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1 62 EW FEATURE IOL calculations February 2015 IOL power calculations and biometry by Michelle Dalton EyeWorld Contributing Writer AT A GLANCE The Fyodorov, Colenbrander, and Binkhorst formulas were among the first, created in the late 60s and early-to-mid 70s. Differing axial lengths require different formulas. Fourth-generation formulas used today include the Holladay 2, Preussner, and Olsen. Physicians offer their thoughts on potential formulas Since the introduction of the IOL, researchers and clinicians alike have been trying to determine the best formula to use to implant the best possible lens for a particular patient, based on numerous characteristics that include refractive error, axial length, ocular comorbidities, and previous surgery. Improved conditions for accurate IOL power calculation include the advent of small incision surgery, corneal scanning devices, IOL manufacturing improvements, laser biometry, and enhanced capsulorhexis techniques. Determining which of the many potential formulas is best depends on all the above, experts say. All formulas are still far from perfect, as the rate of eyes within 0.5 D of the refractive target is only about 75%, said Giacomo Savini, MD, G.B. Bietti Eye Foundation, Rome, Italy. With one-quarter of patients left with a suboptimal result, I am investigating the role of corneal asphericity and lens thickness even in thin lens third-generation formulas, he said, adding that he presented some data on the topic at the 2014 ASCRS ASOA Symposium & Congress. 1 IOL power calculation formulas started as theoretical, with the Fyodorov, Colenbrander, and Binkhorst formulas in the late 60s and early-to-mid 70s, said Thomas Olsen, MD, University Eye Clinic, Aarhus, Denmark. The fourthgeneration formulas used today include the Holladay 2, Preussner, Ray tracing software allows accurate no-history IOL power calculation even in cases like decentered radial keratotomy with residual corneal astigmatism. Source: Giacomo Savini, MD and Olsen, he said. Dr. Olsen is the author of the Olsen formula and the originator of the PhacoOptics PC software (IOL Innovations, Aarhus, Denmark) using the newly described C-constant approach for the prediction of the IOL position. Normal eyes Healthy eyes (those without any comorbidities or previous surgery) can have fairly accurate readings from the third-generation formulas, including Hoffer Q, Holladay 1, and SRK/T, Dr. Savini said. I also rely on the Haigis formula, although I find it difficult to optimize its constants by myself. I am interested in investigating whether the C-concept by Dr. Olsen will carry any advantage, but until evidence of any advantage from different studies is available, I will go on with the standard formulas, he said. A modern IOL power calculation formula should fulfill a number of requirements in order to be safe and effective, Dr. Olsen said, including that it should be accurate in normal eyes. In fact, almost any formula would work within the normal range by establishing average values for the outcome based on the clinical environment, he said. For example, the SRK I formula used little optical modeling and was effective in the normal range, but not so in the extreme range. Noting that modern diagnostic instruments can provide significantly more data to help determine which lens would be best for an individual patient also means the term normal may need to be explored further, Dr. Olsen said. Do we limit it to normal axial length? Normal K-reading? Normal anterior segment? What about the posterior curvature of the cornea? he said. The challenge is to take advantage of the more detailed information in our clinical practice. Dr. Savini agreed, noting that differing axial lengths require different formulas. For very short eyes I use the Hoffer Q formula, which has been shown to be the best in these cases by many studies, Dr. Savini said. For long eyes, I rely on the SRK/T for the same reason. In long eyes, I also follow the approach suggested a few years ago by Prof. Haigis, who dramatically changes the constants of the IOLs. He does not use the Holladay 2 formula as it does not offer any advantage and it requires many more data [and time] points compared to the others, he said. I am also awaiting the results of the Hoffer H5 formula, which considers gender and race, but this will still take some time. Non-virgin eyes Patients who present post-laser vision surgery, either LASIK or PRK, pose a different challenge, Dr. Savini said. Data he presented at the 2014 ASCRS ASOA Symposium & Congress indicated the Savini method combined with double-k SRK/T, the Seitz/Speicher method combined with the same double-k SRK/T, the Masket method with SRK/T, and the Shammas no history method were the most accurate, he said. 1 These methods allow me to have the same accuracy as with unoperated eyes, i.e., more than 70% of cases within 0.5 D of intended refraction, Dr. Savini said. Dr. Savini does not change his formula of choice when other morbidities such as corneal disorders, diabetes, or glaucoma are present. Ray tracing The advantage of ray tracing is that it only requires Snell s law and needs no other assumptions than the physical shape and refractive index of the material, Dr. Olsen said.

