A Comparative Study to Assess the Predictability of Different IOL Power Calculation Formulas in Eyes of Short and Long Axial Length

Comparison of Refractive Prediction Error by Axial Length in Flanged Intrascleral Intraocular Lens Fixation

Purpose

To evaluate the refractive prediction error in flanged intrascleral intraocular lens (IOL) fixation using the SRK/T formula and compare the axial length using a single IOL.

Methods

Seventy-six eyes from 70 patients (45 males and 25 females) were included in this study. The mean age at the time of surgery was 73.4 ±12.3 years. The patients underwent flanged IOL fixation using a PN6A (Kowa). All surgeries were performed by two surgeons (Y. K. and T. O.) between Jan 2020 and Dec 2022 at Jikei University Daisan Hospital. IOL power was calculated using the SRK/T formula with IOL Master 700 (Carl Zeiss) as the bag power. The recommended value of 119.0 was used for the A-constant. The actual refractive spherical equivalent was calculated and compared with preoperative predictions. Refractive prediction errors were defined as the deviation of the actual postoperative spherical equivalent refraction in diopters from the predicted preoperative spherical equivalent refraction. The patients were divided into three groups according to axial length: <22.0 mm (short eyes), 22.0-24.5 mm (medium eyes), and >24.5 mm (long eyes), and the refractive prediction errors and mean absolute errors were compared.

Results

The mean refractive prediction error was -0.20 ± 0.52D. The mean absolute error was 0.44 ± 0.33D. The mean refractive prediction errors were not significantly different between the 22.0-24.5 mm (medium eyes) and >24.5 mm (long eyes) groups. (P=0.06) The mean absolute errors were not significantly different between the two groups (P=0.10).

Conclusion

The SRK/T formula worked well regardless of whether the eyes were medium or long according to the axial length in the flanged intrascleral IOL fixation.

[Evaluation of the accuracy of modern intraocular lens calculation formulas when optical biometry is not possible]

PURPOSE

This study evaluates the accuracy of modern intraocular lens (IOL) calculation formulas using axial length (AL) data obtained by ultrasound biometry (UBM) compared to the third-generation SRK/T calculator.

MATERIAL AND METHODS

The study included 230 patients (267 eyes) with severe lens opacities that prevented optical biometry, who underwent phacoemulsification (PE) with IOL implantation. IOL power calculation according to the SRK/T formula was based on AL and anterior chamber depth obtained by UBM (Tomey Biometer Al-100) and keratometry on the Topcon KR 8800 autorefractometer. To adapt AL for new generation calculators - Barrett Universal II (BUII), Hill RBF ver. 3.0 (RBF), Kane and Ladas Super Formula (LSF) - the retinal thickness (0.20 mm) was added to the axial length determined by UBM, and then the optical power of the artificial lens was calculated. The mean error and its modulus value were used as criteria for the accuracy of IOL calculation.

RESULTS

A significant difference (p=0.008) in the mean IOL calculation error was found between the formulas. Pairwise analysis revealed differences between SRK/T (-0.32±0.58 D) and other formulas - BUII (-0.16±0.52 D; p=0.014), RBF (-0.17±0.51 D; p=0.024), Kane (-0.17±0.52 D; p=0.029), but not with the LSF calculator (-0.19±0.53 D; p=0.071). No significant differences between the formulas were found in terms of mean error modulus (p=0.238). New generation calculators showed a more frequent success in hitting target refraction (within ±1.00 D in more than 95% of cases) than the SRK/T formula (86%).

CONCLUSION

The proposed method of adding 0.20 mm to the AL determined by UBM allows using this parameter in modern IOL calculation formulas and improving the refractive results of PE, especially in eyes with non-standard anterior segment structure.

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.

Comparison of Accuracy of Six Modern Intraocular Lens Power Calculation Formulas

PURPOSE

To compare the accuracy of modern intraocular lens (IOL) power calculation formulas in predicting refractive outcomes after standard cataract surgery.

