Comparación de dos métodos empíricos para el cálculo del radio de curvatura base en lentes de contacto blandos esféricos

Abstract

Introduction: Soft contact lens fitting is a routine clinical procedure. One of the fundamental parameters for a successful fit is the calculation of the base curve radius (BC), as it determines the physiological interaction of the lens with the cornea. Traditionally, the method of adding 1 mm to the flattest keratometry value (K flat) has been used (Method 1). Alternatively, other authors and manufacturers have proposed adjusting this value according to the horizontal visible iris diameter (HVID), adding between 0.6 and 0.9 mm to the K flat (Method 2), depending on the estimated sagittal height of the eye. However, there is no universal consensus nor sufficient comparative clinical studies to validate which of these methods provides a better clinical fit. Objective: To determine which of these two empirical methods for calculating the base curve radius (BC) offers better clinical fitting results in university students with normal corneas. Materials and methods: A cross-sectional diagnostic test evaluation design was used. The population consisted of 15 optometry students (30 eyes) enrolled in their ninth semester at Santo Tomás University during the first semester of 2025. Students diagnosed with dry eye, ocular surface abnormalities (pinguecula or pterygium), previous refractive surgeries, and astigmatism greater than -0.75 were excluded. Each participant was fitted with two identical spherical soft contact lenses, with only the base contour (BC) varying according to the assigned method. Conclusions: Neither method proved to be absolutely superior; rather, they presented specific advantages. Method 2 is recommended when centration and stability are prioritized, while Method 1 is more suitable when a dynamic fit and greater mobility are desired. The final choice should be based on the desired clinical balance between stability, comfort, and corneal health.