Wang-Koch formula for optimization of intraocular lens power calculation: Evaluation at a Canadian center

Investigation of the myopic outcomes of the newer intraocular lens power calculation formulas in Korean patients with long eyes

This study investigated the underlying causes of the myopic outcomes of the optic-based newer formulas (Barrett Universal II, EVO 2.0, Kane, Hoffer-QST and PEARL-DGS) in long Korean eyes with Alcon TFNT intraocular lens (IOL) implantation. Postoperative data from 3100 randomly selected eyes of 3100 patients were analyzed to compare the reference back-calculated effective lens positions (ELPs) based on the Haigis formula using conventional axial length (AL) and Cooke-modified AL (CMAL) with the predicted ELP of each single- and triple-optimized Haigis formula applied to AL- and CMAL. Contrary to the AL-applied Haigis formula, the predicted ELP curve of the CMAL-applied, single-optimized Haigis formula, simulating the methods of the newer formulas, exhibited a significant upward deviation from the back-calculated ELP in long eyes. The relationship between the AL and anterior chamber depth in our long-eyed population differed from that in the base population of the PEARL-DGS formula. The myopic outcomes in long eyes appeared to stem from the substantial overestimation of the postoperative IOL position with AL modification, leading to the implantation of inappropriately higher-powered IOLs. This discrepancy may be attributed to the ethnic differences in ocular biometrics, particularly the relatively smaller anterior segment in East Asian patients with long AL.

Does the Difference in Axial Length Affect the Refractive Outcome?

Background

The purpose of this study is to compare axial length (AL) and the refractive outcome after phacoemulsification surgery from 2014 to 2019 at Hospital Sultanah Nur Zahirah, Terengganu, Malaysia.

Method

This was a retrospective record review of all cataract patients who met the inclusion criteria and underwent uneventful superior wound phacoemulsification with nontoric intraocular lens (IOL) by a single surgeon from 2014 to 2019. Using optical biometry or immersion technique, the preoperative AL determined solely via the Sanders, Retzlaff and Kraff 2 (SRK2) formula was selected. The postoperative spherical equivalent (SE) at 6 weeks-12 weeks was retrieved. Using Statistical Package for the Social Sciences version 24.0, the mean differences between targeted and actual postoperative SE were analysed based on the AL.

Result

In this study, 490 eyes of 472 patients aged 25 years old-88 years old (mean age 65.72 years old [SD 8.83]) were involved. There were 162 eyes (33%) in Group A (< 23 mm), 189 eyes (39%) in Group B (23.01 mm-24.0 mm) and 139 eyes (28%) in Group C (> 24.0 mm). The mean AL was 23.63 mm (SD 1.19). The mean differences between the targeted and actual postoperative SE were: -0.09 D (SD 0.60) in Group A, -0.07 D (SD 0.53) in Group B and -0.16 D (SD 0.52) in Group C. No significant difference was found between these groups (P = 0.327).

Conclusion

There was no significant difference in the refractive outcome using the SRK2 formula in different ALs after phacoemulsification surgery. Hence, there is no reason to modify or adjust the targeted SE based on AL.

Choice of intraocular lens calculation formula for cataract patients with prior pars plana vitrectomy

PURPOSE

To determine the optimal intraocular lens (IOL) calculation formula for vitrectomized eyes with diverse surgical and biometric characteristics.

SETTING

Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China.

DESIGN

Retrospective consecutive case series study.

METHODS

This study included 974 vitrectomized eyes (974 patients) scheduled for phacoemulsification with IOL implantation. 11 formulas were evaluated: Barrett Universal II (BUII), Emmetropia Verifying Optical, Hoffer-QST, Kane, Ladas Super Formula, Pearl-DGS, Radial Basis Function (RBF), Haigis, HofferQ, Holladay1, and SRK/T. Risk factors for prediction error (PE) exceeding 1 diopter (D) were determined using multiple logistic regression. Subgroup analyses were performed based on surgical history and biometric parameters.

