EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
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80 EW REFRACTIVE SURGERY March 2013 IOL implantation followed by femtosecond arcuate relaxing incisions by David Hardten, M.D. F emtosecond arcuate relaxing incisions are often useful for patients with mild to moderate corneal toricity who would benefit from a change in the shape of their corneas. The femtosecond laser is used to create relaxing incisions in the periphery to achieve this shape change. Incisions made with a laser have several advantages over incisions made with a blade. For example, with a diamond blade, surgeons can set the blade to a certain depth, and we can control depth and location of the incision. We can also make the incision shorter or longer; however, we can't control the angle of the entry of the blade. Additionally, surgeons really can't see the tissue that is directly underneath the blade so it can be harder to see where we are going next in the corneal tissue. With the femtosecond laser, surgeons now have the ability to look on the screen and set the incisions exactly where they want to in relation to the pupil and the limbus. We can create incisions vertical to the corneal surface. We can angle them in or out, and we can still control things like length and optical zone or distance from the center of the pupil. This provides incisions that are more tailored or customized. Surgeons can also control depth more accurately because, as opposed to setting a diamond blade where it depends on how hard the surgeon pushes down or how hard the eye is, we now have the ability to set it to a certain number of microns, and the incision can be created in that fashion. We can titrate the incisions to achieve the desired effect. Another advantage of femtosecond lasers is that they can be used to create intrastromal incisions, which have several benefits. For example, intrastromal incisions do not penetrate the epithelium, which minimizes the chance of infection. Case report Figure 1. Pentacam examination showed 0.4 D of astigmatism in the right eye in the 130-degree orientation, with pachymetry at the 8.5-mm optical zone of 580 µm. Figure 2. In the left eye, Pentacam showed 0.9 D of astigmatism at the 32-degree meridian centrally, yet more peripheral curvatures showed an orientation at the 48degree meridian, which was consistent with the front elevation areas of depression. Source (all): David Hardten, M.D. Many patients are good candidates for this procedure. Recently, a 55year-old man presented to my office and was interested in reducing his dependence on glasses and contact lenses. His uncorrected vision was hand motion in both eyes. His refractive error was –17.50 +2.25 x 130 in his right eye and –20.00 +2.00 x 150 in his left eye; both eyes corrected to 20/30 for distance. His exam was normal except for mild nuclear sclerosis that did not appear visually significant. He had seen a retina specialist for vitreous syneresis earlier in the year and had no highrisk retinal lesions. Pentacam (Oculus, Arlington, Wash.) examination showed 0.4 D of astigmatism in the right eye in the 130-degree orientation, with pachymetry at the 8.5-mm optical zone of 580 µm (Figure 1). In the left eye, Pentacam showed 0.9 D of astigmatism at the 32-degree meridian centrally, yet more peripheral curvatures showed an orientation at the 48-degree meridian, which was consistent with the front elevation areas of depression (Figure 2). The patient underwent natural lens replacement in each eye with placement of a monofocal IOL (+1.0 D in the right eye and –2.0 D in the left eye). The left eye was targeted for slight myopia. On the day of the IOL implantation, in each eye femtosecond arcuate relaxing incisions were performed with the iFS system (Abbott Medical Optics, AMO, Santa Ana, Calif.). Surgery was performed on the left eye first, with the right eye done two weeks later. The procedure for placing the femtosecond relaxing incisions was similar for each eye. The flat axis was marked for proper alignment during the femtosecond incisions. Intrastromal incision creation with the femtosecond was planned to allow more careful titration of the effect. The suction ring for the iFS femtosecond laser was placed. SubBowman's membrane arcuate cuts were made with 30 degrees of tissue cut at an 8.5-mm optical zone at the 130-degree and 210-degree meridians in the right eye and at the 48degree and 228-degree meridians in the left eye. A depth in glass of –60 was used to cut just below Bowman's membrane. A side-cut angle of 75 degrees was used. The arcuate incisions were opened partially for 20 degrees in each incision using a Sinskey hook. At three months post-op, the patient had 20/20 uncorrected distance vision in the right eye with a refraction of –0.50 +0.25 x 115. In the left eye, his uncorrected distance visual acuity was 20/25 and near J3. With a refraction of –1.00 +0.75 x 167, he saw 20/20. He was functioning well with only occasional use of reading glasses. This case shows the usefulness of the femtosecond laser in creating corneal arcuate incisions in a patient with corneal shape problems. This patient achieved improved function after the procedure. Corneal relaxing incisions have become a very useful part of corneal surgery, especially with the increased accuracy, safety, and titratability afforded with the femtosecond laser. EW Editors' note: Dr. Hardten is in practice at Minnesota Eye, Minneapolis. He has financial interests with AMO. Contact information Hardten: drhardten@mneye.com