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J Erazo, O Baca, R Velasco, L Perdiz, J Ramírez; IOL Power Calculation in Patients with Lasik . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4140.
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Purpose: To make a more accurate calculation IOL (intraocular lens implantation) power in patients with refractive surgery ( LASIK). To make a comparison between the preoperative and postoperative IOL power calculation and compare it with corrected refractive defect. Methods: Thirty patients who underwent LASIK no matter age, gender o refractive defect were included. IOL power calculation was made with 5 different formulas (hoffer, holladay, binkhorst II, SRK II and SRK T) and with 3 different types of keratometric values (optic and topographic keratometries and corneal power by topography) the topographer used was the Humprey Atlas. Thirty calculations were made for each eye with Alcon Ocuscan biometer, patients underwent LASIK with Visx S2 and Chiron Technolas 217 using Hansatome microkeratome. The difference between the preoperative and postoperative IOL calculation was made and compared with the difference of preoperative and postoperative refraction by spherical equivalent (SE) the correlation was made with the pearson´s P Statistical analysis looking for the formula and way of measuring the corneal power and its correlation with the difference of refraction. Results: The range by SE was from 4.5 to -14.37 difference of refraction depending on the ametropia. The SRK II formula had the best correlation with corneal power (P=.9502) followed by the binkhorst formula (P=.9499). There was no significant differences between the different formulas and corneal power values in low refractive defects neither in the preoperative nor in the postoperative calculations. There was a significant difference in the power calculation between formulas in the preoperative as in the postoperative calculation as well as in the different ways of measuring the corneal power in patients with large refractive defects. Conclusion: There is a higher probability of having an underestimated IOL power calculation leading to a large hyperopia after cataract surgery in patients with larger refractive defect before LASIK than those with low defects. The best way by our results is to use SRK II and corneal power by topography to make the IOL calculation in this patients.
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