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Cataract extraction is often combined with the implantation of intraocular lens (IOL) with the diopter matching the operated eye to restore optimal visual function after surgery.However, there are often errors between the actual refractive power of the operated eye and the predicted value.One of the major causes of postoperative refractive error is the change in IOL position compared with the expected position.In order to improve the accuracy of postoperative refraction prediction, Holladay proposed to introduce the concept of effective lens position (ELP) into the IOL diopter calculation formula.The differences in the parameters and algorithms incorporated in the calculation of ELP lead to differences in the accuracy of IOL calculation formulas.With the application of multi-parameter calculation methods, especially the formula based on the artificial intelligence algorithm, the accuracy of IOL calculation formula has been significantly improved.ELP is also affected by various factors such as differences in ocular anatomy, IOL design and material, and surgical procedures, especially the factors affecting the stability of the capsular bag that increase the difficulty of accurately predicting ELP.Therefore, the changes in postoperative ELP need to be further discussed in order to obtain more accurate postoperative refraction.This article aimed to give a review of the development of calculation formulas and the influencing factors of ELP.
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AIM: To measure the changes of ocular biological parameters before and after phacoemulsification, and compared the choice of intraocular lens(IOL)power calculation formulas based on the new optical biometric instrument IOL Master 700.METHODS: A prospective study. Clinical data were collected from 52 patients(57 eyes)with cataract at the First Affiliated Hospital of Soochow University from January to June 2021. The axial length(AL), anterior chamber depth(ACD)and corneal curvature(Km)were measured and analyzed before and 3mo after phacoemulsification by IOL Master 700. The target refractive value reserved in the calculation of different IOL formulas and the actual refractive value of the automatic refractor 3mo after phacoemulsification were compared and statistically analyzed.RESULTS: The average values of AL measured before and after phacoemulsification were 24.20±1.86, 24.09±1.86mm, the postoperative AL shortened by 0.11mm, and the ACD values were 3.08±0.44, 4.55±0.36mm(P<0.001), ACD deepened by 1.49mm after phacoemulsification. The Km values were 44.14±1.86, 44.14±1.82D(P>0.05). The refractive error of the results measured by the Barrett Universal Ⅱ formula was the smallest before operation, followed by Holladay Ⅱ and the SRK/T formula, the Holladay Ⅰ formula had the largest error and the difference was statistically significant(P<0.05). CONCLUSION: The AL was shortened and the ACD was deepened after phacoemulsification. A correction factor of 0.1mm is suggested to add when calculating the degree. The Barrett Universal Ⅱ formula has the best predictability in the IOL power calculation formulas, follow by Holladay Ⅱ and SRK/T formula.
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Cataract with high myopia is a kind of complicated cataract with highly blinding disease. Surgery has always been the only treatment, but there is always a difference between actual postoperative refraction and target refraction. The cataract patients with high myopia have increasing demands for postoperative refractive status and visual quality now. The intraocular lens(IOL)calculation formulas have been updating for higher predictive accuracy. A variety of alternative IOL calculation formulas can be applied to clinical practice. However, there is no consensus on the selection of a more suitable formula for cataract patients with high myopia. Based on the principles and clinical application of different formulas, this paper reviews the development of IOL calculation formulas and research progress of IOL calculation formulas for cataract patients with high myopia, in order to provide reference for clinical application.
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@#With the progress in refractive cataract surgery, the refractive effects after cataract surgery are more accurate and predictable. Various types of intraocular lens have been applied to clinical practice and there is an increasingly higher demand on the precision of intraocular lens(IOL)calculation formula. According to calculation principles and different parameters required, this article aims to give a review on the research progress of IOL calculation formula.
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@#High myopia is one of the major blinding diseases in China and even in the world, and high myopia with cataract is a kind of complex cataract with a high risk of blindness. At present, surgery is the only treatment. Because high myopia can lead to a series of complex changes in the eye, compared with the normal axial eye, it is easier to produce the refractive error and refractive drift after surgery. In this paper, the influencing factors of refractive error after cataract surgery for high myopia are reviewed, including the accuracy of preoperative biological measurement, the choice of intraocular lens calculation formula, and the change of effective intraocular lens position.
