Comparative study of the videokeratoscopic algorithms for idiopathic and surgery-induced astigmatism analysis

Purpose: To compare the accuracy and reproducibility of the Eye Sys((R)) vi deokeratoscope algorithms for analyzing idiopathic and surgery-induced asti gmatism analysis. Methods: Refractive astigmatism, videokeratoscopy (axial tangential and ref ractive power), autorefractometry, autokeratometry, and keratometry were re corded in 20 patients with idiopathic astigmatism, 40 patients who had unde rgone cataract surgery and 40 patients who had undergone penetrating kerato plasty. For each eye, 2 successive videokeratascopy were recorded. Results : Both cylinder and axis provided by the tangential algorithm are s ignificantly less reproducible than the cylinder and axis provided by the a xial and refractive algorithms (P<0.001). Cylinders provided by the axial a nd refractive algorithms showed a stronger correlation with subjective cyli nder (r(s) > 0.89; p < 0.001) than the cylinder provided by the tangential algorithm (r(s) = 0.66; P < 0.001). Both keratometric axis and autokeratome tric axis showed the strongest correlation with subjective axis (r(s) < 0.9 2; p < 0.001). The accuracy and reproducibility were higher for the topogra phic "bow tie" patterns than for the other topographic patterns; Conclusion: The axial and refractive algorithms of the Eye Sys((R)) videoke ratoscope are more accurate and reproducible than the tangential algorithm for analyzing idiopathic or surgery-induced astigmatism.