Accuracy of intraocular lens power calculation formulae for the Yamane technique of secondary fixation: a systematic review and meta-analysis.

OBJECTIVE: This systematic review and meta-analysis aims to assess the refractive outcomes of the Yamane technique for intrascleral fixation of intraocular lenses (SF-IOL) and compare the predictive ability of the various intraocular lens power calculation formulae commonly used in conjunction with the technique. METHODS: A literature search was conducted in the Medline, Scopus, and Cochrane Library databases for articles published from January 2014 to May 2023. Studies that met the predetermined inclusion criteria were included and subjected to analysis. The primary outcome evaluated was the refractive predictive error, defined as the difference between predicted refraction and post-operative manifest refraction. RESULTS: Eleven studies met the inclusion criteria, with a cumulative sample size of 615 patients (mean age: 66.6 years). Various IOL formulae were used, with SRK/T being the most frequently adopted formula. The overall mean refractive predictive error for all formulae combined was -0.02 D, which was not statistically significant (p = 0.99). Subgroup analysis for individual formulae also showed no significant difference from predicted error for any formula (p > 0.05). CONCLUSION: The Yamane technique for SF-IOL shows promising refractive outcomes, and the choice of IOL power calculation formula should be tailored based on patient characteristics and surgeon preference. No formula demonstrated superior predictive ability over others. Further research is needed to develop formulae specifically for eyes with secondary aphakia and poor capsular support.

The effect of corneal power on the accuracy of 14 IOL power formulas.

BACKGROUND: This study evaluates the impact of corneal power on the accuracy of 14 newer intraocular lens (IOL) calculation formulas in cataract surgery. The aim is to assess how these formulas perform across different corneal curvature ranges, thereby guiding more precise IOL selection. METHODS: In this retrospective case series, 336 eyes from 336 patients who underwent cataract surgery were studied. The cohort was divided into three groups according to preoperative corneal power. Key metrics analyzed included mean prediction error (PE), standard deviation of PE (SD), mean absolute prediction error (MAE), median absolute error (MedAE), and the percentage of eyes with PE within ± 0.25 D, 0.50 D, ± 0.75 D, ± 1.00 D and ± 2.00 D. RESULTS: In the flat K group (Km < 43 D), VRF-G, Emmetropia Verifying Optical Version 2.0 (EVO2.0), Kane, and Hoffer QST demonstrated lower SDs (± 0.373D, ± 0.379D, ± 0.380D, ± 0.418D, respectively) compared to the VRF formula (all P < 0.05). EVO2.0 and K6 showed significantly different SDs compared to Barrett Universal II (BUII) (all P < 0.02). In the medium K group (43 D ≤ Km < 46 D), VRF-G, BUII, Karmona, K6, EVO2.0, Kane, and Pearl-DGS recorded lower MAEs (0.307D to 0.320D) than Olsen (OLCR) and Castrop (all P < 0.03), with RBF3.0 having the second lowest MAE (0.309D), significantly lower than VRF and Olsen (OLCR) (all P < 0.05). In the steep K group (Km ≥ 46D), RBF3.0, K6, and Kane achieved significantly lower MAEs (0.279D, 0.290D, 0.291D, respectively) than Castrop (all P < 0.001). CONCLUSIONS: The study highlights the varying accuracy of newer IOL formulas based on corneal power. VRF-G, EVO2.0, Kane, K6, and Hoffer QST are highly accurate for flat corneas, while VRF-G, RBF3.0, BUII, Karmona, K6, EVO2.0, Kane, and Pearl-DGS are recommended for medium K corneas. In steep corneas, RBF3.0, K6, and Kane show superior performance.

Prospective comparison of accuracy of intraocular lens calculation formulas in phacovitrectomy: a pilot study in a real-world clinical practice.

