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Purpose: To compare 2 different datasets, using Eyetemis, an online analytical tool designed for assessing the spherical equivalent prediction errors (SEQ-PEs) of intraocular lens (IOL) power calculation formulas after cataract surgery., Setting: Institutional., Design: Retrospective case series., Methods: The study comprised 2 distinct datasets of patients who had undergone successful cataract surgery. Dataset 1 includes standard eyes, whereas Dataset 2 includes eyes with keratoconus. An online tool was used for SEQ-PE analysis across the 2 datasets, adhering to ISO standards for evaluating accuracy based on trueness and precision. The tool incorporates robust t tests for comparing the trimmed mean of the data, adjusting for heteroscedasticity. IOL constants in Dataset 1 were optimized for the comparison of Hoffer Q, Holladay 1, SRK/T, Haigis, and Barrett Universal II (BUII) formulas. In Dataset 2, IOL constants from the IOLCon website were used for the comparison of the BUII and its designated KCN version: Barrett TrueK Keratoconus (TrueK [KCN])., Results: For Dataset 1, the trimmed mean SEQ-PE values of all formulas were not significantly different from zero. BUII had superior precision and accuracy compared with all other formulas, except from Haigis ( P ≤ .04). For Dataset 2, BUII's trimmed-mean SEQ-PE was significantly different from zero (0.59 diopters [D], P < .01), unlike the TrueK (KCN) (0.12 D, P = .10). In addition, TrueK (KCN) exhibited enhanced precision and accuracy relative to BUII ( P < .01)., Conclusions: The online analysis tool provides a streamlined approach for assessing the prediction accuracy of SEQ refraction after cataract surgery, effectively evaluating trueness, precision, and overall accuracy through the use of advanced statistical methods., (Copyright © 2024 Published by Wolters Kluwer on behalf of ASCRS and ESCRS.)

Purpose: To investigate whether standard keratometry (K) or total corneal power (TCP) leads to more accurate refractive outcomes for intraocular lens (IOL) power calculation., Setting: Public hospital., Design: Retrospective evaluation of a diagnostic test instrument., Methods: Preoperatively, all patients underwent optical biometry with Anterion, a swept-source optical coherence tomography device providing both K and TCP. The same IOL model was implanted in all cases. The whole sample was divided into a training dataset, used to optimize the formula constants, and a testing dataset, used to investigate the spherical equivalent prediction error (SEQ-PE) of 8 IOL power formulas. Trueness, precision, and accuracy were evaluated by means of the robust 2-sample t test. Cochran Q test was performed to assess whether the percentage of eyes with an SEQ-PE within each threshold was significantly different; in such an event, the McNemar test was then applied., Results: Both the training and testing datasets included 317 eyes. No significant differences were detected for trueness because of constant optimization. Precision and accuracy were better when K was entered, although a statistically significant difference was observed only with the EVO (precision: P = .02 and accuracy: P = .03) and Haigis ( P < .01 for both precision and accuracy) formulas. No significant differences were observed for the percentage of eyes with an absolute SEQ-PE within any threshold., Conclusions: With most formulas, IOL power calculation is not more accurate when TCP is used instead of K., (Copyright © 2024 Published by Wolters Kluwer on behalf of ASCRS and ESCRS.)

Purpose: To compare the accuracy of intraocular lens (IOL) power calculation formulas for myopic eyes requiring negative diopter powered IOLs., Design: Retrospective case series., Setting: K… hospital and Y… Hospital, …, …., Methods: Sixty-one eyes that underwent phacoemulsification with implantation of a negative power IOL were investigated. The trueness, precision and accuracy of IOL power calculation were assessed for the Barrett Universal II (BUII), EVO 2.0, Haigis, Hoffer QST, Holladay 1 and SRK/T formulas using the Eyetemis online tool. The analysis was performed using 1) the ULIB IOL constants and 2) after constant optimization., Results: With ULIB constants, the Haigis, Holladay 1 and SRK/T resulted in a hyperopic mean prediction error (PE) >1.00 diopter (D), which was significantly different from zero (adjusted p <0.05). The mean PE of the remaining formulas was closer to zero. The absolute PE was significantly higher with the Holladay 1 and SRK/T (adjusted p <0.05) with respect to the remaining formulas. After constant optimization, the outcomes of traditional formulas improved and no statistically significant differences were found among any of the formulas in terms of trueness, precision and accuracy. The percentage of eyes with an absolute PE within 0.50 D was low (<50%) even after constant optimization., Conclusions: With ULIB constants, the BUII, EVO 2.0 and Hoffer QST were more accurate than traditional formulas in eyes with negative-diopter IOLs. The results of IOL power calculation in these eyes remain poor even after constant optimization., (Copyright © 2024 Published by Wolters Kluwer on behalf of ASCRS and ESCRS.)

Objective: To describe a novel method called "three variable optimization" that entails a process of doing just one calculation to zero out the mean prediction error of an entire dataset (regardless of size), using only 3 variables: (1) the constant used, (2) the average intraocular lens (IOL) power, and (3) the average prediction error (PE as actual refraction - predicted refraction)., Design: Development, evaluation, and testing of a method to optimize personal IOL constants., Methods: A dataset of 876 eyes was used as a training set, and another dataset of 1,079 eyes was used to test the method. The Barrett Universal II, Cooke K6, Haigis, RBF 3.0, Hoffer Q, Holladay 1, Holladay 2, SRK/T, and T2 were analyzed. The same dataset was also divided into 3 subgroups (short, medium, and long eyes). The three variable optimization process was applied to each dataset and subset, and the obtained optimized constants were then used to obtain the mean PE of each dataset. We then compared those results with those obtained by zeroing out the mean PE in the classical method., Results: The three variable optimization showed similar results to classical optimization with less data needed to optimize and no clinically significant difference. Dividing the dataset into subsets of short, medium and long eyes, also shows that the method is useful even in those situations. Finally, the method was tested in multiple formulas and it was able to reduce the PE with no clinically significant difference from classical optimization., Conclusion: This method could then be applied by surgeons to optimize their constants by reducing the mean prediction error to zero without prior technical knowledge and it is available online for free at http://wwww.ioloptimization.com., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Purpose: To present a reproducible method to calculate the toricity needed at the intraocular lens (IOL) plane with toric phakic IOLs (ICL, Staar Surgical) and compare its results with those obtained with the online calculator provided by the manufacturer., Design: Retrospective case series., Setting: Private practice, Buenos Aires, Argentina., Methods: The formula originally described by Holladay to calculate the IOL power in phakic eyes was used to calculate the required spherical power along the less refractive meridian and along the more refractive meridian. Meridional analysis was applied to calculate the required toricity at the IOL plane and the surgically induced corneal astigmatism was incorporated into the calculations. The refractive cylinder predicted by this method and by the online calculator of the manufacturer were compared to the postoperative refractive cylinder by means of vector analysis. The possible changes in the ratio of toricity in patients with different amounts of astigmatism and anterior chamber depth are assessed in a theoretical section., Results: In 35 eyes, the measured mean postoperative refractive cylinder was 0.09 D @ 99°, the mean predicted postoperative refractive astigmatism was 0.04 D @ 102° according to the manufacturer's online calculator and 0.09 D @100° according to our method. With both methods, 91.43% of eyes had an absolute cylinder prediction error within ±0.50 diopters., Conclusions: The method described in this article to calculate the toricity of phakic IOLs has a refractive accuracy similar to that of the original calculator developed by the manufacturer., Competing Interests: Declaration of Conflicting InterestsThe authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Purpose: To compare simulated keratometry (SimK) and total corneal power (TCP) in keratoconic eyes, to determine whether the differences are systematic and predictable and to evaluate an adjusted TCP-based formula for intraocular lens (IOL) power calculation., Methods: In a consecutive series of keratoconic eyes, measurements of SimK, TCP, posterior keratometry, and anterior and posterior corneal asphericities (Q-values) were retrospectively collected. The difference between SimK and TCP was linearly correlated to the biometric parameters. In a separate sample of keratoconic eyes that had undergone cataract surgery, IOL power was calculated with the Barrett Universal II, Hoffer QST, Holladay 1, Kane, and SRK/T formulas using the SimK and an adjusted TCP power. The respective prediction errors were calculated., Results: A total of 382 keratoconic eyes (271 patients) were enrolled. An increasing overestimation of SimK by TCP was detected from stage I to III, with a significant correlation between the SimK and TCP difference and SimK in the whole sample ( P < .0001, r = 0.1322). Approximately 7% of cases presented an underestimation of SimK by TCP. IOL power calculation with the adjusted TCP improved outcomes, achieving a maximum of 80% of eyes with a prediction error within ±0.50 diopters with the Hoffer QST, Holladay 1, and Kane formulas.2 = 0.1322). Approximately 7% of cases presented an underestimation of SimK by TCP. IOL power calculation with the adjusted TCP improved outcomes, achieving a maximum of 80% of eyes with a prediction error within ±0.50 diopters with the Hoffer QST, Holladay 1, and Kane formulas., Conclusions: Overall, SimK overestimated TCP. Such a difference could not be predicted by any variable. The proposed TCP-adjustment formula (TCP adj = TCP + 0.56 diopters) in keratoconic eyes for IOL power calculation might be valuable for improving refractive outcomes. [ J Refract Surg . 2024;40(4):e253-e259.] .

