Clinical Assessment of Refractometry and Keratometry with two Hand-held Auto-refracto-keratometers (Nidek), the IOL-Master (Zeiss) and a Automated Refracto-keratometer (Topcon)
Fakultät für Klinische Medizin, Universitäts-Augenklinik, Karl-Ruprechts-Universität Heidelberg, Mannheim
Purpose: Measurements of the anterior corneal curvature are important for calculation of the intraocular lens power of patients undergoing cataract surgery, for proper fitting of contact lenses or for monitoring changes in the shape of the cornea of keratoconus patients. The purpose of this study was to compare the corneal astigmatism measured by two hand-held automated refracto-keratometers (Nidek), the IOL-Master (Zeiss) and the automated refracto-keratometer (Topcon).
Method: In 40 eyes of 20 patients the keratometry was performed by one investigator with these four different instruments. The measurements were repeated three times on each machine.
Results: The subjective spherical refraction ranged from +11.5 to 3.0 D and the cylindric refraction to -3.25D. There was a broad agreement between the measured refractions of the four instruments and the subjective refractions. The comparison of the astigmatism measured by the hand keratometers, the auto-keratometer and the IOL-Master demonstrated a statistically significant (p<0,01) relationship. There was no significant difference between the measurements of the spherical equivalent, the spherical refraction, the astigmatism and the cylindric degrees with either instrument. In two cases of irregular corneal
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