RESULTS

The risk of hyperopic PE (>1 D) was higher in patients with silicone oil tamponade (odds ratio [OR], 1.82) and longer axial length (AL) (OR, 1.55), while patients with previous scleral buckling (OR, 2.43) or ciliary sulcus IOL implantation (OR, 6.65) were more susceptible to myopic PE (<-1 D). The Kane formula had the highest overall prediction accuracy, and also the best in silicone oil-filled eyes and the flat cornea subgroup. The BUII and RBF displayed the optimal performance in eyes with previous scleral buckle and steep cornea, respectively. In eyes with an AL ≥ 26 mm, the Holladay1 with the nonlinear version of the Wang-Koch AL adjustment (Holladay1-WKn) showed the lowest absolute PE and highest percentage within ± 1.0 D of PE.

CONCLUSIONS

The Kane achieved the highest overall prediction accuracy in vitrectomized eyes. The optimal formula for eyes with previous scleral buckle, steep cornea, or long AL was BUII, RBF, and Holladay1-WKn, respectively.

Cataract surgery in myopic eyes

PURPOSE OF REVIEW

We discuss the preoperative, intraoperative, and postoperative considerations for cataract surgery in eyes with high myopia. We also reviewed the recent literature on refractive outcomes and complications of cataract surgery in myopic eyes.

RECENT FINDINGS

Several novel intraocular lens (IOL) power calculation formulas have recently been developed to optimize refractive outcomes. Haigis formula is the most accurate among the third-generation IOL formulas. Novel formulas such as Barrett Universal II, Kane, and modified Wang-Koch adjustment for Holladay I formula provide a better refractive prediction compared with old formulas. Intraoperatively, the chopping technique is preferred to minimize pressure on weak zonules and reduce the incidence of posterior capsule rupture. Anterior capsular polishing is recommended to reduce the risk of postoperative capsular contraction syndrome (CCS). Postoperatively, complications such as refractive surprises, intraocular pressure spikes, and CCS remain higher in myopic eyes. Only 63% of myopic patients with axial length more than 26 mm achieve a visual acuity at least 20/40 after cataract surgery, mainly because of coexisting ocular comorbidities.

SUMMARY

There are multiple preoperative, intraoperative, and postoperative considerations when performing cataract surgery in myopic eyes. Further research is needed to optimize the refractive outcomes in these eyes and determine the best IOL formula. Surgeons should be adept and knowledgeable with different techniques to manage intraoperative complications.

Comparative analysis of visual quality between unilateral implantation of a trifocal intraocular lens and a rotationally asymmetric refractive multifocal intraocular lens

AIM

To compare visual quality after unilateral cataract surgery with implantation of trifocal intraocular lens (IOL) and asymmetric refractive multifocal IOL.

METHODS

The prospective nonrandom, comparative study consisted of 60 eyes of 60 patients suffering unilateral cataract surgery with implantation of two different IOLs: AT LISA tri 839MP (30 eyes; Carl Zeiss Meditec, Germany) and LS-313 MF30 (30 eyes; Oculentis GmbH, Germany). Visual acuity, refractive outcome, contrast sensitivity, defocus curves, quality of vision, and optical phenomena were evaluated at 3mo postoperatively.

RESULTS

There were no statistical differences between groups in uncorrected distance visual acuity (P=0.13) and uncorrected near visual acuity (P=0.54). In contrast, uncorrected intermediate visual acuity was better in trifocal group compared to the refractive multifocal group (P=0.02). No significant statistical between-group difference was detected in cylinder (P=0.43). Compared to trifocal group, spherical refraction and spherical equivalent in refractive multi focal group were more myopic (P<0.01). Under photopic conditions, no significant statistical differences were found between groups in contrast sensitivity at 3 and 6 cycles per degree (cpd). The refractive multifocal group performed better at 12 and 18 cpd than the trifocal group (P=0.01, P=0.034, respectively). The questionnaires of quality of vision and optical phenomena showed no differences between groups.

CONCLUSION

Trifocal IOL is superior to refractive multifocal IOL in intermediate visual acuity. Rotationally asymmetric refractive multifocal IOL is more myopic in automated refraction and significantly better for the photopic contrast sensitivity at high frequency.