Purpose: This study aimed to explore the concept of total keratometry (TK) by analyzing extensive international datasets representing diverse ethnic backgrounds. The primary objective was to quantify the disparities between traditional keratometry (K) and TK values in normal eyes and assess their impact on intraocular lens (IOL) power calculations using various formulas., Design: Retrospective multicenter intra-instrument reliability analysis., Methods: The study involved the analysis of biometry data collected from ten international centers across Europe, the United States, and Asia. Corneal power was expressed as equivalent power and astigmatic vector components for both K and TK values. The study assessed the influence of these differences on IOL power calculations using different formulas. The results were analyzed and plotted using Bland-Altman and double angle plots., Results: The study encompassed a total of 116,982 measurements from 57,862 right eyes and 59,120 left eyes. The analysis revealed a high level of agreement between K and TK values, with 93.98% of eyes exhibiting an absolute difference of 0.25 D or less. Astigmatism vector differences exceeding 0.25 D and 0.50 D were observed in 39.43% and 1.08% of eyes, respectively., Conclusions: This large-scale study underscores the similarity between mean K and TK values in healthy eyes, with rare clinical implications for IOL power calculation. Noteworthy differences were observed in astigmatism values between K and TK. Future investigations should delve into the practicality of TK values for astigmatism correction and their implications for surgical outcomes., (Copyright © 2023 The Author(s). Published by Elsevier Inc. All rights reserved.)

Purpose: To investigate the new Hoffer QST (Savini/Taroni) formula (HQST) and compare it with the original Hoffer Q (HQ) and 4 latest generation formulas., Setting: I.R.C.C.S.-G.B. Bietti Foundation, Rome, Italy., Design: Retrospective case series., Methods: Refractive outcomes of the HQST, Barrett Universal II (BUII), Emmetropia Verifying Optical (EVO) 2.0, HQ, Kane, and Radial Basis Function (RBF) 3.0 formulas were compared. Subgroup analysis was performed in short (<22 mm) and long (>25 mm) axial length eyes. The SD of the prediction error (PE) was investigated using the heteroscedastic method., Results: 1259 eyes of 1259 patients divided in a White group (n=696), implanted with the AcriSof SN60AT (Alcon Labs), and an Asian group (n=563), implanted with the SN60WF (Alcon Labs), were investigated. In the Asian group, the heteroscedastic method did not disclose any significant difference among the SD of the 4 modern formulas (range from 0.333 to 0.346 D), whereas the SD of the HQ formula (0.384 D) was significantly higher. Compared with the original HQ formula, in both White and Asian groups, the HQST formula avoided the mean myopic PE in short eyes and the mean hyperopic PE in long eyes., Conclusions: The new HQST formula was superior to the original HQ formula and reached statistical and clinical results comparable with those achieved by the BUII, EVO, Kane, and RBF formulas., (Copyright © 2023 Published by Wolters Kluwer on behalf of ASCRS and ESCRS.)

Purpose: To scrutinize the accuracy of 24 intraocular lens (IOL) power calculation formulas in unoperated eyes., Methods: In a series of consecutive patients undergoing phacoemulsification and implantation of the Tecnis 1 ZCB00 IOL (Johnson & Johnson Vision), the following formulas were evaluated: Barrett Universal II, Castrop, EVO 2.0, Haigis, Hoffer Q, Hoffer QST, Holladay 1, Holladay 2, Holladay 2 (AL Adjusted), K6 (Cooke), Kane, Karmona, LSF AI, Naeser 2, OKULIX, Olsen (OLCR), Olsen (standalone), Panacea, PEARL-DGS, RBF 3.0, SRK/T, T2, VRF, and VRF-G. The IOLMaster 700 (Carl Zeiss Meditec AG) was used for biometric measurements. With optimized lens constants, the mean prediction error (PE) and its standard deviation (SD), the median absolute error (MedAE), the mean absolute error (MAE), and the percentage of eyes with prediction erros within ±0.25, ±0.50, ±0.75, ±1.00, and ±2.00 D were analyzed., Results: Three hundred eyes of 300 patients were enrolled. The heteroscedastic method revealed statistically significant differences ( P < .05) among formulas. Newly developed methods such as the VRF-G (standard deviation [SD] ±0.387 D), Kane (SD ±0.395 D), Hoffer QST (SD ±0.404 D), and Barrett Universal II (SD ±0.405) were more accurate than older formulas ( P < .05). These formulas also yielded the highest percentage of eyes with a PE within ±0.50 D (84.33%, 82.33%, 83.33%, and 81.33%, respectively)., Conclusions: Newer formulas (Barrett Universal II, Hoffer QST, K6, Kane, Karmona, RBF 3.0, PEARL-DGS, and VRF-G) were the most accurate predictors of postoperative refractions. [ J Refract Surg . 2023;39(4):249-256.] .

Purpose: To evaluate the accuracy of nine formulas to calculate the power of a new extended depth-of-focus intraocular lens (EDOF IOL), the AcrySof IQ Vivity (Alcon Laboratories, Inc), using measurements from two optical biometers, the IOLMaster 700 (Carl Zeiss Meditec AG) and Anterion (Heidelberg Engineering GmbH)., Methods: After constant optimization, the accuracy of these formulas was analyzed in 101 eyes: Barrett Universal II, EVO 2.0, Haigis, Hoffer Q, Holladay 1, Kane, Olsen, RBF 3.0, and SRK/T. Both standard and total keratometry from the IOLMaster 700 and standard keratometry from the Anterion were used for each formula., Results: Constant optimization provided slightly different values for the A-constant, which ranged between 118.99 and 119.16, depending on the formula and the optical biometer. According to the heteroscedastic test, within each keratometry modality the standard deviation of the SRK/T was significantly higher compared to that of the Holladay 1, Kane, Olsen, and RBF 3.0 formulas. The SRK/T formula provided less accurate results also when the absolute prediction errors were compared by Friedman test. According to McNemar's test with Holm corrections, statistically significant differences were found within each keratometry modality between the percentage of eyes with a prediction error within ±0.25 diopters obtained with the Olsen formula compared to the Holladay 1 and Hoffer Q formulas., Conclusions: Constant optimization remains a mandatory step to achieve the best outcomes with the new EDOF IOL: the same constant should not be used for all formulas and for both optical biometers. Different statistical tests revealed that older IOL formulas have lower accuracy compared to newer formulas. [ J Refract Surg . 2023;39(3):158-164.] .

