Intraocular lens bicylindric power calculation method: Using both flat and steep K readings to improve intraocular lens power prediction

Calvo-Sanz, Jorge A; Ruiz-Alcocer, Javier; Sánchez-Tena, Miguel Ángel

doi:10.1177/1120672117754170

Cited by 6 publications

(11 citation statements)

References 30 publications

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“…Previous studies comparing the accuracy of IOL power calculation for cataract surgery among post LVC patients have generally been limited by using spherical equivalent to compare the intended and postoperative outcome, or in some cases treating the cylinder as an independent variable 45. Using the spherical equivalent is analogous to prescribing spectacles as a spherical equivalent rather than as a sphero-cylinder.…”

Section: Discussionmentioning

confidence: 99%

Refractive outcomes following cataract surgery in patients who have had myopic laser vision correction

et al. 2019

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ObjectivePrediction errors are increased among patients presenting for cataract surgery post laser vision correction (LVC) as biometric relationships are altered. We investigated the prediction errors of five formulae among these patients.Methods and analysisThe intended refractive error was calculated as a sphero-cylinder and as a spherical equivalent for analysis. For determining the difference between the intended and postoperative refractive error, data were transformed into components of Long's formalism, before changing into sphero-cylinder notation. These differences in refractive errors were compared between the five formulae and to that of a control group using a Kruskal-Wallis test. An F-test was used to compare the variances of the difference distributions.Results22 eyes post LVC and 19 control eyes were included for analysis. Comparing both groups, there were significant differences in the postoperative refractive error (p=0.038). The differences between the intended and postoperative refractive error were greater in post LVC eyes than control eyes (p=0.012), irrespective of the calculation method for the intended refractive error (p<0.01). The mean difference between the intended and postoperative refractive error was relatively small, but its variance was significantly greater among post LVC eyes than control eyes (p<0.01). Among post LVC eyes, there were no significant differences between the mean intended target refraction and between the intended and postoperative refractive error using five biometry formulae (p=0.76).ConclusionBiometry calculations were less precise for patients who had LVC than patients without LVC. No particular biometry formula appears to be superior among patients post LVC.

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Section: Discussionmentioning

confidence: 99%

Refractive outcomes following cataract surgery in patients who have had myopic laser vision correction

et al. 2019

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“…Haigis formula[ 13 ] was used to calculate the IOL power using bicylindric method described in a previous study. [ 12 ] This method considers both keratometry meridians (flat and steep), and the surgically induced astigmatism torque effect in the corneal astigmatism after a vector analysis. Therefore, this method calculates the IOL power for each corneal meridian, obtaining two refractive outcomes predictions (one for steep and one for flat keratometry readings) which will describe the expected final refraction in spherocylindrical format.…”

Section: Methodsmentioning

confidence: 99%

“…This also leads to a better choice of final IOL power and provides more accuracy on the expected residual refraction after surgery, in sphere, cylinder, and axis, instead of spherical equivalent. [ 12 ]…”

Section: Methodsmentioning

confidence: 99%

“…Sample size was calculated using GRANMO Software (Ver 7.12 - Institut Municipal d'InvestigacióMèdica, Barcelona, Spain. Accessed June 2018) following the data variability according previous study,[ 12 ] determining a minimum sample size of 56 subjects for a statistical level of α = 0.05 and risk β = 0.10.…”

Section: Methodsmentioning

confidence: 99%

“…In a previous paper,[ 12 ] we described mathematically a new method that uses both keratometry readings and the surgically induced astigmatism to improve the IOL power calculation and the refractive outcomes prediction. In this study we use the bric method to calculate the IOL power to implant and the final refraction after surgery.…”

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Clinical application of bicylindric intraocular lens power calculation method

