Accuracy of intra ocular lens calculation formulae in patients with pseudoexfoliation syndrome.

BACKGROUND: The purpose of this study was to investigate the visual and refractive outcomes in patients with pseudoexfoliation (PXF) undergoing routine cataract surgery and to compare the accuracy of intraocular lens (IOL) power calculation formulae. METHODS: Retrospective case-series study from Shamir medical center, a public hospital, Israel. Medical records of patients who underwent routine cataract surgery between January 2019 and August 2021 were investigated. Postoperative visual acuity and manifest refraction were examined. The error in predicted refraction and IOL power calculation accuracy within a range of ± 0.50 to ± 1.00 diopters were compared between different IOL calculating formulae. RESULTS: 151 eyes of 151 patients ages 73.9 ± 7.1 years were included in this study- 58 eyes in the PXF group and 93 eyes in the control group. The mean absolute error (MAE) for the BUII formula was 0.63D ± 0.87 for the PXF group and 0.36D ± 0.48 for the control group (p < 0.05). The MAE for the Hill-RBF 3.0 formula was 0.61D ± 0.84 for the PXF group and 0.42D ± 0.55 for the control group (p = 0.05). There were significant differences in MAE and MedAE between PXF group and control group measures (p < 0.05). In the PXF group there were no significant differences between the different formulae. CONCLUSIONS: There were significant differences in accuracy of IOL power calculations in all formulae between PXF group and control group measures. PXF patients show hyperopic shift from predicted refraction. Barret universal II formula had the highest proportion of eyes with absolute error in prediction below or equal to 0.50 D in both PXF and control groups.

Fungal Keratitis Post-FemtoLASIK: A Novel Therapeutic Approach with LASIK Flap Autograft and Penetrating Keratoplasty: A Case Report.

Introduction: This case report describes a rare case of fungal keratitis following femtoLASIK. Despite targetted antifungal therapy, this case necessitated an innovative surgical approach to manage an unexpected corneal perforation. Case Presentation: A 35-year-old male presented 3 weeks post-femtoLASIK for myopic astigmatism with discomfort and reduced vision in his right eye. He was diagnosed with fungal keratitis surgery caused by Purpureocillium lilacinum and was treated with a myriad of therapy. Unfortunately, the patient developed corneal perforation during flap lift and flap bed irrigation. An innovative approach involving a tectonic autograft using a viable LASIK flap, followed by prompt penetrating keratoplasty, was utilised. Conclusion: This technique was effective and able to mitigate the progression to an open globe.

Accuracy of Toric Intraocular Lens Calculations Using Estimated Versus Measured Posterior Corneal Astigmatism.

PURPOSE: To compare the prediction accuracy of toric intraocular lens calculations using estimated vs measured posterior corneal astigmatism (PCA). DESIGN: Retrospective case series. METHODS: A total of 110 eyes of 110 patients with uncomplicated toric intraocular lens implantation were included in this study. Predicted postoperative refractive astigmatism was calculated with the Barrett Toric Calculator using the estimated PCA (E-PCA), the measured IOLMaster 700 PCA (I-PCA), and the measured Pentacam PCA (P-PCA). Refractive astigmatism prediction errors (RA-PEs), including their trimmed (tr-) centroid (mean vector), spread (precision), tr-mean absolute RA-PE (accuracy), and percentage within a certain threshold, were determined using vector analysis and compared between groups. SETTING: University Eye Clinic, Maastricht University Medical Center+, the Netherlands. RESULTS: The tr-centroid RA-PEs of the E-PCA (0.02 diopter [D] at 82.2°), the I-PCA (0.08 D at 35.5°), and the P-PCA (0.09 D at 69.1°) were significantly different from each other (P < .01), but not significantly different from zero (P = .75, P = .05, and P = .05, respectively). The E-PCA had the best precision (tr-mean 0.40 D), which was not significantly lower than the I-PCA (0.42 D, P = .53) and P-PCA (0.43 D, P = .06). The E-PCA also had the best accuracy (0.40 D), which was not significantly different from the I-PCA (0.42 D, P = .26) and significantly better than the P-PCA (0.44 D, P < .01). The precision and accuracy of the I-PCA did not significantly differ from those of the P-PCA. There were no statistically significant differences in the percentage of eyes within a certain absolute RA-PE threshold. CONCLUSIONS: The Barrett Toric Calculator using the E-PCA, I-PCA, or P-PCA showed a comparable prediction of postoperative refractive astigmatism in standard clinical practice.

Comparison of toric intraocular lens calculation with the integrated K method and three single biometric devices.

