Adi Abulafia

Intraocular lens power calculation for eyes with an axial length greater than 26.0 mm: Comparison of formulas and methods

Purpose To evaluate and compare the accuracy of formulas and methods for calculating the intraocular lens (IOL) power for eyes with an axial length (AL) greater than 26.0 mm. Setting Ein‐Tal Eye Center, Tel‐Aviv, Israel. Design Retrospective case series. Methods The postoperative refraction results in myopic eyes with an AL over 26.0 mm were compared with the predicted refractions calculated using standard formulas (Holladay 1, SRK/T, Hoffer Q, and Haigis) with optical IOL constants, User Group for Laser Interference Biometry constants, and an AL‐adjustment method and using new‐generation formulas (Barrett Universal II, Holladay 2, and Olsen). Results In 76 (71.7%) of 106 eyes, the IOL was 6.0 diopters (D) or more (Group A) and in 30 eyes (28.3%) was less than 6.0 D (Group B). In Group A, the SRK/T, Hoffer Q, Haigis, Barrett Universal II, Holladay 2, and Olsen methods met the benchmark criteria of having a prediction error of ±0.5 D in at least 71.0% of eyes and ±1.0 D in 93.0% of eyes. In Group B, only the Barrett Universal II formula and the Holladay 1 and Haigis formulas using the AL‐adjusted method met those criteria. Conclusion When selecting IOLs for high and extreme myopia, choosing appropriate formulas and methods can yield accurate refractive results that meet benchmark criteria. Financial Disclosure No author has a financial or proprietary interest in any material or method mentioned.

Prediction of refractive outcomes with toric intraocular lens implantation

Purpose To evaluate and compare the accuracy of different methods to measure and predict postoperative astigmatism with toric intraocular lens (IOL) implantation. Setting Ein‐Tal Ophthalmology Center, Tel‐Aviv, Israel. Design Retrospective case series. Methods Postoperative corneal astigmatism was measured with 3 devices (IOLMaster 500; optical low‐coherence reflectometry [OLCR]–based Lenstar LS 900; Atlas topographer) and compared with the manifest astigmatic refractive outcome in patients with toric IOLs. The error in the predicted residual astigmatism was calculated by vector analysis according to the measurement and calculation method used to predict the required toric IOL cylinder power. Results The centroid errors in predicted residual astigmatism were against the rule with the Alcon and Holladay toric calculators (0.53 to 0.56 diopter [D]), were lower with the Baylor nomogram (0.21 to 0.26 D), and were lowest for the Barrett toric calculator (0.01 to 0.16 D) (P <.001). The Barrett toric calculator had the lowest median absolute error in predicted residual astigmatism (0.35 to 0.54 D, all devices) compared with the Alcon and Holladay toric calculators with or without the Baylor nomogram (P <.021). The Barrett toric calculator and the OLCR device achieved the most accurate results; 75.0% and 97.1% of eyes were within ±0.50 D and ±0.75 D of the predicted residual astigmatism, respectively. Conclusion Prediction of astigmatic outcomes with toric IOLs can be improved with appropriate measuring devices and methods to establish the required toric IOL power. 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.

Accuracy of predicted refraction with multifocal intraocular lenses using two biometry measurement devices and multiple intraocular lens power calculation formulas

To evaluate the accuracy of predicted refraction using multifocal intraocular lenses (IOLs) with power calculation based on two biometric devices and multiple IOL power calculation formulas.