2 [Ray tracing] is recognized as the most effective tool in optical engineering it makes sense to use this technique on the eye. Thomas Olsen, MD This is far more accurate than the first-order approximations used by the thin lens formulas, and it has the advantage over thick lens formulas that higher order aberrations (HOA) can be taken into account. [Ray tracing offers] full independence from perioperative data; surgeons just have to enter the axial length and software will predict the position of the lens, its power, and the final refraction, taking into consideration the corneal power and asphericity, Dr. Savini said. Dr. Olsen added that ray tracing is recognized as the most effective tool in optical engineering it makes sense to use this technique on the eye. Most formulas only use a single constant, the A-constant or the anterior chamber depth [ACD] constant, which normally is derived from the actual postoperative refraction, back-calculating what the constant should have been to ensure an average prediction error of zero, Dr. Olsen said. When this optimization has been accomplished, the performance of the formula is compared using metrics of the scatter like the standard deviation, the mean absolute error, or the median error. But the C-constant defines the physical IOL position from the preoperative ACD and lens thickness, Dr. Olsen said, meaning it is not dependent upon the K-reading or the axial length. In a recent study, 2 Dr. Olsen and Peter Hoffmann, MD, evaluated 2,043 cases to determine the accuracy of the C-constant for ray tracing and found it a promising concept. In their analysis, using the C-constant for unbiased prediction of the true position of the IOL, the Olsen formula also modifies exact ray tracing to correct for spherical aberrations of the cornea and IOL. This approach corresponded to a 15% reduction in mean absolute errors, and the number of large errors (1.0 D) dropped 39% in public hospital series and 85% in private clinic series when compared to the SRK/T formula. A great deal of the improved accuracy was the result of improved accuracy in predicting the IOL position, in normal eyes over a large axial length range, Dr. Olsen said. Both physicians said the future looks promising for even more accurate IOL power calculations. EW References 1.Savini G, Hoffer KJ, Casamenti V. Clinical Comparison of Methods to Calculate IOL Power After Myopic LASIK and PRK. Paper presented at: American Society of Cataract & Refractive Surgery. April 2014, Boston. 2. Olsen T, Hoffmann P. C constant: New concept for ray-tracing assisted intraocular lens power calculation. J Cataract Refract Surg ;40: Olsen T. Use of fellow eye data in the calculation of intraocular lens power for the second eye. Ophthalmology. 2011;118(9): Olsen T, Funding M. Ray-tracing analysis of intraocular lens power in situ. J Cataract Refract Surg. Apr 2012;38(4): Editors note: Dr. Olsen is the founder of IOL Innovations and has financial interests with Haag-Streit (Koniz, Switzerland). Dr. Savini has no financial interests related to his comments. Contact information Olsen: tkolsen@dadlnet.dk Savini: giacomo.savini@alice.it

3 64 EW FEATURE IOL calculations February 2015 Improving accuracy by Rich Daly EyeWorld Contributing Writer AT A GLANCE An average of multiple IOL calculation formulas may help increase accuracy in IOL surgery in patients who have previously undergone refractive surgery for myopia. Encourage IOL candidates to track down medical records from previous refractive procedures. Develop a plan for recalculating the correct power to address any instance of surprise error that necessitates IOL replacement. A growing number of power calculation options in myopic patients with previous refractive surgery has increased predictability of IOL placement in these patients T The development of photorefractive surgery in the mid-1990s has provided less dependence on spectacles, but it has also created an ever-growing pool of complex patients. The unknown corneal refractive power changes from refractive surgery have drawn a growing number of IOL power calculation formulas specifically designed to address this problem. Developers of some of the latest IOL calculation formulas report progressively more reliable outcomes for the growing number of previously treated refractive surgery patients. However, critical limitations can still affect the accuracy of results. The ASCRS website, org, offers an online post-refractive surgery IOL calculator, which provides a variety of published calculation algorithms for eyes after refractive surgery. Harry Geggel, MD, head of the ophthalmology