Warren Hill

Evaluation of intraocular lens power prediction methods using the American Society of Cataract and Refractive Surgeons Post-Keratorefractive Intraocular Lens Power Calculator.

PURPOSE: To evaluate the accuracy of methods of intraocular lens (IOL) power prediction after previous laser in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK) using the American Society of Cataract and Refractive Surgery IOL power calculator. SETTING: Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, and private practice, Mesa, Arizona, USA. METHODS: The following methods were evaluated: methods using pre‐LASIK/PRK keratometry (K) and surgically induced change in refraction, methods using surgically induced change in refraction, and methods using no previous data. The predicted IOL power was calculated with each method using the actual refraction after cataract surgery as the target. The IOL prediction error was calculated as the implanted IOL power minus the predicted IOL power. Arithmetic and absolute IOL prediction errors, variances in mean arithmetic IOL prediction error, and percentage of eyes within ±0.50 diopter (D) and ±1.00 D of refractive prediction errors were calculated. RESULTS: Methods using surgically induced change in refraction or no previous data had significantly smaller mean absolute IOL prediction errors, smaller variances, and a greater percentage of eyes within ±0.50 D and ±1.00 D of refractive prediction errors than methods using pre‐LASIK/PRK keratometry (K) values and surgically induced change in refraction (all P<.05 with Bonferroni correction). There were no statistically significant differences between methods using surgically induced change in refraction and methods using no previous data. CONCLUSION: Methods using surgically induced change in refraction and methods using no previous data gave better results than methods using pre‐LASIK/PRK K values and surgically induced change in refraction. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned.

Expected effects of surgically induced astigmatism on AcrySof toric intraocular lens results

PURPOSE: To evaluate the expected effects of including surgically induced astigmatism (SIA) in surgical planning for the AcrySof toric intraocular lens (IOL) (Alcon Laboratories, Inc.). SETTING: Private practice, Mesa, Arizona, USA. METHODS: Keratometric data were obtained for a large patient population (806 eyes) with preoperative corneal astigmatism of 2.50 diopters (D) or less. Anticipated residual astigmatism was calculated using nominal SIA values in the AcrySof Toric IOL Calculator for superior and temporal incisions. Anticipated residual astigmatism was also calculated without considering SIA in the planning process but with a nominal value applied when calculating the surgical result. RESULTS: Using a 0.50 D SIA value for superior or temporal incisions, there was a statistically, but not clinically significant, difference (mean approximately 0.05 diopter [D]) in the anticipated residual astigmatism by incision location (P<.05). Anticipated residual astigmatism, when including or not including SIA in the planning process, was statistically significantly different by IOL and incision location (P<.05), with anticipated differences that were clinically significant (>0.50 D) for all toric IOLs. These large differences appeared to be driven by changes in IOL selection as a result of including SIA in the AcrySof Toric IOL Calculator. CONCLUSIONS: With the AcrySof toric IOL, consideration of SIA from temporal or superior incisions resulted in statistically and clinically significantly lower anticipated residual astigmatism. The most important effect of including SIA appears to be more appropriate IOL selection.

Multifocal intraocular lenses: relative indications and contraindications for implantation.

UNLABELLED This article presents an extensive overview of best clinical practice pertaining to selection and use of multifocal intraocular lenses (IOLs) currently available in the United States. Relevant preoperative diagnostic evaluations, patient selection criteria, counseling, and managing expectations are reviewed, as well as how to approach patients with underlying ocular intricacies or challenges and best practices for intraoperative challenges during planned implantation of a multifocal IOL. Managing the unhappy multifocal IOL patient if implantation has been performed is also addressed. FINANCIAL DISCLOSURE No author has a financial or proprietary interest in any material or method mentioned.

Evaluation of a new IOLMaster algorithm to measure axial length.

PURPOSE: To evaluate the ability of the new IOLMaster with Advanced Technology version 5 software (Carl Zeiss Meditec, AG) to measure axial length (AL) in patients having preoperative cataract extraction evaluation. SETTING: Private practice, Arizona, USA. METHODS: This single‐center study comprised 54 eyes (33 patients) scheduled for cataract extraction. Visual acuity, manifest refraction, and Lens Opacities Classification System III (LOCS III) scores were recorded. Twenty AL measurements per eye were acquired using an IOLMaster with Advanced Technology version 5 software. The AL measurements were analyzed and classified into 4 methods: standard, standard manipulated, composite‐5, and composite‐20. RESULTS: Axial length measurements were successfully obtained in 55.6%, 94.4%, 92.6%, and 96.3% of eyes with the standard, standard manipulated, composite‐5, and composite‐20 methods, respectively. Axial length measurement availability (ability of the software to provide an AL measurement) was not statistically significantly affected by nuclear color, nuclear opalescence, or cortical changes with any method. However, posterior subcapsular changes statistically significantly affected the standard and composite methods (P<.05) and marginally affected the standard manipulated method in measuring the AL (P = .0868). Axial length availability was significantly reduced in eyes with posterior subcapsular cataract of LOCS III grade 5.0 or higher. CONCLUSIONS: The 2 composite methods performed as well as the more time consuming, complicated standard manipulated method in measuring AL. More than 90% of eyes could be measured by the composite methods. Dense posterior subcapsular cataracts significantly reduced the ability of the composite and standard manipulated methods to successfully measure AL.

