Lecture: Wavefront Aberrometry and iTrace: Screening and Planning Surgeries

DR PAWAR: Welcome to Cybersight live webinar. I’m Dr. Neelam Pawar from India, and tonight I will be presenting on wavefront aberrometry and iTrace, screening and planning surgeries. I’m having no financial interest in this presentation. So during the presentation, I will have a few poll questions for you, and I will be happy to take any queries and questions at the end of the presentation. So here the poll question first. What is your current position? Are you a cataract surgery? Are you a refractive surgeon? Comprehensive ophthalmologist? Fellow/resident, medical student, ophthalmic technician or allied health? So let’s see who has joined us today. It’s good that most of our people are fellows today evening. And second are comprehensive ophthalmologists and ophthalmic technicians, and some of you are refractive surgeons. None of you are cataract surgeons. So we’ll have a short talk on the basics of wavefront aberrometry and screening of patients with multifocal IOL candidates, dysfunction lens syndrome, dissatisfied refractive and multifocal patients, precision in toric IOLs, and other non-surgical applications of iTrace. So today we are in the era of supranormal vision, where not only the surgeon, but patients also want vision beyond 20/20, and one can tailor patients’ outcomes with advanced different technology. And ray tracing wavefront aberrometry and corneal topography fulfill this requisite. In the process of image formation by the human eye, the sources of degradation are diffraction, scattering, and most common is optical aberration. So what is wavefront aberration? It’s a measure of aberropia, the light coming from the distance, and whenever this passes through a convex lens, a spherical wavefront is formed. And any departure from this parameter leads to a wavefront error. Aberrations are mainly lower order aberrations and higher order aberrations. Lower order consist of myopia and astigmatism. Higher order aberration causes blur and double voicing, glare and halo caused by spherical aberration, and starburst aberrations are caused by trefoil. Do you have any aberrometer in your hospital? So it will be good to teach those people who are not having so much exposure to aberrometers. So how do we quantify wavefront aberrations? These wavefront aberrations are represented by Zernike mode pyramid, where m is the angular meridional frequency and n is the radial order. So the first two rows include lower order aberration, vertical tilt and horizontal tilt are included in first order aberration, oblique astigmatism, defocused and vertical astigmatism are included in second order aberration, while the bottom rows of this Zernike pyramid includes higher order aberration, vertical trefoil, horizontal coma, and oblique coma are included in third order, and vertical pentafoil, vertical secondary trefoil are included in fifth order aberrations. The Zernike coefficients are represented as these Zernike polynomials, and the value is expressed in microns, and these values are expressed as bars, and these are displayed in iTrace. The commercially available aberrometers, which are widely used worldwide, are Nidek OPD scan, WASCA, by Carl Zeiss Meditec, Zywave by Bausch and Lomb, multispot Hartmann, and Allegretto wave analyzer. iTrace is based on the principle of ray tracing. Rozema did a wonderful comparison of six aberrometers, and they found that all these aberrometers have different technical specifications, but when studied in normal healthy eyes they found that most of the parameters globally were similar, but there were some parameters in which there were significant differences. And they found that higher order measurements, higher order aberration measurements obtained with iTrace tended to be larger than those obtained with Shack-Hartmann aberrometers and significant differences between the devices were found in coma measurements also. Other studies have stated aberrometers based on the ray tracing principle and aberrometers based on the Hartmann-Shack principle should not be interchanged in clinical applications. Here comes the poll question three. If you’re using aberrometers in your clinic, what is your preferred choice of aberrometry in your clinic? Zywave, WASCA, iTrace, Nidek OPD Scan, or any other aberrometer, or you’re not having any other experience with aberrometry? Let’s wait for the answer. Oh, good. 13% of the people are using iTrace. Where the rest of the people are not using any other iTrace, and most of the people are not having any experience with aberrometers. iTrace is a five in one system, and it provides autorefraction, corneal topography, ray tracing aberrometry, pupillometry, and autokeratometry. Unlike with other machines, it has also some pitfalls, with age there is increased internal aberration, and with age the pupil size also changes. Wavefront