Intraocular Lens Power Calculation Formulas Research Articles

Quantitative biometric cutoffs for the choice of the intraocular lens power calculation formula for a recently introduced nondiffractive extended depth-of-focus intraocular lens.

This study aimed to analyze biometry values cutoffs for the choice of the best intraocular lens power calculation formula for AcrySof IQ Vivity intraocular lens. The study was designed as interventional case series with 3 months of follow-up. Intraocular lens power calculation formulas included Barrett Universal II and SRK/T. The first was adopted for the intraocular lens power choice. The quantitative analysis focused on the identification of specific biometric cutoffs considering axial length, anterior chamber depth, and corneal powers. We included only the dominant eye in the statistical analysis. One hundred and eight eyes of 54 patients (23 males; mean age 62 ± 5 years) with no ocular diseases were included. Best-corrected visual acuity improved from 0.3 ± 0.2 to 0.0 ± 0.0 logMAR. All the eyes reached spectacles-free far and intermediate visions; a spherical addition of + 1.0D was necessary to adjust near vision. We identified significant quantitative cutoffs based on axial length and anterior chamber depth. Barrett Universal II resulted the best formula for eyes disclosing an axial length >25 mm, whereas SRK/T turned out to be the best choice for the eyes characterized by an anterior chamber depth <2.8 mm. Our analysis disclosed an overall sensitivity of 0.8 and a specificity of 0.7 (p < 0.01). Axial length and anterior chamber depth influence the choice of Barrett Universal II and SRK/T formulas. Quantitative biometric cutoffs may be useful to discriminate the best formula to be adopted.

Accuracy of IOL Power Calculation Formulas for Quadrifocal Acrysof IQ PanOptix TFNT Implantation in Patients With Previous Corneal Refractive Surgery: Comparison of SS-OCT-Based Biometers.

To evaluate the accuracy of intraocular lens (IOL) power calculation formulas from two biometers using swept-source optical coherence tomography for quadrifocal Acrysof IQ Panoptix TFNT IOL (Alcon Laboratories, Inc) implantation in patients with visually significant cataract with previous corneal refractive surgery. This retrospective study comprised 50 eyes from 50 patients with a history of corneal refractive surgery and TFNT IOL implantation. Candidate formulas were Shammas-PL and Barrett True-K in the Argos (Movu, Inc), Barret True-K and Haigis-L in the IOLMaster 700 (Carl Zeiss Meditec AG), and Haigis using the total keratometry (TK) mode in the IOLMaster 700. The main outcome measure was the mean absolute error (MAE) detected at postoperative 6 months. The refractive accuracy was also evaluated as number and percentage of eyes within ±0.25, ±0.50, and ±0.75 diopters (D) of the prediction error. The uncorrected distance and near visual acuity were 0.32 ± 0.34 and 0.46 ± 0.20 logMAR at baseline, and significantly improved to 0.04 ± 0.07 and 0.03 ± 0.06 logMAR at postoperative 6 months (P < .001 for all analysis) with a mean spherical equivalent of -0.20 ± 0.39 D. The MAE was smallest for the Barrett True-K formula in the IOLMaster 700 (0.36 ± 0.26 D) and largest for the Shammas-PL formula in the Argos (0.59 ± 0.37 D). The Barrett True-K formula from both devices showed that 90% of eyes were within ±0.75 D of MAE. The visual and refractive outcomes of TFNT IOL implantation in patients with previous corneal refractive surgery were favorable. The Barrett True-K formula in the IOLMaster 700 showed the best refractive outcome for TFNT IOL implantation. [J Refract Surg. 2021;37(11):836-841.].

Factors affecting prediction error after cataract surgery with implantation of various multifocal IOLs in patients with previous refractive laser surgery.

