| Refractive Surgery Update |
| Intacs: Old Myths, New Uses Paul M. Karpecki, O.D. Steve H. Linn, O.D. Eighteen months have passed since the FDA approved KeraVision’s Intacs. During this time, there have been some significant discoveries regarding the safety and potential benefits of this new technology. Here’s a look. Old Myths When Intacs were first introduced, many thought the procedure was too time-consuming and that channel deposits would be dangerous. Surgical time. Intacs procedures are following a course similar to LASIK—in that experience and improved instrumentation have reduced surgical time. Now, surgeons can complete the procedure in less than 5 minutes. Plus, new instruments and techniques have led to quicker patient recovery and less frequent side effects. Channel deposits. Research is finding that deposits within the segment channels are not an inflammatory or infiltrative response. C.J. Senft at Louisiana State University Eye Center used confocal microscopy to evaluate corneal deposits following Intacs. His study determined that the deposits are not inflammatory because they don’t appear to be cellular. Another study by A.E. Kummer at Mount Sinai Medical School in New York confirmed the inert nature of the deposits and noted that it has no clinical significance. Finally, T.E. Burris at the Casey Eye Institute in Portland found deposits to be cholesterol-like crystals or acellular, amorphorous lipid material. Deposits don’t cause problems. It’s simply a way for the body to “fill-in” space. Looking ahead, thinner channel dissectors, which allow for less space around the segment, will make deposits a rarity. New Applications Intacs may provide benefits beyond correcting refractive error. LASIK under-corrections. Optometrists who comanage LASIK patients are well aware that you should have a minimum post-op corneal thickness of 410µ —a 160µ flap plus 250µ of untouched cornea. But, many high myopes remain under-corrected and measure near 410µ. You can’t remove more tissue because it could destabilize the cornea and lead to poorer optics, halos or glare. For these patients, Intacs as an additive procedure is an option because it won’t make the cornea thinner. In fact, it can stabilize the cornea and widen the optical zone. As the accompanying image shows, this patient was originally a -9.75D myope who at 3 months post-LASIK measured -1.50D, but had a pachymetry reading of 418µ. If we tried a LASIK enhancement, the cornea would measure 392µ, or the equivalent of 232µ in the bed—too thin. With Intacs, the pachymetry doesn’t change. The Orbscan also shows a wider optical zone after LASIK. In the end, this patient had a full -1.50D correction, a significantly wider optical zone and a reduction in halos and glare. Keratoconus. Studies are underway to investigate if doctors can use Intacs to delay or avoid penetrating keratoplasty (PKP). Joseph Colin, M.D., performed the first Intacs treatment on a keratoconic patient in 1997, and research continues. The segments are implanted horizontally with a thicker segment inferiorly (to strengthen the thinner stroma) and a thinner segment superiorly. Dr. Colin’s studies show that Intacs can lead to improved corneal symmetry and decreased topographical ectasia. This allows patients to obtain improved best-corrected visual acuity with spectacles. Plus, it can delay the need for PKP. If the keratoconus increases, or if the patient isn’t satisfied, the surgeon can remove the segments and perform PKP. Intacs provides a safe option for patients who are difficult to treat. Plus, experience has enhanced the procedure time, patient comfort, recovery and outcome. u Dr. Karpecki is clinical director of corneal disease and refractive surgery at Hunkeler Eye Centers and NovaMed EyeCare Management in Kansas City. Dr. Linn is director of education for NovaMed and practices at Hunkeler Eye Centers. Neither doctor has a financial interest in KeraVision Intacs. |
| © Review of Optometry OnLine October 15, 2000 |
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