aberrations are pupil size dependent, and here you can see that as the pupil size increases, the wavefront aberrations also increase. And the location of the pupil center is also an important factor. Pharmacological dilatation of the pupil induces a shift in the pupil center. While natural pupil dilation results in very minimal change in the location of the pupil center, compared to the pupil center location in the photopic condition. So natural pupil dilation in mesopic light conditions is optimal to take measurements. Sometimes because of the patient’s head movements and different observers there can be variations in the result. So iTrace works on the principle of ray tracing technology, where 256 individual and consecutive light rays enter the pupil and land on the retina. From there, they are reflected, and a detector detects this, and data is processed, and then it is displayed in iTrace, in different display mechanisms. So why do we need iTrace aberrometers? It integrates wavefront aberrometry with corneal topography, it subtracts corneal from total aberrations in order to isolate the internal aberrations, it’s useful in refractive lensectomies and dysfunctional lens syndrome, and is useful for aspheric, accommodative, and multifocal IOLs and for postop evaluation of these, and toric IOLs. So better information about the patient’s optical system’s alignment is always required, so that you can decide which IOL is best for your patient. What data do we get from iTrace? iTrace gives total aberrations of an eye, and along with internal Zernike, it gives the root mean square, the combination of all the aberrations, it gives the optical quality metrics in a function of modular transfer function, and point spread function, which tells about the image quality, and also shows you the simulated vision of a patient. So let’s see how the iTrace screening looks. Here if you see, this is the overview screen of iTrace. And we can see here — this is OD wavefront and OD corneal topography. And here is OS wavefront and OS corneal topography. And in my right hand side, you can see various blocks. The first block shows the vision diagnostic. Cataract diagnostic. Corneal diagnostic. Toric planner. And accommodation analysis. This is the overview screen of the wavefront verification display. And this is the diagram which tells about whatever points which have entered inside the eye, whether they are reflected back or not. So it gives about the horizontal and vertical point profile — more of the points are centered toward the cornea. Towards the center. It shows that image quality is good. So normal eye, if you see, these points are centered, more centered, and if you see the point spread function, it is a perfect point. In irregular eyes, the lenticular aberrations — and in a keratoconic eye, you can have spread out of these points, and then point spread function will also be distorted. So with the view of retinal spot diagram only, you can imagine or qualitate the image quality. So in cataract evaluation, if you click the Chang analysis, it is displayed, as you can see, in my screen. Here it shows all the Zernike aberrations. The corneal, the internal, and then entire eye, Zernike coefficient, presented as astigmatism, trefoil… Coma, astigmatism, and tetrafoil. And if you see this upper part, it shows the multizone refraction. Here is the higher order total aberration. Here is angle alpha D, which is very important in case of multifocal IOL. Here is the effective refractive power, which is again important in calculation of IOL power, in postrefractive surgery. Here is the corneal spherical aberration at 6 millimeters. And it also gives inferior-superior power at 6 millimeters. So this is the Chang analysis. This display shows the internal optic analysis. And all the aberrations, they are presented here. And more green is the value — it is less steep aberration. This is the wavefront analysis or visual function analysis. And it shows how the patient perceives the image. So the more blurry is the E, the more decreased is the quality of vision. And here is the potential visual complaints. Either the patient is experiencing blur or double vision or a starburst. This screen displays the point spread function, and actually, this screen tells us about the image quality. Here if you see this is the modulation transfer function, and this graph shows the values at 5, 10, 15, 20, 25 cycles per degree of frequency, and here it shows the higher order total MTA function. This is the point spread function, and this is the ratio. As I have already explained that if the point spread function is more clear, it suggests that the patient is having very good quality image, and a ratio that is near towards one suggests that image quality is good. So let’s see an example, where this night/day vision changes. This patient has double vision and blurred vision at night. So