section, Virginia Mason Medical Center, Seattle, has found that choosing the proper IOL power in former myopic refractive surgery patients undergoing routine cataract surgery was challenging using standard accepted formulas. That is because many reported methods rely on pre-refractive data or the verified change in spherical equivalent refraction. It is not infrequent that patients come in with no data available from the type of surgery or type of treatment that was done, Dr. Geggel said. Dr. Geggel has developed a consensus formula, which is an average of 6 formulas Geggel, Shammas, Haigis-L, Latkany average, Savini, and Seitz (Hoffer Q). Three of those formulas Geggel, Shammas, and Haigis-L do not require any previous refractive surgery history. What s nice about my consensus formula is that each of the formulas I m using tries to solve this puzzle in a different way, Dr. Geggel said. Savini plays around with the refractive index of the cornea; the Seitz (Hoffer Q) employs the Hoffer equation and alters the K reading of the cornea by how much laser treatment was done; and the Latkany formula uses the SRK/T formula with a modification. In addition to published results that show the consensus formula provides refractive outcomes for 70% within 0.5 D and 96% within 1 D of the intended result, the approach avoids overcorrections.¹ Surgeons want a technique that minimizes hyperopia postop, and if the patient is a little bit nearsighted they can still do some reading, Dr. Geggel said. All patients are told upfront that we lose a little bit of precision in the picking of the proper implant in such eyes. If they don t have any data then we re averaging 3 formulas, and if they have data we re averaging 6 formulas. Another averaged approach Kazuno Negishi, MD, PhD, associate professor, Department of Ophthalmology, Keio University School of Medicine, Tokyo, primarily uses an approach known as the modified anterior-posterior corneal curvature method (A-P method). As another approach that does not require historical data to calculate IOL power for eyes after LASIK, Dr. IOL power (D) Estimated postoperative spherical equivalent (D) Negishi and her colleagues presented on the modified A-P method at the 2014 ARVO meeting. Dr. Negishi uses an average of the modified A-P method, the Haigis-L, and Camellin-Calossi if after comparing the results there is more than 1 D of difference. The original A-P method is the modified double-k SRK/T formula based solely on the current measurement of the corneal peripheral power. It uses the estimated pre- LASIK K value, which is calculated based on the post-lasik posterior corneal curvature of the central zone, instead of the actual pre-lasik K value in the double-k method. In the modified A-P method, to prevent a hyperopic shift, it simply shifts the results using the A-P method to 0.98 D of myopia based on the third quartile of the hyperopic error of the A-P method (0.98 D). Corneal peripheral power approach A newer approach that Dr. Negishi has helped to develop is the centralperipheral corneal curvature method (C-P method), which is a modified double-k SRK/T formula based solely Actual postop refraction after primary cataract surgery (D) Estimated refraction after IOL exchange (in the bag fixation) (D) N/A N/A Figure 1. Example of the calculation for IOL exchange. The area surrounded with a square is an IOL calculation sheet for primary cataract surgery. The IOL power for IOL exchange is calculated on the basis of hyperopic shift (1.13 D) in the primary cataract surgery. Source: Kazuno Negishi, MD, PhD on the current measurement of the corneal peripheral power. This approach uses the estimated pre-lasik K value, which is calculated based on the post-lasik peripheral corneal curvature. The concept of this method is very similar to the A-P method, Dr. Negishi said. It allows predictable outcomes of IOL power calculations in eyes that underwent corneal refractive laser surgery for myopia. Accurate measurement of the peripheral corneal data is important in the C-P method, and it should be strictly checked before calculating the IOL power. However, it is sometimes hard to maintain the width of the palpebral fissure during measurement, especially in older patients with a narrow palpebral fissure. In such cases, Dr. Negishi shifts to the modified A-P method because it only needs the data of the central zone, which is easier to obtain. The modified A-P method provided greater accuracy than the original A-P method in published results.² The approach has provided Dr. Negishi even better results, with 63% of eyes within 0.5 D of target results and 91.3% within 1 D.