PURPOSE: To compare the accuracy of intraocular lens (IOL) power calculations among IOL formulas after phacovitrectomy. METHODS: We prospectively enrolled 206 eyes of 206 patients who underwent 25-gauge phacovitrectomy, without gas tamponade, for macular pathology. Pre-operative optical biometry used the IOLMaster 700 to calculate the IOL power with the new formulas, i.e. the Barrett Universal II (BU II), Emmetropia Verifying Optical version 2.0, Hill-Radial Basis Function (RBF) version 3.0, Kane, and Ladas Super Formula, and conventional formulas, i.e. Haigis, Hoffer Q, Holladay 1, Holladay 2, and Sanders-Retzlaff-Kraff/T (SRK/T). A single-piece foldable IOL was implanted in all cases. Manifest refractions were measured before and 3 months after surgery. RESULTS: The BU II formula showed the lowest standard deviation and mean and median absolute errors and had the highest percentage of eyes with a refractive prediction error within ± 0.25 D. The absolute error was significantly lower with the four new formulas, except the Hill-RBF, than with the Hoffer Q (all p = ≤ 0.010) and Holladay 1 formulas (all p = < 0.010). The absolute error with the BU II formula was also lower than that with the Holladay 2 (p = 0.012) and SRK/T (p = 0.024) formulas. CONCLUSION: Overall, the new IOL formulas, except the Hill-RBF, were superior to some of the conventional formulas for calculating IOL power in phacovitrectomy.

Accuracy of refractive outcomes using standard or total keratometry for intraocular lens power formulas in conventional cataract surgery.

PURPOSE: To evaluate if total keratometry (TK) is better than standard keratometry (K) for predicting an accurate intraocular lens (IOL) refractive outcome in virgin eyes using four IOL power calculation formulas. METHODS: 447 eyes that underwent monofocal intraocular lens implantation were enrolled in this study. IOLMaster 700 (Carl Zeiss Meditech, Jena, Germany) was used for optical biometry. Prediction error (PE), mean absolute prediction error (MAE), median absolute prediction error (MedAE), proportions of eyes within ± 0.25 diopters (D), ± 0.50 D, ± 0.75 D, ± 1.00 D, ± 2.00 D prediction error, and formula performance index (FPI) were calculated for each K- and TK-based formula. RESULTS: Overall, the accuracy of each TK and K formula was comparable. The MAEs and MedAEs showed no difference between most of the K-based and the TK-based formula; only the MAE of TK was significantly higher than that of K using the Haigis. The percent of eyes within ± 0.25 D PE for TK was not significantly different from that for K. The analysis of PE across various optical dimensions revealed that TK had no effect on the refractive results in eyes with different preoperative axial length, anterior chamber depth, keratometry, and lens thickness. The K-based Barrett Universal II formula performed excellently, showed the leading FPI score, and had the best refractive prediction outcomes among the four formulas. CONCLUSION: TK and K can be used for IOL power calculation in monofocal IOL implantation cataract surgery in virgin eyes, as both are comparable. In all investigated formulas, the predictive accuracy of TK-based formulas is not superior to that of standard K-based formulas.

Comparative analysis of IOL power calculations in postoperative refractive surgery patients: a theoretical surgical model for FS-LASIK and SMILE procedures.

BACKGROUND: As the two most prevalent refractive surgeries in China, there is a substantial number of patients who have undergone Femtosecond Laser-assisted In Situ Keratomileusis (FS-LASIK) and Small Incision Lenticule Extraction (SMILE) procedures. However, there is still limited knowledge regarding the selection of intraocular lens (IOL) power calculation formulas for these patients with a history of FS-LASIK or SMILE. METHODS: A total of 100 eyes from 50 postoperative refractive surgery patients were included in this prospective cohort study, with 25 individuals (50 eyes) having undergone FS-LASIK and 25 individuals (50 eyes) having undergone SMILE. We utilized a theoretical surgical model to simulate the IOL implantation process in postoperative FS-LASIK and SMILE patients. Subsequently, we performed comprehensive biological measurements both before and after the surgeries, encompassing demographic information, corneal biometric parameters, and axial length. Various formulas, including the Barrett Universal II (BUII) formula, as a baseline, were employed to calculate IOL power for the patients. RESULTS: The Barrett True K (BTK) formula, demonstrated an mean absolute error (AE) within 0.5 D for both FS-LASIK and SMILE groups (0.28 ± 0.25 D and 0.36 ± 0.24 D, respectively). Notably, the FS-LASIK group showed 82% of results differing by less than 0.25 D compared to preoperative BUII results. The Barrett True K No History (BTKNH) formula, which also incorporates measured posterior corneal curvature, performed similarly to BTK in both groups. Additionally, the Masket formula, relying on refractive changes based on empirical experience, displayed promising potential for IOL calculations in SMILE patients compared with BTK (p = 0.411). CONCLUSION: The study reveals the accuracy and stability of the BTK and BTKNH formulas for IOL power calculations in myopic FS-LASIK/SMILE patients. Moreover, the Masket formula shows encouraging results in SMILE patients. These findings contribute to enhancing the predictability and success of IOL power calculations in patients with a history of refractive surgery, providing valuable insights for clinical practice. Further research and larger sample sizes are warranted to validate and optimize the identified formulas for better patient outcomes.

