A clinical trial of the SUN SK-2000 computer-assisted videokeratoscope.

A clinical trial was performed on 20 optometry students in order to evaluate the suitability of the SUN SK-2000 (SUN contact lens company, Japan) computer-assisted videokeratoscope for use in clinical practice. Suitability was assessed by observing three factors: the accuracy, repeatability and agreement for central mean corneal power (MCP) with a keratometer (Javal Schiotz). Measurements of eight peripheral points and the central radius of curvature were made on 20 optometry students and on an 8 mm calibration surface using the SUN SK-2000. The SUN SK-2000 accurately determined the 8 mm calibration surface (supplied by manufacturers) to be spherical (SD = +/- 0.013, P = 0.776). Careful alignment was found to be an important factor in determining the actual radius of the calibration sphere. Unfortunately, the system required measurements to be taken at a point which was not coincident with the line of sight. A simple improvement to this has been suggested. Readings were most repeatable for central corneal radii. Peripheral radii showed the most repeatability for the horizontal and inferior corneal radii. It has been suggested that the ocular adnexa may be a possible cause for the poor repeatability in the superior area of the cornea. The level of agreement between the Javal Schiotz keratometer and the SUN SK-2000 in terms of mean refractive error (MRE) was not found to be sufficient for the two instruments to be interchangeable (P = 0.011). The C0 and C45 components of corneal astigmatism were found to have little association with the keratometer.