Purpose: Optical devices are the gold standard for ocular biometry; however, they are unable to obtain high-quality optical coherence tomography (OCT) images. The current study aimed to evaluate ocular measurements and intraocular lens (IOL) calculation used in an anterior/posterior segment OCT device and to compare the results with those of a validated biometer., Design: Prospective evaluation of a diagnostic tool., Methods: This study enrolled healthy subjects at the Hygeia Clinic, Gdańsk, Poland, between October 2021 and November 2021. All individuals had ocular biometry measured with a validated biometer (Pentacam AXL) and with a new module of an anterior/posterior segment OCT device (Revo 80, Optopol Technologies). All IOL calculations were performed for the right eye with keratometric values from the Pentacam for one IOL: the Alcon AcrySof IQ SN60WF, with plano target setting., Results: The mean age of the 144 participants was 25.23 ± 7.15 years. The axial length measured with Revo was longer than with Pentacam AXL (24.08 ± 1.13 vs 23.98 ± 1.13; P < .0001), a 0.10 ± 0.04 mm difference. This translated into a significantly lower IOL power to achieve emmetropia for all formulas (-0.34 ± 0.15, -0.32 ± 0.13, -0.34 ± 0.19, and -0.30 ± 0.15 for the Hoffer Q, Holladay I, Haigis, and SRK/T formulas, respectively). The study showed high agreement between the devices: nearly 90% of eyes were within ±0.50 diopters for all of the analyzed formulas (r > 0.99)., Conclusions: The present study demonstrates that the results of IOL calculation with the OCT biometer have a very strong correlation with those obtained with the Pentacam AXL; however, axial length measurements and calculated IOL power cannot be considered interchangeable., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Purpose: To evaluate the repeatability of the measurements provided by a new optical biometer (EyeStar 900) based on swept-source optical coherence tomography (SS-OCT) and their agreement with the measurements given by 2 validated biometers based on the same technology, the IOLMaster 700 and Argos., Setting: IRCCS G.B. Bietti Foundation, Rome, Italy., Design: Prospective evaluation of diagnostic test., Methods: In a series of unoperated eyes, 3 consecutive scans were acquired with the EyeStar 900, and 1 with the IOLMaster 700 and the Argos. The following biometry parameters were analyzed: axial length (AL), keratometry (K), corneal astigmatism, central corneal thickness, corneal diameter (CD), anterior chamber depth (ACD), lens thickness (LT), and lens tilting. Repeatability was assessed using test-retest variability, the coefficient of variation (CoV), and the intraclass correlation coefficient (ICC); agreement was based on the 95% limits of agreement., Results: 56 eyes of 56 patients were analyzed. High repeatability was achieved for all measured parameters, as the CoV was <1% in most cases and ICC was >0.95 for all parameters. Good to high agreement was found among the measurements of the 3 optical biometers, although some statistically significant differences were detected between the EyeStar 900 and Argos (mean K, ACD, LT, and CD were higher with the Argos). The Argos measured a shorter AL in eyes >25 mm., Conclusions: The new generation SS-OCT EyeStar 900 optical biometer produces highly repeatable measurements that are in good agreement with those provided by 2 previously validated instruments., (Copyright © 2022 Published by Wolters Kluwer on behalf of ASCRS and ESCRS.)

Purpose: To determine the utility of Split-Window optical coherence tomography OCT (SW-OCT) biometry in measuring ocular axial dimensions as well as imaging the intraocular lens (IOL) and posterior capsule in pseudophakic eyes., Methods: Sixty-nine pseudophakic eyes of 69 subjects were enrolled in the study. The results of SW-OCT biometry implemented in the SD OCT device for posterior and anterior segment imaging (REVO NX, Optopol Technology) were compared with those obtained with the SS-OCT-based biometer IOLMaster 700 (Carl Zeiss Meditec). Differences in measurement values between the two biometers were determined using the paired t-test. Agreement was assessed through intraclass correlation coefficients (ICC) and Bland-Altman plots., Results: The correlation between measurements obtained with SW-OCT and SS-OCT was very high (ICC for: axial length (AL) = 1.000; anterior chamber depth (ACD) = 0.997; IOL thickness (IOL LT) = 0.997; central corneal thickness (CCT) = 0.987). The mean AL measurement difference was 0.003 ± 0.021 mm (the 95% LoA ranged from -0.04 to 0.05); the mean ACD difference was -0.009 ± 0.025 mm (95% LoA, -0.06 to 0.04); mean LT difference was 0.001 ± 0.021 mm (95% LoA, -0.04 to 0.04); and mean CCT difference was 1.4 ± 5.4 μm (95% LoA, -9 to 12)., Conclusion: The study shows small, non-significant differences between the biometric measurements obtained with REVO NX SW-OCT and IOLMaster 700 SS-OCT in pseudophakic eyes. However, SW-OCT offered significantly lower ACD and LT measurement failure rates. With high-resolution imaging, SW-OCT enables accurate assessment of IOL position relative to the posterior capsule and visualization of capsular fibrosis., (© 2022 The Authors. Acta Ophthalmologica published by John Wiley & Sons Ltd on behalf of Acta Ophthalmologica Scandinavica Foundation.)

Purpose: To compare phakic intraocular lens size calculations based on corneal diameter (CD) measurements by 3 instruments., Setting: G.B. Bietti Foundation I.R.C.C.S., Rome, Italy., Design: Retrospective interventional case series., Methods: Preoperatively, CD was measured with the Aladdin, IOLMaster 700, and Pentacam AXL Wave. The simulated ICL size was computed by entering CD measurements into the manufacturer's calculator. Postoperatively, vaulting was measured by anterior segment optical coherence tomography. The optimal ICL size (OIS) was calculated and compared with the commercially available OIS (CAOIS)., Results: 54 eyes (29 patients) with the implantable collamer lens (ICL) were enrolled. The mean CD was 12.02 ± 0.36 mm with the Aladdin, 12.35 ± 0.39 mm with the IOLMaster 700, and 12.22 ± 0.41 mm with the Pentacam AXL Wave ( P &lt; .0001), with the closest agreement between the Pentacam AXL Wave and IOLMaster 700 (95% limits of agreement: -0.43 to +0.17 mm). Vaulting (mean: 558 ± 261 μm) was within 251 and 1000 μm in 49 eyes (83.3%). The mean difference between the simulated ICL size and OIS ranged between -0.11 ± 0.35 mm and 0.10 ± 0.30 mm ( P &lt; .0001), with no statistically significant difference between the IOLMaster 700 and Pentacam AXL Wave. The simulated ICL size was equal to CAOIS in 38 eyes (70.37%) with the Aladdin, 37 eyes (68.52%) with the IOLMaster 700, and 39 eyes (72.22%) with the Pentacam AXL Wave, without any statistically significant difference., Conclusions: CD measurements by the 3 devices lead to similar percentages of eyes with an ICL size equal to the OIS. Agreement is closer between the IOLMaster 700 and Pentacam AXL Wave., (Copyright © 2022 Published by Wolters Kluwer on behalf of ASCRS and ESCRS.)