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.

Evaluation of IOL power calculation with the Kane formula for pediatric cataract surgery.

PURPOSE: To assess the accuracy of the Kane formula for intraocular lens (IOL) power calculation in the pediatric population. METHODS: The charts of pediatric patients who underwent cataract surgery with in-the-bag IOL implantation with one of two IOL models (SA60AT or MA60AC) between 2012 and 2018 in The Hospital for Sick Children, Toronto, Ontario, CanFada, were retrospectively reviewed. The accuracy of IOL power calculation with the Kane formula was evaluated in comparison with the Barrett Universal II (BUII), Haigis, Hoffer Q, Holladay 1, and Sanders-Retzlaff-Kraff Theoretical (SRK/T) formulas. RESULTS: Sixty-two eyes of 62 patients aged 6.2 (IQR 3.2-9.2) years were included. The SD values of the prediction error obtained by Kane (1.38) were comparable with those by BUII (1.34), Hoffer Q (1.37), SRK/T (1.40), Holaday 1 (1.41), and Haigis (1.50), all p > 0.05. A significant difference was observed between the Hoffer Q and Haigis formulas (p = 0.039). No differences in the median and mean absolute errors were found between the Kane formula (0.54 D and 0.91 ± 1.04 D) and BUII (0.50 D and 0.88 ± 1.00 D), Hoffer Q (0.48 D and 0.88 ± 1.05 D), SRK/T (0.72 D and 0.97 ± 1.00 D), Holladay 1 (0.63 D and 0.94 ± 1.05 D), and Haigis (0.57 D and 0.98 ± 1.13 D), p = 0.099. CONCLUSION: This is the first study to investigate the Kane formula in pediatric cataract surgery. Our results place the Kane among the noteworthy IOL power calculation formulas in this age group, offering an additional means for improving IOL calculation in pediatric cataract surgery. The heteroscedastic statistical method was first implemented to evaluate formulas' predictability in children.

Optimizing intraocular lens power calculation using adjusted conventional keratometry for cataract surgery combined with Descemet membrane endothelial keratoplasty.

PURPOSE: To evaluate the utility of intraocular lens (IOL) power calculation using adjusted conventional keratometry (K) according to postoperative posterior to preoperative anterior corneal curvature radii (PPPA) ratio for eyes with Fuch's dystrophy undergoing cataract surgery combined with Descemet membrane endothelial keratoplasty (triple DMEK). METHODS: A fictitious refractive index (FRI) was determined (Pentacam HR®) based on the PPPA ratio in 50 eyes undergoing triple DMEK. Adjusted corneal power was calculated in every eye using adjusted K values: K values determined by the IOLMaster were converted to adjusted anterior corneal radius using the mean FRI. Posterior corneal radius was calculated using the mean PPPA ratio. Adjusted corneal power was determined based on the calculated corneal radii and thick lens formula. Refractive errors calculated using the Haigis, SRK/T, and HofferQ formulae based on the adjusted corneal power were compared with those based on conventional K measurements. RESULTS: Calculated PPPA ratio and FRI were 0.801 and 1.3271. Mean prediction error based on conventional K was in the hyperopic direction (Haigis: 0.84D; SRK/T: 0.74D; HofferQ: 0.74D) and significantly higher (P < 0.001) than that based on adjusted corneal power (0.18D, 0.22D, and 15D, respectively). When calculated according to adjusted corneal power, the percentage of eyes with a hyperopic shift > 0.5D fell significantly from 64 to 30% (Haigis), 62 to 36% (SRK/T), and 58 to 26% (HofferQ), respectively. CONCLUSION: IOL power calculation based on adjusted corneal power can be used to reduce the risk of a hyperopic shift after triple DMEK and provides a more accurate refractive outcome than IOL power calculation using conventional K.

Comparing the accuracy of new intraocular lens power calculation formulae in short eyes after cataract surgery: a systematic review and meta-analysis.