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Purpose: Our study was conducted to evaluate and compare the accuracy of the refractive prediction determined by the calculation formulas for different intraocular lens (IOL) powers for high myopia. Methods: This study reviewed 217 eyes from 135 patients who had received cataract aspiration treatment and IOL implantation. The refractive mean numerical error (MNE) and mean absolute error (MAE) of the IOL power calculation formulas (SRK/T, Haigis, Holladay, Hoffer Q, and Barrett Universal II) were examined and compared. The MNE and MAE at different axial lengths (AL) were compared, and the percentage of every refractive error absolute value for each formula was calculated at ±0.25D, ±0.50D, ±1.00D, and ±2.00D. Results: In all, 98 patients were recruited into this study and 98 eyes of them were analyzed. We found that Barrett Universal II formula had the lowest MNE and MAE, SRK/T and Haigis formulas arrived at similar MNE and MAE, and the MNE and MAE calculated by Holladay and Hoffer Q formula were the highest. Barrett Universal II formulas have the lowest MAE among different AL patients, whereas it reached the highest percentage of refractive error absolute value within 0.5D in this study. The MAE of each formula is positively correlated with AL. Conclusion: Barrett Universal II formula rendered the lowest predictive error compared with SRK/T, Haigis, Holladay, and Hoffer Q formulas. Thus, Barrett Universal II formula may be regarded as a more reliable formula for high myopia.
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The purpose of cataract surgery has been raised from blindness prevention to refractive correction.As the quality of IOL impacts postoperative refractive outcomes,IOL plays a vital role in the surgery.Besides,the choice of calculation formulas of IOL influences the quality of IOL.Accordingly,this article aims to give a review on the latest research progress of IOL calculation formulas.
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Objective To clarify the effects of intraocular pressure (IOP) on the selection of intraocular lens (IOL) calculation formulas for cataract and glaucoma surgery in order to provide reference for avoiding refractive error (RE) in clinical.Methods The clinical data of 72 patients (80 eyes) with primary angle-closure glaucoma (PACG) and cataract undergoing combined cataract and glaucoma surgery in our department were enrolled from May 2015 to April 2017.The subjects were divided into normal IOP (10-21 mmHg,1 kPa =7.5 mmHg,n =28) and high IOP group (＞ 21 mm-Hg,n =52) based on preoperative mean IOP.Then the differences between the postoperative actual spherical equivalence (PASE) measured 3 months after operation and the predicted preoperative spherical equivalence (PPSE) of 4 kinds of IOL calculation formulas by IOL Master (SRK/T,Holladayl,Hoffer Q,and Haigis) were compared so as to evaluate the effects of IOP on the postoperative absolute refractive error (ARE) and refractive error (RE) of IOL formulas.Results The postoperative IOP for 3 months of all patients was significantly lower than that of preoperative data(t =9.96,P =0.000),and the decrease level was positively correlated with preoperative mean IOP (r =0.974,P =0.000).There were significant differences in the median ARE from SRK/T,Holladayl,Hoffer Q and Haigis formula in the normal and high IOP groups (P =0.008,0.004),while there was no significant difference in RE (RE ＞ 0) from SRK/T,Holladayl,Hoffer Q and Haigis formulas between the two groups (P =0.633,0.422).In the normal IOP group,there was significant difference in RE (RE ＜ 0) from the four formulas (P =0.000),and LSD comparison showed that the SRK/T formula had the smallest RE (all P＜0.01),and Haigis formula had the largest RE than the other formulas (all P ＜ 0.05).In the high IOP group,there was significant difference in RE (RE ＜ 0) from the four formulas (P =0.000),and LSD comparison showed that the Hoffer Q formula had the smallest RE (all P ＜ 0.01),and there was no significant difference in RE from other formulas (all P ＜ 0.05).Conclusions Combination of cataract and glaucoma surgery can improve visual acuity and intraocular pressure in patients,and the decreased level of postoperative IOP is positively correlated with preoperative mean IOP.As for calculation of the degree of IOL,the SRK/T formula shows a good accuracy when preoperative mean IOP is normal,and Hoffer Q formula should be chosen for patients with high preoperative mean IOP.
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Abstract?AIM: To investigate the effect of pupillary dilation on intraocular lens power calculation.?METHODS: This prospective study included 52 eyes of 45 patients diagnosed with cataract and indicated for phacoemulsification with intraocular lens ( IOL ) implantation at the Faculty of Medicine of Mersin University. For each patient, preoperative corneal topography, autokeratometric measurements and biometric measurements were performed before and after pupil dilation.?RESULTS: Kh ( horizontal ) values obtained through autokeratometry and anterior chamber depth measured by biometric ultrasonography were significantly greater when pupils were dilated compared with values obtained when pupils were undilated. Implanting IOLs with power calculated using measurements taken during pupillary dilation resulted in a significantly higher rate of emmetropia. Comparison of emmetropic eyes and ametropic eyes showed significantly larger anterior chamber depth in emmetropic eyes.? CONCLUSION: Keratometric and biometric measurements are more important in IOL power calculation than the formula used. If biometric ultrasonography is performed using contact technique, care must be taken to avoid corneal compression. Anterior chamber depth should be followed during measurement, and the margin of error can be minimized by using the highest value obtained in IOL power calculation.