when we did E, iTrace of this patient in right hand side — you can see that with 2 mm pupil size, the E is very clear, while with 5 mm pupil size, which simulates night conditions, the E is very blurred. So the iTrace demonstrates the actual vision problems not only to doctors, but also to patients. So evaluation in case of cataract. It is advisable to perform a scan in a dark room, so as to simulate mesopic conditions. Photopic as well as mesopic pupil size is very important in multifocal IOLs. iTrace helps in evaluating spherical aberrations of the eye, angle alpha and angle kappa, and evaluation following cataract surgery. So how can the iTrace help you when selecting aspheric IOLs? Packer et al. did a study on aspheric IOLs selection based on corneal wavefront, IOLs and they measured corneal spherical aberration Z4,0 at the 6 millimeter optical zone, and placed one of the three aspheric IOLs so that corneal spherical aberration plus pseudophakic spherical aberration should be near zero. And they stated that customized selection of aspheric IOLs based on corneal wavefront is feasible, and it produces favorable results compared with studies in which unselected patient populations were implanted with aspheric IOLs. The normal human cornea is having a positive Q value, and if you implant a simple monofocal lens with a positive spherical aberration, you will eventually increase the entire eye positive spherical aberration, leading to decreased contrast sensitivity. Various meta-analyses have also proved that vision of aspheric lenses to spherical monofocal intraocular lenses superiority of aspheric to spherical monofocal lenses, in a large number of studies, compared the ocular wavefront analysis of aspheric lenses to spherical monofocal intraocular lenses, and they found that most of the study revealed that higher order aberrations and coma at 6 millimeters and 4 millimeters were less in aspheric lenses. In the cataract evaluation part, we have this option of IOL selection analysis. And it gets us a clue of the lens which you are going to implant. Here if you see is the entire Zernike coefficients. This is the internal eye Zernike coefficient, and down here are all corneal aberrations. And here is the corneal-spherical aberration function. So if you see on my right hand side, the IOL selection checklist says: Is Tracey refraction normal? No. Are corneal aberrations present? Yes. Are internal higher order aberrations present? Yes. Angle alpha, total coma values, the total astigmatism, and the corneal spherical aberration. So never place a multifocal IOL in an aberrated cornea. So lens to consider: Monofocal non-toric IOL, or advanced balance curve IOL, which will neutralize this aberration. In post-LASIK eye, there is increase in the positive Q value, so it is better to put a lens which is having a negative spherical aberration. Why? Posthyperopic eyes have more increased negative value, so it is always better to put traditional monofocal lenses. Using angle alpha in premium IOL screening. Why is optical alignment critical for multifocal IOL? The angle alpha is considered a confidence metric, because knowing this number helps the surgeon to predict how well the multifocal will align optically with the patient’s visual axis. So here, if you see, in the red issue, the red shows the visual axis, the green shows the pupil center. The angle between them is angle kappa, while the blue shows the limbal or optical center of the eye. The angle between the visual axis and limbal center is known as angle alpha, and it is very important in IOL placement. Whenever there is large angle alpha that is more than 0.5 millimeters, the optical axis or the center of the capsular bag is far away from the visual axis. This leads to potentially unpleasant refractive surprises, and even with good vision, patients are never satisfied. So this flowchart shows the process for iTrace decisions in cases of premium IOL evaluation. In cases of premium IOL after having a good retinoscopy, with good OCT scans, one has to perform iTrace examination and diagnose cataract with DLI, and evaluate optical alignment with angle alpha. If there is high angle alpha, always consider a monofocal lens. And if the angle alpha is not so high, analyze the corneal quality of vision with Chang analysis. If corneal higher order aberrations are more, it is better to place a monofocal lens, and if there’s low corneal higher order aberration, they are good candidates for a multifocal or other premium option. And use the iTrace Toric Planner to calculate and locate the placement axis. If the patient is a toric candidate, then better to place a toric IOL. A large review on multifocal intraocular lenses by the cataract committee suggested that anterior corneal coma values greater than 0.32 millimeters may result in intolerable dysphotopsia in the presence of a diffractive optics multifocal IOL. The