Monte Carlo simulation of expected outcomes with the AcrySof® toric intraocular lens

BackgroundTo use a Monte Carlo simulation to predict postoperative results with the AcrySof® Toric lens, evaluating the likelihood of over- or under-correction using various toric lens selection criteria.MethodsKeratometric data were obtained from a large patient population with preoperative corneal astigmatism <= 2.50D (2,000 eyes). The probability distributions for toric marking accuracy, surgically induced astigmatism and lens rotation were estimated using available data. Anticipated residual astigmatism was calculated using a Monte Carlo simulation under two different lens selection scenarios.ResultsThis simulation demonstrated that random errors in alignment, surgically induced astigmatism and lens rotation slightly reduced the overall effect of the toric lens. Residual astigmatism was statistically significantly higher under the simulation of surgery relative to an exact calculation (p < 0.05). The simulation also demonstrated that more aggressive lens selection criteria could produce clinically significant reductions in residual astigmatism in a high percentage of patients.ConclusionMonte Carlo simulation suggests that surgical variability and lens orientation/rotation variability may combine to produce small reductions in the correction achieved with the AcrySof® Toric® IOL. Adopting more aggressive lens selection criteria may yield significantly lower residual astigmatism values for many patients, with negligible overcorrections. Surgeons are encouraged to evaluate their AcrySof® Toric® outcomes to determine if they should modify their individual lens selection criteria, or their default surgically induced astigmatism value, to benefit their patients.

Matched comparison of rotational stability of 1-piece acrylic and plate-haptic silicone toric intraocular lenses in Asian eyes

PURPOSE: To evaluate and compare the postoperative rotational stability of a 1‐piece acrylic toric intraocular lens (IOL) (Acrysof) and a plate‐haptic silicone toric IOL (Staar) in Asian eyes. SETTING: Singapore National Eye Centre, Singapore. DESIGN: Prospective randomized control trial. METHODS: Eyes of Chinese patients having cataract surgery were randomized to receive the acrylic toric IOL or the silicone toric IOL. Postoperatively, patients returned at 1 day, 1 week, and 1 and 3 months. The eyes were dilated and slitlamp retroillumination photography of the toric IOL was performed to assess rotational stability. RESULTS: The acrylic IOL was implanted in 24 eyes and the silicone IOL in 26 eyes. The mean age of the patients was 68.2 years (range 42 to 82 years). The mean IOL rotation from baseline to 3 months postoperatively was 4.23 ± 4.28 degrees in the acrylic IOL group and 9.42 ± 7.80 degrees in the silicone IOL group; the difference was statistically significant (P=.01). Of the acrylic IOLs, 73% were rotated less than 5 degrees at 3 months; none was rotated more than 15 degrees at 3 months. The silicone toric IOLs showed greater rotational movement, with 37% being rotated less than 5 degrees and 21% being rotated more than 15 degrees. CONCLUSION: The acrylic toric IOL had better rotational stability than the silicone toric IOL. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned.

New regression formula for toric intraocular lens calculations.

Purpose To evaluate and compare the accuracy of 2 toric intraocular lens (IOL) calculators with or without a new regression formula. Setting Ein‐Tal Eye Center, Tel‐Aviv, Israel, and the Lions Eye Institute, Nedlands, Western Australia, Australia. Design Retrospective case series. Methods A new regression formula (Abulafia‐Koch) was developed to calculate the estimated total corneal astigmatism based on standard keratometry measurements. The error in the predicted residual astigmatism was calculated by the Alcon and Holladay toric IOL calculators with and without adjustments by the Abulafia‐Koch formula. These results were compared with those of the Barrett toric calculator. Results Data from 78 eyes were evaluated to validate the Abulafia‐Koch formula. The centroid errors in predicted residual astigmatism were against‐the‐rule with the Alcon (0.55 diopter [D]) and Holladay (0.54 D) toric calculators and decreased to 0.05 D (P < .001 [x‐axis], P = .776 [y‐axis]) and 0.04 D (P < .001 [x‐axis], P = .726 [y‐axis]) with adjustments by the Abulafia‐Koch formula. The Alcon and the Holladay toric calculators had a higher proportion of eyes within ±0.50 D of the predicted residual astigmatism with the Abulafia‐Koch formula (76.9% and 78.2%, respectively) than without it (both 30.8%). There were no significant differences between the results of the Abulafia‐Koch‐modified Alcon and the Holladay toric calculators and those of the Barrett toric calculator. Conclusion Adjustment of commercial toric IOL calculators by the Abulafia‐Koch formula significantly improved the prediction of postoperative astigmatic outcome. Financial Disclosure Dr. Abulafia received a speaker’s fee from Haag‐Streit AG. Dr. Barrett has licensed the Barrett Toric Calculator to Haag‐Streit AG. Dr. Koch is a consultant to Alcon Laboratories, Inc., Abbott Medical Optics, Inc., and Revision Optics, Inc. Dr. Hill is a paid consultant to Haag‐Streit AG and Alcon Laboratories, Inc. None of the other authors has a financial or proprietary interest in any material or method mentioned.