BackgroundThis study aimed to compare the clinical outcomes of implantation of various multifocal intraocular lenses (mIOLs) and the prediction accuracy of two intraocular lens (IOL) power calculation formulas for eyes that underwent previous corneal refractive surgery.MethodsFour types of mIOLs [TECNIS Symfony (Group I), AcrySof IQ PanOptix (Group II), LENTIS Mplus (Group III), and TECNIS ZLB00 (Group IV)] were used and the IOL power was calculated with the two no-history methods, Shammas-PL and Barrett True-K. Visual acuity and refractive outcomes including manifest refraction, prediction error (PE), absolute error (AE), and median absolute error (MedAE) were evaluated at three months after the cataract surgery.ResultsFor all groups the Barrett True-K formula produced a narrower range of PEs and lower MedAE than Shammas-PL. Eyes of lower predictive accuracy (group B, AE >0.5D) showed weak uncorrected distance visual acuity resulting from myopic refractive error and target refraction when compared to that of higher predictive accuracy (group A, AE ≤0.5 D).ConclusionsTargeting emmetropia using the Barrett True-K, which considers both anterior and posterior corneal curvature is recommended in patients undergoing mIOL implantation with prior corneal refractive surgery. Additionally, history of prior large amount of laser ablation seems to be an important factor related to low predictive accuracy.

Accuracy of Intraocular Lens Power Calculation Formulas in Myopic Eyes with Target Refractions of Emmetropia and Intentional Myopia.

PurposeTo compare the accuracy of the intraocular lens (IOL) power calculation formulas for predicting the postoperative refraction in eyes with a target of emmetropia or intentional myopia.Patients and MethodsThis is a retrospective study conducted at Kobe City Eye Hospital, Kobe, Japan. Fifty eyes of 50 patients with axial myopia who underwent uncomplicated phacoemulsification and single-type IOL implantation for a target of emmetropia (plano to −0.5 D) or intentional myopia (−2.0 D to −3.0 D) were selected. Preoperative ocular biometry was performed using IOLMaster700 in all eyes. Refractive prediction errors of 6 IOL formulas integrated into IOLMaster700 were compared between eyes with a target of emmetropia and intentional myopia.ResultsThe mean numerical errors of SRK/T (Sanders, Retzlaff, and Kraft/theoretical), Holladay 1, Hoffer Q, and Holladay 2 significantly differed between the two groups (p < 0.001, p = 0.008, 0.02, and 0.007, respectively). The values for mean numerical errors in eyes with a target of intentional myopia were smaller, showing relatively myopic outcome, as compared with those in eyes with a target of emmetropia. In eyes with a target of emmetropia, the mean numerical errors of Holladay 1 (p < 0.001, 95% confidence interval [CI]: 0.32 to 0.63), Hoffer Q (p = 0.001, 95% CI: 0.12 to 0.42), and Barrett Universal II (p = 0.007, 95% CI: 0.06 to 0.35) were significantly different from zero (hyperopic trend). Furthermore, in eyes with a target of intentional myopia, the mean numerical error of SRK/T (p = 0.001, 95% CI: −0.61 to −0.17) and Holladay 2 (p = 0.023, 95% CI: −0.43 to −0.04) were significantly different from zero (myopic trend).ConclusionIn patients with axial myopia, some IOL formulas may show a myopic trend in the refractive outcome when targeting intentional myopia as compared to emmetropia.

Accuracy of IOL power calculation formulas in Marfan lens subluxation patients with in-the-bag IOLs and implantation of scleral-sutured single-eyelet modified capsular tension rings.

