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A clinical comparison between the Boston Envision and a spherical tricurve RGP on moderately and highly toric corneas

1 May 1993


A clinical companson was made between the Boston Envision aspheric rigid gas permeable (RGP) lens and a spherical tricurve RGP lens on a population with moderately or highly toric corneas. Twenty subjects with greater than 1.00 D of corneal astigmatism wore a Boston Envision lens in one eye and a spherical Boston RXD tricurve lens in the other eye for one month. Each subject was administered a questionnaire asking for a rating of clarity of vision, consistency of vision and physical awareness of each lens. Forced choice comparisons were made between the two designs based on clarity of vision, comfort and overall preference at the dispense, one week and one month follow-up visits. Objective comparisons made were based on differences in corneal staining and changes in keratometry readings and corneal refraction. Subjectively, consistency of vtswn was found to be significantly better with the tricurve lens and a trend towards preference of the tricurve based on physical awareness of the lenses was seen. End of study responses of the forced choice comparisons revealed no significant difference between the two designs. Objectively, corneal flattening was significant in the steep meridians of both the spherical and aspherical design. Both lenses were found to be acceptable in this study and very few differences were observed that could be attributed to design.


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