Autorefraction as an Objective Method to Evaluate Accuracy of Intraocular Lens Calculation Formulas

PURPOSE

To compare the spherical equivalent (SE) and astigmatic prediction error between subjective refraction (SUBref) and autorefraction (AUTOref) after cataract surgery to determine whether the latter is useful as an objective method to compare the accuracy of different methods of intraocular lens (IOL) power calculation.

METHODS

Postoperative refraction was examined using two techniques: SUBref and AUTOref. The results of these two techniques were compared. Predicted postoperative refraction for spherical outcome was calculated with the Barrett Universal II (BUII), Haigis, Holladay I, SRK/T, Hoffer Q, and BUII with measured posterior corneal astigmatism (MPCA) formulas. Predicted postoperative refraction for astigmatic outcome was calculated with the Barrett Toric calculator, vergence-based toric calculator using the Holladay 1 formula for effective lens position, and Barrett Toric calculator MPCA formulas. Formula accuracy and ranking were compared between the two methods of refraction.

RESULTS

Data were obtained from 219 eyes of 155 patients. Statistically significant differences were detected between SUBref and AUTOref for SE, J₀, and J₄₅ (P < .001). The spherical outcome formula analysis demonstrated no significant differences, whereas the predicted cylinder power analysis demonstrated significant differences within individual formulas between SUBref and AUTOref measures. The lowest median absolute error and the highest percentage of eyes achieving their refractive target for both SUBref and AUTOref were achieved with the BUII formula and the Barrett Toric calculator.

CONCLUSIONS

AUTOref is a useful method with adequate accuracy to determine spherical and astigmatic outcome and equally or more effective in being able to discriminate between spherical outcome formulas. The AUTOref method can allow valuable studies to be conducted in less-than-optimal environments and provides the ability to compare studies without the confounding factors of SUBref. [J Refract Surg. 2022;38(9):580-586.].

Investigating the Prediction Accuracy of Recently Updated Intraocular Lens Power Formulas with Artificial Intelligence for High Myopia

The aim of this study was to investigate the prediction accuracy of intraocular lens (IOL) power formulas with artificial intelligence (AI) for high myopia. Cases of highly myopic patients (axial length [AL], >26.0 mm) undergoing uncomplicated cataract surgery with at least 1-month follow-up were included. Prediction errors, absolute errors, and percentages of eyes with prediction errors within ±0.25, ±0.50, and ±1.00 diopters (D) were compared using five formulas: Hill-RBF3.0, Kane, Barrett Universal II (BUII), Haigis, and SRK/T. Seventy eyes (mean patient age at surgery, 64.0 ± 9.0 years; mean AL, 27.8 ± 1.3 mm) were included. The prediction errors with the Hill-RBF3.0 and Kane formulas were statistically different from the BUII, Haigis, and SRK/T formulas, whereas there was not a statistically significant difference between those with the Hill-RBF3.0 and Kane. The absolute errors with the Hill-RBF3.0 and Kane formulas were smaller than that with the BUII formula, whereas there was not a statistically significant difference between the other formulas. The percentage within ±0.25 D with the Hill-RBF3.0 formula was larger than that with the BUII formula. The prediction accuracy using AI (Hill-RBF3.0 and Kane) showed excellent prediction accuracy. No significant difference was observed in the prediction accuracy between the Hill-RBF3.0 and Kane formulas.

Comparison of Formula-Specific Factors and Artificial Intelligence Formulas with Axial Length Adjustments in Bilateral Cataract Patients with Long Axial Length

Introduction

To evaluate and compare the effectiveness for reducing the prediction error (PE) of the second eye using formula-specific factors, artificial intelligence (AI) formulas (PEARL-DGS and Kane), and the Cooke-modified axial length (CMAL) methods in bilateral cataract patients with long axial length (AL).

Methods

A total of 98 patients with long AL who underwent sequential bilateral cataract surgeries were retrospectively enrolled. The second-eye IOL power was calculated by the formula-specific factors, AI formulas, and CMAL methods when the first eye suffered from refraction surprise. The correction factors of eight formulas were calculated by regression analysis.

