Biometry of cataractous eyes using partial coherence interferometry

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Abstract
Purpose: To evaluate the clinical feasibility of the prototype version of a commercial partial coherence interferometry instrument (axial length measurement, ALM, Carl Zeiss Jena) for noninvasive, high-precision biometry in cataractous eyes. Setting: Department of Ophthalmology, Vienna General Hospital, and Institute of Medical Physics, University of Vienna, Austria. Methods: The preoperative axial length in 49 eyes of 37 cataract patients was measured with the commercial (ALM) and laboratory (PCI) prototypes of the partial coherence interferometry instrument, as well as with immersion ultrasound (IUS). Results: Axial length measurements with the ALM and PCI did not differ significantly ( P = .23). Both prototypes assessed longer axial lengths than the IUS technique ( P < .0001; median 203 μm; range −476 to +635 μm). The precision of the axial length measurement was 18 μm, 28 μm, and 54 μm with the PCI, ALM, and IUS, respectively. Conclusions: Partial coherence tomography is a high-precision, high-resolution, noncontact biometric technique.The commercial PCI prototype is practical in clinical use, with improved comfort for patients, no need for anesthesia, and a reduced risk of infection. However, the difference between the PCI and IUS in axial length measurement must be considered when using the constants supplied by intraocular lens (IOL) manufacturers for IOL power calculations.