PURPOSE: To compare astigmatic outcomes using the Integrated K method and anterior surface keratometry from 3 different biometric devices. SETTING: Lions Eye Institute, Perth, Australia. DESIGN: Retrospective case series. METHODS: Eyes of patients who underwent uneventful cataract surgery were analyzed. Predicted postoperative astigmatism was calculated for Integrated K method, IOLMaster 700, Lenstar and Pentacam. The mean centroid error in predicted postoperative refractive astigmatism (PE), mean absolute PE and percentage of eyes within 0.5 diopter (D), 0.75 D and 1 D of absolute magnitude of PE were compared. A subset analysis was done where the difference in cylinder magnitude between the 2 methods was more than 0.25 D. Spherical prediction outcomes were also analyzed. RESULTS: 241 eyes of 139 patients were included in the study. The mean centroid PE of Integrated K method (-0.07 @ 69) was significantly different from IOLMaster and Pentacam. The mean absolute PE with Integrated K method (0.33 ± 0.17) was significantly lower than all 3 devices. The percentage of eyes within 0.5 D and 0.75 D of absolute magnitude of PE was 82% and 99% for Integrated K method, 76% and 95% for IOLMaster and Lenstar, and 60% and 86% for Pentacam. In the subset analysis, the improvement in accuracy of the Integrated K method compared with a single device was greater in terms of the percentage of eyes predicted within 0.5 D. The Integrated K method did not impact the spherical prediction outcomes. CONCLUSIONS: The integrated K method is more accurate and precise than anterior surface keratometry from a single biometric device.

Comparison of biometry measurements and intraocular lens power prediction between 2 SS-OCT-based biometers.

PURPOSE: To evaluate the agreement in biometry measurements and intraocular lens (IOL) power prediction between the Eyestar 900 and the IOLMaster 700. SETTING: Institutional. DESIGN: Retrospective comparative study. METHODS: Patients were evaluated before cataract surgery using both devices on the same visit. Axial length, anterior and posterior keratometry, anterior chamber depth, corneal diameter (CD), central corneal thickness, and lens thickness were recorded by both devices. The agreement in measurements and in IOL power calculations was evaluated using the Barrett Universal II (BU-II) formula with either predicted or measured posterior keratometry. RESULTS: In total, 402 eyes of 402 consecutive patients were included. The mean age was 72.0 ± 9.2 years. Clinically, mean differences in measured variables were small, albeit slightly larger for posterior flat and steep keratometry (0.43 diopters [D] and 0.42 D, respectively). The measurement correlation and agreement between the devices were good for all variables with slightly lower agreement in CD measurements. Consistent bias was seen in measurements of posterior flat and steep keratometry. Good agreement was also found in anterior and posterior astigmatism measurements. Good IOL power calculation agreement was found using either predicted posterior keratometry (95% limits of agreement [LoA] of -0.40 to +0.30 D) or measured posterior keratometry (95% LoA of -0.45 to +0.40 D). The agreement was within ±0.5 D in 394 eyes (98.0%) using predicted posterior keratometry and in 386 eyes (96.0%) using measured posterior keratometry. CONCLUSIONS: The Eyestar 900 and the IOLMaster 700 show strong agreement in biometry measurements and IOL power prediction by the BU-II formula using either standard or total corneal keratometry and can be used interchangeably.

Agreement between a new swept-source ocular coherence tomography and a Placido disc-dual Scheimpflug ocular biometric devices.

PURPOSE: To evaluate the agreement between two biometry devices, the Heidelberg Anterion and the Galilei G6 Lens Professional. METHODS: Eyes were scanned with both biometry devices. Analysis of inter-device agreement was conducted for the following metrics: flat (K1), steep (K2) and mean K (Km) for anterior, posterior and total cornea, lens thickness (LT), central corneal thickness (CCT), anterior chamber depth (ACD), white to white (WTW) and axial length (AL). Generalised Estimating Equations were used to account for inter-eye correlation. Bland-Altman analysis was conducted to derive the mean difference (MD) and limits of agreement (LoA) between devices. Differences were deemed clinically significant if they would result in a change in post-operative refraction of 0.25D or more. RESULTS: 159 eyes of 91 patients were included. For the anterior cornea, no significant MD was found for K1 (-0.11D) and K2 (-0.10D), although a significant MD was found for Km (-0.10D). For posterior cornea, while there were no significant MDs between devices, the LoAs were wide for both posterior K1(-0.70, 0.68) and posterior K2 (-1.01, 1.29). For total corneal power, significant MDs were found in K1 (0.36D), and Km (0.26D) but not for K2 (0.17D). Significant MDs were found for LT (0.179mm), CCT (-0.005mm), ACD (-0.111mm) and WTW (-0.158mm), but not for AL (-0.021mm, p > 0.05).Conclusion: There are statistically but not clinically significant differences between Anterion and Galilei G6 Lens Professional in anterior Km, LT, CCT, ACD and WTW. Measurements of the posterior and total cornea are not interchangeable between devices.