Purpose: To report the results of intraocular lens (IOL) power calculation by ray tracing in eyes with previous myopic excimer laser surgery., Setting: G.B. Bietti Foundation I.R.C.C.S., Rome, Italy., Design: Retrospective interventional case series., Methods: A series of consecutive patients undergoing phacoemulsification and IOL implantation after myopic excimer laser was investigated. IOL power was calculated using ray-tracing software available on the anterior segment optical coherence tomographer MS-39. Axial length (AL) was measured by optical biometry, and 4 values were investigated: (1) that from the printout, (2) the modified Wang/Koch formula, and (3) the polynomial equation for the Holladay 1 and (4) for the Holladay 2 formulas. The mean prediction error (PE), median absolute error (MedAE), and percentage of eyes with a PE within ±0.50 diopters (D) were reported., Results: The study enrolled 39 eyes. Entering the original AL into ray tracing led to a mean hyperopic PE (+0.56 ±0.54 D), whereas with the Wang/Koch formula, a mean myopic PE (-0.41 ±0.53 D) was obtained. The Holladay 1 and 2 polynomial equations lead to the lowest PEs (-0.10 ±0.49 D and +0.08 ±0.49 D, respectively), lowest MedAE (0.37 D and 0.25 D), and highest percentages of eyes with a PE within ±0.50 D (71.79% and 76.92%). Calculations based on the Holladay 2 polynomial equation showed a statistically significant difference compared with other methods used (including Barrett-True K formula), with the only exception of the Holladay 1 polynomial equation., Conclusions: IOL power was accurately calculated by ray tracing with adjusted AL according to the Holladay 2 polynomial equation., (Copyright © 2022 Published by Wolters Kluwer on behalf of ASCRS and ESCRS.)

Purpose: To assess the accuracy of different corneal powers for intraocular (IOL) power calculation in combined Descemet membrane endothelial keratoplasty (DMEK) and cataract surgery and investigate whether preoperative parameters correlate to the prediction error (PE)., Methods: This prospective case series involved patients with Fuchs endothelial dystrophy receiving combined DMEK and cataract surgery. Preoperatively, patients underwent optical biometry and anterior segment OCT (AS-OCT). AS-OCT measurements were repeated 6 months postoperatively, when final refraction was assessed. The PE was calculated using the preoperative average keratometry (K ave ) measured by the optical biometer and User Group for Laser Interference Biometry (ULIB) constants. It was also calculated, after constant optimization, using the preoperative K ave from both devices and the total corneal power (TCP) measured by AS-OCT, as well as the postoperative K ave and TCP measured by AS-OCT., Results: ULIB constants resulted in the highest hyperopic PE ( P < .0001). Constant optimization improved the results, because the PE was zeroed out and the absolute PEs decreased. No significant difference was found among the Barrett Universal II, Emmetropia Verifying Optical 2.0, Haigis, Hoffer Q, Holladay 1, Kane, and SRK/T formulas. Further improvement was achieved with the postoperative K ave and TCP, although the accuracy remained moderate. The PE based on preoperative corneal measurements was correlated to the amount of corneal flattening; the latter could be predicted by multiple linear regression accounting for anterior and posterior corneal radii ( P = .0002) and was correlated to the preoperative anterior/posterior ratio., Conclusions: Constant optimization is beneficial for combined DMEK and phacoemulsification. Predicting postoperative corneal flattening may improve the results of IOL power accuracy. [ J Refract Surg . 2022;38(7):435-442.] .

Purpose: To compare axial length (AL) measurements in long eyes by 2 swept-source optical coherence tomography (SS-OCT) biometers, one based on the group refractive index (IOLMaster 700, Zeiss) and the other based on sum of segments (Argos, Movu Inc.), and compare these measurements with previously published methods to optimize AL., Setting: G.B. Bietti Foundation I.R.C.C.S., Rome, Italy., Design: Prospective case series., Methods: AL was measured with both optical biometers in patients with myopia (AL > 24.0 mm) and compared with the values obtained with Wang-Koch adjustment, polynomial equations for the Holladay 1 and 2 formulas, and Cooke-modified AL (CMAL)., Results: In 102 eyes of 55 subjects, a statistically significant difference (P < .0001) was found among the 6 AL values. Posttest revealed that Argos measurements (26.90 ± 1.61 mm) were significantly lower compared with those provided by all methods (P < .001) but CMAL, whereas IOLMaster 700 measurements (27.01 ± 1.65) were higher (P < .001). No difference was found between the 2 Holladay equations. CMAL values did not reveal any difference compared with those of the Argos, but a proportional bias showed that in longer eyes, CMAL provided smaller values (P < .0001, r = -0.7221). AL overestimation by the IOLMaster 700 AL compared with the Argos was higher, the longer the eye was (P < .0001, r = 0.6959, r2 = 0.4842)., Conclusions: The SS-OCT optical biometer based on the group refractive index overestimates AL compared with the device using segmented AL. CMAL provides the measurements closest to those of the device using segmented AL., (Copyright © 2021 Published by Wolters Kluwer on behalf of ASCRS and ESCRS.)

Purpose: To assess agreement of measurements by 2 swept-source optical coherence tomography biometers and to evaluate the prediction error (PE) in intraocular lens power calculation with 7 formulas., Setting: Tertiary public eye hospital., Design: Consecutive observational., Methods: Axial length (AL), keratometry (K), anterior chamber depth (ACD), lens thickness (LT), and corneal diameter (CD) were measured with the IOLMaster 700 (Biometer A) and Anterion (Biometer B). Agreement was quantified by the limits of agreement and concordance correlation coefficient (CCC). The PE, the median absolute error, and the mean absolute error of the Barrett Universal II, EVO 2.0, Haigis, Hoffer Q, Holladay 1, Kane, and SRK/T formulas were investigated after constant optimization., Results: In 78 eyes from 78 patients, excellent agreement was obtained for AL (CCC >0.99), very good agreement for K, ACD, and LT (CCC >0.95), and strong agreement for CD (CCC >0.72). An additive offset of 0.07 mm was measured for ACD and LT whose mean values were higher with Biometer B (P < .001). No statistically significant difference was found between the PEs and their absolute values when comparing the results of each formula between the 2 biometers., Conclusions: Agreement of biometric measurements by the 2 biometers was high, although Biometer B provided higher mean values of ACD and LT by 0.07 mm. In cataract patients with normal eye length, measurements by the 2 biometers did not lead to different refractive outcomes with the 7 formulas investigated., (Copyright © 2021 Published by Wolters Kluwer on behalf of ASCRS and ESCRS.)