PURPOSE: Calculating the intraocular lens (IOL) power in short eyes for cataract surgery has been a challenge. A meta-analysis was conducted to identify, among several classic and new IOL power calculation formulae, which obtains the best accuracy. METHODS: All studies aiming at comparing the accuracy of IOL power calculation formulae in short eyes were searched up in the databases of PubMed, EMBASE, Web of Science and the Cochrane library from Jan. 2011 to Mar. 2021. Primary outcomes were the percentages of eyes with a refractive prediction error in ± 0.25D, ± 0.5D and ± 1.0D. RESULTS: Totally 1,476 eyes from 14 studies were enrolled in comparison of 13 formulae (Barrett Universal II, Castrop, Haigis, Hoffer Q, Holladay1, Holladay2, Kane, Ladas Super Formula, Okulix, Olsen, Pearl-DGS, SRK/T and T2). Pearl-DGS had the highest percentage within ± 0.25D. In the ± 0.5D range, Pearl-DGS obtained the highest percentage again, and it was significantly higher than Barrett Universal II, Haigis, Hoffer Q, Holladay1, Holladay2 and Olsen (P = 0.001, P = 0.02, P = 0.0003, P = 0.01, P = 0.007, P = 0.05, respectively). In the ± 1.0D range, Okulix possessed the highest percentage, and it was significantly higher than Barrett Universal II, Castrop, Hoffer Q and Holladay2 (P = 0.0005, P = 0.03, P = 0.003, P = 0.02, respectively). CONCLUSION: The new generation formulae, based on artificial intelligence or ray-tracing principle, are more accurate than the convergence formulae. Pearl-DGS and Okulix are the two most accurate formulae in short eyes.

[Alternative method of intraocular lens power calculation in eyes with short axial length]. / Al'ternativnyi sposob rascheta opticheskoi sily intraokulyarnykh linz pri korotkoi perednezadnei osi glaza.

PURPOSE: To develop an alternative method of intraocular lens (IOL) power calculation in eyes with mature cataract and axial length (AL) of less than 22.0 mm using modern formulas Barrett Universal II and Hill RBF. MATERIAL AND METHODS: The study enrolled 41 patients (41 eyes) who underwent phacoemulsification (PE). Ultrasound biometry (Tomey Biometer Al-100) and keratometry (Topcon-8800) were used for IOL power calculation by SRK/T and Haigis formulas. To calculate IOL power by Barrett Universal II and Hill RBF formulas, 0.2 mm were added to AL measured with ultrasonography (retinal thickness). One month after PE, spherical equivalent of refraction was compared with target refraction (calculated by the formulas listed above), and based on that a conclusion was made on the accuracy of calculations. RESULTS: Haigis formula was found to be the least accurate (IOL calculation error -0.39±0.79 D). The calculation error in SRK/T (0.04±0.79 D), Barrett Universal II (0.02±0.79 D) and Hill RBF (-0.05±0.73 D) formulas was much lower. However, among them Hill RBF had the lowest spread of the mean absolute IOL calculation error. Pairwise comparison revealed significant difference of mean IOL calculation error by Haigis formula versus the others. There was no significant difference in the following pairs: SRK/T - Barrett Universal II (p=0.855), and SRK/T - Hill RBF (p=0.167), but there was a significant difference (p=0.043) in the Barrett Universal II - Hill RBF pairdue to the tendency for slight hypermetropic calculation error in the former and the inherent slight myopic shift in the latter.. CONCLUSION: The proposed alternative method of IOL power calculation in eyes with mature cataract and short AL using modern formulas (Barrett Universal II and Hill RBF) shows higher accuracy compared to the formulas embedded in ultrasound biometer (SRK/T and Haigis), and can be recommended for use in everyday practice.

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

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

Assessing the validity of corneal power estimation using conventional keratometry for intraocular lens power calculation in eyes with Fuch's dystrophy undergoing Descemet membrane endothelial keratoplasty.

