Comparison of Keratometry and Total Corneal Power, as measured by a swept-source OCT-based optical biometer, for IOL power calculation in Asian eyes.

ABSTRACT

PURPOSE: To investigate whether standard keratometry (K) or total corneal power (TCP) lead to more accurate refractive outcomes for intraocular lens (IOL) power calculation. SETTING: Public hospital. DESIGN: Retrospective evaluation of a diagnostic test instrument. METHODS: Preoperatively all patients underwent optical biometry with the Anterion (Heidelberg), a swept-source optical coherence tomographer providing both K and TCP. The same IOL model was implanted in all cases. The whole sample was divided into a training dataset, used to optimize the formula constants, and a testing dataset, used to investigate the spherical equivalent prediction error (SEQ-PE) of 8 IOL power formulas. Trueness, precision and accuracy were evaluated by means of the robust two-sample t-test. Cochran's Q test was performed to assess whether the percentage of eyes with an SEQ-PE within each threshold was significantly different; in such an event, the McNemar test was then applied. RESULTS: Both the training and testing datasets included 317 eyes. No significant differences were detected for trueness, due to constant optimization. Precision and accuracy were better when K was entered, although a statistically significant difference was observed only with the EVO (precision p = 0.02 and accuracy p = 0.03) and Haigis formula (p <0.01 for both precision and accuracy). No significant differences were observed for the percentage of eyes with an absolute SEQ-PE within any threshold. CONCLUSIONS: With most formulas, IOL power calculation is not more accurate when TCP is used instead of K.