Differences in corneal astigmatism between partial coherence interferometry biometry and automated keratometry and relation to topographic pattern

To compare the corneal astigmatism values obtained with a partial coherence interferometry (PCI) biometer and an automated keratometer and to evaluate the association between these differences and corneal topographic patterns.

Department of Ophthalmology, Guro Hospital, Korea University College of Medicine, Seoul, Korea.

Comparative case series.

Corneal astigmatism was measured by PCI biometry (IOLMaster) and automated keratometry (RK-F1 autorefractor). Eyes were divided into 3 groups based on the difference in absolute astigmatism values between PCI biometry and automated keratometry (ie, PCI biometry - automated keratometry) as follows: Group 1, more than 0.25 diopter (D); Group 2, within ±0.25 D; Group 3, less than -0.25 D. The topographic maps were grouped into patterns of round, oval, symmetric bow tie, asymmetric bow tie, and irregular. Distributions of topographic patterns according to group and astigmatism values by topographic patterns were evaluated.

The study enrolled 312 eyes. The most common pattern was the asymmetric bow tie (34.6%) followed by symmetric bow tie (20.5%), round (18.9%), irregular (16.3%), and oval (9.6%). The asymmetric bow-tie pattern was the most common in Group 1 and Group 2 (36.1% and 50.0%, respectively); however, in Group 3, the symmetric bow-tie pattern was the most common (32.8%). The distribution of topographic patterns by groups was statistically significantly different (P=.015, Pearson chi-square test).

The difference in corneal astigmatism between the PCI biometer and automated keratometer may depend on the corneal topography pattern.