Purpose: To compare the accuracy of the equivalent keratometry reading (EKR) from a color LED corneal topographer (Cassini) with that of other no-history formulas for intraocular lens (IOL) power calculation in eyes with previous myopic excimer laser surgery., Setting: Centro de Oftalmología Barraquer, Barcelona, Spain., Design: Retrospective case series., Methods: The refractive outcomes of the Cassini EKR entered into the Haigis formula were compared with those of the Barrett True-K, Haigis-L, and Shammas-PL formulas and the Triple-S method combined with the Haigis formula. Optimized lens constants for virgin eyes were used. The mean prediction error (PE), the median absolute error (MedAE), and the percentage of eyes with a PE within ±0.25 diopter (D), ±0.50 D, ±0.75 D, and ±1.00 D were calculated., Results: The study comprised 37 patients (37 eyes). The Haigis-L, Shammas-PL, and Barrett True-K no-history methods produced a myopic mean PE that was significantly different from zero (P < .001, P < .001 and P = .004, respectively), whereas the mean PEs of Cassini EKR and the Triple-S combined with the Haigis formula were not different from zero (P > .05). Repeated-measures analysis of variance disclosed a significant difference among the PE of all methods (P < .0001). The MedAE of the Cassini EKR, Barrett True-K, Haigis-L, Shammas-PL, and Triple-S was, respectively, 0.34 D, 0.34 D, 0.49 D, 0.48 D, and 0.31 D (P = .0026)., Conclusions: The performance of the combination of standard Haigis formula with Cassini EKR was comparable to other no-history formulas in eyes with previous myopic excimer laser surgery., (Copyright © 2021 Published by Wolters Kluwer on behalf of ASCRS and ESCRS.)

Purpose: To compare the accuracy of Total Keratometry (TK) and standard keratometry (K) with the IOLMaster 700 (Carl Zeiss Meditec) in evaluating the corneal refractive change in eyes with previous myopic femtosecond laser-assisted LASIK (FS-LASIK)., Methods: A series of consecutive patients who had undergone myopic FS-LASIK was prospectively enrolled. The refractive change in spherical equivalent (ΔSE) was defined as the difference between the preoperative target correction entered into the laser software and the postoperative cycloplegic refraction. The difference between the postoperative and the preoperative K (ΔK) and the difference between the postoperative and the preoperative TK (ΔTK) were compared to the ΔSE. Only the right eye of each patient was selected for the statistical analysis., Results: Twenty-five eyes of 25 patients were enrolled. The mean ΔSE was -4.41 ± 1.68 diopters (D). The mean ΔK (-3.82 ± 1.60 D) revealed a statistically significant underestimation of the laser-induced refractive change ( P < .0001), whereas the mean ΔTK (-4.36 ± 1.78 D) did not show any significant difference ( P = .45). The difference between ΔK and ΔTK was statistically significant ( P < .0001). Linear regression between the laser-induced refractive change and the individual difference between the postoperative K and TK disclosed a statistically significant relationship ( r = -0.6930, r 2 = 0.4803, P < .0001), thus revealing that higher refractive corrections increase the difference between the postoperative values of K and TK., Conclusions: TK does not underestimate the laser-induced corneal changes and can be considered a reliable option for intraocular lens power calculation after myopic excimer laser surgery. [ J Refract Surg . 2021;37(12):848-852.] .

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

It was almost 40 years ago when one of the authors (K.J.H.) published an organized system to quantify the accuracy of intraocular lens (IOL) power calculation formulas, methods, and instruments. At the behest of the editor of the American Journal of Ophthalmology, the IOL Power Club (along with a statistician) published an editorial in 2015 modernizing and quantifying the proper protocols for these studies. Over the past decade, so many new optical biometers, formulas, and methods (whose accuracies have yet to be completely tested) have been introduced that we were asked to modernize and update these guidelines yet again to help others design and report correctly the results of clinical studies on IOL power calculation and biometry for 2020. We evaluated guidelines to enroll patients, including visual acuity minimums, exclusion of bilateral eyes, sample size issues, demographics (age, gender, and ethnicity), and whether such studies should not be performed using the same data that were used to develop the formula being tested. We showed the absolute need for constant optimization, which formulas should be tested for comparison, refraction measurement (testing distance), as well as the analysis of the prediction error (median and mean absolute errors; standard deviation; range of errors; percentage of eyes with a prediction within ±0.25 diopter [D], ±0.50 D, ±0.75 D, and ±1.00 D; and interquartile displays) and statistical methods of analyses. We present methods of ranking formula accuracy, including the new Haigis IOL Formula Performance Index. We also point out the issues of who programmed the formulas being tested, that all formulas used in the study must be referenced, and the software version number of all instruments used in the study should be stated clearly. The definition of anterior chamber depth should be stated as measured from the corneal epithelium to the lens. We hope that these recommendations will help researchers to improve the validity and accuracy of their studies with the ultimate goal to improve the accuracy of IOL power calculation., (Copyright © 2020 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.)

Purpose: To evaluate the refractive outcomes of the new Carlevale foldable sutureless scleral fixation intraocular lens (SSF-IOL) (Soleko in eyes without capsular support., Methods: This retrospective, single-center, noncomparative interventional case series included 25 consecutive eyes of 25 consecutive patients with either aphakia or lens/IOL dislocation due to capsular or zonular defects. The Hoffer Q, Holladay 1, and SRK/T formulas, which do not need measurements of the anterior chamber depth to predict the IOL position, were used to calculate the IOL power. Constant optimization was performed to zero out the mean prediction error (PE). The main outcome measures were mean PE ± standard deviation, median absolute error (MedAE), mean absolute error (MAE), and percentage of eyes with a PE within ±0.50 and ±1.00 diopters (D)., Results: Mean axial length was 24.09 ± 2.09 mm (range: 21.85 to 32.17 mm). No statistically significant differences were found among the three formulas for any parameter. The PE was zero due to constant optimization and its standard deviation ranged between 0.89 and 0.95 D. The MedAE ranged between 0.30 and 0.34 D, whereas the MAE ranged between 0.62 and 0.67 D. The percentage of eyes with a PE within ±0.50 D was between 56% and 64% and the percentage of eyes with a PE within ±1.00 D was between 69% and 72%., Conclusions: Reasonably good refractive outcomes can be obtained when implanting SSF-IOLs in eyes with no capsular support, although the accuracy is lower than what is reported for normal in-the-bag IOL implantation. [ J Refract Surg . 2021;37(7):472-476.] .

Purpose: The Revo NX is a new optical biometer, based on spectral-domain optical coherence tomography and able to obtain high-definition scans of both the anterior and posterior segment of the eye. A previous study found that its measurements of axial length (AL) were not interchangeable with those provided by a validated optical biometer; so, the manufacturer updated the instrument to improve agreement of AL values. This study aimed to prospectively compare the measurements by the updated Revo NX (version 9.5.0, biometry module) with those by 2 validated devices, the IOLMaster 700 and Lenstar LS-900., Setting: Optopol Technologies, Zawiercie, Poland., Design: Prospective evaluation of diagnostic test., Methods: Comparison between the devices was performed using repeated measures analysis of variance (ANOVA) with Bonferroni posttest, correlation coefficients, and the Bland-Altman method., Results: The investigation evaluated the results of 63 patients. For AL, anterior chamber depth (ACD), and lens thickness (LT), the differences were not clinically significant because they were less than 0.01 mm. Repeated measures ANOVA, however, detected a statistically significant difference for AL (P < .0001) and central corneal thickness (P < .0001) but not for ACD (P = .0630) or LT (P = .2667). The results obtained with all 3 biometers manifested a high level of agreement in the Bland-Altman analysis and very strong correlation., Conclusions: The measurements by the updated Revo NX had high agreement with the other optical biometers; a clear improvement was detected than the previous analysis between the original Revo NX (version 8.0.3) and the Lenstar LS-900., (Copyright © 2021 Published by Wolters Kluwer on behalf of ASCRS and ESCRS.)

