[Repeatability of a Video Keratography System specially designed for measuring corneal astigmatism in animals with...

This experimental study sought to determine the repeatability of a Video Keratography System specially designed for animals with small eyes. From day 5, ten newly hatched White Leghorn chicks were reared with monocular hyperopic defocus using -5.0D (n = 3), -10.0D (n = 3), -15.0D(n = 4) spherical PMMA lenses on their right eyes; the left eyes served as controls. Two sets of corneal topographical measurements, each set separated by about 5 minutes apart, were collected from both eyes of each animal at the end of 2-wk treatment period (i. e., 19 days of age). Each set of measurements consisted of five consecutive readings of corneal astigmatism. Bland-Altman plots were used to evaluate the repeatability of 3, 4 or all 5 readings from each set of data. When all 5 consecutive readings were used, the mean difference (95% limits of agreement) for the right treated and left untreated eyes were, respectively, -0.09D (-0.81, 0.64) and -0.02D (-0.86, 0.82). There was a tendency that lesser readings from each set of data produced greater difference between the two sets of measurements, although the differences (-0.19D) were not clinically significant. The Video Keratography System specially designed for animals with small eyes produced repeatable measurements for both treated and untreated eyes in chickens. Further studies are needed to validate other biometric features associated with corneal changes during normal and abnormal eye growth.