Assessment of Radial Aspheres by the Arc-Step Algorithm as Implemented by the Keratron Keratoscope

ORBSCAN Accuracy in Measuring Corneal Surface Elevation

“…For the 8.3-mm-radius surface, maximum error was less than 0.5 urn, and for the surface that represented a very steep cornea (r = 7.3 mm), error was approximately 1.0 urn. This is similar to the level of accuracy reported in one study that tested another videokeratoscope, the Keratron (Tripoli et al, 1995). This established the degree of accuracy that we could expect when the EyeSys was used to measure surfaces that were similar in shape to our test objects.…”

Comparison of anterior segment measurements by 3 Scheimpflug tomographers and 1 Placido corneal topographer

“…15 The instrument illuminates the cornea via a wide-angle cone that projects 26 equally spaced rings to cover almost the entire cornea from a radius of 0.165 mm for the first ring to a radius of 4.29 mm for the last ring. Similar to all topographers, the Keratron derives curvature data from the measured distances between the rings projected onto the cornea; specifically, the simulated K is calculated as the mean between the power of the flattest meridian at the 3.0 mm diameter and the power of the meridian 90 degrees away from it, independently from its curvature; therefore, the latter is not the steepest meridian.…”

Corneal topography with Scheimpflug imaging and videokeratography: Comparative study of normal eyes

“…These instruments provide detailed topographical information from thousands of points across the anterior corneal surface. Studies of the accuracy and repeatability of modern Placido disk-based videokeratoscopes have generally found these instruments to be highly accurate and repeatable for measuring spherical, aspheric, and astigmatic inanimate test objects [5][6][7] and highly repeatable for measurements of human corneas. 8 A relatively recently introduced instrument for measuring corneal topography is the Pentacam HR system (Oculus Inc.).…”