The effect of pupillary dilatation on IOL power measurement by using the IOLMaster

The aim of this study is to assess the agreement of IOL power and ocular biometry measurements before and after pupillary dilatation by using the IOLMaster. This was the prospective nonrandomized cohort study. Measurements were taken with the IOLMaster ^® (Carl Zeiss Meditec AG, Jena, Germany) from healthy volunteers at the Department of Ophthalmology, King Chulalongkorn Memorial Hospital. Axial length (AL), keratometry both flattest and steepest (K1, K2), and anterior chamber depth (ACD) were measured before and after the dilatation of the pupil with 1 % tropicamide. The IOL power was calculated using the Sanders–Retzlaff–Kraff/Theoretical (SRK/T) formula. The mean difference of each parameter was assessed by Bland–Altman plot analysis. 384 eyes from 195 healthy volunteers were measured. The mean age of the patients was 52.39 ± 1.02 years (range 21–79). Pupillary dilatation had no significant effect on AL (p = 0.07), keratometry [steepest K (p = 0.95) and flattest K (p = 0.17)], and IOL power (Alcon SN60WF) (p = 0.40) obtained from the IOLMaster. However, ACD was significantly increased post-dilatation (p < 0.05). The Bland–Altman plot indicated good concordance in nearly all parameters except ACD. For ACD measurements, the 95 % limit of agreement between pre-dilatation and post-dilatation was −0.47 to 0.23 mm; therefore, 92.2 % of the measurement differences were with a LoA of −0.47 to 0.23 mm. There were no eyes that could not be measured by the IOLMaster. The dilatation of the pupil had no significant effect on AL, keratometry measurements, and SRK/T calculated IOL power. However, the ACD significantly increased post-dilatation.