EVALUATION OF THE EYESYS MODEL II COMPUTERIZED VIDEOKERATOSCOPE - PART I - CLINICAL-ASSESSMENT

Purpose. To compare the agreement and repeatability of keratometry mea surements with simulated keratometry measurements from the EyeSys (mod el II) corneal analysis system (CAS). Furthermore, to establish any re lationship between the repeatability of peripheral corneal measurement s and the spatial location at the cornea. Methods. Measurements using a Bausch & Lomb keratometer in 19 eyes (19 subjects) were compared wit h the simulated keratometry values using the EyeSys GAS. Repeatability of the keratometer (14 eyes, 14 subjects) and the EyeSys simulated ke ratometry values (10 eyes, 10 subjects) was assessed by comparing the difference of two measurements. Peripheral repeatability of the EyeSys CAS was compared in a similar manner in a sample of 10 eyes (10 subje cts). Results. The 95% confidence limits (-0.529 to +0.149 D) showed a lack of agreement between both instruments. With respect to the repea tability, both the keratometer (SD = +/-0.103 D) and the EyeSys (SD = +/-0.072 D) were found to exhibit approximately similar degrees of rep eatability. The repeatability of peripheral corneal measurements using the EyeSys CAS showed changes in repeatability dependent on the corne al meridian and the distance from the point of alignment. Measurements along the superior and nasal meridians showed poorest repeatability. Repeatability was also found to deteriorate away from the point of ali gnment. Conclusions. EyeSys simulated keratometry values were not inte rchangeable with the keratometer. This could be due to differences in the method of alignment or measurements from different areas on the co rneal surface. Repeatability of both the Bausch & Lomb keratometer and the EyeSys CAS was found to be similar. The spatial dependency of per ipheral corneal radius repeatability measurements could be attributed to interference of the ocular adnexa in those areas of measurement.