Predictability of intraocular lens power calculation in eyes after phototherapeutic keratectomy

Purpose To compare the predictability of intraocular lens (IOL) power calculation using several corneal power measurements in eyes that underwent phototherapeutic keratectomy (PTK). Study design Retrospective case series. Methods We reviewed the clinical charts of 42 eyes of 25 consecutive patients who underwent cataract surgery after PTK for granular corneal dystrophy or band keratopathy. IOL power calculations were performed using the SRK/T formula with four corneal power measurements [automated keratometry (AK) measured with a partial coherence interferometer, simulated keratometry (Sim K), true net power (TNP), and total corneal refractive power (TCRP) measured with a rotating Scheimpflug camera]; we determined the prediction error, absolute error, and percentage within +/- 1.0 D of the targeted refraction, 1 month postoperatively. Results The prediction error in the TCRP group was significantly better than those in the AK, Sim K, and TNP groups. The absolute error was also significantly better than those in the AK and Sim K groups, but not significantly different from that in the TNP group. The percentages of within +/- 0.5 and 1.0 D in the TCRP group were significantly higher than those in the AK and Sim K groups, but not significantly different from that in the TNP group. Conclusions The TCRP provides the highest predictability of IOL power calculation in post-PTK eyes. This result suggests that the use of the TCRP, rather than of conventional anterior keratometry, may be clinically helpful for improving the refractive accuracy of post-PTK eyes.