Accuracy of the refractive prediction determined by intraocular lens power calculation formulas in high myopia

How to choose the intraocular lens power calculation formulas in eyes with extremely long axial length? A systematic review and meta-analysis

OBJECTIVE

To evaluate the accuracy of 10 formulas for calculating intraocular lens (IOL) power in cataract eye with an axial length (AL) of more than 28.0 mm.

METHODS

We searched scientific databases including PubMed, EMBASE, Web of Science and Cochrane Library for research published over the past 5 years, up to Sept 2023. The inclusion criteria were case series studies that compared different formulas (Barrett II, EVO, Kane, Hill-RBF, Haigis, Hoffer Q, Holladay 1, SRK/T, Holladay 1 w-k and SRK/T w-k), in patients with extremely long AL undergoing uncomplicated cataract surgery with IOL implantation. The mean difference (MD) of mean absolute error (MAE) and the odds ratio (OR) of both the percentage of eyes within ±0.50D of prediction error (PPE±0.50D) and the percentage of eyes within ±1.00D of prediction error (PPE±1.00D) among different formulas were pooled using meta-analysis.

RESULTS

A total of 11 studies, involving 1376 eyes, were included to evaluate the 10 formulas mentioned above. Among these formulas, Barrett II, EVO, Kane, and Hill-RBF demonstrated significantly lower MAE values compared to SRK/T. Furthermore, Kane and Hill-RBF had lower MAE values than EVO. Additionally, Barrett II and Kane yielded significantly lower MAE values than Haigis while Hill-RBF showed significantly lower MAE values than Holladay 1. Moreover, Hill-RBF showed the highest values for both PPE±0.50D and PPE±1.00D, followed by Kane. Both EVO and Kane had higher values of PPE±0.50D and PPE±1.00D compared to Haigis and SRK/T.

CONCLUSION

The Wang-Koch adjusted formulas and new-generation formulas have shown potential for higher accuracy in predicting IOL power for cataract patients with extremely long AL compared to traditional formulas. Based on the current limited clinical studies, Hill-RBF and Kane formulas seem to be a better choice for eyes with extremely long AL.

Network Meta-analysis of Intraocular Lens Power Calculation Formula Accuracy in 1016 Eyes With Long Axial Length

PURPOSE

To systematically review the literature and quantitatively synthesize the currently available evidence to compare the accuracy of different intraocular lens calculation formulas in eyes with long axial length (AL).

DESIGN

Network meta-analysis.

METHODS

PubMed, Embase, Web of Science, and the Cochrane Library were systematically searched for studies published between January 2000 and June 2022. Included were prospective or retrospective clinical studies reporting the following outcomes in cataract patients with long AL (ie, ≥26 mm): percentage of eyes with a prediction error (PE) within ±0.25, ±0.50, and ±1.00 diopters (D). Network meta-analysis was conducted using R software (version 4.2.1).

RESULTS

Ten prospective or retrospective clinical studies, including 1016 eyes and 11 calculation formulas, were identified. A traditional meta-analysis showed that for the percentage of eyes with PE within ±0.25 and ±0.50 D, the Olsen, Kane, and Emmetropia Verifying Optical (EVO) all had insignificantly higher percentages compared with others. Considering the percentage of eyes with PE within ±1.00 D, the original and modified Wang-Koch adjustment formulas for Holladay 1 (H1-WK and H1-MWK) and EVO formulas showed superiority, but the difference was insignificant. This network meta-analysis revealed that compared with the widely used Barrett Universal II (BUII) formula, the Olsen, Kane, and EVO formulas had higher percentages of eyes with PE within ±0.25, ±0.50, and ±1.00 D (all odds ratios >1 but P >.05). Based on the surface under the cumulative ranking area (SUCRA) values for the percentage of eyes with PE within ±0.25 D, the Olsen (96.4%), Kane (77.5%), and EVO (75.9%) formulas had the highest probability of being in the top 3 of the 11 formulas.

