AIM: To investigate the effect of pupillary dilation on intraocular lens power calculation.

METHODS: This prospective study included 52 eyes of 45 patients diagnosed with cataract and indicated for phacoemulsification with intraocular lens(IOL)implantation at the Faculty of Medicine of Mersin University. For each patient, preoperative corneal topography, autokeratometric measurements and biometric measurements were performed before and after pupil dilation.

RESULTS: K_h(horizontal)values obtained through autokeratometry and anterior chamber depth measured by biometric ultrasonography were significantly greater when pupils were dilated compared with values obtained when pupils were undilated. Implanting IOLs with power calculated using measurements taken during pupillary dilation resulted in a significantly higher rate of emmetropia. Comparison of emmetropic eyes and ametropic eyes showed significantly larger anterior chamber depth in emmetropic eyes.

CONCLUSION: Keratometric and biometric measurements are more important in IOL power calculation than the formula used. If biometric ultrasonography is performed using contact technique, care must be taken to avoid corneal compression. Anterior chamber depth should be followed during measurement, and the margin of error can be minimized by using the highest value obtained in IOL power calculation.