Date of Award


Degree Type


Degree Name

Master of Science in Vision Science

Committee Chair

Patrick Caroline


Purpose: To evaluate the effect of increasing the treatment zone diameter through a larger optical zone (OZ) lens in orthokeratology.

Methods: This study involved the evaluation of 12 eyes of 6 patients with low to moderate myopia and/or astigmatism. Subjects wore BE Retainer lenses (6.0 mm optic zone) overnight and were evaluated the following morning. Successful subjects then wore these lenses consecutively for 1 week and 1 month from the time of the initial dispensing. The second phase of the study involved switching the subjects from initial phase to larger B zone lens (6.7 mm optic zone). Again, 1 day, 1 week, and 1 month evaluations were conducted. On each follow up visit, subjective questionnaires, case histories, visual acuities, refractions, biomicroscopy, and corneal topographies were performed.

Results: Most subjects reached an uncorrected visual acuity (UCVA) of either 20/20 or 20/16 with both optical zone lenses. No significant improvements or deteriorations in visual acuity were noted with the different optical zone treatment diameters. Refractive error changes also showed similar results between the right and left eyes for each optical zone lens diameter with a mean change of 2.26 0 (R) and 1.94 0 (L) with the 6.0 mm OZ lens and 1.92 0 (R) and 1.81 0 (L) with the 6.7 mm OZ lens. The final average spherical equivalent refractive error was +0.63 OS (R) and +0.60 OS (L) for the 6.0 mm OZ and +0.29 OS (R) and +0.60 OS (L) for the 6.7 mm OZ lens. The subjects did not have significant changes in the treatment zone diameters between the 6.0 mm OZ and 6. 7 mm OZ lenses with a mean average increase of 0.195 mm 00 and 0.162 mm OS. Most subjects had a slightly progressive decrease in nighttime glare from pretreatment to post-treatment with a both optical zone lenses.

Conclusion: An increase in optical zone diameter lens did not significantly increase the treatment zone diameter and did not adversely affect uncorrected visual acuity. There was a small decrease in the effects of nighttime glare with the larger optical zone lens.

Included in

Optometry Commons