CONCLUSIONS

The Olsen, Kane, and EVO formulas may perform better than others in calculating IOL power in eyes with long AL. Nevertheless, there is still considerable uncertainty in this regard and the accuracy of these formulas in highly myopic eyes should be confirmed in studies based on large multicenter registries.

Influence of Ocular Biometry Parameters on the Predictive Accuracy of IOL Power Formulas in Patients with High Myopia

INTRODUCTION

The aim of this study was to investigate the influence of ocular biometry parameters on the predictive accuracy of 10 intraocular lens (IOL) power formulas in patients with high myopia (HM).

METHODS

We analyzed 202 eyes of 202 patients. The ocular biometry was determined preoperatively using an IOLMaster 700. The associations between the biometry parameters and the prediction error (PE) 1 month postoperatively were assessed. HM was defined as an axial length exceeding 26.50 mm.

RESULTS

In patients with HM (n = 108), the K6, Emmetropia Verifying Optical (EVO), Olsen, and Barrett Universal II (BUII) formulas had the lowest absolute PEs among the 10 formulas. The ocular biometry parameters were not associated with the PE of K6, EVO, Olsen, or BUII. A longer axial length in HM eyes was associated with myopic outcomes by Kane, Hoffer QST, and VRF and hyperopic outcomes by Holladay 2 and T2. Steeper keratometry, a deeper anterior chamber, and a thicker lens were associated with a hyperopic shift in HM eyes when using VRF, Kane, and Hoffer QST, respectively. In patients without HM (n = 94), there was no difference between the formulas in absolute PE. The significant associations between the biometry parameters and PE in patients with HM were not present in patients without HM.

CONCLUSIONS

K6, EVO, Olsen, and BUII displayed high accuracy in HM eyes and were not influenced by preoperative biometry parameters. For the remaining formulas, the preoperative keratometry, anterior chamber depth, lens thickness, and axial length were possible error sources underlying an inaccurate IOL power prediction in patients with HM.

Intraocular Lens Power Calculation Formulas-A Systematic Review

PURPOSE

The proper choice of an intraocular lens (IOL) power calculation formula is an important aspect of phacoemulsification. In this study, the formulas most commonly used today are described and their accuracy is evaluated.

METHODS

This review includes papers evaluating the accuracy of IOL power calculation formulas published during the period from January 2015 to December 2022. The articles were identified by a literature search of medical and other databases (PubMed/MEDLINE, Crossref, Web of Science, SciELO, Google Scholar, and Cochrane Library) using the terms "IOL formulas," "Barrett Universal II," "Kane," "Hill-RBF," "Olsen," "PEARL-DGS," "EVO," "Haigis," "SRK/T," and "Hoffer Q." Twenty-nine of the most recent peer-reviewed papers in English with the largest samples and largest number of formulas compared were considered.

RESULTS

Outcomes of mean absolute error and percentage of predictions within ±0.5 D and ±1.0 D were used to evaluate the accuracy of the formulas. In most studies, Barrett achieved the smallest mean absolute error and PEARL-DGS the highest percentage of patients with ±0.5 D in short eyes, while Kane obtained the highest percentage of patients with ±0.5 D in long eyes.

CONCLUSIONS

The third- and fourth-generation formulas are gradually being replaced by more accurate ones. The Barrett Universal II among vergence formulas and Kane and PEARL-DGS among artificial intelligence-based formulas are currently most often reported as the most precise.

Analysis of accuracy of twelve intraocular lens power calculation formulas for eyes with axial myopia

PURPOSE

The aim of this study is to compare twelve intraocular lens power calculation formulas for eyes longer than 25.0 mm in terms of absolute error (AE), the percentage of postoperative emmetropia, and agreement interval in Bland-Altman analysis.

MATERIALS AND METHODS

Data of myopic patients who underwent uneventful phacoemulsification between January 2016 and July 2021 was reviewed. Intraocular lens power was calculated using Holladay 1, SRK/T, Hoffer Q, Holladay 2, Haigis, Barrett Universal II, Hill-RBF, Ladas, Kane, EVO, Pearl-DGS, and K6 formulas. Three months after phacoemulsification, refraction was measured, and mean AE was calculated. The percentage of patients with full visual acuity (VA) without any correction, with ± 0.25D, ±0.5D, ±0.75D, and limits of agreement for each formula were established.