PURPOSE: The present retrospective study was designed to test the hypothesis that the postoperative posterior to preoperative anterior corneal curvature radii (PPPA) ratio in eyes with Fuch's dystrophy undergoing Descemet membrane endothelial keratoplasty (DMEK) is significantly different to the posterior to anterior corneal curvature radii (PA) ratio in virgin eyes and therefore renders conventional keratometry (K) and the corneal power derived by it invalid for intraocular lens (IOL) power calculation. METHODS: Measurement of corneal parameters was performed using Scheimpflug imaging (Pentacam HR, Oculus, Germany). In 125 eyes with Fuch's dystrophy undergoing DMEK, a fictitious keratometer index was calculated based on the PPPA ratio. The preoperative and postoperative keratometer indices and PA ratios were also determined. Results were compared to those obtained in a control group consisting of 125 eyes without corneal pathologies. Calculated mean ratios and keratometer indices were then used to convert the anterior corneal radius in each eye before DMEK to postoperative posterior and total corneal power. To assess the most appropriate ratio and keratometer index, predicted and measured powers were compared using Bland-Altman plots. RESULTS: The PPPA ratio determined in eyes with Fuch's dystrophy undergoing DMEK was significantly different (P < 0.001) to the PA ratio in eyes without corneal pathologies. Using the mean PA ratio (0.822) and keratometer index (1.3283), calculated with the control group data to convert the anterior corneal radius before DMEK to power, leads to a significant (P < 0.001) underestimation of postoperative posterior negative corneal power (mean difference (∆ = - 0.14D ± 0.30) and overestimation of total corneal power (∆ = - 0.45D ± 1.08). The lowest prediction errors were found using the geometric mean PPPA ratio (0.806) and corresponding keratometer index (1.3273) to predict the postoperative posterior (∆ = - 0.01 ± 0.30) and total corneal powers (∆ = - 0.32D ± 1.08). CONCLUSIONS: Corneal power estimation using conventional K for IOL power calculation is invalid in eyes with Fuch's dystrophy undergoing DMEK. To avoid an overestimation of corneal power and minimize the risk of a postoperative hyperopic shift, conventional K for IOL power calculation should be adjusted in eyes with Fuch's dystrophy undergoing cataract surgery combined with DMEK. The fictitious PPPA ratio and keratometer index may guide further IOL power calculation methods to achieve this.

Gender differences in refraction prediction error of five formulas for cataract surgery.

OBJECTIVES: To evaluate gender differences in optical biometry measurements and lens power calculations. METHODS: Eight thousand four hundred thirty-one eyes of five thousand five hundred nineteen patients who underwent cataract surgery at University of Michigan's Kellogg Eye Center were included in this retrospective study. Data including age, gender, optical biometry, postoperative refraction, implanted intraocular lens (IOL) power, and IOL formula refraction predictions were gathered and/or calculated utilizing the Sight Outcomes Research Collaborative (SOURCE) database and analyzed. RESULTS: There was a statistical difference between every optical biometry measure between genders. Despite lens constant optimization, mean signed prediction errors (SPEs) of modern IOL formulas differed significantly between genders, with predictions skewed more hyperopic for males and myopic for females for all 5 of the modern IOL formulas tested. Optimization of lens constants by gender significantly decreased prediction error for 2 of the 5 modern IOL formulas tested. CONCLUSIONS: Gender was found to be an independent predictor of refraction prediction error for all 5 formulas studied. Optimization of lens constants by gender can decrease refraction prediction error for certain modern IOL formulas.

Corneal power values for use with keratoprostheses and intraocular lenses.

PURPOSE: To specify a keratoprosthesis (KPro) power value for use with an intraocular lens (IOL). METHODS: Raytracing software was used to determine the imaging properties of both the natural cornea and conceptual KPro designs, and IOL power calculation methods were reviewed. Traditional calculations use 'thick lens' models for the overall eye, while also using 'thin lens' approximations for the cornea and IOL. The power of the natural cornea acts approximately at the apex, although this is unlikely to be the case for a KPro. The IOL location is determined using an empirical adjustment that is calculated from clinical results for natural eyes. RESULTS: The use of a KPro has a similar optical effect to corneal refractive surgery, where the cornea no longer matches the original eye. A modification of the 'double-K' calculation method can be used by specifying the KPro effective power at the original corneal apex, but still estimating the postoperative IOL location using the original corneal power. The KPro power is measured by assembling the KPro with fluid and a window to simulate the way it is used, recording the best focus power at room temperature with a 3 mm diameter aperture, rescaling to the in situ power at 35°C using refractive index changes, and then rescaling again to the power expected relative to the original corneal apex. When expressed as a K value, a keratometer refractive index of 1.332 is proposed. If necessary, clinical results may be used later to make empirical adjustments to the calculation method. CONCLUSIONS: A KPro power can be specified relative to the expected location of the original corneal apex using a keratometer index of 1.332. A double-K calculation can then be used to determine the correct KPro and IOL power values for a pseudophakic eye.

Could anatomical changes occurring with cataract surgery have a clinically significant effect on effective intraocular lens position?

