Differences between the keratoconus topographic indices with great and small diameter ectasias

Abstract

When making adaptations of rigid contact lenses in patients with Keratoconus based on the computerized corneal topography, to differentiate between ectásias of great and small diameter it is fundamental, to the effects of optimal selection parameters of the lenses. <em><strong>Objective:</strong></em> look for differences between the Keratoconus topographic indices with great and small diameter ectasias to develop a pattern that establishes differences between the two that could be used to define a fitting of contact lenses type. Materials and <em><strong>Methods:</strong></em> a retrospective study of 129 found topographies of Keratoconus was made in the data bank of topographer Tomey TMS 4 of the IIO, and it was divided in 2 groups: ectásias of great diameter with a greater area of 5 millimeters and small ones of 5 millimeters and the topographic indices, the scale of asphericity and the average curvatures of the ectasia and apical zone were analyzed. <em><strong>Results:</strong></em> there were only significant differences in the CSI and DSP indices, the other indices did not have significant differences, there was no significant difference between the more used indices like the SRI and SAI. Ectásias of small diameter have greater tendency to be central, with a slight tendency to present more curved values. Conclusions: the indices are not the only determinants to classify one ectasia like small diameter, also must analyze the size of ectasia. Smaller values to 5mm, without concerning the model of used topografo, define one ectasia of small diameter.