Comparison of partial coherence interferometry and ultrasound for anterior segment biometry.

PURPOSE

To assess the performance of a partial coherence interferometry (PCI)-based device for the determination of anterior segment biometry.

SETTING

Clinica Centrofama, Cartagena, Murcia, Spain.

METHODS

Central corneal thickness (CCT), anterior chamber depth (ACD), and lens thickness (LT) were measured with the ACMaster PCI anterior segment biometer and an Echoscan US-1800 ultrasound (US) biometer/pachymeter with and without cycloplegia. To determine the precision of the instruments, the same examiner took 30 consecutive CCT, ACD, and LT measurements in a single subject under the same conditions and with and without cycloplegia. The same measurements were performed in additional subjects.

RESULTS

Twenty-one eyes (16 subjects) were evaluated. Repeated measurements of the single subject yielded a standard deviation of 4.0 microm for CCT, 106.0 microm for ACD, and 323.0 microm for LT; there were many peaks, mainly in the last 10 readings. There was a high correlation between CCT measurements with both systems with and without cycloplegia (r(2)>0.93), with the US system giving higher values. Differences were significant (P< .001), but not consistent, throughout the range of corneal thicknesses and were greater for thicker corneas. Differences in ACD and LT measurements were similar. Agreement between systems in ACD and LT measurements was considerably lower than for CCT measurements.

CONCLUSIONS

The PCI biometer provided precise CCT measurements. The ACD and LT measurements had a higher variance. Differences in CCT measurements between the 2 systems were greater for thicker corneas, with higher values with the US system.