METHODS

The medical records of 203 eyes from 203 patients that received phacoemulsification and IOL implantation were retrospectively reviewed. Partial coherence interferometry was used to obtain the biometric values. The refractive outcomes of Barrett Universal II (BUII), Emmetropia Verifying Optical (EVO) 2.0, Hill-RBF 3.0, Hoffer QST, Kane, and PEARL-DGS formulas were evaluated. Axial length (AL) subgroup analysis was done separately. The correlations between the prediction error calculated by each formula and AL and corneal power were also analyzed.

RESULTS

Overall, there was no significant difference between the absolute prediction errors predicted by the six formulas after adjusting the mean prediction error (p = 0.058). AL subgroup analysis of absolute error also showed that there is no significant difference between the formulas. The BUII and Hill-RBF 3.0 formulas showed a higher percentage of eyes with prediction error within ±0.50 diopters compared to the Hoffer QST formula (p = 0.022 and p = 0.035, respectively). However, there was no significant difference after Bonferroni correction was applied. The BUII formula showed the highest IOL Formula Performance Index and therefore the highest accuracy, followed by PEARL-DGS, EVO 2.0, Kane, Hill-RBF 3.0, and Hoffer QST formulas. Out of the six formulas, the prediction error calculated by the Hoffer QST was significantly correlated with the AL (p = 0.011). None of the prediction errors calculated by the six formulas showed correlation to the corneal power.

CONCLUSIONS

Analysis of the prediction error showed that the six modern IOL power calculation formulas have comparable accuracy overall and across different ranges of AL.

[Reasonability of accounting for gender in intraocular lens power calculation]

PURPOSE

The study assesses the influence of gender on the accuracy of intraocular lens (IOL) power calculation by formulas SRK/T, Barrett Universal II (BUII), Ladas super formula (LSF), Hill RBF (RBF) and Kane.

MATERIAL AND METHODS

The study enrolled 214 patients (106 men and 108 women) who underwent cataract phacoemulsification (PE). Optical biometry was performed on IOL-Master 500. IOL power calculation was performed either adjusting for gender (formulas SRK/T, BUII, LSF) or without such adjustment (formulas RBF, Kane). Calculation error (CE) was assessed one month after PE by comparing the achieved (autorefractometer Topcon-8800) and target spherical equivalent of refraction.

RESULTS

Significant differences were found in mean IOL CE with gender-unspecific formulas (SRK/T, BUII, LSF) and no differences in gender-specific calculators (RBF, Kane). The Kane formula demonstrated the lowest CE between men and women (-0.01±0.43 versus -0.09±0.41 D; p=0.158), while the SRK/T formula had the highest CE (0.02±0.46 versus -0.21±0.44 D, respectively; p<0.001). Presence of a significant correlation between CE and gender was found for all formulas except Kane (R2=0.005, p=0.158).

CONCLUSION

Patient's gender has a significant impact on IOL calculation accuracy. Using gender-responsive formulas could help achieve better refractive results with PE. The present study showed Kane formula to have the least CE dependence from gender. However, the CE difference (less than 0.25 D) was lower than the value of division (0.5D) in modern IOL models.

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 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.

Assessment of the influence of keratometry on intraocular lens calculation formulas in long axial length eyes

PURPOSE

Hyperopic surprises tend to occur in axial myopic eyes and other factors including corneal curvature have rarely been analyzed in cataract surgery, especially in eyes with long axial length (≥ 26.0 mm). Thus, the purpose of our study was to evaluate the influence of keratometry on four different formulas (SRK/T, Barrett Universal II, Haigis and Olsen) in intraocular lens (IOL) power calculation for long eyes.

METHODS

Retrospective case series. A total of 180 eyes with axial length (AL) ≥ 26.0 mm were divided into 3 keratometry (K) groups: K ≤ 42.0 D (Flat), K ≥ 46.0 D (Steep), 42.0 < K < 46.0 D (Average), and all the eyes were underwent phacoemulsification cataract surgery with Rayner (Hove, UK) 920H IOL implantation. Prediction errors (PE) were compared between different formulas to assess the accuracy of different formulas. Multiple regression analysis was performed to investigate factors associated with the PE.

