I use the hofferq, holladay 1, srkt, holladay 2, haigis, and barrett formulas in combination to choose the spherical power and then calculate the cylindrical power separately. Apr 29, 2005 i believe in this so strongly that i had my hoffer programs iol power calculation system software completely reprogrammed so you can use the doublek, he says. Having this type of information helps determine the best possible calculation and customization for iol implant selection. Many of the old thinlens iol power calculation formulas, such as the binkhorst, hoffer q, holladay 1, and srkt use only the k reading and the al as input. In conclusion, calculation of the iol power can be performed using a great variety of formulas. Effect of anterior chamber depth on the choice of intraocular. Intraocular lens power calculation in eyes with previous. The srk formula uses the following equation to calculate iol power. Using the srkt formula, you calculate for an iol power that seems appropriate. East valley ophthalmology is a dynamic and rewarding place in which to work.
The commonly used and more recent five iol power calculation formulas builtin software of iolmaster 700 software version 1. Biometry for intraocular lens iol power calculation eyewiki. Comparison of okulix raytracing software with srkt and hoffer. Regarding to the iol power calculation in patients with long axial length, both the haigis and srk t formulas would take the axial length and anterior chamber depth into consideration, while the. The olsen formula uses 5 measurements and 1 iol constant. We have a passion for our profession and a worldclass reputation. Because rk patients were once myopic but now have flat corneas, they typically have a deeper anterior depth than patients with similarly flat k readings who do not have a history of myopic refractive surgery. Purpose to compare the performance of okulix raytracing software with srk t and hoffer q formula in intraocular lens iol power calculation in patients presenting with cataract. The implanted iol power was chosen based on okulix ray tracing software calculation aiming for. Oct 27, 2017 three iol brands were used and for all eyes, iol power calculation was performed using srk t, hoffer q formula and also okulix raytracing software. Srk i and ii regression formulae are now regarded as obsolete. To compare the performance of okulix raytracing software with srk t and hoffer q formula in intraocular lens iol power calculation in patients. The purpose of this study was to evaluate the performance of the srk t formula in predicting a target refraction 1.
Update on optical biometry and intraocular lens power calculation nazneen nazm 1, arup chakrabarti 2 1 department of ophthalmology, esipgimsr, esi medical college and hospital, kolkata, west bengal, india 2 chakrabarti eye care centre, thiruvananthapuram, kerala, india. The earliest iol power calculation formulas, in the late 1970s and early 1980s, were either theoretical or regression formulas. To compare the accuracy of intraocular lens iol calculation formulas barrett universal ii, haigis, hoffer q, holladay 1, holladay 2, olsen, and srkt in the prediction of postoperative refraction using a single optical biometry device. The improvements in iol power calculation are the result of improvements in the predictability of the elp. Iol power calculations have become a focal point of cataract surgery. Features for calculating surgicallyinduced astigmatism and backcalculating values to determine the source of refractive surprises only require clicking one button. Double k correction method iol calculation formulas hoffer q. Dick said the software is as accurate as the classic srk formula for averagesized eyes because the mean acd is still calculated from an aconstant. Srkt formula iol power calculations prior rk lasik. Intraocular lens power calculation after corneal refractive. Predicting the refractive outcome and accuracy of iol. Sustained accuracy improvement in intraocular lens power. This calculator uses both the haigis and srkt formula with a variety of fudge factors that have been described in the literature over the past few years.
The srk t formula is a theoretical t approach to iol power calculation under the srk umbrella of empirical formulas using existing aconstants and optimization methods. Srk ii formula in the calculation of intraocular lens power. Firstgeneration formulas, such as the sandersretzlaffkraff srk, used the power of the cornea and the axial length, along with the aconstant of the specific iol, to come up with power. The srkt formula is a theoretical t approach to iol power calculation under the srk umbrella of empirical formulas using existing aconstants and optimization methods. Comparison of formula accuracy for intraocular lens power. Methods this retrospective study involved patients who had uncomplicated cataract surgery. Olsen is the author of the olsen formula and the originator of the phacooptics pc software iol innovations, aarhus, denmark using the newly described cconstant approach for the prediction of the iol position. Since then, cataract and refractive surgery have developed into the most frequent and most successful surgical interventions in the history of medicine. Sayegh believes that hoffer q is a good choice for iol calculation in short eyes, based on consistent evidence in the literature. With 100 million power calculations performed worldwide, the iolmaster 500 is the current gold standard biometer. Development of the srkt intraocular lens implant power calculation formula.
