvature changes are needed for Hyperopic LASIK, which may lead to haloes and glare. Only one curvature change occurs in Myopic LASIK. The transition zone required in H-LASIK thus limits the available optical zone