RESULTS

Ninety-one patients, whose ocular axial length ranged between 25.03 mm and 28.91 mm, were included in the study. The Barrett Universal II formula achieved the lowest mean AE of 0.11 ± 0.11 (P < 0.001) just before Kane (0.13 ± 0.09; P < 0.001 except vs. Haigis and Holladay 2) and SRK/T formulas (0.18 ± 0.12). In addition, the Barrett Universal II formula had the highest percentage of patients with full VA without any correction (72.5%) followed by Kane and Holladay 2 formulas (56.0% and 49.5%, respectively). Finally, Barrett Universal II, Kane, and Haigis formulas obtained the lowest agreement interval (0.5725, 0.6088, and 0.8307, respectively).

CONCLUSION

The Barrett Universal II formula is recommended for intraocular lens power calculation for eyeballs with the axial length longer than 25.0 mm. The Kane formula also gives very promising results in regarding the accuracy of intraocular lens power for myopic eyes.

Comparing the accuracy of the new-generation intraocular lens power calculation formulae in axial myopic eyes: a meta-analysis

PURPOSE

To compare the accuracy of the new-generation intraocular lens power calculation formulae in axial myopic eyes.

METHODS

Four databases, PubMed, Web of Science, EMBASE and Cochrane library, were searched to select relevant studies published between Apr 11, 2011, and Apr 11, 2021. Axial myopic eyes were defined as an axial length more than 24.5 mm. There are 13 formulae to participate in the final comparison (SRK/T, Hoffer Q, Holladay I, Holladay II, Haigis for traditional formulae, Barrett Universal II, Olsen, T2, VRF, EVO, Kane, Hill-RBF, LSF for the new-generation formulae). The primary outcomes were the percentage of eyes with a refractive prediction error in ± 0.5D and ± 1.0D.

RESULTS

A total of 2273 eyes in 15 studies were enrolled in the final meta-analysis. Overall, the new-generation formulae showed a relatively more accurate outcome in comparison with traditional formulae. The percentage of eyes with a predictive refraction error in ± 0.5D (± 1.0D) of Kane, EVO and LSF was higher than 80% (95%), which was only significantly different from Hoffer Q (all P < 0.05). Moreover, another two new-generation formulae, Barrett Universal II and Olsen, had higher percentages than SRK/T, Hoffer Q, Holladay I and Haigis for eyes with predictive refraction error in ± 0.5D and ± 1.0D (all P < 0.05). In ± 0.5D group, Hill-RBF was better than SRK/T (P = 0.02), and Holladay I was better than EVO (P = 0.03) and LSF (P = 0.009), and Hoffer Q had a lower percentage than EVO, Kane, Hill-RBF and LSF (P = 0.007, 0.004, 0.002, 0.03, respectively). Barrett Universal II was better than T2 (P = 0.02), and Hill-RBF was better than SRK/T (P = 0.009). No significant difference was found in other pairwise comparison.

CONCLUSION

The new-generation formula is more accurate in intraocular lens power calculation for axial myopic eyes in comparison with the third- or fourth-generation formula.

Accuracy of Barrett versus third-generation intraocular lens formula across all axial lengths

PURPOSE

The purpose of this study is to evaluate and compare the accuracy of Barrett Universal II versus third-generation formula for different intraocular lens (IOL) powers for Indian eyes with different axial lengths (ALs).

DESIGN

This is a retrospective, nonrandomized consecutive case series.

METHODS

This study reviewed 981 eyes from 825 patients who had uneventful cataract surgery and IOL implantation. The eyes were separated into subgroups based on AL as follows: short (<22.0 mm), medium (22.01-23.99 mm), and long (>24.0 mm). The predicted refractive outcome using formulas was calculated and compared with the actual refractive outcome to give the prediction error. The percentage of every refractive error absolute value for each formula was calculated at <±0.50D, 0.50D-0.75D, and >±0.75D.