4 February 2015 IOL calculations EW FEATURE 65 In comparison, Wolfgang Haigis, PhD, University Eye Hospital, Wurzburg, Germany, said his use of the Haigis-L formula for the IOLMaster (Carl Zeiss Meditec, Jena, Germany) provides refractive outcomes within 0.5 D of target about 55% of the time. 2. Saiki M, Negishi K, Kato N, Ogino R, Arai H, Toda I, Dogru M, Tsubota K. Modified double-k method for intraocular lens power calculation after excimer laser corneal refractive surgery. J Cataract Refract Surg. 2013;39(4): Editors note: Drs. Geggel and Negishi have no financial interests related to their comments. Dr. Haigis has financial interests with Carl Zeiss Meditec. Contact information Geggel: ophhsg@vmmc.org Negishi: fwic7788@mb.infoweb.ne.jp Haigis: wh@ocucalc.de ASCRS BOOTH 2939 Addressing surprise outcomes Dr. Haigis said that in cases of a surprise error after implantation, he also uses the Haigis-L formula to determine the correct power for an IOL exchange after having rechecked all measurement data of the patient. Dr. Negishi does not use any specific formula to determine the correct power for IOL exchange and instead usually calculates the correct power based on the power of the implanted IOL, its target refraction, and the postoperative refractive error. I use the original calculation sheet and estimate the correct power using the difference between postop refractive error and the target refraction, Dr. Negishi said. For example, if the power of the implanted IOL was D, the preop estimated target refraction was 1.11 D, and the postop subjective refraction was D, the IOL power calculation error was D (hyperopic shift) in subjective refraction. The IOL power for IOL exchange is calculated to be D on the basis of the corrected estimated refraction in the primary calculation sheet (Figure 1). Although Dr. Geggel has not had to replace any IOLs because of power miscalculations, he suggested surgeons of patients who had postoperative hyperopia multiply the amount of hyperopia by 1.5 to determine the number of diopters to add to the replacement IOL. That s how we handle overcorrections or undercorrections on anyone, whether they ve had previous refractive surgery or not, Dr. Geggel said. EW References 1. Geggel, HS. Intraocular lens power adjustment after myopic excimer laser surgery: validation studies for Geggel ratio and consensus group. Cornea 2013;32: The specialists in single-use. se. LASIK / LASEK / ReLEx / PRK Phaco Oculoplastics IVT Strabismus Sub-Tenons... Brand new instruments, every time. Zero cross-contamination risk. Increased patient throughput. Malosa s single-use instruments and procedure packs provide optimal patient safety and brand new, flawless instruments for every eye. Prof. Dan Z Reinstein, MD MA(Cantab) FRCSC DABO FRCOphth FEBO - The London Vision Clinic Over 350 Instruments & 400 Packs for all specialties. View our online brochure. Complete range of Instruments and Procedure Packs for all Ophthalmic specialties.

5 66 EW FEATURE IOL calculations February 2015 Barrett Toric Calculator aims for accurate outcomes by Vanessa Caceres EyeWorld Contributing Writer AT A GLANCE Graham Barrett, MD, recently devised the Barrett Toric Calculator for toric IOL calculations. The formula takes into consideration lens position and posterior corneal curvature without actually measuring curvature. The calculator was more accurate compared with other formulas in studies that will be published soon. The calculator is available on the ASCRS and APACRS websites. New formula considers lens position, posterior corneal curvature In the quest for better surgical outcomes for toric IOLs, Graham Barrett, MD, has created the Barrett Toric Calculator. Dr. Barrett is a consultant ophthalmic surgeon at Sir Charles Gairdner Hospital, Nedlands, Western Australia; president of the Australasian Society of Cataract & Refractive Surgeons; and president of the Asia-Pacific Association of Cataract & Refractive Surgeons (APACRS). His work on the calculator began as part of a reflection on improving cataract surgery outcomes. Barrett Toric Calculator Of all the things that have happened over the last 10 to 15 years in cataract surgery, many of them make you wonder about the huge amount of money spent when the improvement for patients is modest or debatable, he said. With a toric lens, it s There s an app for that: toricam Another recent addition to Dr. Barrett s work is a free app he created for iphones and ipads called the toricam. It provides a way to determine axis of the corneal limbal marks used as a reference to find the correct alignment for a toric IOL during surgery, according to the app description. It can also measure the axis of an implanted IOL at the slit lamp postop. If you have an accurate reference axis, then your markings are perfect, Dr. Barrett said. The app is a free and simple method to make sure once you have a calculator with precise measurements. To see an in-depth interview with Dr. Barrett on the app, visit ewreplay.org, search for Graham Barrett toricam or select ESCRS from the Video Archives dropdown menu, then select 2014 and Sunday. Dr. Barrett is featured in the first video that day discussing the app and giving a demonstration of its use. EW quite different. You really change what you can do for the