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D. Epstein, P. Vinciguerra; The Use of Mean Pupillary Power for Iol Calculations in Pathological Corneas. Invest. Ophthalmol. Vis. Sci. 2007;48(13):3528.
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© ARVO (1962-2015); The Authors (2016-present)
To determine whether the use of mean pupillary power, as measured in corneal topography, can substantially increase the predictability of postoperative refraction after intraocular lens (IOL) implantation in eyes with pathological corneas.
In eyes with abnormally steep corneas, irregular astigmatism, keratoconus, pellucid marginal degeneration, and after corneal refractive surgery, IOL power was calculated using standard keratometry (4 measurement points) and topographic mean pupillary power (about 4000 real data points). Normal corneas were also included in the study for comparison purposes. IOLs were selected on the basis of plugging the mean pupillary power into the IOL power calculation formula. A separate calculation was made with the standard keratometry values. The two predicted postoperative refractions were then compared with the effective postoperative refraction obtained, in order to determine which IOL power came closest to the refraction aimed for.
In the presence of normal corneas (and normal axial lengths), the differences between the two calculation methods with respect to the IOL power were on average within 0.50D, although they ranged up to 1.50D. Abnormally steep corneas showed differences up to 3.0D in the recommended IOL power, irregular astigmatism up to 3.50D, keratoconus up to 18.0D, and pellucid marginal degeneration up to 2.50D. After corneal refractive surgery differences in the recommended IOL power ranged from 1.50D to 6.50D. (Topography maps will be used to illustrate each of these categories of pathological corneas.) In all eyes the IOL power obtained from the formula using the mean pupillary power gave a significantly closer approximation of the postoperative refraction aimed for than the calculations using standard keratometry values.
Mean pupillary power, derived from corneal topography, appears to be substantially more reliable than standard keratometry when calculating IOL power in pathological corneas.
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