PURPOSE: To assess if the calculation of the effective lens position (ELP) of two different monofocal intraocular lenses (IOLs) could be optimized by considering the potential anatomical changes occurring after cataract surgery. METHODS: Prospective, descriptive, single-center study involving 472 eyes of 280 subjects (mean age 73.5 years) undergoing cataract surgery that were divided into two groups according to the IOL implanted: group 1330 eyes with AcrySof IQ SN60WF (Alcon), and group 2142 eyes with Akreos MI60L (Bausch + Lomb). Refractive and biometric changes were evaluated during a period of 6-month follow-up with an optical biometer (considering potential measurement artifacts). Comparison of ELP estimated with the SRK-T formula (ELPSRK-T) and ELP calculated considering clinical real data was made (ELPAXL-corrected clinical). RESULTS: Besides significant changes in refraction (p ≤ 0.020), a significant increase in anterior chamber depth (ACD) (p < 0.001) and a significant reduction in the axial length (AXL) (p < 0.001) were detected at 1 month after surgery. Mean 1-month postoperative AXL change was - 0.08 ± 0.06 and - 0.10 ± 0.11 mm in groups 1 and 2, respectively (p = 0.001), with no significant changes afterward. Mean difference between ELPSRK-T and ELPAXL-corrected clinical was 0.17 ± 0.39 and - 0.23 ± 0.43 mm in groups 1 and 2, respectively (p < 0.001). A strong and statistically significant correlation of these differences with the prediction refractive error was found in both groups (group 1, r = - 0.723; group 2, r = - 0.819; p < 0.001). CONCLUSIONS: The estimation of ELP using the SRK-T formula for the two IOLs evaluated may be optimized considering biometric changes with surgery, helping to understand better some problems of refractive unpredictability.

[Calculation of intraocular lens power after trabeculectomy]. / Osobennosti rascheta intraokulyarnykh linz posle sinustrabekulektomii.

PURPOSE: To assess biometric changes in eyes after trabeculectomy (TE) and its impact on refractive outcomes of phacoemulsification (PE) in order to determine the corrections for calculation of intraocular lens (IOL) power. MATERIAL AND METHODS: The study included two groups of patients: the 1st group consisted of 116 patients who were assessed by optical biometry (IOL-Master 500) for mean biometric values before and after TE; the 2nd group included 31 patients with history of TE (study subgroup) and 47 individuals without glaucoma (control subgroup) who underwent PE with subsequent comparison of IOL calculation accuracy. RESULTS: There was significant axial length (AL) shortening in the 1st group from 23.28±0.97 to 23.19±0.97 mm (p<0.001) 6 months after TE, which positively correlated (r=0.296, p=0.001) with intraocular pressure (IOP) decrease (from 25.4±5.34 to 17.2±4.42 mm Hg, p<0.001). Mean keratometry and anterior chamber depth values did not significantly change after TE. Mean IOL power calculation error after PE in the 2nd group was -0.05±0.47 D and 0.003±0.62 D for the control and study subgroups, respectively (p=0.697). However, significant impact of preoperative IOP on IOL power calculation error was discovered in the study subgroup (R2=0.526, p<0.001), but not in the control subgroup (R2=0.061, p=0.052). Based on linear regression, the expected IOL power calculation errors depending on the preoperative IOP were determined for patients with history of TE. CONCLUSION: AL shortening due to decrease in IOP in patients with history of TE leads to IOL power calculation errors. Expected IOL calculation error related to preoperative IOP level was determined, which could help improve refractive outcomes of PE in patients with history of TE.

[Optimization of intraocular lens power calculation in pseudoexfoliation syndrome]. / Optimizatsiya rascheta intraokulyarnykh linz pri psevdoeksfoliativnom sindrome.

PURPOSE: To assess the impact of pseudoexfoliation syndrome (PEX) on the accuracy of intraocular lens (IOL) power calculation. MATERIAL AND METHODS: The study included 243 patients who underwent phacoemulsification (PE); they were divided into the control (no PEX signs, n=131) and study (signs of PEX, n=112) groups. Barrett Universal II formula was used for IOL calculation by optical biometry (IOL-Master 500). Obtained refraction (autorefractometer Topcon-8800) was compared with target refraction to assess IOL calculation accuracy 1 month after PE. RESULTS: Patients with PEX had significantly shallower anterior chamber compared to the control group (2.86±0.43 versus 3.0±0.43 mm, p=0.003) and steeper corneal curvature (44.31±1.5 versus 43.7±2.59 D, p=0.052). There was significant difference in absolute error of IOL calculation between the groups (-0.02±0.45 versus 0.17±0.55 D for control and study groups, respectively, p=0.004). There was no difference in IOL calculation error depending on the implanted IOL models (AcrySof SA60AT and Akreos Adapt AO) in the control group. However, implantation of SA60AT in the study group showed significant difference in IOL calculation error compared with Akreos (0.3±0.57 versus 0.04±0.51 D, p=0.01). Using linear regression, optimized A-constants were suggested for these types of IOLs for patients with PEX (118.83 for SA60AT and 118.44 for Akreos).