Background/aims: To compare the accuracy of 13 formulas for intraocular lens (IOL) power calculation in cataract surgery., Methods: In this retrospective interventional case series, optical biometry measurements were entered into these formulas: Barrett Universal II (BUII) with and without anterior chamber depth (ACD) as a predictor, EVO 2.0 with and without ACD as a predictor, Haigis, Hoffer Q, Holladay 1, Holladay 2AL, Kane, Næser 2, Pearl-DGS, RBF 2.0, SRK/T, T2 and VRF. The mean prediction error (PE), median absolute error (MedAE), mean absolute error and percentage of eyes with a PE within ±0.25, ±0.50, ±0.75 and ±1.00 diopters (D) were calculated., Results: Two hundred consecutive eyes were enrolled. With all formulas, the mean PE was zero. The BUII with no ACD had the lowest standard deviation (±0.343 D), followed by the T2 (0.347 D), Kane (0.348 D), EVO 2.0 with no ACD (0.348 D) and BUII with ACD (0.353 D) formulas. The difference among the MedAEs of all formulas was statistically significant (p<0.0001); the lowest values were achieved with the Kane (0.214 D), RBF 2.0 (0.215 D), BUII with and without ACD (0.218 D) and SRK/T (0.223 D). A percentage ranging from 80% to 88.5% of eyes showed a PE within ±0.50 D and all formulas achieved more than 50% of eyes with a PE within ±0.25 D., Conclusion: All investigated formulas achieved good results; there was a tendency towards better outcomes with newer formulas. Traditional formulas can still be considered an accurate option., Competing Interests: Competing interests: KJH licenses the registered trademark name Hoffer to ensure accurate programming of his formulas to Carl Zeiss-Meditec (IOLMasters), Haag-Streit (LenStar/EyeStar), Heidelberg Engineering (Anterion), Oculus (Pentacam AXL), Movu (Argos), Nidek (AL-Scan), Tomey (OA-2000), Topcon EU/VisiaImaging (Aladdin), Ziemer (Galilei G6) (except Alcon (Verion)) and all A-scan biometer manufacturers. Dr Savini is a consultant to CSO, and has received speaker honoraria from Alcon, Oculus and Zeiss.The remaining authors have no financial interests., (© Author(s) (or their employer(s)) 2021. No commercial re-use. See rights and permissions. Published by BMJ.)

Purpose: To assess the predictive accuracy of 4 no-history intraocular lens (IOL) power formulas in eyes with prior myopic excimer laser surgery, classified in 4 groups according to their axial length (AL), and investigate the relationship between AL and predictive accuracy., Setting: Seoul St. Mary's Hospital, Republic of Korea., Design: Retrospective case series., Methods: IOL power was calculated with the Barrett True-K, Haigis-L, Shammas-PL, and Triple-S formulas in 4 groups classified according to AL. Primary outcomes were the median absolute error (MedAE) and percentage of eyes with a prediction error (PE) within ±0.50 diopter (D)., Results: This study included 107 eyes of 107 patients. The Barrett True-K had the lowest MedAE when AL was <26.0 mm (0.30 D) and between 26.0 and 28.0 mm (0.54 D); in these subgroups, it had the highest percentages with a PE within ±0.50 D (71.4% and 46.2%). For AL between 28.0 and 30.0 mm, the Triple-S method showed the lowest MedAE (0.43 D) and highest percentage with a PE within ±0.50 D (58.3%). For AL ≥30.0 mm, the Shammas-PL formula produced the lowest MedAE (0.41 D) and highest percentage with a PE within ±0.50 D (58.3%). The Barrett True-K was the only formula with a correlation between AL and PE (r = -0.219/P = .023)., Conclusions: The predictive accuracy of no-history IOL formulas depends on the AL. The Barrett True-K had the highest accuracy when AL was < 28.0 mm and the Triple-S when it ranged from 28.0 mm to 30.0 mm, whereas the Shammas-PL was more accurate when AL was ≥30.0 mm., (Copyright © 2021 Published by Wolters Kluwer on behalf of ASCRS and ESCRS.)

Purpose: To investigate whether using lens thickness measurement as an optional input improves the refractive accuracy of four new generation formulas., Methods: Consecutive patients scheduled for cataract surgery were enrolled. Preoperative biometry was performed with an OA-2000 optical biometer (Tomey). All patients received the same monofocal intraocular lens (AcrySof SN-60WF; Alcon Laboratories, Inc). The Barrett Universal II (BUII), Emmetropia Verifying Optical (EVO), Kane, and Radial Basis Function (RBF) formulas were analyzed with and without the inclusion of lens thickness as an input. Postoperative refraction was measured at 1 month. The mean prediction error (PE), the median absolute error (MedAE), and the percentage of eyes with a PE within ±1.00 diopters (D) or less were calculated after constant optimization., Results: The final analysis was performed on 169 eyes of 169 patients. Comparison of the mean PE, MedAE, and the percentage of eyes with a PE within ±0.25, ±0.50, ±0.75, and ±1.00 D resulting from each formula with and without lens thickness did not reveal any statistically significant difference. Cochran's Q test showed a statistically significant difference among formulas in the percentage of eyes with a PE of less than ±0.50 D ( P = .042). However, Dunn's post-hoc test did not show any statistically significant difference between any pair of formulas., Conclusions: Lens thickness measurement did not improve the accuracy of the BUII, EVO, Kane, or RBF formulas. The RBF formula yielded the same results with and without lens thickness, thus making this input useless. [ J Refract Surg . 2021;37(3):202-206.] .

Purpose: To evaluate the visual outcomes and possible complications of a new foldable sutureless scleral fixation intraocular lens (SSF-IOL), the Carlevale IOL (Soleko)., Methods: The SSF-IOL, which has two T-shaped self-blocking plugs on each haptic, was inserted into the posterior chamber. Both haptics was grabbed through two sclerotomies and the two short arms were blocked under the scleral flap, without any suture. A complete clinical evaluation was done preoperatively and at 3, 6, and 12 months postoperatively., Results: A total of 54 eyes of 50 consecutive patients were retrospectively analyzed. The mean corrected distance visual acuity was 0.93 ± 0.61 logMAR preoperatively and improved to 0.42 ± 0.34 logMAR at 3 months, 0.42 ± 0.37 logMAR at 6 months, and 0.38 ± 0.38 logMAR at 12 months postoperatively (all P < .0001). The mean corneal endothelial cell density decreased from 1,725.37 ± 528.06 to 1,612.81 ± 522.91 cells/mm 2 at 12 months postoperatively (P < .0001). The mean IOL tilt value was 3.1 ± 1.1° at 12 months postoperatively. The authors observed 6 cases (11.1%) of intraoperative rupture of the IOL haptics, 4 cases (7.4%) of early hyphema, 4 cases (7.4%) of macular cystoid edema, 2 cases (3.7%) of haptic exposure under the conjunctiva, and 1 (1.8%) late retinal detachment., Conclusions: This newly introduced surgical technique provided promising results regarding efficacy and safety. Complications occurred in a few cases and were successfully managed. The Carlevale IOL seems to be a surgical solution combining the advantages of an easy and minimally invasive implantation with a good functional recovery with minimal complications. [J Refract Surg. 2021;37(2):126-132.]., (Copyright 2021, SLACK Incorporated.)