Comparison of okulix raytracing software with srkt and. The hoffer q, holladay 1, and srkt use 2 biometric measurements and a single iol constant. The authors suggested that the srkt formula should not been used in iol power calculation in eyes with al shorter than 22 mm. The haigis formula uses 3 measurements and 3 iol constants, and the holladay 2 formula uses 7 measurements and 1 iol constant. The power of the intraocular lens implant can be calculated accurately when the corneal refractive power, media type, and axial length are properly measured. To compare the accuracy of intraocular lens iol calculation formulas barrett universal ii, haigis, hoffer q, holladay 1, holladay 2, olsen, and srk t in the prediction of postoperative refraction using a single optical biometry device. The refractive power of the eye primarily depends upon the cornea, the lens, ocular media, and the axial length of the eye. Harold ridley 19062001, who implanted the first intraocular lens in 1949, lived to see cataract surgery evolve into a true refractive procedure, undergoing iol implantations himself in 1989 and 1990.
Empirical optimization methods of the srk t model primarily consist of 1 postoperative acd prediction, 2, a retina thickness correction factor and 3 corneal refractive. Intraocular lens power selection in eyes with axial myopia. The standard iol calculation formulas current used are the hoffer q, 1 holladay i, 2 srk t, 3 and srk ii. Jan 01, 2015 iol power calculations comparing the current third generation formulas holladay2, holladay 1, hoffer q and the srk t are easily performed.
Pdf intraocular lens power calculation using ray tracing. Crstoday iol choice and calculations in a postrk patient. The term was originally used by whewell initially in the 1800s for calculating life expectancy. Three iol brands were used and for all eyes, iol power calculation was performed using srk t, hoffer q formula and also okulix raytracing software. Pdf accuracy of intraocular lens power calculation in.
Consensus recommendation of corneal power and iol calculation formulae. The authors tested srk, srk ii, holladay, hoffer q, and srk t formulas. Comparison of intraoperative aberrometry, octbased iol formula, haigisl, and masket formulae for iol power calculation after laser vision correction. Formulas include barrett universal ii, hillrbf, olsen, holladay, hoffer q, haigis, srk t, ladas.
This iol power calculation method does not need special software, and has the potential to reduce refractive errors after cataract surgery compared to existing iol calculation formulas. Various theoretical and regression iol calculation formulas have been used since fedorov et al in 1967. For the calculation of iol power, a doublek modified formula is necessary to remove the calculation artifact of iatrogenically flat keratometry k readings. Eyeworld iol power calculation iol power calculations and biometry all years 2020 2019 2018 2017 2016 2015 2014 20 2012 2011 2010 2009 2008 2007 all months january february march april may june july august september october november december. Biometry is the method of applying mathematics to biology. Although no formula has been proven to have an advantage, it is preferable to use the theoretical formulas e.
Pdf purpose to compare the performance of okulix raytracing software with srkt and hoffer q formula in intraocular lens iol power. The srkt formula calculations used the same preoperative data and the latest constants from the user group for laser interference biometry. These fudge factors are necessary because the postrefractive surgery cornea does not have the same relationship between anterior and posterior corneal surface that a normal cornea does. Regression formulas topped surgeons preferences, and one of the most successful was the srk formula devised by donald r. Validation of the stop formula for calculating intraocular. Intraocular lens calculation after refractive surgery.
If no number appears, it means that the formula is not applicable for. This dependence on the central corneal power for the effective lens position calculation is one of the drawbacks of older, 2variable, 3rd generation iol power calculation formulas, such as srk t, holladay 1 and hoffer q, which require an aramberri doublek method correction to remove the artifact generated by a falsely flat central cornea. The srk t, holladay 1, and hoffer q formulas require a corneal power correction and the doublek method to accurately measure the iol power in eyes that had prior lasikprk. However, some iol formulas such as the srk t or srk ii formulas assume a relationship between keratometry and anterior chamber depth.
