Relationship between corneal topographic indices and scleral lens base curve

To determine whether parameters of anterior corneal contour as identified by topographic analysis (steep and flat simulated keratometry, reference sphere) predict the base curve of Jupiter scleral lenses in patients with dry eye syndrome and keratoconus.

We identified 33 eyes with dry eye syndrome and 21 eyes with keratoconus that were fit with Jupiter scleral lenses of standard design between June 2006 and July 2009. Steep and flat simulated keratometry powers and shape factor from axial topographic maps, reference sphere from elevation maps, and base curve of the scleral lens prescribed for each eye were recorded. Correlations between topographic indices and base curve were evaluated by using the Pearson correlation coefficient, and significances were completed by using generalized estimating equation models.

In dry eye syndrome, the base curve of the final scleral lens prescribed correlated with the steep keratometric power (r = 0.70, P = 0.05, n = 33), the flat keratometric power (r = 0.71, P<0.001, n = 33), and the reference sphere (r = 0.73, P = 0.002, n = 33). In eyes with keratoconus, base curve also correlated with the steep keratometric power (r = 0.72, P<0.001, n = 19), the flat keratometric power (r = 0.70, P<0.001, n = 19), and the reference sphere (r = 0.68, P<0.001, n = 21). There were no correlations between base curve and shape factor.

In eyes with normal and abnormal ocular contour, base curve of scleral lenses correlates with reference sphere and steep and flat keratometric powers, but the predictive relationship is weak (r ∼0.50). Diagnostic fitting may be the most efficient method of fitting scleral lenses at present.