We assess repeatability of automatic measurements of a new anterior segment optical coherence tomographer and biometer (ANTERION) and their agreement with those provided by an anterior segment-optical coherence tomography device combined with Placido-disk corneal topography (MS-39) and a validated optical biometer (IOLMaster 500). A consecutive series of patients underwent three measurements with ANTERION and one with MS-39. A subgroup of patients underwent biometry also with IOLMaster 500. Repeatability was assessed by means of within-subject standard deviation, coefficient of variation (COV), and intraclass correlation coefficient (ICC). Agreement was investigated with the 95% limits of agreement. Paired t-test and Wilcoxon matched-pairs test were performed to compare the measurements of the different devices. Repeatability of ANTERION measurements was high, with ICC > 0.98 for all parameters except astigmatism (0.963); all parameters apart from those related to astigmatism revealed a COV < 1%. Repeatability of astigmatism improved when only eyes whose keratometric astigmatism was higher than 1.0 D were investigated. Most measurements by ANTERION and MS-39 showed good agreement. No significant differences were found between measurements by ANTERION and IOLMaster, but for corneal diameter. ANTERION revealed high repeatability of automatic measurements and good agreement with both MS-39 and IOLMaster for most parameters.

Objectives: We aimed (1) to assess the repeatability of Total Keratometry (TK) and standard keratometry (K) measurements, as provided by the IOLMaster 700 (Carl Zeiss Meditec), and (2) to compare the corneal astigmatism measured by TK to the total corneal astigmatism (TCA) measured by a Scheimpflug camera (Pentacam AXL, Oculus)., Methods: Two groups of patients were prospectively enrolled: Group A included previously unoperated eyes undergoing cataract surgery, and Group B eyes with previous myopic corneal excimer laser surgery. TK and K were measured three times by the same examiner. Repeatability was assessed based on the within-subject standard deviation (S w ), test-retest variability, coefficient of variation and intraclass correlation coefficient (ICC). In Group A, TCA was measured once and compared to TK astigmatism. Vector analysis was performed according to Næser., Results: In Group A (69 eyes) the mean K and TK were, respectively, 43.14 ± 1.37 D and 43.18 ± 1.37 D. In Group B (51 eyes) the mean K and TK were, respectively, 40.14 ± 2.20 D and 39.71 ± 2.35 D. The repeatability of the average K and TK was high (S w  < 0.10D). All measurements revealed an ICC > 0.9. For most measurements the variance of K and TK did not show any statistically significant difference either within groups or between groups. Vectors KP(45) were significantly different between TK astigmatism and TCA., Conclusions: TK measurements offer high repeatability in unoperated and post-excimer laser surgery eyes. TK astigmatism and TCA measurements could not be considered interchangeable.

Purpose: To evaluate the accuracy of the measurements provided by a Scheimpflug camera combined with partial coherence interferometry for intraocular lens (IOL) power calculation., Setting: I.R.C.C.S.-G.B. Bietti Foundation, Rome, Italy., Design: Prospective case series., Methods: Consecutive patients scheduled for cataract surgery were enrolled. Preoperative biometry was performed with a Pentacam AXL. All patients received the same IOL (AcrySof SN60WF). Measurements were entered into the following formulas: Barrett Universal II, Emmetropia Verifying Optical 2.0, Haigis, Hoffer Q, Holladay 1, Holladay 2 with axial length adjustment, Kane, Ladas Super Formula (LSF) 2.0, Næser 2, Pearl-DGS, SRK/T, T2, and VRF. When refraction was measured at 1 month postoperatively, the mean prediction error (PE), the median absolute error (MedAE), and the percentage of eyes with a PE within ±0.25, ±0.50, and ±1.00 diopter (D) were calculated after constant optimization., Results: Ninety-one eyes of 91 patients were analyzed. Comparison of the mean PE and MedAE did not reveal any statistically significant difference. However, the Pearl DGS formula achieved the lowest MedAE (0.19 D), followed by the LSF 2.0 (0.22). Twelve of the 13 formulas obtained a PE within ±0.50 D in at least 80% of eyes (range 80%-87%) and 7 of them in at least 85%. Twelve formulas yielded a PE within ±0.25 D in at least 50% of eyes (range 51%-64%)., Conclusions: All the investigated formulas performed well using the Pentacam AXL measurements. The newest Pearl DGS formula version and LSF 2.0 showed promising results.

For many decades only a few formulas have been available to calculate the intraocular lens (IOL) power for patients undergoing cataract surgery: the Haigis, Hoffer Q, Holladay 1 and 2 and SRK/T. In recent years, several new formulas for IOL power calculation have been introduced with the aim of improving the accuracy of refraction prediction in eyes undergoing cataract surgery. These include the Barrett Universal II, the Emmetropia Verifying Optical (EVO), the Kane, the Næser 2, the Olsen, the Panacea, the Pearl DGS, the Radial Basis Function (RBF), the T2 and the VRF formulas. Although most of them are unpublished so that their structure is unknown, we give an overview of each formula and report the results of the studies that have compared them. Their performance in short and long eyes is provided and a special focus is given on the issue of segmented axial length, which is a promising method to obtain more accurate outcomes in short and long eyes. Here, the group refractive index originally developed for the IOLMaster may not represent the best method to convert the optical path length into a physical distance. The issue of posterior and total corneal astigmatism (TCA) is discussed in relation to toric IOLs; the latest formulas for toric IOLs and their results are also reported., Competing Interests: Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at http://dx.doi.org/10.21037/atm-20-2290). The series “Recent developments in cataract surgery” was commissioned by the editorial office without any funding or sponsorship. GS reports grants from Italian Ministry of Health, grants from Fondazione Roma, during the conduct of the study; personal fees from Alcon, personal fees from CSO, personal fees from Oculus, personal fees from Zeiss, outside the submitted work. KJH reports personal fees from Carl Zeiss Meditec, personal fees from Haag-Streit, personal fees from Oculus, personal fees from Ziemer, personal fees from Topcon EU/Visia Imaging, personal fees from Tomey, personal fees from Movu, personal fees from Heidelberg Engineering, outside the submitted work. The authors have no other conflicts of interest to declare., (2020 Annals of Translational Medicine. All rights reserved.)

Purpose: To evaluate the refractive impact of centripetal fragmentation using the miLOOP system for nucleus disassembly, which minimizes lens zonulocapsular instability associated with endocapsular lens manipulation., Setting: Private practice, Batesville, Indiana, USA., Design: Retrospective comparative consecutive series., Methods: Refractive outcomes were compared for consecutive patients who underwent cataract surgery and intraocular lens implantation before and after the introduction of a microinterventional endocapsular nucleus disassembly technique using the miLOOP system. Eyes with a history of previous surgery or ocular comorbidities were excluded. The primary outcome was the median absolute error (MedAE) from the preoperative predicted refraction. Secondary outcomes included corrected (CDVA) and uncorrected distance visual acuity (UDVA) and the proportion of eyes within predicted diopter (D) ranges., Results: A total of 118 eyes of 79 patients were analyzed, with 69 eyes undergoing conventional nuclear disassembly and 49 eyes receiving the microinterventional technique. The MedAE for eyes using conventional nucleus disassembly vs the microinterventional technique was 0.191 D vs 0.107 D, respectively (P = .002). For CDVA and UDVA, the microinterventional approach resulted in a trend toward a higher proportion of eyes achieving acuities better than 20/30, 20/25, and 20/20 compared with conventional techniques. The microinterventional approach showed a trend toward more eyes achieving less than ±0.25 D and ±0.50 D of prediction error from the predicted diopter range., Conclusions: Microinterventional nuclear disassembly might improve refractive outcomes by reducing refractive prediction error.

