Eyeworld Supplements

C ataract surgery has advanced to the point where accurate measure- ments are essential to achieving the best visual outcomes. I have found that the LENSTAR LS 900 optical biometer (Haag-Streit USA, Mason, Ohio) gives me the most comprehensive set of information with reliable and accurate measurements for planning cataract surgery with advanced technology IOLs. The need for optical biometry In my opinion, if you are perform- ing state-of-the-art cataract surgery, you should be committed to achiev- ing emmetropia in as many patients as possible regardless of the lens you are implanting. It therefore follows that having reliable and accurate measurements of the eye pre-opera- tively is essential. For many years applanation ultrasound was the method by which physicians gained information to calculate lens pow- ers. Immersion ultrasound was a big step forward but was not uniformly adopted due to the difficulty in performing the procedure as well as the inconvenience to the patient. Optical biometry has made immer- sion ultrasound quality measure- ments available to surgeons and patients alike in an easier format. Crucial measurements Within optical biometry, both the IOLMaster (Carl Zeiss Meditec, Dublin, Calif.) and the LENSTAR LS 900 optical biometer deliver excel- lent results. Like many surgeons, I began to try to improve my outcomes by using a version 5 IOLMaster. While this did much to reduce refractive surprises and speed up the acquisition of data, I still struggled with certain cases. A par- ticular source of frustration was the accuracy of the axis of astigmatism that the IOLMaster found in patients as compared to manual or auto- mated keratometry. When implant- ing toric lenses, this was a concern. Once I started using the LENSTAR LS 900 optical biometer, I began to have consistent, pre- dictable results. I found that the axial length measured between opti- cal biometers was very consistent, but the keratometry as determined by the LENSTAR optical biometer was improved based upon the addi- tional points of measurement. Each LENSTAR optical biometer scan measures the anterior corneal curva- ture at 32 discrete points divided be- tween two different zones—one at 2.3 mm and the other offset at 1.65 mm. That means that when the in- strument acquires five scans, you have sampled over 600 measure- ments on the cornea per eye. I believe that the additional measure- ments on the cornea provided better outcomes for my toric IOL patients or for multifocal or accommodating lens patients in whom I needed to do limbal relaxing incisions. In fact, a recently published study using simulated outcomes suggested that overall results for a group of patients whose toric IOL surgery planning was performed with the LENSTAR optical biometer was equivalent to manual Ks, but with a reduced site- to-site variability. 1 With the IOLMaster, the black box was in play. You got a set of numbers but without confidence values and without the ability to see examples of the actual scans. If a surgeon's K readings produce high standard de- viations, either in the values or the axis, it is often unwise to proceed with surgery until the cause can be determined. It may be that the patient's ocular surface needs to be improved or that the tear film needs to be addressed. My advice is to cor- rect those issues as best you can and then to repeat the K readings. One can also get a sense of the problem by looking at the Placido disc images. Distorted mires, ectatic areas, or poor images are all warning signs that should be heeded. Quantity plus quality equals greater efficiency While the difference between ultra- sound and optical biometry is huge, the difference between the LENSTAR optical biometer and the IOLMaster is smaller but meaningful. We all love to be efficient in what we do. In one scan, the LENSTAR optical biometer measures lens thickness, pachymetry, pupillometry, keratom- etry, axial length, anterior chamber depth, and the white-to-white lim- bal distance. The LENSTAR optical biometer provides additional param- eters—such as the lens thickness— that are often included in newer fourth-generation formulas and pro- vide a measured, rather than a calcu- lated, anterior chamber depth. This increased data along with the use of the newer, more sophisticated for- mulas should eliminate some of the surgeon's reliance on estimations. Additionally, the LENSTAR optical EW Chicago 2012 9 Optimized outcomes with advanced optical biometry by Joseph Sokol, M.D. What role does advanced technology play in your practice? " The keratometry as determined by the LENSTAR optical biometer was improved based upon the additional points of measurement " Joseph Sokol, M.D. continued on page 10 Alcon Sunday supplement_Chicago2012-12pages_Layout 1 4/20/12 4:51 PM Page 9

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