patient. However, using a toric lens requires more legwork for the surgeon than a conventional IOL. It s more demanding than a non-toric lens. If you want to get the best outcomes, you have to think about 4 things: 1) the device used to measure the cornea, 2) interpreting those measurements, 3) a measurement of prediction that s accurate, and 4) when you have the right method, you need something to let you put the lens on the right axis, he said. Those 4 concepts put the Barrett Toric Calculator in context. About the calculator Surgeons may feel bewildered by the sheer number of toric IOL calculators available, Dr. Barrett said. He said that his is unique because it takes into account the posterior cornea and considers lens position for each individual patient versus using what is known about the average eye. My formula uses the Universal II, which is a method of predicting IOL power to work out where the Source: Graham Barrett, MD lens is and uses that to calculate what is the effect of the cylinder power at the cornea, he said. Dr. Barrett also devised the Universal II formula. Dr. Barrett s formula considers the thickness and shape of the lens as well, which provides a more sophisticated way of predicting and translating the cylinder power, he said. The formula is able to predict posterior corneal curvature without actually measuring it. The reason it can do so is I looked at all the observations that people have made, especially Doug Koch [MD, Houston], about the posterior cornea, he said. It has long been known that the posterior cornea tends to have a half diopter of against-the-rule effect on the astigmatism of the eye, he said. Although that has been known since the late 1800s, it has not been accounted for in other toric lens calculations, Dr. Barrett said. The reality is, if you have against-the-rule astigmatism, it s aligned in the vertical meridian. I

6 February 2015 IOL calculations wondered why that is. It s odd and not obeying the rules you would expect from an optical surface. My basic theory is that the normal cornea tends to be elliptical. The diameter is wider in the horizontal meridian. Therefore, that means the curvature of the posterior cornea has to be steeper than the vertical. That means you have against-the-rule astigmatism because the posterior cornea is convex. That also explains why almost all corneas exhibit against-the-rule behavior, he said. Using that background, Dr. Barrett was able to calculate a measurement for the diameter of the cornea for each patient and calculate the posterior corneal curvature. Looking at the evidence Because the Barrett Toric Calculator is relatively new it has only been online since the summer of 2013 clinical evidence to support it is just now reaching peer-reviewed journals. In a submission that is in press, Dr. Barrett said his calculator was found to be within half a diopter of residual astigmatism 75% of the time compared with only 33% of the time for the Alcon AcrySof calculator (Fort Worth, Texas) or the Holladay calculator. By adding the Baylor nomogram, the accuracy of the Alcon and Holladay calculators increased to 50%, he said. The [Barrett Toric] theoretical method is doing significantly better than actually measuring the posterior cornea, he said. The Barrett Toric Calculator is available on the websites of ASCRS ( and APACRS (apacrs.org). The APACRS website also features Dr. Barrett s True-K formula and Universal II formula. The calculator was also recently built into the LENSTAR LS900 (Haag-Streit, Koniz, Switzerland). Dr. Barrett encourages surgeons to think carefully about other variables that affect their toric IOL use, such as selecting one primary tool to measure the cornea and then always using secondary tools, a concept he learned from Warren Hill, MD, Mesa, Ariz. You may have the LENSTAR or other tool for your primary measurement, but you also have to have a secondary tool to confirm your primary is giving you the correct reading, he said. Warren uses the analogy of a pilot who doesn t have just one instrument. The pilot has other instruments to make sure the primary instrument is correct. EW EW FEATURE 67 Editors note: Dr. Barrett has no financial interests related to this article. Contact information Barrett: graham.barrett@uwa.edu.au

7 72 EW FEATURE IOL calculations February ASCRS Clinical Survey IOL calculations: U.S. and international surgeons differ on formula preference by EyeWorld staff Many physicians customize their formula choice for each patient There are a variety of IOL calculation formulas currently in use in the U.S. and abroad, and choice depends on several surgeon- and patient-related factors. IOL choice and selection of IOLs is a personal thing, and every doctor has his or her preferences for particular cases, said Sumit Sam Garg, MD, Gavin Herbert Eye Institute, University of California, Irvine. Generally, in shorter eyes, we hedge toward the Hoffer Q. For normal eyes, we choose the Holladay 1, and for longer eyes, we use SRK/T. Doug Koch [MD] and colleagues have a modification that you can use for patients with really long axial lengths. The Holladay 2 [available on Holladay IOL Consultant Software] is a great formula that takes into account more variables than some of the other formulas, he said. Newer versions of