extended depth of focus IOLs are also promising, and clinical outcomes and higher order aberrations after bilateral implantation of extended depth of focus intraocular lenses have proved that with these lenses, the higher order aberrations are less, but still we are having very limited literature on these EDF IOLs, and aberrometry by ray tracing in these IOLs. With a newer version of iTrace, we are having even — if you click there, you are having calculations for depth of focus which is very useful in extended depth of focus IOLs. Now, let’s see the examples of some postop unhappy and happy patients. This particular patient was implanted with multifocal IOL, had vision 20/20, but his higher order aberrations were 0.360 microns, and angle alpha was very large. It was 0.716 millimeters. If you see here, all the plus… The optical axis is far from the center of the pupil. And if you see the E, simulated E, the E is very blurred. And here if you see the potential visual complaint, the patient is having blur and double vision, which is showing plus-plus, starburst is plus. So even after having vision of 20/20, the patient was not satisfied, because of angle alpha. Second example of an unhappy multifocal ReSTOR. Here if you see the coma values and higher order aberrations are 0.27 microns, but angle alpha is borderline, 0.413 millimeters. But if you see the wavefront and corneal topography display, if you see the E, the E is very blurred, and therefore patients, though it was a borderline case, the patient was — even with vision 20/20, he was unhappy. So sometimes it is very useful not only for the doctor but also to explain to patients why their IOL is not working. And if patients are not satisfied, there is always exchange option, of IOL exchange. A third example of a happy patient. If you see the aberrations in internal and cornea, you can find very minimal bias. Entire eye also has very few aberrations, and if you see the higher order aberrations, they are very low. The angle alpha is 0.11, which is very low. So definitely a patient will be very happy, because he is having very less aberrations in cornea. And lens. And if you see the simulated E, the E is in both eyes — OD and OS — the E is very clear. If you see here in potential visual complaint, the patient is not having any complaint at all. Again, if you see here, no potential visual complaints, so seeing these happy patients, the surgeons are also always very happy. Now, the fourth example is again a borderline patient. And these patients are very difficult to deal with. Here if you see, in the internal aberrations, comas are present. Cornea is not having so much comas, and entire eye also is not having so much coma. The higher order aberrations, total are 0.448. Angle alpha D is very less, 0.280, and this is a pre-op cataract patient. So here one has to decide, one has to go for a monofocal lens or a multifocal lens, because sometimes in these borderline cases, you can have different results, postoperatively. Here is the poll question four. Whether you use term dysfunctional lens syndrome in your clinical practice. Yes, no, or cannot comment on dysfunctional lens syndrome. Let’s wait for the answer from the audience. So none of you uses this term in your practice. And 30% of the audience say they cannot comment on this term, dysfunctional lens syndrome. So what is dysfunctional lens syndrome? It is not a fancy term. It was described long back by George O Waring, and actually, it is described as decrease in the functional vision related to the effect of increasing optical aberrations, as well as subtle age-related opacification. So it is characterized by difficulty seeing at distance and at near. So the clinical finding typically include: Lens opacities, whether they are cortical lens changes or nuclear changes, the inability to accommodate due to presbyopia, and an aberration profile that has changed. This term, dysfunctional lens syndrome, whether you include it in your practice or not, or any surgery or decision based on dysfunctional lens syndrome should never be oriented towards any medical insurance. A surgeon has always to consider the patient visual needs. So what is dysfunctional lens index or DLI? First objective measure of performance of the lens, and with iTrace, one can calculate the DLI. Using this dysfunctional lens display, the surgeon can quickly determine if the patient is experiencing any syndromes of dysfunctional lens syndrome. A value of 10 is perfectly clear lens, and values towards 0 is a dense cataract. Anything below 5 is significant for cataract, and if patient is approaching towards 6 or 7, he is getting close to cataract. So here in this example if you see this dysfunctional lens patient display, with the new software version of iTrace, you see here the DLI is 6.61. Though the E is a little blurred. Opacity is less, DLI is high, and the patient claims good