KERATOCONUS DETECTION BASED ON VIDEOKERATOSCOPIC HEIGHT DATA

Purpose. To develop a videokeratoscopic-based keratoconus detection sc heme that avoids the ambiguity of dioptric power definitions and video keratoscope design. Methods. Corneal height data obtained with a comme rcial videokeratoscope are decomposed into the set of orthogonal Zerni ke polynomials. Expansion coefficients of a ''normal'' group and a ker atoconus group are compared to find significant differences. Elevated Zernike terms are used to detect the disease in these populations. The performance of this detection scheme is compared to other videokerato scopic keratoconus indices. Results. Two low-order Zernike polynomial terms are identified as being elevated in keratoconus patients and com bined to form a new detection index. This index performed at least as well as keratoconus detection schemes based on the inferior-superior ( I-S) value, the steepest radial axes (SRAX), and the Surface Asymmetry Index (SAI) for the samples studied. Conclusion. The proposed Zernike scheme offers a potentially viable algorithm for detecting keratoconu s that avoids the ambiguities of dioptric power definitions and is ind ependent of videokeratoscope design.