RESULTS

The mean absolute error was higher for all evaluated formulas in Steep group (ranging from 0.66 D to 1.02 D) than the Flat (0.34 D to 0.67 D) and Average groups (0.40 D to 0.74D). The median absolute errors predicted by Olsen formula were significantly lower than that predicted by Haigis formula (0.42 D versus 0.85 D in Steep and 0.29 D versus 0.69 D in Average) in Steep and Average groups (P = 0.012, P < 0.001, respectively). And the Olsen formula demonstrated equal accuracy to the Barrett II formula in Flat and Average groups. The predictability of the SRK/T formula was affected by the AL and K, while the predictability of Olsen and Haigis formulas was affected by the AL only.

CONCLUSIONS

Steep cornea has more influence on the accuracy of IOL power calculation than the other corneal shape in long eyes. Overall, both the Olsen and Barrett Universal II formulas are recommended in long eyes with unusual keratometry.

Comparison of accuracy of intraocular lens power calculation for eyes with an axial length greater than 29.0 mm

PURPOSE

To evaluate and compare the accuracy of six different formulas (Emmetropia Verifying Optical version 2.0, Kane, SRK/T, Barrett Universal II, Haigis and Olsen) in intraocular lens (IOL) power calculation for extremely long eyes.

METHODS

Retrospective case-series. Seventy-three eyes with axial length (AL) ≥ 29.0 mm and underwent phacoemulsification cataract surgery with Rayner (Hove, UK) 920H IOL implantation from January 2018 to March 2020 were included. Prediction errors (PE) were calculated and compared between different formulas to evaluate the accuracy of formulas. Multiple regression analysis was performed to investigate factors associated with the PE.

RESULTS

The Kane formula had mean prediction error close to zero (- 0.01 ± 0.51 D, P = 0.841), whereas the EVO 2.0, SRK/T, Barrett Universal II, Haigis and Olsen formulas produced hyperopic outcomes (all P < 0.001). The median absolute error [inter-quartile range] produced by the EVO 2.0, Kane, Barrett Universal II and Olsen formulas showed no significant difference (0.33 D [0.48], 0.30 D [0.44], 0.34 D [0.39], 0.29 D [0.37], respectively, pairwise comparison P > 0.05), but was significantly lower than that of the SRK/T and Haigis formulas (0.85 D [0.66], 0.80 D [0.54], respectively, pairwise comparison P < 0.001). The AL and the PE produced by the SRK/T formula were significantly positively correlated in extremely myopic eyes (β = 0.248, P < 0.001), whereas the trend was not demonstrated in other formulas.

CONCLUSIONS

For cataract patients with axial length greater than 29.0 mm, the accuracy of the EVO 2.0, Kane, Barrett Universal II and Olsen formulas is comparable and significantly better than that of the SRK/T and Haigis formulas.

Effectiveness, Sensitivity, and Specificity of Intraocular Lens Power Calculation Formulas for Short Eyes

Objectives:

Materials and Methods:

Results:

Conclusion:

Outcomes of the Haigis-L formula for calculating intraocular lens power in extreme long axis eyes after myopic laser in situ keratomileusis

PURPOSE

To evaluate the accuracy of refractive prediction by the Haigis-L formula compared to four other IOL power calculation formulas in eyes with extremely long axial lengths (AL > 29.0 mm) after LASIK.

SETTING

Shanghai Eye Disease and Prevention Treatment Center, Shanghai, China.

DESIGN

Retrospective case series.

METHODS

Twenty-nine eyes from 19 patients were available for analysis. The primary outcome measure was the arithmetic refractive prediction error (RPE), defined as the difference between the actual postoperative refractive error and the intended formula-derived refractive target. The main outcome measure was the median absolute refraction prediction error (MedAE). The accuracy of the Haigis-L was compared with Barrett True K No History, Shammas-PL, SRK/Tcorrected K, and Holladay 2corrected K methods to calculate IOL power.