Purpose: To compare the refractive results of 4 different options for the Barrett True-K formula in eyes with previous myopic excimer laser surgery., Setting: IRCCS-Fondazione Bietti, Rome, Italy., Design: Retrospective case series., Methods: Biometric measurements obtained with a rotating Scheimpflug camera (Pentacam) were entered into the Barrett True-K formula. Clinical history (laser-induced refractive change) and the measured posterior corneal curvature were entered as optional. Four variants of the Barrett True-K formula were investigated: (1) with history and measured posterior corneal power, (2) with history and predicted posterior corneal power, (3) no history with measured posterior corneal power, and (4) no history with predicted posterior corneal power. The prediction error (PE) was calculated as the difference between the measured and predicted postoperative refraction values., Results: In 50 eyes (50 patients), the Barrett True-K formula with history and measured posterior corneal power resulted in the lowest standard deviation of the PE (0.52 diopters [D]), lowest median (0.245 D) and mean (0.413 D) absolute errors, and highest percentage of eyes with a PE within ±0.25 D (54%), ±0.50 D (70%), and ±0.75 D (84%). The Barrett True-K no-history formula with predicted posterior corneal power yielded the worst refractive outcomes. When the 4 options were compared, statistically significant differences were detected among the median absolute errors (P = .0017) and the percentage of eyes with a PE within ±0.25 D (P < .0001)., Conclusions: Using historical data and measured posterior corneal power improved the refractive accuracy of the Barrett True-K formula in eyes with previous myopic excimer laser surgery.

Purpose: To analyze the results of intraocular lens (IOL) power calculation using measurements by a swept-source optical coherence tomography (SS-OCT) optical biometer., Setting: IRCCS G.B. Bietti Foundation, Rome, Italy., Design: Evaluation of a diagnostic test instrument., Methods: Preoperative measurements by the OA-2000 (Tomey Inc.) were taken in a consecutive series of patients undergoing cataract surgery with one IOL model (AcrySof SN60WF; Alcon Laboratories, Inc.). Measurements were entered into the following formulas: Barrett Universal II, Emmetropia Verifying Optical (EVO), Haigis, Hoffer Q, Holladay 1, Holladay 2, Holladay 2 with axial length adjustment, Kane, Olsen, Panacea, SRK/T, T2, and VRF. When refraction was measured at 1 month postoperatively, the mean arithmetic prediction error, the median absolute error (MedAE), and the percentage of eyes with a error of ±0.50 D or less were calculated after constant optimization., Results: We enrolled 150 eyes. All formulas yielded excellent outcomes. The MedAE ranged between 0.200 D and 0.259 D, with a statistically significant difference among formulas (P = .0004). The lowest MedAE values were obtained with the Barrett, EVO, Kane, Olsenstandalone, Radial Basis Function (RBF), and T2 formulas. The percentage of eyes with a prediction error of ±0.50 D or less ranged between 80.00% and 90.67%, with a statistically significant difference (P < .0001). The Barrett, EVO, Holladay 2 with axial length adjustment, Kane, RBF, and T2 achieved the highest percentages (≥88%)., Conclusions: Measurements provided by the SS-OCT optical biometer enable accurate IOL power calculation because all formulas yielded a prediction error within 0.50 D in at least 80% of eyes.

Purpose: To examine the repeatability and reproducibility of biometry provided by a new anterior-posterior segment spectral-domain optical coherence tomography (SD-OCT) device (Revo NX) and compare it with that provided by a validated optical low-coherence reflectometry (OLCR) biometer (Lenstar LS 900)., Setting: Hygeia Clinic, Gdańsk, Poland., Design: Prospective evaluation of diagnostic test., Methods: The axial length (AL), lens thickness (LT), central corneal thickness (CCT), and anterior chamber depth (ACD) (corneal epithelium to lens) were measured in eyes of volunteers. Two skilled operators obtained 3 measurements in random order with the SD-OCT device. Repeatability was calculated for each observer, while reproducibility was assessed by a change in observer. To compare agreement between the SD-OCT device and OLCR device, the first observer took 3 measurements with both devices., Results: The study evaluated 63 eyes of 63 volunteers. The mean AL measurement (+0.11 mm ± 0.02 [SD]) and mean ACD measurement (0.05 ± 0.04 mm) were significantly higher with the SD-OCT device than with the OLCR device; the CCT measurements did not differ between the devices. A very strong correlation was found for all parameters, while Bland-Altman analysis showed narrow 95% limits of agreement for AL (0.06 to 0.15 mm), ACD (-0.02 to 0.12 mm), LT (-0.23 to 0.17 mm), and CCT (-7.83 to 6.17 μm)., Conclusions: The new SD-OCT device provided repeatable and reproducible AL, ACD, LT, and CCT measurements. The results with the SD-OCT device showed strong correlations with those obtained with the OLCR device. However, the AL and ACD measurements of the 2 devices cannot be considered interchangeable., (Copyright © 2019 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.)

Purpose: To assess the refractive accuracy of different formulas for intraocular lens (IOL) power calculation in eyes with keratoconus., Setting: IRCCS Fondazione Bietti, Rome, Italy., Design: Multicenter retrospective interventional study., Methods: A consecutive series of eyes with keratoconus that had cataract surgery were evaluated. Keratometry, anterior chamber depth, and axial length were measured preoperatively with optical biometry; IOL power was calculated with the Barrett Universal II, Haigis, Hoffer Q, Holladay 1, and SRK/T formulas. Subjective refraction was assessed at 1 month. The mean prediction error (PE), median absolute error (MedAE) and percentage of eyes with a PE within ±0.50 diopters (D), ±0.75 D, and ±1.00 D were calculated., Results: The final spherical equivalent was -0.52 D ±1.61 (SD). In the whole sample (41 eyes), the mean PE was positive (hyperopic surprise) with all formulas; the lowest PE (0.91 D) and MedAE (0.62 D) were obtained with the SRK/T formula. In stage I eyes (n = 21), the MedAE ranged between 0.43 and 0.91 D; the SRK/T formula achieved the lowest MedAE and the highest rate of eyes with a PE within ±0.50 (61.9%). In stage II eyes (n = 13), the MedAE ranged between 0.75 D and 1.50 D; the SRK/T formula achieved the lowest MedAE and the highest rate of eyes with a PE within ±0.50 (30.8%). In stage III eyes (n = 7), the MedAE was higher than 2.50 D with all formulas., Conclusions: In keratoconus eyes, all formulas led to a hyperopic refractive outcome. The SRK/T was the most accurate formula. The results were worse in advanced stages of the disease., (Copyright © 2018 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.)

Purpose: To compare lens thickness measurements provided by immersion ultrasound (US) biometry and optical biometry., Setting: IRCCS-Fondazione Bietti, Rome, Italy., Design: Evaluation of diagnostic technology., Methods: Immersion US biometry and optical biometry were performed in a consecutive series of eyes having cataract surgery. Three optical biometers (OA-2000, Aladdin, and Galilei G6) were used. To assess how the differences in lens thickness measurements influenced intraocular lens (IOL) power calculation, the lens thickness values were entered into the Olsen formula., Results: Eighty-eight eyes were analyzed. Ultrasound immersion biometry yielded significantly higher lens thickness values than all of the optical biometers (P < .0001). The mean difference ranged between 0.29 mm and 0.43 mm. Although the differences between the 3 optical biometers were smaller, they were still statistically significant (P < .001). With respect to the immersion US biometry, lens thickness measurements using the optical biometric measurements would have resulted in the selection of a lower IOL power in between 43.2% and 62.5% of eyes, depending on the optical biometer. Comparison of the measurements of the 3 optical biometers showed that a different IOL power would have been selected in between 9.1% and 19.3% of eyes., Conclusions: Lens thickness measurements by immersion US biometry and optical biometry cannot be considered interchangeable. Minor, but still significant, differences between the 3 optical biometers tested were also found., (Copyright © 2018 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.)