RESULTS

In all, 981 eyes were analyzed. There were no significant differences in the median absolute error predicted by Barrett and the third-generation formulae. The Barrett Universal II formula resulted in significantly lowest mean spherical equivalent in short eyes (P = 0.0047) as well as a higher percentage of eyes with prediction errors within <±0.50D, 0.50D-0.75D, and >±0.75D. We found that the Barrett Universal II formula had the lowest predictive refraction error and mean absolute error across all ALs.

CONCLUSION

The Barrett Universal II formula rendered the lowest predictive error compared with SRK/T, Holladay, and Hoffer Q formulas. Thus, the Barrett Universal II formula may be regarded as a more reliable formula for achieving emmetropia and reducing postoperative refractive surprises across all ALs.

Accuracy of Six Intraocular Lens Power Calculations in Eyes with Axial Lengths Greater than 28.0 mm

The purpose of this study was to compare the accuracy of several intraocular (IOL) lens power calculation formulas in long eyes. This was a single-site retrospective consecutive case series that reviewed patients with axial lengths (AL) > 28.0 mm who underwent phacoemulsification. The Wang−Koch (WK) adjustment and Cooke-modified axial length (CMAL) adjustment were applied to Holladay 1 and SRK/T. The median absolute error (MedAE) and the percentage of eyes with prediction errors ±0.25 diopters (D), ±0.50 D, ±0.75 D, and ±1.00 D were used to analyze the formula’s accuracy. This study comprised a total of 35 eyes from 25 patients. The Kane formula had the lowest MedAE of all the formulas, but all were comparable except Holladay 1, which had a significantly lower prediction accuracy with either AL adjustment. The SRK/T formula with the CMAL adjustment had the highest accuracy in predicting the formula outcome within ±0.50 D. The newer formulas (BU-II, EVO, Hill-RBF version 3.0, and Kane) were all equally predictable in long eyes. The SRK/T formula with the CMAL adjustment was comparable to these newer formulas with better outcomes than the WK adjustment. The Holladay 1 with either AL adjustment had the lowest predictive accuracy.

Predictability of 6 Intraocular Lens Power Calculation Formulas in People With Very High Myopia

Purpose

To investigate the accuracy of 6 intraocular lens (IOL) power calculation formulas in predicting refractive outcomes in extremely long eyes.

Setting

Department of Ophthalmology, Far Eastern Memorial Hospital, Taiwan.

Design

Retrospective comparative study.

Methods

In this retrospective single-center study, we reviewed 70 eyes of 70 patients with axial length (AL) ≥ 28 mm who had received an uneventful 2.2 mm corneal wound phacoemulsification and in-the-bag IOL placement. The actual postoperative refractive results were compared to the predicted refraction calculated with 6 formulas (Haigis, Hoffer Q, Holladay 1, SRK/T, T2, Barrett Universal II formulas) using IOLMaster 500 as optical biometry in the User Group for Laser Interference Biometry (ULIB) constants.

Results

Overall, the Haigis and Barrett formulas achieved the lowest level of mean prediction error (PE) and median absolute error (MedAE). Hoffer Q, Holladay 1, SRK/T, and T2 had hyperopic prediction errors (p < 0.05). The Hoffer Q and Holladay 1 had significantly more MedAE between the 6 formulas. After the mean PE was zeroed out, the MedAE had no significant difference between each group. The absolute error tends to be larger in patients with longer AL. The absolute errors were 30.0–37.1% and 60.0–64.3% within 1.0 D of all patients compared to predicted refraction calculated using various formulas.

Conclusion

The Haigis and Barrett Universal II formulas had a better success rate in predicting IOL power in high myopic eyes with AL longer than 28 mm using the ULIB constant in this study. The postoperative refractive results were inferior to the benchmark standards, which indicated that the precision of IOL power calculation in patients with high myopia still required improvement.

