The TMS-1 Corneal Topography Measurement Applied to Calibrated Ellipsoidal Convex Surfaces

Regular and Irregular Refractive Powers of the Front and Back Surfaces of the Cornea

“…However, a variation of 0n27 mm in the radius of curvature represents a change of 0n25 D in refraction when the cornea is in contact with the aqueous humor. This level of error would be within the limit of reproducibility of modern videokeratoscope (McCarey, Zurawski and O'Shea, 1992 ;Douthwaite, 1995 ;Douthwaite and Matilla, 1996). Considering the satisfactory repeatability of the measurements shown by the current tests on calibration lens and normal human eyes, we suppose that the relative values like astigmatism obtained herein would hold reasonable accuracy even if some doubt may exist about the absolute measurement values of the videokeratoscope (Douthwaite, 1995 ;Douthwaite and Matilla, 1996).…”

Comparison of Keratometric and Topographic Cylinder and Axis Measurements on Normal Corneas with Low Astigmatism

“…The performance of the videokeratography device used here (TMS-1) was probably below the expectations arising from previous studies on test spherical surfaces (1)(2)(3)5), but this emphasizes the difference between experiments on spheres and in vivo tests. On the other hand, the same model has been shown to give readings for the vertex radius that were higher than those of the calibrated ellipsoidal convex surfaces, up to 0.09 mm greater (24), as the surface becomes increasingly aspheric. Although keratometry and CVK share some common assumptions, they also differ in other respects (25).…”

Corneal Asphericity and Apical Curvature in Children: A Cross-sectional and Longitudinal Evaluation

“…32 When data obtained from the TMS-1 are used, this graphical method has been found to be very accurate when measuring aspheric surfaces near Q ϭ Ϫ0.2 as demonstrated on calibrated conicoid surfaces. 33 A demonstration of the graphical method for one topography reading of a subject included in the study can be found in Figure 2. Corneal asphericity and r o obtained using the graphical method can be consid- ered particularly useful in comparative studies, considering the high repeatability of the TMS-1.…”

“…Corneal asphericity and r o obtained using the graphical method can be consid- ered particularly useful in comparative studies, considering the high repeatability of the TMS-1. [33][34][35] The Q and r o found for the videokeratoscopic images were averaged for each child. Corneal asphericity data obtained in this study are reported as global asphericity, representing the cornea as a whole and encompassing all meridians.…”