Results

There was a significant correlation between bilateral preoperative biometric parameters (P < 0.05) as well as bilateral PE (P < 0.05). The Kane formula displayed the lowest median absolute error (MedAE) and highest proportion of PE within ± 0.50 and ± 1.00 D compared with other formulas for the first eye. For the second-eye refinement, all three methods could reduce the second-eye MedAE. The formula-specific correction factors were 0.250, 0.331, 0.343, 0.394, 0.409, 0.452, 0.503, and 0.520 for Kane, Barrett Universal II (BUII), PEARL-DGS, Holladay 2, Holladay 1, Haigis, Hoffer Q, and SRK/T, respectively. The new AI-based Kane and PEARL-DGS with or without the CMAL methods could improve the refractive outcomes of the second eye in sequential bilateral cataract patients with long AL. The Kane, BUII, and PEARL-DGS with specific correction factors displayed higher accuracy compared with the other two methods (P < 0.05).

Conclusions

The new AI-based Kane and PEARL-DGS with or without the CMAL methods could improve the refractive outcomes of the second eye in sequential bilateral cataract patients with long AL. Notably, the Kane, PEARL-DGS, and BUII with specific correction factors displayed higher accuracy.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40123-022-00551-6.

IOL power calculation with ray tracing based on anterior segment OCT and adjusted axial length after myopic excimer laser surgery

PURPOSE

To report the results of intraocular lens (IOL) power calculation by ray-tracing in eyes with previous myopic excimer laser surgery.

SETTING

G.B. Bietti Foundation I.R.C.C.S., Rome, Italy.

DESIGN

Retrospective interventional case series.

METHODS

A series of consecutive patients undergoing phacoemulsification and IOL implantation after myopic excimer laser was investigated. IOL power was calculated using ray-tracing software available on the anterior segment optical coherence tomographer MS-39 (CSO, Italy). Axial length (AL) was measured by optical biometry and 4 values were investigated: 1) that from the printout, 2) the modified Wang/Koch formula, 3) the polynomial equation for the Holladay 1 and 4) for the Holladay 2 formula. The mean prediction error (PE), median absolute error (MedAE), percentage of eyes with a PE within ±0.50 diopters (D) were reported.

RESULTS

We enrolled 39 eyes. Entering the original AL into ray-tracing led to a mean hyperopic PE (+0.56 ±0.54 D), whereas with the Wang/Koch formula a mean myopic PE (-0.41 ±0.53D) was obtained. The Holladay 1 and 2 polynomial equations lead to the lowest PEs (-0.10 ±0.49 and +0.08 ±0.49 D respectively), lowest MedAE (0.37 and 0.25 D) and highest percentages of eyes with a PE within ±0.50 D (71.79 and 76.92%). Calculations based on the Holladay 2 polynomial equation showed a statistically significant difference compared to other methods used (including Barrett-True K formula), with the only exception of the Holladay 1 polynomial equation.

CONCLUSIONS

IOL power can be accurately calculated by ray-tracing with adjusted AL according to the Holladay 2 polynomial equation.

Assessing Accuracy of Okulix Ray-Tracing Software in Calculating Intraocular Lens Power in the Long Cataractous Eyes

Purpose

To investigate the accuracy of Okulix ray-tracing software in calculating intraocular lens (IOL) power in the long cataractous eyes and comparing the results with those obtained from Kane, Holladay 1 with optimized constant, SRK/T with optimized constant, Haigis with optimized constant, and Barret Universal 2 formulas.

Methods

The present study evaluates the refractive results of cataract surgery in 85 eyes with axial length > 25 mm and no history of ocular surgery and corneal pathology. IOL power calculation was performed using the Okulix software. The performances of Okulix software in comparison with the five other formulas were evaluated by predicted error, mean absolute error, and mean numerical error 6 months after surgery.

Results

The mean calculated IOL power by the Okulix software was +13.48 ± 4.19 diopter (D). The mean of the 6-month postoperative sphere and spherical equivalent were +0.18 ± 0.63 and -0.34 ± 0.78 D, respectively. Also, the 6-month spherical equivalent in 56.6% and 80% of eyes were within ±0.05 and ±1.00 D, respectively. The predicted error (P < 0.001) and the mean numerical error (P < 0.001) were different between the six studied methods; however, we were not able to find any significant differences in the mean absolute error among six studied methods (P: 0.211).