To investigate the accuracy of intraocular lens (IOL) formulas for the prediction of postoperative refraction in lens subluxation in Marfan syndrome. Eye and ENT Hospital of Fudan University, Shanghai, China. Consecutive retrospective clinical observational case series. 60 eligible eyes with lens subluxation from 39 young patients with Marfan syndrome (8.53 ± 4.38 years) underwent phacoemulsification combined with single-eyelet modified capsular tension ring (MCTR) and IOL implantation. The prediction error values with mean zero out (relative prediction error) and their absolute values (AE) were calculated. Generally, the SRK/T formula with Wang-Koch (WK) adjustment had the lowest median AE at 0.418 diopters (D), and the Holladay 1 with WK adjustment had the lowest mean AE at 0.499 D. The median AE of the other 10 formulas, in order from lowest to highest, were Haigis with WK (0.494 D), Holladay 1 with WK (0.495 D), Hoffer Q with WK (0.508 D), Haigis (0.525 D), T2 (0.542 D), Hoffer Q (0.624 D), SRK/T and Holladay 1 (0.660 D), Super (0.680 D), and Barrett Universal II (0.714 D) formulas. Haigis formula was found to be statistically significantly different from SRK/T, Holladay 1, and Barrett Universal II (all 3 P < .001) but not Hoffer Q (P = .236) formula. The Haigis formula was recommended for young Marfan lens subluxation patients with in-the-bag IOLs and scleral-sutured single-eyelet MCTR implantation. WK adjustments were successful in those cases where the axial length was longer than 25.0 mm.

Advancements in intraocular lens power calculation formulas.

We review recent studies comparing intraocular lens (IOL) formulas with an emphasis on selection of the highest performing formulas based on patient axial length, age, and history of previous corneal refractive surgery. The Barrett Universal II formula based on a theoretical model has consistently demonstrated high accuracy. The Olsen four-factor formula using ray tracing optics and the Hill-RBF calculator using artificial intelligence have also demonstrated good prediction results after being updated. Notably, the Kane formula, incorporating artificial intelligence, has overall shown the best performance for all axial lengths. Although newly developed and updated IOL formulas have improved refractive prediction in patients with short or long axial length eyes or prior history of corneal refractive surgery, these challenging cases still require special consideration. The Barrett True-K formula has shown accurate results regardless of preoperative data in eyes with previous myopic refractive surgery. Advancements in optical biometry and IOL calculation formulas continue to improve refractive outcomes. The clinician can optimize refractive outcomes in the majority of patients with the use of formulas that have shown consistent results and accuracy in several large studies.

Accuracy of intraocular lens power calculation formulas in a steep cornea: A case report

There is no enough knowledge about the accuracy of intraocular lens (IOL) power calculation formulas in steep corneas. This study may be the first one that compares the accuracy of the SRK II formula with Holladay1, Hoffer Q and Haigis formulas in steep corneas. We reported a case of a 60-year-old female, with a cataract in the left eye and with a steep cornea. We used the modern formulas; Holladay1, Hoffer Q and Haigis. The result (+7.0D) was unexpected compared to the manifest refraction and to the IOL power calculated in the right eye using the same formulas which was (+17.0D). We implanted (+12.0D) Sensar 1-piece IOL depending on our clinical experience. The post-operative refraction was (+0.00/-1.75axis106). Postoperative, we used the patient data to find the best formula in this case. We found that the SRK II (A118) result was (+11.5D) and thus this formula was the most accurate in this case. Keywords: SRK II; Holladay1; Hoffer Q; Haigis

Refractive outcomes of second-eye adjustment methods on intraocular lens power calculation in second eye.

To investigate the refractive outcomes of second-eye adjustment (SEA) methods in different intraocular lens (IOL) power calculation formulas for second eye following bilateral sequential cataract surgery. This retrospective consecutive case-series study included 234 eyes from 234 patients who underwent bilateral sequential phacoemulsification and implantation of enVista MX60 in a hospital setting. Postoperative refraction outcomes calculated by standard formulas (SRK/T and Barrett Universal II, BUII) with SEA method were compared with those calculated by an artificial intelligence-based IOL power calculation formula (PEARL DGS) under second eye enhancement (SEE) method. The median absolute error (MedAE), mean absolute error (MAE) and percentage prediction errors (PE) of eyes within ±0.25 diopters (D), ±0.50 D, ±0.75 D and ± 1.00 D were determined. Overall, the improvement in MedAE after SEA was significant for PEARL DGS (p < 0.01), SRK/T (p < 0.001) and BUII (p=0.031), which increased from 74.36, 71.37, and 77.78% to 83.33, 80.34, and 79.49% of eyes within a PE of ±0.50 D, respectively. For first eyes with a medium axial length (22-26 mm), PEARL DGS with SEE had the lowest MedAE (0.21 D). For a first-eye MAE over 0.50 D, SEA method led to significant improvement in the second eye (p < 0.01). Interocular axis length differences exceeding 0.3 mm were associated with weaker effects using SEA in the studied formulas (p > 0.05). Either SEA method with SRK/T and BUII formulas or second-eye enhancement method based on the PEARL DGS formula can improve postoperative refractive outcomes in second eye.

