April 2009 Insert April 2009 Insert

Dual Scheimpflug Advantageous in Second-Opinion Patients

In candidates with irregular corneas, we show them a pictorial graph and a corneal printout to explain the contraindication for LASIK.

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As a refractive specialist, I see a lot of patients who are seeking second opinions. I like to use the Galilei Dual Scheimpflug Analyzer (Ziemer Group, Port, Switzerland) to ensure that not only the patient's central pachymetry spread is good, but also that the pachymetry spreads over the entire corneal surface. There are two subtle signs that LASIK may not be a viable option for a certain case: (1) there is a big difference in the pachymetric readings in the superior and inferior cornea; or (2) the thinnest point of the cornea is displaced inferiorly.

I typically perform 100-µm thin-flap LASIK; however, if either subtle sign is present, I do not hesitate to switch to a surface ablation procedure. I also use Intacs (Addition Technology, Inc., Irvine, CA) as an alternative to LASIK in corneas that show signs of forme fruste keratoconus.

The greatest advantage of the Galilei is that it provides real data—topographic and pachymetric maps—simultaneously. I am somewhat obsessive-compulsive with my measurements, performing repeat ultrasound pachymetry. It is amazing how the Galilei and corneal pachymetry correlate almost every time, within 1 µm of each other. Therefore, the Galilei can also be used as a screening tool. The Galilei also provides the anterior and posterior elevation of the cornea. Another big advantage is that I am able to show my patients their cornea. In the case of an individual who is a poor candidate for LASIK but has been told elsewhere that he is a good candidate, we can show him the pictorial graph to help explain his contraindication.

I also implant presbyobia-correcting IOLs. The Galilei images an early cataract; I can explain to my patients where the presbyopic implants will be placed because the dual Scheimpflug's color picture shows the iris, lens, and cornea. Patients' understanding and acceptance is higher, because you can show them this live animation of their own eye.

Before the Galilei, I used the Orbscan topographer (Bausch & Lomb, Rochester, NY) on thousands of patients. The data never seemed to accurately correlate with ultrasound results—perhaps because it does not use true data points. I stopped using the Orbscan because I found topography more helpful. When I learned of the Galilei, which uses both technologies, I decided to try it. The Galilei provides a good correlation between topography and ultrasound. If I have to place Intacs, it scans the depth of the cornea at different points, thus providing the optimal incision depth.

I have been using the Galilei for approximately 3 years. At that time, I was only relying on topography and corneal pachymetry. I was seeing many cases of post-LASIK ectasia that were referred from other practices. Even though we knew pachymetry was a good predictor of ectasia, I decided it was time to invest in a technology that allowed me to avoid ectasia in my patients as well as manage borderline patients more effectively.

When I was looking into what technology to purchase, I did a demo on several machines. I found the Galilei to be the most reliable. Additionally, the engineers of the Galilei visited my clinic, providing me with valuable information on its principles. I am a passionate surgeon, and I want to do the best for my patients. I could see that same kind of passion from those engineers.

I have multiple offices, but I only have the Galilei in one office. In one instance, the topographer showed subtle differences in the superior and inferior cornea. Although things looked OK to proceed, I still was not convinced that I should perform LASIK. Before deciding to proceed or switch to surface ablation, I asked that the patient visit my other office so that I could use the Galilei. Patients are always reluctant to travel, but I am glad he agreed. When we looked at his cornea on the Galilei, it picked up more LASIK contraindications, especially the superior/inferior pachymetry difference and displacement of the thinnest point. I therefore performed surface ablation.

When we use corneal pachymetry with nine or 10 test points, it is accurate enough to screen 98% of patients; however, that 1% to 2% of patients who have a subtle discrepancy that we may not catch is enough to make the switch to the Galilei. The thinnest point is easily missed when you screen for it manually. The more knowledge we acquire and apply using such machines makes us better physicians and makes surgery safer for our patients.

One of the most important principles to follow in order to provide the best results and the maximum benefit for patients is to thoroughly understand whatever machine you use. Make sure that your technicians understand it as well.

Patients must not move during preoperative measurements. The eye should also be well lubricated to give the best output. The Galilei assists the user by pointing out the accuracy of the measurements. It also interprets the data and makes analysis user friendly. Rather than repeating measurements and wondering why you are not getting good results, follow these steps from the start. Additionally, perform measurements in a semi-darkened room. These tips have helped us decrease the time required to take pictures from 10 to 15 minutes to 2 to 3 minutes.

One of the biggest challenges we will face in the near future is post-LASIK patients who will come in for presbyopia-correcting IOLs. To measure the central corneal keratometry is challenging, and then applying the correct formula is even more challenging. The Galilei will make these measurements easier.

Rajesh Khanna, MD, is Director of the Khanna Institute of LASIK and Refractive Surgery, Westlake Village, California. He acknowledged no financial interest in the products or companies mentioned. Dr. Khanna may be reached at (805) 230-2126;

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