Extended Depth of Focus Versus Monofocal IOLs in Patients With High Myopia: Objective and Subjective Visual Outcomes

PURPOSE

To compare the objective and subjective outcomes between the extended depth of focus (EDOF) Mini Well intraocular lens (IOL) and the aspheric monofocal Mini-4-Ready IOL (both SIFI S.p.A.) in patients with high myopia.

METHODS

In this prospective comparative study, 40 patients with high myopia (axial length ≥ 26 mm) were enrolled: 20 patients were bilaterally implanted with the EDOF Mini Well IOL (EDOF group) and 20 patients were bilaterally implanted with the Mini-4-Ready IOL (monofocal group). Three-month follow-up data included corrected and uncorrected distance visual acuity at 4 m and 80, 67, and 40 cm, defocus curves, subjective and objective contrast sensitivity, objective optical quality (calculated with Optical Quality Analysis System; Visiometrics SL), halometry, and reading performance. Subjective visual quality was evaluated with National Eye Institute Refractive Error Quality of Life Instrument 42 scores.

RESULTS

All visual acuities were significantly better in the EDOF group (P ⩽ .04) except monocular and binocular uncorrected and corrected distance visual acuities for distance (P ≥ .50). Defocus curves for myopic and hyperopic values were better in the EDOF group (P ⩽ .05), apart from +0.50 to -0.50 D (P ≥ .16). Contrast sensitivity curves was worse in the EDOF group in the mesopic-with-glare condition (P ⩽ .04). No differences were found in halometric values (P ≥ .15) and OQAS outcomes (P ≥ .47). National Eye Institute Refractive Error Quality of Life Instrument 42 subscale scores were better for expectation, near vision, activity limitations, and dependence on correction in the EDOF group (P ⩽ .04).

CONCLUSIONS

Intermediate and near visual acuities were better in the EDOF group than in the monofocal group, with a comparable visual quality index between groups. [J Refract Surg. 2022;38(3):158-166.].

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

PURPOSE

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.

METHODS

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.

RESULTS

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).

CONCLUSION

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.

Correlating Kane formula with existing intraocular lens formulae for corneal curvatures and axial lengths

BACKGROUND:

To evaluate the predictability of the Kane formula in estimating postoperative refractive outcome with various corneal curvatures and axial lengths (ALs) besides comparing with existing intraocular lens (IOL) formulae.

MATERIALS AND METHODS:

A prospective cross-sectional study was carried out among patients having uneventful cataract surgery at an eye hospital. A total of 50 eyes were considered for the study. The corresponding A-constant for the model of IOL implanted into the patient's eye was taken along with the actual power of IOL implanted and corresponding predicted power for the IOL power inserted were taken for all the chosen formulae and was termed as "Adjusted Predicted Refractive Power." This was compared with the actual refractive outcome and the absolute error (AE) was measured. The eyes were separated into groups in terms of corneal curvature as flat (<42D), medium (42D–46D), and steep (>46D) corneas. In terms of AL, it was grouped as short (≤22 mm), medium (>22.0–<24.0 mm), and long (>24.0 mm) eyes.

RESULTS:

The study included 50 eyes and the mean AE for all the selected formulae were calculated for each group. Over the entire corneal curvature range, none of the formulae showed any significance when compared with the Kane formula (P > 0.05). In short AL, SRK-T formula had a statistical significance over the Kane formula (P = 0.043), whereas no other group had any significance over the Kane formula in AL groups.

CONCLUSION:

The study shows, all formulae (SRK-T, Holladay1, Hoffer Q, Hill RBF, Barrett Universal II, Kane) are interchangeable to predict the IOL power for any of the corneal curvature and ALs.

Correlating Kane formula with existing intraocular lens formulae for corneal curvatures and axial lengths

BACKGROUND

To evaluate the predictability of the Kane formula in estimating postoperative refractive outcome with various corneal curvatures and axial lengths (ALs) besides comparing with existing intraocular lens (IOL) formulae.