Comparison of the accuracy of six intraocular lens power calculation formulas for eyes of axial length exceeding 25.0 mm

To compare intraocular lens power calculation formulas for eyes longer than 25.0mm in terms of absolute error and the percentages of postoperative emmetropia and hyperopia. The data for myopic patients who underwent uneventful phacoemulsification between October 2015 and June 2019 were reviewed. Intraocular lens power was calculated using Holladay 1, SRK/T, Hoffer Q, Holladay 2, Haigis, and Barrett Universal II formulas. The power of the lens implanted was based on Holladay 2. Three months after phacoemulsification, the refraction was measured, and the mean absolute error was calculated. The percentage of patients with good uncorrected visual acuity and percentage of hyperopic patients for each formula was established. ROC curves with a cut-off point of axial length were drawn for each formula and the area under the curve was evaluated. Seventy patients (81 eyes) whose ocular axial length ranged between 25.01mm and 28.57mm were included. The Barrett Universal II formula achieved the lowest mean absolute error of 0.08±0.08D. Additionally, with the Barrett Universal II, the percentage of patients with good uncorrected visual acuity (81.5%) was the highest, and the percentage of hyperopic patients (4.9%) was the lowest. The Barrett Universal II and Holladay 1 formulas had the largest area under curve (0.764 and 0.718, respectively). 1.The Barrett Universal II formula is recommended for intraocular lens power calculation for eyes with axial length greater than 25.0mm. 2.Considering the ROC curve method, the Barrett Universal II and Holladay 1 formulas appear to be the most appropriate.

Comparison of prediction accuracy of five different biometric formulas

ABSTRACT Objective To compare the performance of Sanders-Retzlaff-Kraft/Theoretical, Hoffer Q, Barrett Universal II, Kane, and Hill-radial basis function formulas to calculate intraocular lens power in eyes with normal axial length, in terms of predicting target refraction by using partial coherence interferometry technology. Methods Phacoemulsification and intraocular lens implantation were performed in 135 eyes of 135 patients with an axial length between 22 and 24.5 mm. Axial length, keratometry, and anterior chamber depth were measured by intraocular lens Master 500. Sanders-Retzlaff-Kraft/Theoretical, Hoffer Q, Barrett Universal II, Kane, and Hill-radial basis function formulas were used for intraocular lens power calculations. The difference between the expected postoperative refraction and the mean absolute prediction error was calculated for each eye. Statistical significance was evaluated at the level of p 0.05). Conclusion The study showed the third-generation (Sanders-Retzlaff-Kraft/Theoretical and Hoffer Q), fourth-generation (Barrett Universal II) and new-generation (Kane and Hill-radial basis function) intraocular lens power calculation formulas had similar performances regarding calculation of intraocular lens power to predict target refraction after phacoemulsification in eyes with normal axial length.

Intraocular lens power calculation formulas accuracy in combined phacovitrectomy: an 8-formulas comparison study