RESULTS

The Haigis-L formula had a significantly larger MedAE than Shammas-PL and SRK/Tcorrected K formulas (P = 0.005 and P = 0.015, respectively), a smaller percentage of eyes within ±1.50 diopter (D) of predicted error in refraction compared with Shammas-PL and SRK/Tcorrected K formulas (P = 0.014 and P = 0.005, respectively). The refractive prediction errors of 6 eyes with corneal keratometry of less than 35 D by Haigis-L all had more than 1.95 D of myopic overestimation, while none of the other four methods resulted in an absolute error over 1.95 D.

CONCLUSIONS

The Haigis-L formula was relatively accurate in predicting extreme long axis (>29.0 mm) eyes after myopic LASIK surgery but less accurate for eyes with extremely flat corneas (<35 D). SRK/Tcorrected K and Shammas-PL performed better than the other methods for refractive prediction in this type of eyes.

SYNOPSIS

Haigis-L performed worse than SRK/Tcorrected K and Shammas-PL in predicting IOL power in extremely long axis (>29.0 mm) eyes after myopic LASIK, especially with extremely flat corneas (K < 35 D).

THE EXACTNESS OF INTRAOCULAR LENS POWER CALCULATION FORMULAS FOR SHORT EYES AND CORRELATION BETWEEN METHOD ACCURACY AND EYEBALL AXIAL LENGTH

PURPOSE

To compare the accuracy of intraocular lens power calculation formulas and to examine the correlation of this exactness with the axial length for eyes shorter than 22.00 mm Methods: The data of hyperopic patients who underwent uneventful phacoemulsification between October 2015 and June 2019 were reviewed. The intraocular lens power for each patient was calculated using 6 formulas (Holladay1, SRK/T, Hoffer Q, Holladay 2, Haigis and Barrett Universal II) before cataract surgery. Postoperative refraction was measured, and refractive prediction error was calculated 3 months after phacoemulsification. The correlation between axial length and absolute error was evaluated.

RESULTS

Fifty-six patients (62 eyes) whose ocular axial length ranged between 20.58 mm and 21.97 mm were included in the study. The Hoffer Q formula achieved the lowest mean absolute error of 0.09 (±0.08 D). A significant correlation for the Hoffer Q (&#961; = -0.329, p = 0.009) and the SRK/T (&#961; = 0.321, p = 0.011) formula was observed.

CONCLUSIONS

1. The Hoffer Q formula obtained the lowest absolute error and was recommended for intraocular lens power calculation for eyeballs with axial length shorter than 22.0 mm. 2. The correlation between axial length and absolute error is a factor which should be considered when calculating intraocular lens power.

IOL Power Calculation After Radial Keratotomy Using the Haigis and Barrett True-K Formulas

PURPOSE

To compare the accuracy of intraocular lens (IOL) power calculation in patients with previous radial keratotomy using the Haigis and Barrett True-K formulas.

METHODS

In a retrospective cases series of patients with previous radial keratotomy and minimum follow-up of 1.2 months, preoperative data from an IOLMaster 500 or 700 (Carl Zeiss Meditec AG), the IOL power implanted, and the postoperative refraction were used to calculate the refractive prediction error. The primary outcomes were the mean absolute and arithmetic refractive prediction errors and the percentage of eyes with a refractive prediction error within ±0.50 and ±1.00 diopters (D).

RESULTS

One hundred eight eyes were evaluated with a mean follow-up of 6.9 ± 4.9 months. The Haigis formula yielded a mean arithmetic refractive prediction error of -0.29 ± 1.00 D, which was significantly different than that of the Barrett True-K formula, which was -0.03 ± 0.96 D (P < .001). The mean absolute refractive prediction error was 0.80 ± 0.67 for the Haigis formula and 0.74 ± 0.60 for the Barrett True-K formula (P > .05). The percentages of eyes with a refractive prediction error within ±0.50 and ±1.00 D were 43.5% and 65.7% for the Haigis formula and 42.6% and 75.9% for the Barrett True-K formula, respectively (all P > .05). The subgroup analysis revealed that for flat corneas (K1 < 38.00 D), the Barrett True-K formula resulted in more hyperopic results than the Haigis formula.

CONCLUSIONS

The Barrett True-K formula exhibited better arithmetic predictability than the Haigis formula; however, it showed a tendency for hyperopic results in very flat corneas. [J Refract Surg. 2020;36(12):832-837.].

