Orthokeratology. Part II: Evaluating the Tabb method.

This summary of the experimental design and methodology of a study evaluating ocular response to orthokeratology presents a method of orthokeratology that involves modifying the optic zone diameter, intermediate, and peripheral curve zones of a PMMA contact lens. An evaluation of the Tabb method of orthokeratology to determine the ocular tissue changes most responsible for observed refractive and acuity changes found that noncorneal parameters measured did not change, whereas two corneal parameters measured did change as orthokeratology occurred. The corneal parameters that appeared most involved in refractive and acuity changes were corneal thickness and shape factor. The Tabb method of orthokeratology did not cause an increase in corneal with-the-rule astigmatism.