BackgroundOur study aimed to assess and compare the accuracy of 8 intraocular lens (IOL) power calculation formulas (Barrett Universal II, EVO 2.0, Haigis, Hoffer Q, Holladay 1, Kane and PEARL-DGS) in patients submitted to combined phacovitrectomy for vitreomacular (VM) interface disorders.MethodsRetrospective chart review study including axial-length matched patients submitted to phacoemulsification alone (Group 1) and combined phacovitrectomy (Group 2). Using optimized constants in both groups, refraction prediction error of each formula was calculated for each eye. The optimised constants from Group 1 were also applied to patients of Group 2 – Group 3. Outcome measures included the mean prediction error (ME) and its standard deviation (SD), mean (MAE) and median (MedAE) absolute errors, in diopters (D), and the percentage of eyes within ± 0.25D, ± 0.50D and ± 1.00D.ResultsA total of 220 eyes were included (Group 1: 100; Group 2: 120). In Group 1, the difference in formulas absolute error was significative (p = 0.005). The Kane Formula had the lowest MAE (0.306) and MedAE (0.264). In Group 2, Kane had the overall best performance, followed by PEARL-DGS, EVO 2.0 and Barrett Universal II. The ME of all formulas in both Groups 1 and 2 were 0.000 (p = 0.934; p = 0.971, respectively). In Group 3, a statistically significant myopic shift was observed for each formula (p < 0.001).ConclusionSurgeons must be careful regarding IOL power selection in phacovitrectomy considering the systematic myopic shift evidenced—constant optimization may help eliminating such error. Moreover, newly introduced formulas and calculation methods may help us achieving increasingly better refractive outcomes both in cataract surgery alone and phacovitrectomy.

Optimal Dataset Sizes for Constant Optimization in Published Theoretical Optical Formulae

ABSTRACT Purpose: To determine the optimal number of data points required for optimization of formulae for classical lens power calculation. Methods: A large dataset of preoperative biometric values was used to assess the convergence of formula constants in a number of established intraocular lens power calculation formulae. Results: In formulae with a single constant, 80–100 clinical data points are sufficient to obtain convergence. The Haigis formula (three constants) requires 200–300 data points although refractive error converges more rapidly. Conclusions: In all formulae, 80–100 clinical data points are sufficient to achieve a stable mean refractive error.

Algorithmic intraocular lens power calculation formula selection by keratometry, anterior chamber depth and axial length.

PurposeTo compare the prediction accuracy of algorithmic intraocular lens (IOL) power calculation formula selection method using conventional formulas (Haigis, Hoffer Q, Holladay 1, SRK/T and/or Barrett Universal II) based on keratometry (K), anterior chamber depth (ACD) and axial length (AL).MethodsA total of 1653 patients (1653 eyes) implanted with Tecnis ZCB00 IOL during cataract surgery were enrolled in this study. Intraocular lens (IOL) power calculation formulas with a small absolute value in the sum of the area under the curve measured by K, ACD and AL subgroup were selected to calculate IOL power in the relevant biometry subgroup. The median absolute error (MedAE) calculated by the Haigis, Hoffer Q, Holladay 1, SRK/T and Barrett Universal II formulas individually was compared to that calculated by the algorithmic selection method using four formulas, Haigis, Hoffer Q, Holladay 1 and SRK/T, or five formulas when Barrett is included.ResultsThe MedAE was 0.27 D in the Haigis, 0.30 D in the Hoffer Q, 0.27 D in the Holladay 1, 0.29 D in the SRK/T and 0.26 D in the Barrett Universal II formulas. The MedAEs determined by the algorithmic selection method using four (019 D) and five (0.21 D) formulas were significantly lower than those by the conventional IOL power calculation formulas.ConclusionsThe IOL power calculation formula selection method by biometry subgroup combined with biometric parameters K, ACD and AL may offer a more superior postoperative refractive error prediction in cataract surgery.

Comparison of IOL Power Calculation Formulas for a Trifocal IOL in Eyes With High Myopia.