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.

Changes in the Ocular Parameters of Patients with Graves' Disease after Antithyroid Drug Treatment

Background and Objectives: To find the differences in ocular axial length, keratometric measurements, and intraocular lens (IOL) power in patients with Graves’ disease (GD) after treatment with a thionamide antithyroid drug (ATD), methimazole. Materials and Methods: The medical charts of 28 patients (4 males and 24 females; mean age: 47.2 ± 21.2 years) were studied. Each patient was examined twice using an IOL Master Device and keratometry at the first visit (before ATD treatment) and after 1 month of ATD treatment. The IOL power was calculated for each patient using the Hoffer Q, SRK-2, and SRK/T formulas according to axial length. Results: After 1 month, the axial length increased (right and left eyes: p < 0.001 and p = 0.05, respectively). Based on keratometry, changes in the horizontal and vertical optical power [in diopters (D)] were not statistically significant. However, the IOL power changed after 1 month of ATD treatment in 64.3% of the patients. In 14 patients (50%), there was a 0.5–1.0 D IOL power decrease in single eyes; in two patients (7.1%), an IOL power decrease of 0.5–1.0 D in both eyes; and in two patients (7.1%), a 0.5 D IOL power increase in single eyes. The calculated IOL power values were lower after ATD treatment (right and left eyes, p = 0.010 and p = 0.018, respectively). Conclusions: The IOL power changed in 64.3% of GD patients after ATD treatment. Therefore, avoiding cataract surgery at the early stage of ATD treatment would be appropriate for selecting a more accurate IOL power.

Evaluation of a New IOL Power Calculator in Cataract Patients with Normal and Long Axial Lengths

Purposes: To evaluate the accuracy of Ophtha Top and consistency between Ophtha Top and IOLMaster 500 in intraocular lens refractive power calculation among cataract patients with normal and long axial lengths. Methods: This study included cataract patients scheduled for phacoemulsification and IOL implantation surgery. The IOL power was calculated using Ophtha Top and IOLMaster 500 (integrated with SRK/T, Hoffer Q, Holladay 1 formula). The accuracy of IOL power calculation between Ophtha Top and IOLMaster 500 was compared. Bland-Altman plots were also used to assess agreement between Ophtha Top and IOLMaster 500. Results: Ninety-four patients (94 eyes) were included. The mean values of the arithmetic and absolute prediction errors of Ophtha Top were -0.22 ± 0.62 D and 0.52 ± 0.40 D for whole sample. Absolute refractive error showed no significant difference between Ophtha Top and IOLMaster 500 using 3 traditional formulas in eyes with normal and long axial lengths. In normal eyes, mean and medium absolute error of Ophtha Top was 0.49D and 0.48D, which were comparable to that of IOLMaster 500 (Hoffer Q:0.47D; 0.40D & Holladay 1: 0.48D; 0.37D). Similar trend was found in long eyes (Ophtha Top:0.58 D & IOLMaster using SRK/T:0.53D). Conclusions: Ophtha Top based on real ray-tracing method could provide predictable outcomes in all eyes, which was comparable to outcomes from IOLMaster 500 using SRK/T, Hoffer Q, Hollday 1 formula. Ophtha Top would be a promising alternative choice for IOL power calculation.

Clinical application of bicylindric intraocular lens power calculation method

Purpose:

To analyze the reliability of the refractive results prediction obtained in intraocular lens (IOL) calculation using bicylindric power calculation method, with the use of steep and flat keratometry readings compared with the classical mean keratometry calculation method.

Methods:

Fifty-seven eyes of 57 subjects who underwent cataract surgery were included in this prospective study. Optical biometry was performed with IOLMaster 700 and IOL power calculation was performed using both keratometry readings and the surgically induced astigmatism. Four weeks after surgery, subjective refraction was done. Finally, results obtained with both IOL calculation methods were compared.