We strive to employ a team of the most talented and responsible professionals in ophthalmology. The employment of optical al instead of anatomic al has significantly improved the refractive results of cataract surgery. The hillrbf calculator is an advanced, selfvalidating method for iol power selection employing pattern recognition and sophisticated data interpolation. Accuracy of intraocular lens power calculation formulas. It has been optimized for use with the haagstreit lenstar, using optical biometry for all axial measurements and high density autokeratometry. The present study was a retrospective analysis, which included 38 eyes with an al iol implantation to compare the predictive accuracy of various iol power calculation formulae. The difference between the predicted postoperative residualrefraction rr of the iol determined by ray tracing and the rr of the same iol obtained using 3rd generation iol calculation formulas namely the srkt, hofferq, holladay1, and haigis formulas 18,19,20,21, was calculated and analyzed. This translates into a 510fold precision in al measurement. Preoperative axial length al was divided into four subgroups. Iol power calculations comparing the current third generation formulas holladay2, holladay 1, hoffer q and the srk t are easily performed.
The middle line appearing in bold type indicates which refraction of the corresponding iol comes closest to the desired target refraction. The effective lens positions for vergence thin lens formula elp o and for thick lens formula elp k are shown. Development of a new intraocular lens power calculation. The iol power was calculated using srkt formula and okulix ray tracing software. This nomogram is easy to use by just look up the axial length of the patient and add or subtract the adjusted iol power to the iol power calculated using the srk t, hoffer q, and holladay 1 formulas. To compare the performance of okulix raytracing software with srkt and hoffer q formula in intraocular lens iol power calculation in patients.
Pdf comparison of okulix raytracing software with srkt. Previous studies have shown that it provides repeatable and reproducible measurements that are similar to those of the main benchmark for comparison, the iolmaster 500 carl zeiss meditec. The new sandersretzlaffkraff srk ii formula was more accurate than the original srk and binkhorst ii formulae. However, some iol formulas such as the srkt or srkii formulas assume a relationship between keratometry and. Intraocular lens power calculation using ray tracing following excimer laser surgery article pdf available in eye 216. The best known modern formulas are srkt, holladay 1, holladay 2, hofferq and haigis.
After iol implantation in eyes with previous lasik, prk or rk, a refractive surprise can occur because i the altered ratio between the anterior and posterior corneal. Intraocular lens iol power calculation in eyes with previous excimer laser. Every year more than 11 mio lenses are implanted worldwide, providing excellent chances for the majority of patients to regain good. Accuracy of intraocular lens calculation formulas sciencedirect. Pdf srk ii formula in the calculation of intraocular lens power.
Standard iol calculation formulae such as srkt, holladay 1 or hoffer q all estimate the effective lens position elp based on axial length and k measurements. The hoffer q, holladay i, and srk t formulae are all commonly used. The srkt variant of the stop formula is one of the best formulas for this purpose. The major drawback is that you have to pay to use it. Okulix ray tracing has a software interface to all tomey devices, to the. After refractive corneal surgery the haigisl formulae may be selected. The haigis formula does not need doublek calculations because elp calculation does not depend on the corneal curvature to determine its value. Purpose to investigate the effect of anterior chamber depth acd on the refractive outcomes of the srkt, holladay 1, hoffer q and haigis formulae in short, normal, long and extremely long eyes. Crstoday iol power calculation after refractive surgery. The difference in rr for the same iol calculated by oculix and by the 3rd generation formulas srkt, hofferq, holladay1, and haigis was statistically significant all formulas.
According to clinical studies, the srk t formula is recommended for rather long eyes whereas the hoffer q formula is recommended for rather short eyes. The decision of how much emmetropic iol power was to be undercorrected was based on age of the child at. This calculator uses both the haigis and srk t formula with a variety of fudge factors that have been described in the literature over the past few years. Sanders, retzlaff and kraff developed the srk formula which was. Theoretical calculation of correct iol power after corneal. Empirical optimization methods of the srkt model primarily consist of 1 postoperative acd prediction, 2, a retina thickness correction factor and 3 corneal refractive. Preoperative refraction and corneal power are unknown. The srk t formula is one of the third generation iol calculation formulas.
Pdf comparison of okulix raytracing software with srkt and. The a constant formulae in use currently utilize constants, which are based on various factors that affect the refractive state of the eye postoperatively. Theres not one, but dozens of papers, and each of those papers has 100, 200 or maybe thousands of eyes, so theres some consistency there, where you know that this has been tested again and again. Currently, the most recommended formulas for iol power calculation for short eyes are the thirdgeneration formula hoffer q64,65,43 and the fourthgeneration formula holladay2. To compare the performance of okulix raytracing software with srkt and hoffer q formula in intraocular lens iol power calculation in patients presenting. The development of better instrumentation for measuring the eyes axial length al and the use of more precise mathematical formulas to perform the appropriate calculations have significantly improved the accuracy with which the.
