Purpose: It is possible that many reports of topographical and refractive changes associated with silicone hydrogel contact lens wear are the result of inadvertent wearing of inverted lenses. We wished to investigate differences in subjective, topographic, and refractive impact of wearing inverted silicone hydrogel lenses in comparison to wearing lenses in the normal (non-inverted) configuration.
Methods: Baseline uncorrected visual acuity and topographical maps were taken for 14 subjects, and a comfort survey was completed for each. The subjects were then fit with Focus Night & Day (Ciba Vision) silicone hydrogel contact lenses; one of the two lenses was inverted on each subject, as determined by a randomized, masked schedule. Lenses were removed after 12 hours that included overnight wear. Acuities, topographical maps and the comfort survey were then repeated.
Results: Significant change was noted from baseline for both lens conditions for acuities (p < 0.01) and the topographical maps (p < 0.05). The comfort of the two lenses did not significantly differ. Although the topographical maps were often distinctly different in appearance for the two conditions, numerical differences were small.
Conclusions: Subjects' inability to distinguish inverted from non-inverted lens comfort supports the suggestion that silicone hydrogel lenses may in fact often be worn insideout. Topographic changes occur with the lenses whether inverted or not, although the appearance of the maps are noticeably different. A potential exists for corneal reshaping with silicone hydrogel lenses.
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