vision. Sometimes some patients, even with this DLI, can complain that they are not having good vision. Second example… If you see the E is very blurred. There’s significant opacity, and DLI is low. DLI is 3.22, and patient claims less vision. As the cornea is perfect, so this cornea will support a premium lens, and the patient will be benefited definitely from a premium lens. Here, if you see, this is the opacity map. The darker the color, the decrease is in the clarity, and opacity map usually correlates well to the slit lamp examination. On comparison of this dysfunctional lens index and Scheimpflug lens densitometry in the evaluation of age-related nuclear cataracts, DLI was correlated with LOCS III, and had a stronger correlation with CDVA compared to the LOCS III classification or the Scheimpflug-based lens density. The DLI may improve the preoperative evaluation of nuclear cataract, and also the monitoring of its progression. And sometimes it can seen help the surgeon to decide their parameters for phacoemulsification or for femto-assisted laser cataract. We do sometimes see the patient entering in your clinic, and this patient will suddenly come to you in your clinic one day, complaining that their vision has decreased since some months, even. They will have a vision of 20/20. So on these post-LASIK patients, if you do iTrace, you will find the problem is not in their cornea. Their LASIK has not worn off. But the problem is in their lens, and the lens is not functioning properly. If you see the dysfunctional lens display of this post-LASIK patient, there is minimal aberration in cornea, and there is little blurriness of E. And if we see the internal letter E, it is very blurred. The DLI is 4.76. That is below 5. And in these cases, you can easily offer the patient the option of removal of their aberrated lens. And definitely by removing this aberrated lens, and implanting a premium IOL, it will give a good result to post-LASIK patients. The iTrace can locate the cylinder axis of toric IOL, and therefore is pretty helpful in planning toric IOLs, and even the postoperative toric IOL assessment. The iTrace toric check display guides the cataract surgeon to monitor postop torics, and to determine if rotation is necessary or not. And it is also helpful to know whether a toric IOL is off-axis or off-power, and to understand the change to the best corrected visual acuity that is likely with lens rotation. The wavefront Ks also improves your toric precision, and most of the studies have shown that the K value, the same K values, based on other topography, slightly less inferior on comparison with wavefront Ks, in cases of toric IOL. Because these wavefront Ks are calculated based on the best Zernike fit on the cornea. So let’s see an example of toric IOL. In this patient, the toric IOL was intended to be placed at 81 degrees, and here you can see the pre-op point spread function. You can see the point spread function is distorted. And after placing the toric IOL, the point spread function is somewhat better. But in the first postoperative day the lens was at axis of 90 degrees, so having toric check display in iTrace you can know how much rotation you have to do for your toric IOL which is not in its intended axis. So in this particular case, the toric calculator showed that 14-degree rotation clockwise will change 1.2 diopter change in cylinder. So the lens was at position of 90 degrees, and it has to be rotated 14 degrees clockwise, in order to reduce the astigmatism. But this particular patient was not willing for surgery. So no rotation was done for this particular case. Obviously another toric unhappy patient. In this patient, the axis of placement was 129 degrees, but the actual placement has to be 180 degrees. So actually 51-degree rotation will result in 1.13-diopter change in cylinder power. So before pre-enhancement, the patient has very blurred E, and after enhancement, we see the lens is rotated, and it must be at 174 degrees, so this is estimated prescription prior to rotation, and measured refraction after rotation is this much. So even after a good rotation, the machine will always say some rotation, which need not to be done in any case. So let’s see some examples of how your toric precisions with postop axis analysis… How iTrace helps you. So this is the case first, and if you see here, the toric check display in iTrace shows 8 degrees rotation clockwise. Will change 0.21-diopter change in cylinder. So in this case, rotation does not provide much improvement. So better not to rotate this lens. In case two, if you see this display, it shows 25-degree rotation clockwise will change 3.72 diopters in cylinder. So rotation will improve results dramatically. So better to rotate the lens. And here is the case three. You see the toric display shows 6 degrees rotation clockwise will result in 0.11 diopter change in cylinder. So here the