Conclusion

The present study showed acceptable performance of the Okulix software in IOL power calculation in long eyes in comparison with the other five methods based on the postoperative refractive error, calculated mean absolute error, and mean numerical error.

A comparison of different methods to calculate the axial length measured by optical biometry

ABSTRACT

PurposeTo compare axial length (AL) measurements in long eyes by two swept-source optical coherence tomography (SS-OCT) biometers, one based on the group refractive index (IOLMaster 700, Zeiss) and the other based on sum of segments (Argos, Movu), and compare these measurements to previously published methods to optimize AL.SettingI.R.C.C.S. - G.B. Bietti Foundation, Rome, ItalyDesignProspective case seriesMethodsAL was measured with both optical biometers in myopic patients (AL > 24.00 mm) and compared to the values obtained with Wang-Koch adjustment, polynomial equations for the Holladay 1 and 2 formulas and Cooke modified AL (CMAL).ResultsIn 102 eyes of 55 subjects, a statistically significant difference (p<0.0001) was found among the 6 AL values. Post-test revealed that Argos measurements (26.90 ±1.61 mm) were significantly lower compared to those provided by all methods (p <0.001) but CMAL, whereas IOLMaster 700 measurements (27.01 ±1.65) were higher (p <0.001). No difference was found between the two Holladay equations. CMAL values did not reveal any difference compared to those of the Argos, but a proportional bias showed that in longer eyes CMAL provided smaller values (p <0.0001, r = -0.7221). AL overestimation by the IOLMaster 700 AL compared to the Argos was higher the longer the eye was (p <0.0001, r = 0.6959, r2 = 0.4842).ConclusionThe SS-OCT optical biometer based on the group refractive index overestimates AL compared to the device using segmented AL. CMAL provides the measurements closest to those of the device using segmented AL.

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

PURPOSE

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/T_modified-W/K and H1_modified-W/K) in Chinese patients with long eyes.

METHODS

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.

RESULTS

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/T_modified-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 H1_modified-W/K and Haigis formulas. The SRK/T_modified-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.

CONCLUSIONS

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/T_modified-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.].

Short-Term Changes in Prediction Error after Cataract Surgery in Eyes Receiving 1 of 3 Types of Single-Piece Acrylic Intraocular Lenses

PURPOSE

To compare short-term changes in refractive prediction error (PE) after phacoemulsification among eyes receiving different types of single-piece acrylic intraocular lenses (IOLs).

DESIGN

Randomized clinical trial.

METHODS

A total of 195 eyes of 195 patients scheduled for implantation of a single-piece acrylic IOL were randomly assigned to receive 1 of 3 IOLs: 1) an Alcon model SN60WF, 2) a Hoya model XY-1, or 3) an AMO model ZCB00V. Manifest spherical equivalent (MRSE) value, PE, and changes in PE were examined at 1 day and at 1 and 2 months postoperatively and were compared among groups.

RESULTS

The mean MRSE and PE significantly changed toward myopia between 1 day and 2 months postoperatively in all groups (P < .0001). The MRSE and PE did not differ significantly among groups at 1 day and 1 month postoperatively and were significantly smaller in the SN60WF group than in the XY-1 and ZCB00V groups at 2 months (P ≤ .0006). The PE change between 1 day and 2 months postoperatively was significantly smaller in the SN60WF group than in the other groups (P = .0062). IOL type and changes in anterior chamber depth and corneal curvature independently correlated with PE changes.

CONCLUSIONS

The MRSE and PE showed a significant myopic change for 2 months postoperatively in eyes implanted with 1 of 3 types of single-piece acrylic IOLs and were significantly smaller in the SN60WF than in the XY-1 and ZCB00V groups. Changes in PE during the 2 postoperative months were smaller in the SN60WF IOLs than in the other IOLs, suggesting that postoperative refractive stability differs among single-piece acrylic IOLs.

Comparison of intraocular lens power calculation formulas in Chinese eyes with axial myopia

PURPOSE

To assess the accuracy of intraocular lens (IOL) power calculation formulas in Chinese eyes with axial lengths (ALs) longer than 26.0 mm.

SETTING

Department of Cataract Surgery, Shanxi Eye Hospital, China.

DESIGN

Prospective case series.

