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      Axial Length Shortening After Cataract Surgery: New Approach to Solve the Question

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          Abstract

          Purpose

          To check if optical biometry can detect eventual corneal power (Km) and axial length (AL) cataract surgery-related changes that could influence the refractive outcome.

          Methods

          Patients scheduled for sequential bilateral cataract surgery between January and September 2017 were included in the present study. One hundred ninety-six eyes of 98 patients (48 males) were selected. Before surgery of the first eye, patients underwent a complete ophthalmic examination, including IOLMaster biometry; the same evaluations were repeated in both eyes the day before the fellow eye cataract surgery, performed at least 2 months after the first one. The differences in Km and AL in the first operated eyes were evaluated, and the fellow eyes were used as controls.

          Results

          Km differences in the operated eyes ranged from −1.97 to +0.98 diopter (D) (mean = −0.02 ± 0.36 D) ( P = 0.89); in the nonoperated eyes they ranged from −0.6 to +0.7 D (mean = 0 ± 0.20 D) ( P = 0.91). The AL differences (pseudophakic option) in the operated eyes ranged from −0.35 to +0.15 mm (mean = −0.10 ± 0.08 mm) ( P < 0.001); with the aphakic option they ranged from −0.24 to + 0.26 mm (mean = 0.01 ± 0.08 mm) ( P= 0.38). In the nonoperated eyes, the AL differences ranged from −0.04 to +0.06 mm (mean= 0 ± 0.02 mm) ( P = 0.02).

          Conclusions

          The modern phaco-technique seems not to induce changes in Km and AL, supporting the hypothesis that the differences in AL are due to an incorrect estimation in pseudophakic eyes.

          Translational Relevance

          The results of our study may improve the AL measurements in pseudophakic eyes.

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          Most cited references27

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          Comparison of immersion ultrasound biometry and partial coherence interferometry for intraocular lens calculation according to Haigis.

          The precision of intraocular lens (IOL) calculation is essentially determined by the accuracy of the measurement of axial length. In addition to classical ultrasound biometry, partial coherence interferometry serves as a new optical method for axial length determination. A functional prototype from Carl Zeiss Jena implementing this principle was compared with immersion ultrasound biometry in our laboratory. In 108 patients attending the biometry laboratory for planning of cataract surgery, axial lengths were additionally measured optically. Whereas surgical decisions were based on ultrasound data, we used postoperative refraction measurements to calculate retrospectively what results would have been obtained if optical axial length data had been used for IOL calculation. For the translation of optical to geometrical lengths, five different conversion formulas were used, among them the relation which is built into the Zeiss IOL-Master. IOL calculation was carried out according to Haigis with and without optimization of constants. On the basis of ultrasound immersion data from our Grieshaber Biometric System (GBS), postoperative refraction after implantation of a Rayner IOL type 755 U was predicted correctly within +/- 1 D in 85.7% and within +/- 2 D in 99% of all cases. An analogous result was achieved with optical axial length data after suitable transformation of optical path lengths into geometrical distances. Partial coherence interferometry is a noncontact, user- and patient-friendly method for axial length determination and IOL planning with an accuracy comparable to that of high-precision immersion ultrasound.
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            Biometry of 7,500 cataractous eyes.

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              Sources of error in intraocular lens power calculation.

              The hypothesis that the minimum error in predicted refraction after implantation of an intraocular lens (IOL) of calculated power is the sum of the random error in (1) the measurement of the axial length, (2) the measurement of the corneal power, and (3) the estimation of the pseudophakic anterior chamber depth (ACD) is proposed. Based on preoperative and postoperative biometry of 584 IOL implantations, 54% of the error was attributed to axial length errors, 8% to corneal power errors, and 38% to errors in the estimation of the postoperative ACD, when a fixed ACD was used in the IOL calculations. However, if the ACD was predicted according to a previously described regression method, the contribution of error from the ACD source was reduced to 22%, thereby reducing the total refractive prediction error from +/- 1.03 diopters (D) (+/- SD) to +/- 0.92 D (+/- SD). These predictions accord with clinical results.
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                Author and article information

                Journal
                Transl Vis Sci Technol
                Transl Vis Sci Technol
                tvst
                Transl Vis Sci Technol
                TVST
                Translational Vision Science & Technology
                The Association for Research in Vision and Ophthalmology
                2164-2591
                November 2018
                27 December 2018
                : 7
                : 6
                : 34
                Affiliations
                [1 ]Department of Medicine and Surgery, University of Salerno, Baronissi, Salerno, Italy
                Author notes
                Correspondence: Giulio Salerno, Department of Medicine, Surgery and Dentistry, University of Salerno, Via Salvador Allende, 84081 Baronissi (SA), Italy. e-mail: giuliosalerno@ 123456hotmail.it
                Article
                tvst-07-06-35 TVST-18-1006
                10.1167/tvst.7.6.34
                6314107
                30619654
                bc8e0567-9603-4629-a5e8-bba11f58a70c
                Copyright 2018 The Authors

                This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

                History
                : 19 July 2018
                : 16 October 2018
                Categories
                Articles

                axial length,cataract surgery,partial coherence interferometry,corneal power

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