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Aspheric Rigid Gas Permeable Contact Lenses: Practitioner Discrimination of Base Curve Increments Using Fluorescein Pattern Evaluation

Evaluation of the fluorescein pattern is the main clinical indicator of the fit of a rigid gas permeable (RGP) contact lens to the cornea. Traditionally, manufacturers inventory RGP lenses in 0.05-mm base curve increments. The objective of this study was to test the hypothesis that experienced practitioners are not able to discern base curve/cornea relations of aspheric design lenses correctly to within ±0.05 mm. Eleven clinicians with expertise in fitting rigid lenses were asked to interpret fluorescein patterns and lens fittings of the Bausch & Lomb Quantum aspheric RGP lens on five adapted rigid lens wearers. The results showed that the experienced practitioners used in this study were not able to discriminate cornea/base curve relations of Quantum aspheric lenses within ± 0.05 mm more than 67% of the time (p < 0.05). There were no patient-topatient differences based on type of lens fit (interpalpebral or lid attachment) or degree of corneal toricity. Lenses fitted in 0.10-mm base curve steps were judged as being as acceptable as lenses fitted in 0.05 mm steps (p < 0.05). It was concluded that Quantum aspheric design lenses need only be trial fitted in 0.10-mm base curve steps.