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Muriel Schornack, Cherie B Nau, Jeff Pyle, Sanjay V Patel; Relationship Between Anterior Chamber Depth and Base Curve in 15-mm Scleral Lens Fitting. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4649.
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Unlike corneal rigid gas permeable lenses, scleral lenses rest upon the sclera and vault the cornea and limbus. Although the base curve of a scleral lens may vary considerably from corneal keratometry, diagnostic scleral lenses are frequently designated by base curve. In this study, we examined the relationship between base curve of 15 mm diameter scleral lenses and anterior chamber depth, sagittal depth to the limbal chord, and sagittal depth to a 14 mm chord.
Twenty-eight participants (19 females; mean age 29 years, range,22-44 years) with healthy eyes (no history of eye disease or surgery and no previous scleral lens wear) were fitted with a 15-mm-diameter Jupiter scleral lens (Visionary Optics, Front Royal, VA) on a randomly selected eye. Lenses were selected from a diagnostic fitting set to provide 100-400 μm clearance between the lens and central cornea. Within 5 minutes of placement, anterior segments were examined by Scheimpflug photography (Pentacam, Oculus, Inc.). Anterior chamber depth (distance between anterior surface of the crystalline lens and the anterior corneal surface), sagittal depth to a limbal chord, sagittal depth to a 14 mm chord across the anterior chamber, and vault (distance between the anterior corneal surface and posterior scleral lens surface) were measured in horizontal Scheimpflug images Correlations between the anterior chamber parameters and base curve of the selected scleral lens were assessed by the Pearson correlation coefficient.
Base curve of 15-mm-diameter scleral lenses was correlated with sagittal depth to a 14 mm chord (r = 0.49, p = 0.009), and with sagittal depth at a 14 mm chord plus the vault (r = 0.62, p<0.001). Scleral lens base curve was not correlated with anterior chamber depth (r = -0.17, p = 0.39) or sagittal depth to a limbal chord (r = 0.35, p = 0.06).
Base curve of 15 mm-diameter scleral lenses increases with greater sagittal depth to a 14 mm chord across the anterior chamber, but the predictive relationship (from r2) remains weak even when combining the sagittal depth with vault. Variation in anterior segment anatomy might explain weak correlations between scleral lens base curve and anterior chamber morphology . Diagnostic fitting may remain the most efficient method of base curve selection.
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