Relation between qualitative vision and qualitative over-keratometry in hydrogel contact lens wearers

In a single masked experiment qualitative vision (QV) and qualitative over-keratometry (QK) were determined in 10 patients wearing a variety of hydrogel lenses. Better QV (right eye vs. left eye) was reported by the patients. Better QK was judged by the author using a modified Bausch & Lomb keratometer. The two measures correlated in all 10 patients. Slitlamp observations confirmed the supposition that the variable quality of the over-keratometry (over-K) images was due to alterations of the prelens tear film. Over-K revealed a secondary image due to reflection at the concave surface of the contact lens. Observations of the nature of the primary and secondary images lead to the conclusion that the lenses do not buckle; hence, the quality of vision in the 10 patients studied was dependent upon the quality of the prelens tear film. Photographic examples of over-K images are shown.