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

PURPOSE: To compare the spherical equivalent (SE) and astigmatic prediction error between subjective refraction (SUBref) and autorefraction (AUTOref) after cataract surgery to determine whether the latter is useful as an objective method to compare the accuracy of different methods of intraocular lens (IOL) power calculation. METHODS: Postoperative refraction was examined using two techniques: SUBref and AUTOref. The results of these two techniques were compared. Predicted postoperative refraction for spherical outcome was calculated with the Barrett Universal II (BUII), Haigis, Holladay I, SRK/T, Hoffer Q, and BUII with measured posterior corneal astigmatism (MPCA) formulas. Predicted postoperative refraction for astigmatic outcome was calculated with the Barrett Toric calculator, vergence-based toric calculator using the Holladay 1 formula for effective lens position, and Barrett Toric calculator MPCA formulas. Formula accuracy and ranking were compared between the two methods of refraction. RESULTS: Data were obtained from 219 eyes of 155 patients. Statistically significant differences were detected between SUBref and AUTOref for SE, J0, and J45 (P < .001). The spherical outcome formula analysis demonstrated no significant differences, whereas the predicted cylinder power analysis demonstrated significant differences within individual formulas between SUBref and AUTOref measures. The lowest median absolute error and the highest percentage of eyes achieving their refractive target for both SUBref and AUTOref were achieved with the BUII formula and the Barrett Toric calculator. CONCLUSIONS: AUTOref is a useful method with adequate accuracy to determine spherical and astigmatic outcome and equally or more effective in being able to discriminate between spherical outcome formulas. The AUTOref method can allow valuable studies to be conducted in less-than-optimal environments and provides the ability to compare studies without the confounding factors of SUBref. [J Refract Surg. 2022;38(9):580-586.].

Agreement between 2 SS-OCT biometry devices.

PURPOSE: To assess the agreement between 2 swept-source optical coherence tomography biometry devices, Anterion and IOLMaster 700. SETTING: Tertiary referral center, Brisbane, Australia. DESIGN: Prospective comparative study. METHODS: Bland-Altman analysis was used to assess agreement between devices for flat (K1), steep (K2), and mean (Km) keratometry for anterior, posterior, and total cornea, lens thickness (LT), anterior chamber depth (ACD), central corneal thickness (CCT), white to white (WTW), and axial length (AL). Generalized estimating equations were used to control for within-patient between-eye correlations. Interdevice differences were considered clinically significant if they were likely to alter the spherical refractive outcome by 0.25 diopter (D) or more. RESULTS: 159 eyes of 91 patients (41 male, 50 female) were included. Statistically significant differences were found for K1, K2, and Km for anterior, posterior, and total cornea. When the Anterion was compared with the IOLMaster 700, the mean differences were as follows: anterior K1: -0.17 D, anterior K2: -0.18 D, anterior Km: -0.17 D, posterior K1: -0.38 D, posterior K2: -0.36 D, posterior Km: -0.37 D, total K1: -0.65 D, total K2: -0.82 D, and total Km: -0.74 D. The difference in posterior and total K metrics was clinically significant. Statistically significant differences were noted for LT: 0.159 mm, CCT: -0.004 mm, ACD: 0.054 mm, and WTW: -0.152 mm, although these were not found to be clinically significant. There was no significant difference between devices for AL. CONCLUSIONS: This study found statistically and clinically significant differences for both posterior and total keratometry between the Anterion and the IOLMaster 700. Posterior and total corneal parameters cannot be considered interchangeable between devices.

Measured Corneal Astigmatism Versus Pseudophakic Predicted Refractive Astigmatism in Cataract Surgery Candidates.