After hyperopic keratorefractive surgery iol power adjustment table for srkt formula. The manufacturer iol constant was used for power calculation. Iol power calculation by ray tracing with sirius costruzione strumenti oftalmici. Update on optical biometry and intraocular lens power. Iol power calculation formulas zeiss medical technology. Authors concluded that all 5 iol power calculation formulas were unsatisfactory in achieving target refraction. In this prospective case series study, we have shown the performance of okulix software raytracing iol power calculation was not significantly different compared with the other two routine and reliable iol power calculation formulas, srkt and hoffer q. Jun 14, 2016 using the correct iol calculation formula is important for good surgical outcomes. I utilize intraoperative aberrometry to finetune both the iols spherical power and the axis, but i rarely change the cylindrical power unless i am using aberrometry. According to clinical studies, the srkt formula is recommended for rather long eyes whereas the hoffer q formula is recommended for rather short eyes. The aim of an accurate intraocular lens power calculation is to provide an intraocular lens iol that fits the specific needs and desires of the individual patient.
Holladay iol consultant hic program uses holladay 2 formula and. Effective ocular biometry and intraocular lens power. Six decades have passed since the first implantation of an artificial intraocular lens iol into a human eye. Other formulas that should be taken into consideration are the triples, masket, besst, and savini. The purpose of this study was to evaluate the performance of the srkt formula in predicting a target refraction 1. Srk ii formula in the calculation of intraocular lens. Terzi, wang, and kohnen studied the accuracy of holladay 2, hoffer q, srkt, and haigis iol power calculation formulas in refractive lens exchange. Srkt, hoffer q, haigis, holladay 2, and barrett universal ii. For all patients, axial length and keratometry data was obtained with iolmaster 500 device and iol power was determined using hoffer q and srk t formula. Iol power calculation was performed in all eyes using the srkt formula. A major shortcoming of most 3rd generation, 2variable formulas, such as srk t, is that they often assume that the anterior and posterior segments of the eye are mostly proportional and use only the axial length and keratometric corneal power to estimate the postoperative location of the iol, known as the effective lens position elpo. This works fine in the average eye but leads to limited prediction accuracy in unusual as well as long or short eyes.
We studied 400 eyes which underwent cataract extraction with posterior chamber intraocular lens iol implantation to compare the predictive accuracy of various iol power calculation formulae. The srkt formula is one of the third generation iol calculation formulas. The holladay 1 and hoffer q formulas are equally good for eyes with an al between 21. Iol powers for a target refraction default is emmetropia are calculated using the corrected srk t and haigis formulae, with the exception of the aramberri doublek method, which only uses the srk t formula and the walter method, which is currently only implemented for emmetropia. Iol power calculations comparing the current third generation formulas holladay2, holladay 1, hoffer q and the srkt are easily performed. Iol power calculator for cataract surgery hillrbf calculator. Calculated iol data in iol calculation window srkt in the columns below each specified lens you will find the calculated refractive powers and target refractions for those lenses. It is intended to be used in conjunction with a comprehensive ophthalmic examination and the appropriate diagnostic tests and measurements necessary for cataract surgery candidates with a history of prior refractive surgery. In this prospective case series study, we have shown the performance of okulix software raytracing iol power calculation was not significantly different compared with the other two routine and reliable iol power calculation formulas, srk t and hoffer q. A new device, the iol master, yields accurate axial length measurements using optical coherence techniques. Even if you dont know what the preop k was, youll be better off putting in a standard k like 43 or 44 than using the postop estimated value.
New approach for the calculation of the intraocular lens. Software simplifies iol calculations for odd eyes healio. Comparison of iol power calculation formulae for pediatric. Based on the aramberri double k method, the numbers in each row of the hyperopic refractive correction represent the amount in diopters that must be subtracted from the calculated iol power when using the srkt formula. These formulas are programmed into the iolmaster, lenstar and most modern ultrasonographic instruments, thus eliminating any need for regression formulas. One of the interesting aspects of this case was the patient had a significant angle kappathe distance between the pupil center and the visual axis. The binkhorst and the hoffer formulae use the postoperative ac depth, the srk ii. The iol calculator is meant to serve as an adjunct tool to assist physicians in selecting the appropriate iol for a particular patient.
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