Refractive outcomes and accuracy of IOL power calculation with the SRK/T formula for sutured, scleral-fixated Akreos AO60 intraocular lenses.

BACKGROUND: Scleral fixation of intraocular lenses has become a popular procedure for treating aphakia in the absence of capsular support. However, the lens formulas used to predict refractive outcomes were designed for in-the-bag lens placement. This study evaluates the accuracy of the SRK/T formula in predicting a target postoperative refraction when suturing a scleral-fixated intraocular lens (IOL) implant 3 mm posterior to the limbus. METHODS: This is a retrospective, case series including 20 eyes of 20 patients who underwent scleral fixation of Akreos AO60 IOLs (Bausch & Lomb, Rochester, NY) by a single surgeon at the OSU Wexner Medical Center. Preoperative measurements were performed with optical biometry, and IOL power was calculated with the SRK/T formula. Following surgery, the actual refractive spherical equivalent (SE) was performed and compared with the preoperative prediction. Prediction error (PE), defined as the deviation of actual postoperative SE refraction in diopters (D) from preoperative predicted SE refraction, was the primary outcome measure. RESULTS: The mean attempted (predicted) SE was - 1.12 D (± 0.87). Mean achieved SE was - 0.96 D (± 1.04). Mean PE (actual postoperative SE versus predicted preoperative SE) was 0.16 D (± 0.69). A total of 9 eyes (45%) were within ± 0.5 D of the predicted SE, 16 eyes (80%) were within ± 1.0 D, and all 20 eyes (100%) were within ± 1.5 D. CONCLUSION: IOL power calculation using the SRK/T formula with optical biometry demonstrates reliable postoperative refractive outcomes in patients undergoing scleral fixation of an IOL (Akreos AO60). Further studies are needed to refine the predictive value of the SRK/T and other formulas for application in scleral fixation of IOLs.

Correlation of binocular refractive error and calculation of intraocular Lens power for the second eye.

BACKGROUND: Reducing refractive error has always been a tricky problem. The aim of this study was to verify the correlation between binocular refractive error (RE) after sequential cataract surgery and explore an individualized calculation method of intraocular lens (IOL) for the second eye. METHODS: This was a prospective study. One hundred eighty-eight affected eyes in 94 age-related cataract patients who underwent sequential cataract surgery in the Department of Ophthalmology, Tangdu Hospital, China, were recruited. Complete case data were included for a correlation analysis of binocular RE. Data obtained in patients with RE values greater than 0.50 diopters (D) in the first eye were extracted and the patients divided randomly into two groups: Group A and B. In the adjustment group, group A, we modified the IOL power for the second eyes as 50% of the RE of the first eye. In group B, the control group, there was no modification. The mean absolute refractive error (MARE) values of the second eyes were evaluated one month after surgery. RESULTS: The correlation coefficient of the binocular RE after sequential cataract surgery was 0.760 (P < 0.001). After the IOL power of the second eyes was adjusted, the MARE of the second eyes was 0.57 ± 0.41 D, while the MARE of the first eyes was 1.18 ± 0.85 D, and the difference was statistically significant (P < 0.001). CONCLUSIONS: Binocular REs were positively correlated after sequential cataract surgery. The RE of the second eye can be reduced by adjusting the IOL power based on 50% of the postoperative RE of the first eye.

[Cataract surgery in megalocornea (case report)]. / Fakokhirurgiya pri megalokornea (klinicheskoe nablyudenie).

The article presents a clinical case of bilateral cataract surgery on megalocornea eyes of a 20-year-old male. The Haigis formula has demonstrated the greatest potential accuracy for IOL calculation in such eyes, while the use of other formulas was associated with a higher risk of significant hyperopic refractive error. An unusually high level of pseudoaccommodation was obtained in both eyes.