MATERIALS AND METHODS

A prospective cross-sectional study was carried out among patients having uneventful cataract surgery at an eye hospital. A total of 50 eyes were considered for the study. The corresponding A-constant for the model of IOL implanted into the patient's eye was taken along with the actual power of IOL implanted and corresponding predicted power for the IOL power inserted were taken for all the chosen formulae and was termed as "Adjusted Predicted Refractive Power." This was compared with the actual refractive outcome and the absolute error (AE) was measured. The eyes were separated into groups in terms of corneal curvature as flat (<42D), medium (42D-46D), and steep (>46D) corneas. In terms of AL, it was grouped as short (≤22 mm), medium (>22.0-<24.0 mm), and long (>24.0 mm) eyes.

RESULTS

The study included 50 eyes and the mean AE for all the selected formulae were calculated for each group. Over the entire corneal curvature range, none of the formulae showed any significance when compared with the Kane formula (P > 0.05). In short AL, SRK-T formula had a statistical significance over the Kane formula (P = 0.043), whereas no other group had any significance over the Kane formula in AL groups.

CONCLUSION

The study shows, all formulae (SRK-T, Holladay1, Hoffer Q, Hill RBF, Barrett Universal II, Kane) are interchangeable to predict the IOL power for any of the corneal curvature and ALs.

Recurring themes during cataract assessment and surgery

The aim of this review was to discuss frequently encountered themes such as cataract surgery in presence of age-related macular degeneration (AMD), dementia, Immediate Sequential Bilateral Cataract Surgery (ISBCS), discussing non-standard intraocular lens (IOL) options during consultation in the National Health Services (NHS) and the choice of the biometric formulae based on axial length. Individual groups of authors worked independently on each topic. We found that cataract surgery does improve visual acuity in AMD patients but the need for cataract surgery should be individualised. In patients with dementia, cataract surgery should be considered 'sooner rather than later' as progression may prevent individuals presenting for surgery. This should be planned after discussion of patients' best interests with any carers; multifocal IOLs are not proven to be the best option in these patients. ISBCS gives comparable outcomes to delayed sequential surgeries with a low risk of bilateral endophthalmitis and it can be cost-saving and efficient. Patients are entitled to know all suitable IOL options that can improve their quality of life. Deliberately withholding this information or pressuring patients to choose a non-standard IOL is inappropriate. However, one should be mindful of the not spending inappropriate amounts of time discussing these in the NHS setting which may affect care of other NHS patients. Evidence suggests Hoffer Q, Haigis, Hill-RBF and Kane formulae for shorter eyes; Barrett Universal II (BU II), Holladay II, Haigis and Kane formulae for longer eyes and BU II, Hill-RBF and Kane formulae for medium axial length eyes.

Comparison of refractive outcomes using Scheimpflug Holladay equivalent keratometry or IOLMaster 700 keratometry for IOL power calculation

PURPOSE

This study aims to compare postoperative refractive error results using Pentacam (Oculus Optikgeräte GmbH) Holladay equivalent keratometry readings (EKR) or IOLMaster 700 (Carl Zeiss Meditec AG) keratometry (K) values in IOL power calculation.

MATERIAL AND METHODS

This retrospective study included 54 eyes of 31 patients who underwent cataract surgery. Preoperative biometric measurements of all patients were obtained using IOLMaster 700 followed by Pentacam measurements. IOLMaster 700 K measurements on horizontal (K1) and vertical (K2) axes and EKR measurements on 2 mm (EKR2mm), 3 mm (EKR3mm) and 4.5 mm (EKR4.5 mm) corneal zones were recorded. EKR4.5 mm value and IOLMaster 700 K values were used in Holladay-II, SRK/T, Haigis, and Hoffer-Q formulas to calculate predictive refractive error (PRE). Absolute refractive error (ARE) was calculated as the absolute difference between actual postoperative refractive error (APRE) and PRE values.