Accuracy of the Barrett True-K formula for intraocular lens power prediction after laser in situ keratomileusis or photorefractive keratectomy for myopia.

Purpose To compare the accuracy of the Barrett True‐K formula with other methods available on the American Society of Cataract and Refractive Surgery (ASCRS) post‐refractive surgery intraocular lens (IOL) power calculator for the prediction of IOL power after previous myopic laser in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK). Setting Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, and private practice, Mesa, Arizona, USA. Design Retrospective case series. Methods The accuracy of the Barrett True‐K formula was compared with the Adjusted Atlas (4.0 mm zone), Masket, modified‐Masket, Wang‐Koch‐Maloney, Shammas, and Haigis‐L methods to calculate IOL power. A separate analysis of 2 no‐history methods (Shammas and Haigis‐L) was performed and compared with the Barrett True‐K no‐history option. Results Eighty‐eight eyes were available for analysis. The Barrett True‐K formula had a significantly smaller median absolute refraction prediction error than all other formulas except the Masket, smaller variances compared with the Wang‐Koch‐Maloney, Shammas, and Haigis‐L, and a greater percentage of eyes within ±0.50 diopter (D) of predicted error in refraction compared with the Adjusted Atlas, Masket, and modified Masket methods (all P < .05). In eyes with no historical data, the Barrett True‐K no‐history formula had a significantly smaller median absolute refraction prediction error and a greater percentage of eyes within ±0.50 D of the predicted error in refraction than the Shammas and the Haigis‐L formulas (both P < .05). Conclusion The Barrett True‐K formula was either equal to or better than alternative methods available on the ASCRS online calculator for predicting IOL power in eyes with previous myopic LASIK or PRK. Financial Disclosures Dr. Barrett has licensed the Barrett True‐K formula to Haag‐Streit. Dr. Hill is a paid consultant to Haag‐Streit and Alcon Surgical, Inc. None of the other authors has a financial or proprietary interest in any material or method mentioned.

Comparison of Methods to Predict Residual Astigmatism After Intraocular Lens Implantation.

PURPOSE To evaluate and compare the accuracy of three toric intraocular lens (IOL) calculators using keratometry measurements derived from the anterior corneal curvature and direct measurements of the posterior corneal curvature. METHODS Postoperative corneal astigmatism was measured by the IOLMaster (Carl Zeiss Meditec, Jena, Germany) and Pentacam (Oculus Optikgeräte, Wetzlar, Germany). The data were processed by the Alcon, Holladay, and Barrett toric IOL calculators. The error in predicted residual astigmatism (PredRA) was calculated by subtracting the PredRA from the postoperative subjective refraction by vector analysis. RESULTS The centroid errors in PredRA were against-the-rule (ATR) with the Alcon (0.56 diopters [D]) and Holladay (0.55 D) toric calculators using the IOLMaster (Carl Zeiss Meditec, Jena, Germany) measurements. The centroid errors in PredRA were lower when Pentacam (Oculus Optikgeräte, Wetzlar, Germany) measurements were used (0.38 D, ATR). The Barrett toric calculator using the IOLMaster measurements had the lowest centroid errors in PredRA (0.02 D, P < .001) and achieved the most accurate results: 75.8% and 92.9% of eyes were within 0.50 and 0.75 D of the PredRA, respectively. CONCLUSIONS The prediction of the postoperative astigmatic outcome can be improved by using appropriate methods of adjustment for posterior corneal astigmatism.

Prospective Multicenter Study of Toric IOL Outcomes When Dual Zone Automated Keratometry Is Used for Astigmatism Planning

PURPOSE To evaluate clinical outcomes when toric intraocular lens (IOL) calculations are based on the keratometric output from the Lenstar LS-900 dual zone automated keratometer (Haag-Streit AG, Koeniz, Switzerland). METHODS Eligible subjects presenting for toric IOL implantation at five sites were measured with a dual-zone automated keratometer. The data were used to plan the power and angle of the toric IOL to be implanted. Refractive and visual acuity status were checked at 1 and 3 months postoperatively. RESULTS A total of 102 eyes had relevant data for analysis. More than 76% of eyes had 0.50 diopter or less of refractive astigmatism at 1 and 3 months, with no difference by level of astigmatism corrected. More than half of the eyes had uncorrected distance visual acuity of 20/20 or better and 78% were 20/25 or better. A new measure of effectiveness of toric correction power is described that suggested lens selection was appropriate. Results appeared better than those obtained in previous studies when the IOL cylinder power and alignment were calculated using manual keratometry. CONCLUSIONS In this series of eyes from multiple centers, the calculation of toric IOL power using dual-zone automated keratometry measurements produced clinical results that were better than results in the literature where manual keratometry was used.