PURPOSE: To compare standard and total corneal astigmatism measurements to the predicted pseudophakic (nontoric) refractive astigmatism in candidates for cataract surgery. DESIGN: A retrospective, cross-sectional study. METHODS: A single-center analysis of consecutive eyes measured with a swept-source optical coherence tomography biometer at a large tertiary medical center between February 2018 and June 2020. Corneal astigmatism was calculated based on standard keratometry astigmatism (KA), total corneal astigmatism (TCA), and predicted refractive astigmatism (PRA) for a monofocal nontoric intraocular lens (IOL) implantation calculated by the Barrett toric calculator using the predicted posterior corneal astigmatism (PRA(Predicted-PCA)) and the measured posterior corneal astigmatism (PRA(Measured-PCA)) options. Separate analyses were performed for each eye. SETTING: Ophthalmology Department, Shaare Zedek Medical Center, Jerusalem, Israel. RESULTS: In total, 8152 eyes of 5320 patients (4221 right eyes [OD] and 3931 left eyes [OS], mean age 70.6±12.2 years, 54.2% females) were included in the study. The mean vector values (centroid) for KA, TCA, PRA(Predicted-PCA), and PRA(Measured-PCA) were 0.07 diopters [D] at 19.5°, 0.27 D at 7.5°, 0.44 D at 2.9°, and 0.43 D at 179.3°, respectively (P < .01), for OD and 0.02 D at 150.3°, 0.23 D at 169.7°, 0.40 D at 179.4°, and 0.42 D at 169.5°, respectively (P < .01), for OS. More than 73% of eyes had a PRA >0.5 D. CONCLUSIONS: Standard and total corneal astigmatism measurements differ significantly from the PRA by the Barrett toric calculator. The PRA, rather than the KA or TCA, should be used as the reference guide for astigmatism correction with toric IOL implantation.

Toric intraocular lens power calculation in cataract patients with keratoconus.

PURPOSE: Intraocular lens (IOL) power calculation in eyes with keratoconus typically results in hyperopic postoperative refractive error. The purpose of this study was to investigate the visual and refractive outcomes in patients with keratoconus having cataract surgery with a toric IOL and compare IOL power calculation accuracy of conventional formulas and keratoconus-specific formulas. SETTING: Ein-Tal Eye Center, Tel-Aviv, Israel. DESIGN: Retrospective case-series study. METHODS: Postoperative visual acuity and manifest refraction were examined. The error in predicted refraction and IOL power calculation accuracy within a range of 0.50 to 2.00 diopters (D) were compared between different IOL calculating formulas. RESULTS: 32 eyes with keratoconus were included. Visual acuity improved in all cases, and subjective astigmatism decreased from -2.95 ± 2.10 D to -0.95 ± 0.80 D (P < .001). The mean absolute errors were as follows: Barrett True-K formula for keratoconus with measured or predicted posterior corneal power, 0.34 D; Barrett Universal II formula, 0.64 D; Kane formula, 0.69 D; Kane formula for keratoconus, 0.49 D; SRK/T formula, 0.56 D; Haigis formula, 0.72 D; Holladay 1 formula, 0.71 D, and Hoffer Q formula, 0.87 D. Barrett True-K formula with measured posterior corneal power, SRK/T formula, and Kane formula for keratoconus resulted in a prediction error within ±0.50 D of 87.5%, 59.4%, and 53.1%, respectively. CONCLUSIONS: Cataract removal with a toric IOL significantly improves visual acuity and decreases astigmatism in keratoconic eyes with a topographic central relatively regular astigmatic component. Keratoconus-specific formulas resulted in lower mean error in predicted refraction compared with conventional calculating formulas. Using the posterior corneal power within the Barrett True-K formula for keratoconus improved IOL power prediction accuracy.

Results of the Barrett True-K formula for IOL power calculation based on Scheimpflug camera measurements in eyes with previous myopic excimer laser surgery.

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.

Total keratometry in intraocular lens power calculations in eyes with previous laser refractive surgery.

IMPORTANCE: Intraocular lens (IOL) calculations in post-refractive cases remain a concern. Our study identifies improved options for surgeons. BACKGROUND: To evaluate and compare the prediction accuracy of IOL power calculation methods after previous laser refractive surgery using standard keratometry (SK), measured posterior corneal astigmatism (PCA) and total keratometry (TK). DESIGN: Retrospective consecutive cohort. PARTICIPANTS: A total of 50 consecutive patients (72 eyes) at a private institution who underwent cataract surgery with prior laser refractive procedures. METHODS: Methods using SK included ASCRS mean, Barrett True-K no history, Haigis-L and Shammas IOL formulae. Barrett True-K using posterior values (True K TK), Haigis and Holladay 1 Double-K methods using TK were also assessed. Post-surgery refraction was undertaken at minimum 3 weeks following surgery. MAIN OUTCOME MEASURES: Arithmetic and absolute IOL refractive prediction errors, variances in mean arithmetic IOL prediction error, and percentage of eyes within ±0.25D, ±0.50D, ±0.75D and ±1.00D of refractive prediction errors were compared. RESULTS: The Barrett True-K (TK) provided the lowest mean refractive prediction error (RPE) and variance for both prior myopes and hyperopes undergoing cataract surgery. The Barrett True-K (TK) exhibited the highest percentages of eyes within ±0.50D, ±0.75D and ±1.00D of the RPE compared to other formulae for prior myopic patients. CONCLUSIONS AND RELEVANCE: Accuracy of IOL power calculations in post-laser eyes can be improved by the addition of posterior corneal values as measured by the IOLMaster 700. The use of total keratometry may supplement outcomes when no prior refraction history is known.