Results:

Mean spherical equivalent using bicylindric IOL power calculation method was - 0.082 ± 0.296D, and achieved mean spherical equivalent using classical IOL power method with Haigis formula was - 0.088 ± 0.405D. Achieved mean spherical equivalent obtained in subjective refraction after surgery was - 0.101 ± 0.265D. Linear correlation between bicylindric method spherical equivalent calculation and achieved spherical equivalent was statistically significant (r = 0.761, P < 0.001), also correlation between Haigis spherical equivalent calculation and achieved spherical equivalent was statistically significant (r = 0.339, P = 0.010). Emmetropia was achieved in 49 of 57 (85.86%) subjects and bicylindric method calculated that 49 of 57 (85.86%) of subjects would get emmetropia (P = 1.000). Classical IOL power calculation estimated that 38/57 subjects would get emmetropia (66.67%) (P = 0.026).

Conclusion:

The IOL power calculation including both keratometry readings and surgically induced astigmatism seems to be more accurate and provides more precision in refractive prediction than classical calculation method.

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

Purpose:

Our study was conducted to evaluate and compare the accuracy of the refractive prediction determined by the calculation formulas for different intraocular lens (IOL) powers for high myopia.

Methods:

This study reviewed 217 eyes from 135 patients who had received cataract aspiration treatment and IOL implantation. The refractive mean numerical error (MNE) and mean absolute error (MAE) of the IOL power calculation formulas (SRK/T, Haigis, Holladay, Hoffer Q, and Barrett Universal II) were examined and compared. The MNE and MAE at different axial lengths (AL) were compared, and the percentage of every refractive error absolute value for each formula was calculated at ±0.25D, ±0.50D, ±1.00D, and ±2.00D.

Results:

In all, 98 patients were recruited into this study and 98 eyes of them were analyzed. We found that Barrett Universal II formula had the lowest MNE and MAE, SRK/T and Haigis formulas arrived at similar MNE and MAE, and the MNE and MAE calculated by Holladay and Hoffer Q formula were the highest. Barrett Universal II formulas have the lowest MAE among different AL patients, whereas it reached the highest percentage of refractive error absolute value within 0.5D in this study. The MAE of each formula is positively correlated with AL.

Conclusion:

Barrett Universal II formula rendered the lowest predictive error compared with SRK/T, Haigis, Holladay, and Hoffer Q formulas. Thus, Barrett Universal II formula may be regarded as a more reliable formula for high myopia.

[Calculation of intraocular lens power in surgical treatment of extreme hyperopia]

Accuracy of calculation of the intraocular lens (IOL) power in eyes with short axial length is inferior to one in emmetropic eyes. Most studies focus on relatively standard eyes.

PURPOSE

To assess the accuracy of power calculation for IOL used to correct extreme hyperopia and to compare available formulas based on their predictive capacity.

MATERIAL AND METHODS

Results of 13 implantations involving IOLs of at least 40 Diopters (D) in power were retrospectively evaluated. IOL power was calculated using five formulas: Haigis, Hoffer Q, HolladayI, SRKII, SRK/T. Mean numerical refractive prediction error (RPE) and mean absolute refractive prediction error (ARPE) were calculated. Mean and median ARPE were computed after optimizing the A₀ constant. Proportions of eyes within certain RPE limits were compared between the formulas.

RESULTS

Mean RPE ranged from 1.43 to 11.71 D before adjustment and from 1.08 to 5.34 D after adjustment (p<0.0001). Haigis formula produced the least RPE, and SRKII - the most. Pairwise comparison by mean ARPE after adjustment revealed no statistically significant difference between Haigis and Hoffer Q formulas. Comparison of formulas by percentage of eyes with minimal RPE identified Haigis and Hoffer Q as the most accurate, while the difference between the two was not statistically significant. The difference between the most accurate formulas (Haigis and Hoffer Q) and the least accurate (SRKII) was statistically significant.

CONCLUSION

In eyes with extremely short anterior-posterior axis, prediction errors in IOL power calculations are relatively frequent (only 31-46% of eyes are within ±0.5 D) and warrant reduction. Among the evaluated formulas, Haigis and Hoffer Q are the most accurate. In order to improve the accuracy of IOL power calculations, it is necessary to employ personalized constants.