the IOLMaster [Carl Zeiss Meditec, Jena, Germany] and LENSTAR [Haag-Streit, Koniz, Switzerland] have direct links to the software. The major drawback is that you have to pay to use it. The Hoffer Q, Holladay 1, and SRK/T use 2 biometric measurements and a single IOL constant. The Haigis formula uses 3 measurements and 3 IOL constants, and the Holladay 2 formula uses 7 measurements and 1 IOL constant. The Olsen formula uses 5 measurements and 1 IOL constant. In the 2014 ASCRS Clinical Survey, ASCRS members were surveyed about their preferred lens formula for the majority of cataract surgeries. Of the U.S. respondents, the majority (29.8%) prefer the Holladay 2, 27.9% prefer to use multiple formulas based on axial length, 19.2% prefer the SRK/T, 15.4% prefer the Holladay 1, 3.8% prefer the SRK II, and 2.9% prefer Haigis. In contrast, most of the non-u.s. respondents (24.2%) prefer multiple formulas based on axial length, 22.1% prefer Haigis, 18.9% prefer SRK/T, 13.7% prefer Holladay 2, 10.5% prefer SRK II, 7.4% prefer Holladay 1, and 1.1% prefer Hoffer Q. The difference in responses between U.S. and non-u.s. surgeons was statistically significant. Warren E. Hill, MD, Mesa, Ariz., was not surprised by the discrepancy in the preferences between U.S. surgeons and non-u.s. surgeons. Haigis has always been a popular formula for European ophthalmologists due to the fact that it is readily available on most biometers and it is familiar, Dr. Hill said. Here in the United States, Holladay 2 has steadily increased in ASCRS members were surveyed about their preferred lens formula for the majority of cataract surgeries. Source: ASCRS popularity over the past 5 years, due mostly to a combination of ease of use [it is resident on the IOLMaster 500 and an automatic import feature from the LENSTAR] and increasing pressure from patients for optimal outcomes. Dr. Hill uses the Holladay 2, Olsen, and Barrett Universal II formulas. Lately, I have come to trust the Olsen and Barrett Universal II formulas the most. In a large series of patients I recently reviewed, Olsen and Barrett had the best

8 February 2015 IOL calculations outcomes and also require no axial length adjustment for the high to extreme axial myope. By several percentage points, Barrett seems to have the overall advantage, especially for the high to extreme myope and the high hyperope, he said. Both Olsen and Barrett are now part of the LENSTAR EyeSuite software. For those without the LENSTAR, the Barrett Universal II formula can be accessed without charge on the Asia-Pacific Association of Cataract & Refractive Surgeons website, barrett_universal2. In addition to IOL calculation formulas, Dr. Garg relies on intraoperative aberrometry. I use the formulas and then use intraoperative aberrometry to confirm or change the lens power. The downsides to this are that it takes a couple of extra minutes in the OR, you have to pay for the equipment, and in really difficult eyes, it sometimes doesn t work, Dr. Garg said. For eyes that have undergone previous refractive surgery, specifically LASIK to correct myopia, Dr. Garg uses Haigis L followed by intraoperative aberrometry. I don t have any experience with the Holladay 2 formula myself, but it has been shown to be a very accurate measurement. These days, I m relying more and more on intraoperative aberrometry, Dr. Garg said. He noted that residents at his institution are taught to use multiple formulas. Instead of using just one formula, they are encouraged to use multiple formulas on the same eye and look for agreement between formulas. That s a smart way to look at formulas for any patient. If you look at 3 of them, and 2 of them are in agreement and 1 is way off, try to figure out why the 1 is off. I think it Global Trends in Ophthalmology Copyright 2015 Global Trends in Ophthalmology and the American Society of Cataract & Refractive Surgery. All rights reserved. is always better to err on the side of myopia because it can be corrected with refractive surgery much easier than hyperopia can, Dr. Garg said. EW Editors note: Drs. Garg and Hill have no financial interests related to this article. EW FEATURE Contact information Garg: gargs@uci.edu Hill: hill@doctor-hill.com FOR REFRACTIVE AND CATARACT SURGERY Reaching a new level in corneal tomography Patented Dual Scheimpflug system provides highly accurate pachymetry and ray-tracing, even when the measurement is decentred. The only true solution Placido and Scheimpflug for highly accurate pachymetry, elevation and curvature data in all eyes. Iris-based eye motion compensation Have confidence in your follow-up measurements with realignment of maps in 3-D. One platform, one solution. We simplify the daily workflow in your clinic with an all-in-one solution, from refractive to cataract surgery. Only the GALILEI G4 unites Placido and Dual Scheimpflug technologies in one measurement. With the GALILEI G4, you get highest precision measurements for posterior and anterior curvature, Pachymetry, ray-traced Total Corneal Power (TCP), ray-traced Total Corneal Wavefront and the full anterior segment of your patient s eye. The new GALILEI G4, for unrivalled clinical results. The GALILEI G4 is a modular platform which can be upgraded according to your needs. Learn more on galilei.ziemergroup.com. 73