[Comparative results of keratometry with three different keratometers after LASIK]

Postoperative hyperopia is a frequent result of cataract surgery in eyes after previous myopic kerato-refractive surgery. One reason for the underestimation of intraocular lens (IOL) power is the wrong corneal refractive power measurement obtained by keratometers and corneal topography systems after LASIK. The aim of this study was to compare the precision of measurements of three different keratometers after LASIK.

We studied 58 eyes of 34 refractive patients aged between 20 and 51 years. The preoperative measurements and the measurements one month after LASIK were performed with the Keratometer (Zeiss), the corneal topograph (EyeSys Technologies) and the IOL-Master (Zeiss). We compared our postoperative measurement results obtained with the three keratometers with the results obtained by using the clinical history method (chm).

The smallest mean deviation was achieved with the IOL-Master (measured mean +/- SD: 38.94 +/- 1.88 D, vs. chm: 38.35 +/- 2.13 D). The Keratometer (Zeiss) showed a larger deviation (measured: 39.12 +/- 1.76 D, chm 38.34 +/- 2.07 D) and the largest deviation was shown with the corneal topograph (measured: 39.84 +/- 1.85 D, chm: 38.86 +/- 2.10 D), which measured in mean one diopter higher than what was obtained utilizing the chm. A positive correlation between corrected myopia and the postoperative difference between the measured and calculated value for each keratometer was found.

This study demonstrates that with common keratometers central corneal power is measured too high after LASIK. For IOL calculation in patients after LASIK, the wrongly positive deviation from measured central corneal power has to be taken into account.