Accuracy of intraocular lens power calculation methods when targeting low myopia in monovision.

PURPOSE: To investigate the accuracy of IOL power calculation methods for refractive targets of myopia compared with emmetropia. SETTING: Lions Eye Institute, Perth, Australia. DESIGN: Retrospective analysis. METHODS: Patients undergoing bilateral, sequential cataract surgery with a plan of modest monovision were analyzed. Target refraction was plano (distance eye) and -1.25 diopters (D) (near eye). Prediction error was determined by comparing the actual postoperative refraction with the predicted postoperative refraction, calculated by the Barrett Universal II (BUII), Hill-RBF version 2.0 (Hill-RBF 2.0), Haigis, Holladay 1, SRK/T, and Hoffer Q formulas. The dataset was divided into distance and near eye subgroups. Mean and median absolute error and percentage of eyes within ±0.25, ±0.50, ±0.75, and ±1.00 D of refractive target were compared. RESULTS: The study included 88 consecutive patients. There was a consistent trend for lower refractive accuracy in the near eyes. BUII and Hill-RBF 2.0 were the most accurate overall and least affected by this phenomenon, with 1 (1.1%) and 4 (4.6%) fewer eyes, respectively, in the near subgroup achieving ±0.50 D of target. Haigis and SRK/T were most affected, with 14 (15.9%) and 11 (12.5%) fewer near eyes achieving ±0.50 D of target (P < .05). Holladay 1 and Hoffer Q occupied the middle ground, with 6 (6.8%) and 9 (10.2%) fewer near eyes achieving ±0.50 D of target. CONCLUSIONS: IOL-power calculation formulas appear to be less accurate when targeting myopia compared with emmetropia. BUII and Hill-RBF 2.0 represented good options when planning pseudophakic monovision as they were least affected by this phenomenon and can be used for both distance and near eyes.

Methods for Intraocular Lens Power Calculation in Cataract Surgery after Radial Keratotomy.

PURPOSE: To compare methods of calculating the required intraocular lens (IOL) power for patients undergoing cataract surgery after radial keratotomy (RK), including the 2016 update of the True K formula. DESIGN: Retrospective case series. PARTICIPANTS: A total of 52 eyes of 34 patients who had sequential RK and cataract surgery performed in the same institution by 1 of 2 surgeons. METHODS: Seven IOL calculation formulae were evaluated: True K [History], True K [Partial History], True K [No History], Double-K Holladay 1 (DK-Holladay-IOLM), Potvin-Hill, Haigis, and Haigis with a -0.50 diopter (D) offset. Biometry was obtained with the IOLMaster 500 (Carl Zeiss Meditec AG, Jena, Germany) and Pentacam (OCULUS Inc, Arlington, WA) devices. Subjective refraction was performed at 4 to 6 weeks postoperatively. The achieved spherical equivalent outcome was compared with the target outcome to calculate the absolute error for each eye with each formula. MAIN OUTCOME MEASURES: Median absolute error (MedAE) and mean absolute error (MAE), and percentage of patients within ±0.50 D, ±0.75 D, and ±1.00 D of refractive target. Mean error (ME) was also calculated to demonstrate whether a formula tended toward more myopic or hyperopic outcomes. RESULTS: Best results were achieved with the True K [History]. The MedAE was higher (0.382 vs. 0.275) with the True K [Partial History], but a similar percentage of patients (75.0%-76.6%) achieved within ±0.50 D of target. Of the methods that do not require refractive history, the True K [No History] and unadjusted Haigis were most accurate (69.2% within ±0.50 D of target), with the True K [No History] returning the lowest MedAE but also more of a tendency toward hyperopia (ME +0.269 vs. -0.006 for Haigis). The DK-Holladay-IOLM and Potvin-Hill methods were the least accurate. CONCLUSIONS: Knowledge of the refractive history significantly improves the accuracy of IOL calculations in patients undergoing cataract surgery after previous RK. The post-RK refraction appears to be the most important parameter, with inclusion of the pre-RK refraction offering a further slight improvement in MedAE. When no refractive history is available, the True K [No History] and Haigis formulae both perform well, with the added advantage of not requiring data from separate biometric devices.