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M. Tang, Y. Li, D. Huang; Intraocular Lens Power Calculation Based on Fourier-Domain Optical Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2010;51(13):5692.
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To calculate intraocular lens (IOL) power using corneal power measured by Fourier-domain optical coherence tomography (FD-OCT) and assess its performance in cataract patients who had previous laser vision correction (LVC).
Cataract patients with prior LVC were enrolled in the prospective observational study. An FD-OCT (RTVue) was used to measure net corneal power (OCT-K). The corneal power was also measured by automated keratometry (Auto-K by IOL-Master), clinical history (CH-K), rigid contact lens overrefraction (CL-K). The corneal powers were plugged into standard theoretic formulae (SRK/T, Hoffer Q, Holladay II). The formulae prediction was compared with the one-month postoperative manifest refraction spherical equivalent (MRSE). The accuracy of the IOL calculation was assessed by the prediction error, which is equal to predicted MRSE minus the postoperative MRSE. The primary outcome measure was the mean absolute error (MAE), which is the absolute value of the prediction error.Wilcoxon rank-sum non-parametric test to compare the MAEs.
Twenty-seven cataract patients (34 eyes) were enrolled. Of these, 11 patients (13 eyes) had uncomplicated surgery with monofocal IOL implantation and completed study measurements. The previous LVC correction was -7.03 ± 2.99D (mean standard deviation) with a range of -12.46D to -3.75D. Using the best among the 3 standard IOL formulae (Table 1), OCT corneal power measurement provided more accurate IOL power calculations than the other methods(Auto-K, p = 0.069; CL-K, p = 0.026; CH-K p = 0.047).Table 1. Prediction Error for IOL Calculation by Formula and Method of Corneal Power Measurement
In post-myopic LVC eyes, corneal power measured by OCT was more accurate than that measured by contact lens overrefraction and clinical history. This provided for more accurate IOL power calculation using standard theoretic formulae. Furthermore, OCT directly measures posterior corneal power and does not rely an assumed keratometric index (unlike Auto-K), a complete clinical record (unlike CH-K), or good preoperative vision (unlike CL-K).
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