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C. S. Chiu, Y. Han; Comparison of Partial Coherence Interferometry and Immersion A-Scan Ultrasound for Intraocular Lens Calculation. Invest. Ophthalmol. Vis. Sci. 2008;49(13):397.
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(1) To compare the axial length measured by using immersion A-scan ultrasound and partial coherence interferometry. (2) To compare the accuracy in predicting postoperative refractive error determined by each method.
Axial length was measured in 32 cataractous eyes in 23 patients by using partial coherence interferometry (IOLMaster, Zeiss) and immersion ultrasound, and the results were compared. The Holladay IOL power calculation formula was used to select the intraocular lens in each case. Postoperative refraction was performed one month after surgery. The spherical equivalent was then calculated and compared to the predicted refractive error based on axial length measurements taken from the two methods.
Although axial length measurements obtained by immersion ultrasonography and partial coherence interferometry are highly correlated (R square= 0.99, p value <0.001), on average partial coherence interferometry measured longer axial length by 0.266 mm than immersion ultrasound (axial length from immersion ultrasonography = 1.009 x axial length from partial coherence interferometry - 0.266). The percentage of the eyes within +/- 0.5 diopter of predicted refractive error were 60.0% by using partial coherence interferometry and 43.8% by using immersion A-scan ultrasound (p value = 0.001)
In contrast to previous studies1, we found that the partial coherence interferomentry measures axial length more accurately than does immersion A-scan ultrasound. Using partial coherence interferometry significantly improves the ability to predict postoperative refractive error.Reference:1. Packer M, Fine IH, Hoffman RS, et al. Immersion A-scan compared with partial coherence interferometry: outcomes analysis. J Cataract Refract Surg. 2002;28:239-42.
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