To analyze the results of new intraocular lens (IOL) formulas (Emmetropia Verifying Optical [EVO], Kane, Olsen, and Barrett Universal II), traditional formulas (Haigis and SRK/T), and modified Wang-Koch axial length adjustment formulas with the SRK/T and Holladay 1 (SRK/Tmodified-W/K and H1modified-W/K) in Chinese patients with long eyes. In this retrospective case series, patients with an axial length of 26 mm or greater having uneventful femtosecond laser-assisted cataract surgery with one trifocal IOL model were enrolled. The actual postoperative spherical equivalent of the manifest refraction was compared with the formula-predicted refraction based on the implanted IOL power. A subgroup analysis was performed based on the axial length. A total of 113 eyes was enrolled. Using User Group for Laser Interference Biometry constants, the modified Wang-Koch formulas had the lowest percentage of eyes with hyperopic outcomes. The Barrett Universal II, Olsen, Kane, and EVO 2.0 formulas produced a statistically lower median absolute error than the SRK/Tmodified-W/K and SRK/T formulas (P < .05). The Barrett Universal II formula produced higher percentages of eyes within ±0.50 diopters (D) of the prediction error than the SRK/T formula (P < .05). In eyes with axial lengths of less than 28 mm, there were no significant differences in the prediction accuracy of the eight formulas. In eyes with axial lengths of 28 mm or greater, the new IOL formulas yielded the lowest median absolute error, followed by the H1modified-W/K and Haigis formulas. The SRK/Tmodified-W/K formula had the highest mean absolute error and the lowest percentages of eyes within ±0.25 and ±0.50 D of endpoint. The traditional formulas yielded the highest risk of refractive surprise. All formulas achieved good results in eyes with axial lengths of less than 28 mm with trifocal IOL implanted. The newer formulas tend to produce better outcomes for eyes with high myopia. The SRK/Tmodified-W/K formula provided improved accuracy only in eyes with axial lengths of 30 mm or greater. [J Refract Surg. 2021;37(8):538-544.].

Clinical Accuracy of 18 IOL Power Formulas in 241 Short Eyes

ABSTRACT Purpose To analyze the accuracy of 18 intraocular lens (IOL) power calculation formulas in eyes with axial length (AL) ≤ 22 mm. Methods We analyzed 241 eyes of 241 patients. Eighteen formulas were evaluated: Barrett Universal II (BUII), EVO 2.0, Haigis, Hoffer Q, Holladay 1 and 2, Cooke K6, Kane, LadasSuperFormula AI, Naeser 2, Olsen, Panacea, Pearl-DGS, RBF 2.0, SRK/T, T2, VRF and VRF-G. Optical biometry was performed with an IOLMaster 700 (Carl Zeiss Meditec, Jena, Germany). With lens constants optimized for the whole range of AL, the mean prediction error (PE) and its standard deviation (SD), the median absolute error (MedAE), the mean absolute error (MAE) and the percentage of eyes with PEs within ±0.25 D, ±0.50 D and <±1.00 D were calculated. Results Post-hoc analysis of the absolute PE revealed statistically significant differences (P < .05) between some of the newer formulas (K6, Kane, Naeser 2, Olsen and VRF-G), which obtained the lowest MedAE (respectively, 0.308, 0.300, 0.277, 0.310 and 0.276 D) and the remaining ones. These formulas yielded also the highest percentage of eyes with a PE within ±0.50 D (70.54%, 72.20%, 71.37%, 70.95% and 73.03%, respectively), whereas Panacea and SRK/T yielded the lowest percentage (62.24%), with a stastically significant difference (P < .05) with respect to most formulas. Conclusion In eyes with AL ≤22.0 mm, new formulas (K6, Kane, Naeser 2, Olsen and VRF-G) offer the most accurate predictions of postoperative refraction.

Clinical Accuracy of 6 Intraocular Lens Power Calculation Formulas in Elongated Eyes, According to Anterior Chamber Depth