lens is actually not off-axis. The lens is actually off-powered. So there is no need to rotate the lens. Here it is better to change the lens. The decentered rhexis usually causes trefoil, and tilted multifocal IOLs and decentered lenses shows increase in spherical aberration. And in this picture, if you see — more of the colors are becoming dark, towards violet. It shows more of the colors are towards yellow or green, less the aberration. So iTrace can demonstrate cases of tilted multifocal IOL, and whenever there is decentered IOL, it is helpful for the surgeon to not only understand where the problem lies, but it also helps to educate the patient where they are having problems, because multifocal patients usually do complain with their different pupil size and with the different varying lights. We presented a paper at AAO 2016 in Chicago on internal aberrations Strehl ratio, modulation transfer function and corneal aspheric function after femtosecond laser assisted cataract surgery with iTrace, and found a very interesting result. That in most of the cases, it significantly reduced the internal aberrations. Most of the cases have higher modulation transfer function. And most of the patients have very good image quality in comparison to traditional phacoemulsification. But the only limitation of the study was that there was a limited number of patients. We have not set any particular pupil size, because aberrations can vary with different pupil size. And we don’t have different subsets of lenses, because the aberrations can definitely vary with spheric and aspherical and multifocal lenses. So here is a wonderful example of non-surgical application of iTrace. In this patient who had SA60AT lens implanted in both eyes, had 20/20 vision in left eye, and the patient was complaining of blurred vision at night, and if you see… In this wavefront, and CT summary display, you will see that entire eye RMS at 5.70, the higher order aberrations were 0.538 microns, and if you see this display at periphery, you will have more colors towards blue, green, and red, and after this patient had — after contract or posterior capsular opacification, although he had vision of 20/20, but after YAG capsulotomy, if you see his entire eye RMS total, it has decreased to 0.2. If you see the pictures here, there is more greener and yellower, compared to pre-YAG capsulotomy. So most of the studies have also shown that the YAG capsulotomy have improved wavefront aberration profile in pseudophakic eyes. But there are very limited studies on this, and one has to be very careful if they are claiming these types of things, which types of lenses they are using. Either hydrophilic or hydrophobic intraocular lens. The other application of iTrace include: It helps in corneal inlay planning. In cases of overrefraction to spectacle or contact lenses, iTrace is very helpful in cases where the intracorneal segment rings are placed, and before and after surgery, you can easily compare the higher order aberrations, and you can even explain the patient who are going for cornea inlay or any segments, or patients going for C3R, how this procedure can help in reducing their corneal aberrations. iTrace is also helpful in predicting overrefraction through spectacle or contact lenses. In cases of vitreolysis, laser floater removal, you can educate the patient about how their vision was before the laser and how their vision is after laser. It is also helpful in detecting the higher order aberrations and aberrations because of cornea in dry eye, and also doing studies on these patients, you can tell patients that after dry eye management how the aberration profile can change. We have already discussed about the dysfunctional lens syndrome. Along with dysfunctional lens syndrome, iTrace is very helpful in accommodation studies, and one can easily do accommodation studies in young patients with this iTrace. So what is the future of iTrace? It is not only a diagnostic tool, but it’s also proving to be a research tool, with newer IOLs and with newer technology. It is already used as a research tool, and it also helps in educating patients how this procedure is going to help them, and sometimes it is also important to tell them why their problem is there, whether the problem is in cornea, or is in their lens. So most of the patients are satisfied when you explain them where the problem lies. So better understanding of this technology can help to have more implications in the future, and one has to always keep this thing in mind, that a surgeon should always titrate his surgical and clinical knowledge, and patients need and should not be totally dependent on the machine in any case. So thank you, Cybersight, for providing this opportunity, and thank you, our audience, for listening to this presentation. So welcome to questions. If you are having any questions or queries, we can take them right now.