RESULTS

Mean age was 72.2 ± 8.3 (51-87) years and mean IOL power was 21.5 ± 2.9 D (18-23 D). There was no significant difference between PRE values when IOLMaster 700 K measurements and EKR4.5 mm K measurements were used in Holladay-II, SRK/T, Haigis, and Hoffer-Q formulas (p = 0.571, p = 0.833, p = 0.165, p = 0.347, respectively). There was no significant difference between APRE and ARE values (p = 0.124). According to mean ARE results, the closest estimate was achieved when the IOLMaster 700 K values were used in the Holladay-II formula (p = 0.271).

CONCLUSION

IOLMaster 700 K measurement and Pentacam EKR4.5 mm measurements can be used interchangeably. IOLMaster 700 K values yielded the most predictive measurement of the refractive result using the Holladay-II formula.

Five Pearls for Long Eyes

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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.

Accuracy of five intraocular lens formulas in eyes with trifocal lens implant

Accuracy of intraocular lens (IOL) calculation formulas SRK/T, Hoffer Q, Holladay 1, Haigis and Barrett Universal II were compared in prediction of postoperative refraction for multifocal and implants using a single optical biometry device. The authors included 88 refractive lens exchange and cataract surgeries, with AcrySof IQ PanOptix implant (Alcon Laboratories, Inc.). All eyes were divided into three groups based on axial length (AL), group 1: <22 mm (14 eyes), group 2: 22-24.5 mm (68 eyes) and group 3: >24.5 mm (6 eyes). The refractive prediction error (RPE) and mean absolute error (MAE) were calculated for 5 different formulas: SRK/T, Hoffer Q, Holladay 1, Haigis and Barrett Universal II. For eyes with the AL between 22 mm and 24.5 mm the greatest percentage of eyes with RPEs within ±0.25 D was 32.4% for Haigis formula, followed by Barrett Universal II, Hoffer Q and Holladay 1 with 29.4%. The percentage of eyes with RPEs within ±0.50 D was 100% only for Barrett Universal II and Holladay 1, 94.1% for SRK/T and 91.2% for Haigis and Hoffer Q. The first and third group with AL <22 and >24.5 mm were too small to have statistical significance due to the reluctancy to use multifocal IOLs on extreme ALs. ANOVA test showed no statistical difference (P=0.166) between the RPEs measured for each formula in this cohort. This study showed no statistical difference between formulas for this trifocal lens implant. There was a tendency for the RPE to be within ±0.25 D for most of the eyes with the Haigis formula, and within ±0.50 D for all the eyes with the Barrett Universal II formula in the group with the AL between 22 and 24.5 mm.

Accuracy of the Hill-radial basis function method and the Barrett Universal II formula

PURPOSE

The aim was to assess the postoperative results of a biometric method using artificial intelligence (Hill-radial basis function 2.0), and data from a modern formula (Barrett Universal II) and the Sanders-Retzlaff-Kraft/Theoretical formula.

METHODS

Phacoemulsification and biconvex intraocular lens implantation were performed in 186 cataractous eyes. The diopters of intraocular lens were established with the Hill-radial basis function method, based on biometric data obtained using the Aladdin device. The required diopters of the intraocular lens were also calculated by the Barrett Universal II formula and with the Sanders-Retzlaff-Kraft/Theoretical formula. The differences between the manifest postoperative refractive errors and the planned refractive errors were calculated, as well as the percentage of eyes within ±0.5 D of the prediction error. The mean- and the median absolute refractive errors were also determined.

RESULTS

The mean age of the patients was 70.13 years (SD = 10.67 years), and the mean axial length was 23.47 mm (range = 20.72-28.78 mm). The percentage of eyes within a prediction error of ±0.5 D was 83.62% using the Hill-radial basis function method, 79.66% with the Barrett Universal II formula, and 74.01% in the case of the Sanders-Retzlaff-Kraft/Theoretical formula. The mean- and the median absolute refractive errors were not statistically different.

CONCLUSION

Clinical success was the highest when using the biometric method, based on pattern recognition. The results obtained using Barrett Universal II came a close second. Both methods performed better compared to a traditionally used formula.