Evaluation of Axial Length Measurement of the Eye Using Partial Coherence Interferometry and Ultrasound in Cases of Macular Disease

Abstract

The present study evaluated the accuracy of using partial coherence interferometry (PCI) and ultrasound (US) to measure axial length in eyes with macular disease, the nature of the double peak (DP) in PCI measurements, and the applicability of intraocular lens (IOL) power calculation. Retrospective noncomparative case series. We studied 132 eyes with macular edema, epiretinal membrane, and macular hole in 132 patients who underwent combined cataract and vitrectomy surgery. Axial length was measured using PCI and US. If a DP was observed in the PCI measurement, the posterior peak was used for the IOL calculation. The central retinal thickness (CRT) was measured using optical coherence tomography. Measurements were made of the frequency of DP observation in PCI measurement and the postoperative refractive errors when either PCI or US measurements were applied. A DP was observed in 25 (18.7%) of 132 eyes in the axial length measurement using PCI. There was a significant correlation between the interpeak distance and the CRT (P<0.001, r(2)=0.3869). The 6-month postoperative refractive errors in the DP and single peak (SP) groups were predicted correctly within +/-0.5 diopters in 56.0% (DP) and 61.7% (SP) of the cases and within +/-1.0 diopters in 92.0% (DP) and 92.2% (SP) of the cases. The accuracy of the axial length measurement was similar between PCI and US. Our results suggest that the longer axial length of the DP observed in PCI represents retinal pigment epithelium. If a DP was observed in PCI measurement, application of the longer peak for the IOL calculation resulted in a refractive error similar to that in the SP group.