Calvo-Sanz

Bonnin-Arias

Arias-Puente

2020

Indian J Ophthalmol

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Purpose: To analyze the reliability of the refractive results prediction obtained in intraocular lens (IOL) calculation using bicylindric power calculation method, with the use of steep and flat keratometry readings compared with the classical mean keratometry calculation method. Methods: Fifty-seven eyes of 57 subjects who underwent cataract surgery were included in this prospective study. Optical biometry was performed with IOLMaster 700 and IOL power calculation was performed using both keratometry readings and the surgically induced astigmatism. Four weeks after surgery, subjective refraction was done. Finally, results obtained with both IOL calculation methods were compared. Results: Mean spherical equivalent using bicylindric IOL power calculation method was - 0.082 ± 0.296D, and achieved mean spherical equivalent using classical IOL power method with Haigis formula was - 0.088 ± 0.405D. Achieved mean spherical equivalent obtained in subjective refraction after surgery was - 0.101 ± 0.265D. Linear correlation between bicylindric method spherical equivalent calculation and achieved spherical equivalent was statistically significant ( r = 0.761, P < 0.001), also correlation between Haigis spherical equivalent calculation and achieved spherical equivalent was statistically significant ( r = 0.339, P = 0.010). Emmetropia was achieved in 49 of 57 (85.86%) subjects and bicylindric method calculated that 49 of 57 (85.86%) of subjects would get emmetropia ( P = 1.000). Classical IOL power calculation estimated that 38/57 subjects would get emmetropia (66.67%) ( P = 0.026). Conclusion: The IOL power calculation including both keratometry readings and surgically induced astigmatism seems to be more accurate and provides more precision in refractive prediction than classical calculation method.

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Intraoperative aberrometry compared to preoperative Barrett True-K formula for intraocular lens power selection in eyes with prior refractive surgery

Gasparian

Nassiri

You

et al. 2022

Sci Rep

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To compare the predictive refractive accuracy of intraoperative aberrometry (ORA) to the preoperative Barrett True-K formula in the calculation of intraocular lens (IOL) power in eyes with prior refractive surgery undergoing cataract surgery at the Loma Linda University Eye Institute, Loma Linda, California, USA. We conducted a retrospective chart review of patients with a history of post-myopic or hyperopic LASIK/PRK who underwent uncomplicated cataract surgery between October 2016 and March 2020. Pre-operative measurements were performed utilizing the Barrett True-K formula. Intraoperative aberrometry (ORA) was used for aphakic refraction and IOL power calculation during surgery. Predictive refractive accuracy of the two methods was compared based on the difference between achieved and intended target spherical equivalent. A total of 97 eyes (69 patients) were included in the study. Of these, 81 eyes (83.5%) had previous myopic LASIK/PRK and 16 eyes (16.5%) had previous hyperopic LASIK/PRK. Median (MedAE)/mean (MAE) absolute prediction errors for preoperative as compared to intraoperative methods were 0.49 D/0.58 D compared to 0.42 D/0.51 D, respectively (P = 0.001/0.002). Over all, ORA led to a statistically significant lower median and mean absolute error compared to the Barrett True-K formula in post-refractive eyes. Percentage of eyes within ± 1.00 D of intended target refraction as predicted by the preoperative versus the intraoperative method was 82.3% and 89.6%, respectively (P = 0.04). Although ORA led to a statistically significant lower median absolute error compared to the Barrett True-K formula, the two methods are clinically comparable in predictive refractive accuracy in patients with prior refractive surgery.

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Intraocular lens bicylindric power calculation method: Using both flat and steep K readings to improve intraocular lens power prediction

Abstract: Intraocular lens calculation with bicylindric method could be more accurate and had more reliability than classical intraocular lens calculation method. Bicylindric method adds astigmatism control and provides a reliable expected spherocylindrical refraction.

Cited by 6 publications

References 30 publications

Refractive outcomes following cataract surgery in patients who have had myopic laser vision correction

Refractive outcomes following cataract surgery in patients who have had myopic laser vision correction

Clinical application of bicylindric intraocular lens power calculation method

Intraoperative aberrometry compared to preoperative Barrett True-K formula for intraocular lens power selection in eyes with prior refractive surgery

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