METHODS

This study evaluated (1) two new formulas (Barrett Universal II and Hill-RBF 2.0), (2) three vergence formulas (Haigis, Holladay 1, and SRK/T), and (3) the original and modified Wang-Koch AL adjustment formulas with Holladay 1 and SRK/T. The User Group for Laser Interference Biometry lens constants were used for IOL power calculation. The refractive prediction error was calculated by subtracting the predicted refraction from the actual refraction postoperatively. The mean numerical error (MNE), percentage of eyes with hyperopic outcomes, and mean absolute error (MAE) were determined.

RESULTS

The study comprised 136 eyes. The Barrett and Hill-RBF formulas had MNEs close to zero (-0.09 D to 0.03 D), the Haigis, Holladay 1, and SRK/T produced hyperopic MNEs (0.25 to 0.70 D), and the original and modified Wang-Koch AL adjustment formulas induced myopic MNEs (-0.48 to -0.22 D). The original Wang-Koch formulas produced significantly lower percentages of eyes with hyperopic outcomes (15% to 18%) than all other formulas (28% to 91%). There were no significant differences in MAEs between the Barrett, Hill-RBF, Haigis, and original and modified Wang-Koch adjustment with the Holladay 1 (0.32 to 0.41 D).

CONCLUSION

The performances of the Barrett and Hill-RBF were comparable in long eyes. The incidence of hyperopic outcome with the Wang-Koch AL adjustment formula was significantly lower than other formulas.

Accuracy of New Generation Intraocular Lens Calculation Formulas in Vitrectomized Eyes

PURPOSE

To compare the prediction accuracy of new intraocular lens (IOL) calculation formulas (Barrett Universal II [BUII], Emmetropia Verifying Optical [EVO], Kane and Ladas Super formula) and traditional formulas (Haigis, Hoffer Q, Holladay 1, and SRK/T) with Wang-Koch (WK) axial length (AL) adjustment in vitrectomized eyes.

DESIGN

Retrospective consecutive case-series study.

METHODS

One hundred eleven eyes of 111 patients underwent uneventful phacoemulsification and enVista MX60 implantation after vitrectomy were enrolled and divided into 4 groups according to whether the vitreous cavity was filled with silicone oil. The performance of each formula was evaluated with or without lens constant optimization.

RESULTS

Before lens constants optimization, the mean prediction errors (MEs) of all formulas were statistically different from zero (0.14-0.46 diopters [D]) in vitrectomized eyes, except for the Kane formula. The BUII, EVO, Kane, and Haigis had relatively lower mean absolute error (MAE) and median absolute error (MedAE) with optimized constants. No significant systemic bias was found in new formulas for vitrectomized eyes with AL >26 mm (P > .05). The Hoffer Q and Holladay 1 displayed significantly hyperopic shift (0.39 and 0.51 D) for long eyes, which was corrected by the WK adjustment. There were no significant differences in the prediction accuracy of all formulas among 4 subgroups (P > .05).

CONCLUSIONS

The BUII, EVO, Kane, and Haigis displayed comparable performance in vitrectomized eyes with optimized constants. In vitrectomized highly myopic eyes, the new formulas and traditional formulas with WK adjustment exhibited satisfactory prediction accuracy. Silicone oil tamponade did not affect the prediction accuracy of formulas using IOLMaster 700.

Intraocular Lens Power Formulas, Biometry, and Intraoperative Aberrometry: A Review