To investigate the influence of anterior chamber depth (ACD) on the accuracy of the Kane, EVO 2.0, Barrett Universal II (BU II), Olsen, SRK/T, and Haigis formulas in patients with elongated eyes. Retrospective case series study. A total of 106 patients (106 eyes) diagnosed with high myopia (axial length ≥26 mm) were enrolled and divided into 3 subgroups according to preoperative ACD. Mean refractive error (ME), mean absolute refractive error (MAE), median absolute refractive error (MedAE), and proportions of eyes within ±0.25 D, ±0.50 D, ±0.75 D, and ±1.00 D were calculated. In all patients, the MedAE was lowest for the Kane formula (0.28 D), followed by the BU II (0.34 D). In the shallow ACD subgroup, EVO 2.0 formula produced the lowest MedAE (0.22D), and the highest proportion of eyes within ±0.25 D (58%); the BU II (0.23 D, 50%) and Kane (0.25 D, 50%) formulas produced similar proportions. In the deep ACD group, the MedAEs of the Haigis and SRK/T formulas (0.68 D and 0.50 D, respectively) were significantly higher than those of the EVO 2.0 (0.37 D), Kane (0.30 D), BU II (0.43 D), and Olsen (0.34 D) formulas (P < 0.05). Overall, the Kane and EVO 2.0 formulas had the highest accuracy. EVO 2.0 and BU II formulas are recommended for patients with shallow ACD; the Kane formula is recommended for patients with deep ACD (especially patients with extremely elongated eyes). The SRK/T and Haigis formulas should be avoided as much as possible.

Accuracy of intraocular lens power calculation in primary angle-closure disease: comparison of 7 formulas.

To assess the accuracy of intraocular lens power calculation formulas Barrett Universal II (BUII), Hill-Radial Basis Function (RBF) 3.0, Kane, Ladas Super Formula (LSF), Haigis, Hoffer Q, and SRK/T in primary angle-closure disease (PACD). A total of 129 PACD eyes were enrolled. Prediction refraction was calculated for each formula and compared with actual refraction. Accuracy was determined by formula performance index (FPI), median absolute error (MedAE) and percentage of eyes with a prediction error (PE) within ± 0.50D. Subgroup analysis was performed according to axial length (AL). Overall, FPI was ranked as follows: Kane (0.067), RBF 3.0 (0.064), Haigis (0.062), SRK/T (0.060), BUII (0.058), Hoffer Q (0.055), and LSF (0.049). Kane got the highest (71.3%) percentage of eyes with PE within ± 0.50 D. In medium AL eyes (22mm < AL ≤ 25mm), FPI ranked the same as in total group. MedAEs were equal across all formulas (P = 0.121). In short eyes (AL ≤ 22mm), FPI was Kane (0.055), RBF 3.0 (0.050), SRK/T (0.050), Haigis (0.049), BUII (0.047), Hoffer Q (0.045), and LSF (0.033). MedAEs were significantly different across all formulas (P = 0.033). Haigis showed the lowest MedAE (0.35 D), Haigis and Kane got the highest percentage (63.6%) of eyes with PE within ± 0.50 D. Kane outperformed in total PACD eyes; RBF 3.0, Haigis, and SRK/T achieved satisfying performance. When dealing with PACD eyes shorter than 22mm, Kane achieved the best accuracy. RBF 3.0, SRK/T, Haigis, and BUII achieved comparable outcomes. No formula showed superiority over others for medium AL PACD eyes.

Comparison of the accuracy of intraocular lens power calculation formulas based on the new swept-source optical coherence tomography biometry

