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Investigation of a rigid gas permeable contact lens for overnight corneal refractive therapy

1 May 2006


Purpose This evaluation was conducted as part of a FDA study for the approval of Menicon Z™ (tisilfocon A) rigid gas permeable contact lenses for overnight corneal refractive therapy with the purpose of evaluating its safety and efficacy.

Methods Eleven subjects were enrolled in the study at Pacific University College of Optometry. The subjects presented wearing soft contact lenses or spectacles who wanted to try an alternative to their current modality. The participants slept in the lenses approximately 8 hours each night, over the course of 6 months, during which time their refractive errors were evaluated at fixed intervals. Each was fitted with a Menicon Z™ (tisilfocon A), reverse geometry lens exhibiting a DK permeablility rating of 163. Upon a successful fit, subjects were evaluated at 24 hours, 2 weeks as well as 1, 2, and 3 months following their baseline visit. At the 3 month visit, the subjects were instructed to discontinue lens wear and return for scheduled visits at 8, 24, 48 and 72 hours post-removat to assess the reversal effects. They then resumed their wearing regiment for 3 more months before returning for a final assessment. Visits for any other reason were recorded as an unscheduled appointment.

Results Five of the eleven subjects completed the study with reportedly good subjective vision and comfort while four subjects withdrew from the study due to unsatisfied acuities and/or excessive lens awareness. Two subjects were discontinued by the investigators because one developed a corneal infiltrate and the other required a lens that was outside the fitting parameters of the protocol.

Conclusion This study suggests that the test lens works most favorably for spherical refractive errors below -3.00 diopters and negligible astigmatism. This lens is safe and effective for corneal refractive therapy, when fit and managed by a qualified practitioner.


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