The refractive outcome of cataract surgery is influenced by the choice of intraocular lens (IOL) power formula and the accuracy of the various devices used to measure the eye (including intraoperative aberrometry [IA]). This review aimed to cover the breadth of literature over the previous 10 years, focusing on 3 main questions: (1) What IOL power formulas currently are available and which is the most accurate? (2) What biometry devices are available, do the measurements they obtain differ from one another, and will this cause a clinically significant change in IOL power selection? and (3) Does IA improve refractive outcomes? A literature review was performed by searching the PubMed database for articles on each of these topics that identified 1313 articles, of which 166 were included in the review. For IOL power formulas, the Kane formula was the most accurate formula over the entire axial length (AL) spectrum and in both the short eye (AL, ≤22.0 mm) and long eye (AL, ≥26.0 mm) subgroups. Other formulas that performed well in the short-eye subgroup were the Olsen (4-factor), Haigis, and Hill-radial basis function (RBF) 1.0. In the long-eye group, the other formulas that performed well included the Barrett Universal II (BUII), Olsen (4-factor), or Holladay 1 with Wang-Koch adjustment. All biometry devices delivered highly reproducible measurements, and most comparative studies showed little difference in the average measures for all the biometric variables between devices. The differences seen resulted in minimal clinically significant effects on IOL power selection. The main difference found between devices was the ability to measure successfully through dense cataracts, with swept-source OCT-based machines performing better than partial coherence interferometry and optical low-coherence reflectometry devices. Intraoperative aberrometry generally improved outcomes for spherical and toric IOLs in eyes both with and without prior refractive surgery when the BUII and Hill-RBF, Barrett toric calculator, or Barrett True-K formulas were not used. When they were used, IA did not result in better outcomes.

Effect of Axial Length Adjustment Methods on Intraocular Lens Power Calculation in Highly Myopic Eyes

PURPOSE

To evaluate the performance of Holladay 1 and SRK/T formulas with the axial length (AL) adjustment methods including the linear and nonlinear versions of Wang-Koch AL adjustment methods and Cooke-modified AL (CMAL); and to determine whether the CMAL should be extended to the latest Barrett Universal II, Ladas Super formula (LSF), and Emmetropia Verifying Optical formulas in highly myopic eyes.

DESIGN

Retrospective, consecutive case-series study.

METHODS

A total of 164 eyes of 164 patients with AL ≥26.0 mm were included and divided into 2 groups: AL <28.0 mm (Group 1) and AL ≥28.0 mm (Group 2). The average arithmetic spherical equivalent prediction error (PE), mean absolute PE, median absolute error (MedAE), and the percentage of eyes within ±0.25 diopter (D), ±0.50 D, and ±1.0 D of PE were determined.

RESULTS

The Holladay 1 formulas showed the smallest MedAE when combined with the first linear or nonlinear version of Wang-Koch AL adjustment methods, both in total and in subgroups. The SRK/T formula displayed the highest prediction accuracy in combination with the first linear version of Wang-Koch adjustment method in total and subgroups. The CMAL reduced the absolute PE of LSF in total (P = .003) and in Group 1 (P = .017).

CONCLUSIONS

The Holladay 1 and SRK/T formulas combined with specific AL adjustment methods had accuracy similar to the fourth-generation formulas for highly myopic eyes. Moreover, the CMAL can improve the accuracy of the LSF for highly myopic eyes.

Effect of lens constants optimization on the accuracy of intraocular lens power calculation formulas for highly myopic eyes

AIM

To evaluate the effect of different lens constant optimization methods on the accuracy of intraocular lens (IOL) power calculation formulas for highly myopic eyes.

METHODS

This study comprised 108 eyes of 94 consecutive patients with axial length (AL) over 26 mm undergoing phacoemulsification and implantation of a Rayner (Hove, UK) 920H IOL. Formulas were evaluated using the following lens constants: manufacturer's lens constant, User Group for Laser Interference Biometry (ULIB) constant, and optimized constant for long eyes. Results were compared with Barrett Universal II formula, original Wang-Koch AL adjustment method, and modified Wang-Koch AL adjustment method. The outcomes assessed were mean absolute error (MAE) and percentage of eyes with IOL prediction errors within ±0.25, ±0.50, and ±1.0 diopter (D). The nonparametric method, Friedman test, was used to compare MAE performance among constants.

RESULTS

Optimized constants could significantly reduce the MAE of SRK/T, Hoffer Q, and Holladay 1 formulas compared with manufacturer's lens constant, whereas the percentage of eyes with IOL prediction errors within ±0.25, ±0.50, and ±1.0 D had no statistically significant differences. Optimized lens constant for long eyes alone showed non-significant refractive advantages over the ULIB constant. Barrett Universal II formula and formulas with AL adjustment showed significantly higher accuracy in highly myopic eyes (P<0.001).

CONCLUSION

Lens constant optimization for the subset of long eyes reduces the refractive error only to a limited extent for highly myopic eyes.