Objective: To compare the accuracy of 6 intraocular lens power calculation formulas based on the new swept-source optical coherence tomography biometry and to analyze the prediction error. Methods: Retrospective case series study. Clinical data were collected from 599 patients (599 eyes) who had underwent uncomplicated phacoemulsification and the IOLMaster 700 examination at the Eye Hospital of Wenzhou Medical University between November 2018 and November 2019. Among the patients, there were 208 males and 391 females with an age of (69±10) years. According to the axial length (AL), eyes were divided into the short AL group (≤22.5 mm, n=100), the normal AL group (>22.5 mm and<25.5 mm, n=375); and the long AL group (≥25.5 mm, n=124). Eyes were also grouped based on the mean keratometry (Km) as flat (≤42.00 D, n=47), normal (>42.00 D to<46.00 D, n=461), and steep (≥46.00 D, n=91), and by anterior chamber depth (ACD) as shallow (≤2.5 mm, n=71), normal (>2.5 mm to<3.5 mm, n=436), and deep (≥3.5 mm, n=92). The median absolute errors (MedAEs) of the Barrett Universal Ⅱ, Haigis, Hoffer Q, Holladay Ⅰ, Holladay Ⅱ, and SRK/T formulas in different AL, Km, and ACD groups were compared using the Friedman test. Results: The differences in MedAE among the 6 formulas of 599 patients (599 eyes) were statistically significant (χ²=120.549, P<0.001). The MedAE of the Barrett Universal Ⅱ formula was smallest (0.35 D), followed by the SRK/T formula (0.36 D). There was no significant difference between the MedAEs of the Barrett universal Ⅱ and Haigis, SRK/T formula (all P=1.000), but there were statistically significant differences among the other formulas (all P<0.01). In different AL groups, the MedAE of each formula was statistically different (χ²=38.307, 38.779, 112.997; all P<0.01).The Barrett Universal Ⅱ formula resulted in the lowest MedAE in the short AL group (0.40 D) and the long AL group (0.31 D). The MedAE of the SRK/T in the normal AL group was lowest (0.35 D). The 6 formulas showed significant differences in MedAE values in different Km groups (χ²=12.284, 90.924, 39.387; all P<0.05).The Haigis formula achieved the lowest MedAE in the flat Km group (0.26 D) and the steep Km group (0.34 D). The Barrett UniversalⅡ formula achieved the lowest MedAE in the normal Km group (0.33 D). The differences in MedAE values of the 6 formulas in different ACD groups were statistically significant (χ²=37.389, 57.643, 52.845; all P<0.01), and the MedAE values of the Barrett Universal Ⅱ in different ACD groups were smallest (0.46, 0.33, 0.31 D). Conclusions: The Barrett Universal Ⅱ formula perform the best over the entire AL range, followed by the Haigis and SRK/T formulas. The Barrett Universal Ⅱ formula result in the lowest prediction error in the short AL group, the long AL group, and all ACD groups. The Haigis formula may be more accurate when the Km was ≤42.00 D or ≥46.00 D. (Chin J Ophthalmol, 2021, 57: 502-511).

Nationwide multicentre comparison of preoperative biometry and predictability of cataract surgery in Japan

AimTo compare the preoperative biometric data and the refractive accuracy of cataract surgery among major surgical sites in a nationwide multicentre study.MethodsWe prospectively obtained the preoperative biometric data of 2143...

Determining the Theoretical Effective Lens Position of Thick Intraocular Lenses for Machine Learning-Based IOL Power Calculation and Simulation.

PurposeTo describe a formula to back-calculate the theoretical position of the principal object plane of an intraocular lens (IOL), as well as the theoretical anatomic position in a thick lens eye model. A study was conducted to ascertain the impact of variations in design and IOL power, on the refractive outcomes of cataract surgery.MethodsA schematic eye model was designed and manipulated to reflect changes in the anterior and posterior radii of an IOL, while keeping the central thickness and paraxial powers static. Modifications of the shape factor (X) of the IOL affects the thick lens estimated effective lens position (ELP). Corresponding postoperative spherical equivalent (SE) were computed for different IOL powers (–5 diopters [D], 5 D, 15 D, 25 D, and 35 D) with X ranging from –1 to +1 by 0.1.ResultsThe impact of the thick lens estimated effective lens position shift on postoperative refraction was highly dependent on the optical power of the IOL and its thickness. Design modifications could theoretically induce postoperative refraction variations between approximately 0.50 and 3.0 D, for implant powers ranging from 15 D to 35 D.ConclusionsThis work could be of interest for researchers involved in the design of IOL power calculation formulas. The importance of IOL geometry in refractive outcomes, especially for short eyes, should challenge the fact that these data are not usually published by IOL manufacturers.Translational RelevanceThe back-calculation of the estimated effective lens position is central to intraocular lens calculation formulas, especially for artificial intelligence–based optical formulas, where the algorithm can be trained to predict this value.