>> Thank you, Dr. Pawar. You can go ahead and stop sharing your screen, and so far there’s one Q and A question we can open up. So can you stop your screen share? If not, I can do it. If you open up the Q and A box, so far there’s one question.

DR PAWAR: So we are having one question. What parameters do we check before inserting multifocal IOL? For a candidate with multifocal IOL, not only their cornea, but their retina should also be absolutely free from any RP defect. They should be free from any diabetic retinopathy. Cornea should be absolutely clear. And moreover, as I have already explained, that you should not place a multifocal IOL in cases which are having aberrated corneas. And not only with iTrace. With other aberrometers also, you can have these coma values, but iTrace specifically gives you alpha value, which is very important, and it is always better not to place a multifocal in cases which are having very high angle alpha. Because if this angle is small, always the visual axis will be placed on these diffractive rings. If you are having an IOL which is having a very large inner diameter, where there are no diffractive rings, it is fine, but in most of the IOLs, if there is a slight increase in this alpha angle, patients are never satisfied. The other question is: What is monochromatic and chromatic aberrations? These aberrations are basically because of property of our lens that the light is not — it is more color dependent. Whatever the color. It’s not appreciated. It will result more in the color perception changes.

>> Okay. We’ll wait another minute and see if any last minute questions come in.

DR PAWAR: Okay. Yeah, there is a question: In pediatric cataract, multifocal IOL? There is always a big no for pediatric multifocal IOL, because all the studies done worldwide and with all the experts’ opinions from worldwide pediatric surgeons there is always no to MF IOLs in pediatric cases. Because these pediatric patients in adulthood — how they are going to behave, we don’t know. They will always have a problem of glare and halos, and in pediatric cases, there is always a chance of increased posterior capsular opacification, which need to have a YAG capsulotomy. So it is better not to place multifocal IOLs in pediatric patients. Those studies have claimed putting multifocal IOLs in pediatric cases, but they are very few. There was one very nice paper on this discussion, and there was consensus on these issues, and most of the experts, the 7 to 8 experts from pediatric fields, they said no to multifocal IOLs. Toric IOL you can consider later in life. But not multifocal in pediatric. So what are the absolute values of angle alpha and aberrations that you would not insert multifocal IOL? The angle alpha cutoff is 0.5 millimeters. So beyond 0.5 millimeters, you should not insert multifocal IOL. But as I’ve shown in my presentation, even sometimes with a very borderline value patients can complain of visual dissatisfaction. These aberration values… Okay. There’s another question. When corneal aberrations are high, and multifocal IOL is already in place, would wavefront-guided LASIK help? I’m not a refractive surgeon, so I’m not having so much experience with this, but I don’t think so. When your corneal aberrations are very high, a multifocal is already in place, whether it will help so much. But definitely with newer innovations, with topography guided LASIK, it can improve. Here is a question. Can you see the aberration value on Pentacam? No, Pentacam is basically used for topography. It will show you more the sagittal values of cornea, and not the aberrations. One has to understand the basic distance, what an aberrometer can do and what a topography machine can do. In patients with antecedent of keratometry can I use multifocal IOL? I think there’s some spelling mistake. And if I can understand… Whether in case of RK patient, one can use a multifocal IOL? In RK patients who have already gone 8 or 16 or 32 cuts, it is better not to place a multifocal IOL.