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First Author: V.De Juan SPAIN
Co Author(s): R. Martin V. Garcia C. Garcia I. Perez G. Rodriguez J. Herreras
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The accurate calculation of intraocular lens (IOL) power is essential to achieve the desired refractive outcomes after cataract surgery. The overall accuracy depends on some factors such as axial length (AL), corneal power or postoperative IOL position. The purpose of the study was to determine the intraocular lens position (ILP) after uncomplicated cataract surgery by means slit-scan topography and its relationship with preoperatively factors such as AL, anterior chamber depth (ACD) and automated spherical refraction and the refractive outcome after surgery.
IOBA-Eye Institute and Department of Physics TAO, School of Optometry, University of Valladolid, Valladolid, Spain.
This was a prospective, non-randomized, and open label study that included 3 visits by patients undergoing cataract surgery. Before surgery, the AL for the designated surgical eye was measured using partial coherence interferometry (PCI) (IOLMaster V.5; Carl Zeiss Meditec) by experienced practitioners. Preoperative spherical refraction was conducted by means automated refraction (ARK-30, Nidek, Nidek Co., LTD) and ACD was measured with slit-scan topography (Orbscan II, Bausch & Lomb). Inclusion criteria were uneventful cataract surgery and follow-up. A single experienced surgeon performed all procedures with the same technique and type of intraocular lens (SN60WF, Alcon Laboratories). ILP measured from corneal apex (ILPa) and measured from corneal endothelium (ILPe) and corneal pachymetry were monitored one day (V2) and one month (V3) after surgery by means Orbscan II. Refractive outcome was measured 1 month after surgery by the same experienced optometrist. Descriptive statistics included means, standard deviations (DS) and 95% confidence intervals (95%CI). Differences in ILP between visits were detected with one-way ANOVA and Games and Howell test for pairwise comparisons. Relationship with different parameters was conducted by Pearson correlation coefficient. P<0.05 were statistically significant.
153 eyes (mean age 69.53ḟ12.94 years, 95%CI 67.39 to 71.18) were scheduled for cataract surgery and included in this study. Before surgery, mean AL was 24,91ḟ3,03mm (95%CI 24,44 to 25,38) and ACD was 2.73ḟ0.43 mm (95%CI 2.66 to 2.79). Mean automated spherical refraction was -2.41ḟ5.95 D (95%CI -3.34 to -1.49). One month after surgery, mean subjective spherical refraction was 0.13ḟ0.69 D (95%CI 0.13 to 0.69). Corneal pachymetry before surgery was 497.28ḟ15.29 ṁm (95%CI 474.27 to 520.30) and changed significantly one day [622.56ḟ10.83 ṁm (95%CI 606.25 to 638.87, p<0.05] and one month after surgery [548.62ḟ4.06 ṁm (95%CI 542.50 to 554.73, p<0.05]. Mean difference between V1-V2 was 12.53 ṁm and V2-V3 was 7.40 ṁm. The change in ILPa was not significantly different between postsurgical visits [mean ILPa V2 4.57ḟ0.78 mm (95%CI 4.45 to 4.68), mean ILPa V3 4.51ḟ0.44 mm (95%CI 4.44 to 4.57)], mean difference V2-V3 was 0.06 mm, p=0.657. Besides, ILPe showed a smaller difference between postsurgical visits (0.01 mm, p=0.976) than ILPa [mean ILPe V2 3.94ḟ0.79 mm (95%CI 3.82 to 4.06), mean ILPe V3 3.96ḟ0.44 mm (95%CI 3.89 to 4.02)]. No lineal correlation was found between the change in ILP and AL (r=0.115), ACD (r=0.191) or refraction (r=0.155).
There are not statistically significant differences in intraocular lens position between one day and one month after uncomplicated cataract surgery, although the mean difference is smaller measured from corneal endothelium than corneal apex. Changes in corneal pachymetry are very similar to changes in intraocular lens position from corneal apex, so this difference could be due to corneal swelling instead of a movement of the intraocular lens. Besides, no relation was found with axial length, anterior chamber depth or refraction.