Pursuing perfection in intraocular lens calculations: I. Logical approach for classifying IOL calculation formulas

This year marks the 50th anniversary of the publication of Fyodorovs paper describing the first theoretical intraocular lens (IOL) calculation formula. Despite the remarkable progress that has occurred since that time, difficult challenges remain. Today, IOL calculations in their fullest extent comprise a complex scientific and therapeutic endeavor that includes some combination of the following steps:

Reversal of cystoid macular edema in gyrate atrophy patients

ABSTRACT Purpose: This study reports the presentation of two families with gyrate atrophy (GA). The aim of this study was to characterize the potential effect of therapeutic regimens on macular edema. Methods: Two unrelated patients with GA were studied for the potential effect of low protein diet (≤ 0.8 g/kg/d), and oral administration of pyridoxine (500 mg/day), on serum ornithine levels, best corrected visual acuity (BCVA), slit-lamp, OCT, and auto-fluorescence findings. Blood samples for DNA, mRNA, and exons of the OAT gene were screened for mutations and splicing effect when relevant. Results: At presentation, both patients manifested typical ophthalmic features of GA including cystoid macular edema (CME). One patient also exhibited optic nerve head hamartoma. Following treatment ornithine levels have lessened, BCVA improved, and central macular thickness (CMT) markedly decreased in all four studied eyes. The molecular pathologic features included a novel splice site mutation (c.900+1G>A). Conclusions: We have identified a novel mutation and two formerly described mutations in patients with GA. Of them, one patient comprised an unusual phenotype including bilateral astrocytic hamartomas. We have recognized for the first time improvement in CME following treatment with low protein intake and pyridoxine supplement. This finding may have significance in the understanding of treatment options for macular edema regardless of underlying etiology.

Guest editorialPursuing perfection in intraocular lens calculations: III. Criteria for analyzing outcomes

In our first 2 guest editorials in the series “Pursuing perfection in intraocular lens calculations,” we suggested a methodologic classification of intraocular lens (IOL) calculation formulas, addressed limitations of current formulas and technologies, and discussed a number of measurement issues that can contribute to IOL calculation errors in outcomes and in reporting. In this editorial, we focus on criteria for analyzing outcomes. As with all outcomes analyses, the goal must be to present outcomes in a way that accurately and concisely provides data that clinicians need for their practices and that researchers need to make new advances. In studies evaluating the accuracy of IOL power prediction using different IOL formulas or different ocular biometers, fundamentally we are interested in the difference between the predicted outcome preoperatively and the actual outcome achieved postoperatively. Various parameters have been analyzed and reported, and we recommend using the following parameters for all IOL calculation studies (Figure 1), recognizing that additional parameters might be included to describe unique features of the outcome:

Temperature profiles of sleeveless and coaxial phacoemulsification

Purpose To study the temperature profile at the corneal wound during 2 sleeveless techniques versus 2 coaxial phacoemulsification techniques. Setting Department of Ophthalmology, Meir Medical Center, Kfar Saba and Ein‐Tal Eye Center, Tel‐Aviv, Israel. Design Experimental study. Methods Thirty‐six porcine eyes were randomized into 4 groups: Group 1: conventional coaxial system (3.0 mm incision); Group 2: coaxial microincision cataract surgery (MICS) system (2.2 mm incision); Group 3: bimanual MICS (1.1 mm incision); Group 4: sleeveless tri‐MICS (1.1 mm incision) using a 19‐gauge anterior chamber maintainer as the sole fluid source. Temperature measurements were taken using a thermocouple and an infrared thermal imaging system. Measurements were taken in 2 settings; that is, with and without occlusion. Results With no occlusion, corneal burns did not occur in any group. However, corneal temperatures were lower with the sleeveless systems (Groups 3 and 4) than with the coaxial systems (Groups 1 and 2) (P=.0003). When occlusion was induced, temperatures were kept constantly low in the sleeveless groups, whereas in the coaxial groups, temperatures increased rapidly, causing corneal burns within seconds. The mean temperature elevations at the incision sites were 39°C, 48.5°C, 13.6°C, and 11.3°C in Groups 1, 2, 3, and 4, respectively (P<.0001). Conclusions Sleeveless phacoemulsification maintained lower tissue temperatures than sleeved coaxial methods. During occlusion, fluid flow around the naked tip of the sleeveless systems prevented heat accumulation and corneal burns. Financial Disclosure No author has a financial or proprietary interest in any material or method mentioned.