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CW R Winkler von Mohrenfels, B Gabler, CP Lohmann; New Elliptic Shaped LASEK Instruments to Enhance Astigmatic Correction in LASEK: First Results . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2068.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Correction of astigmatism can be achieved with the excimer laser by photorefractive keratectomy (PRK) or laser in situ keraomileusis (LASIK). A new technique in corneal refractive surgery is the Laser epithelial keratomileusis (LASEK), where an epithelial flap is created. LASEK causes less pain and haze than PRK and avoids the stromal cut of LASIK. Commercially available LASEK instruments have a round design (8 to 9 mm diameter). Such a curved epithelial flap however does not expose the stroma in the astigmatic axis, where the laser ablates tissue also in the peripheral cornea almost out to the limbus. In fact, our results for astigmatic LASEK correction with such circular instruments were not very impressive. Therefore we have developed new elliptic shaped LASEK instruments for astigmatic LASEK. In this study we present our first results with these new elliptic LASEK instruments. Methods: The new set consists of an elliptic (11x8mm) microtrepan with a 70 µm calibrated blade and an elliptic alcohol cone (11,5x8,5 mm). We have performed astigmatic LASEK in 15 eyes so far with astigmatism ≥1 D using the new astigmatic instruments, 20% ethanol for 20 seconds and the keracor 217 excimer laser (Chiron Technolas, USA). Maximum follow-up is now currently 6 months. Astigmatic outcome was analysed with vector analysis (Alpins 1983) . Results: The spheric refraction was between – 0,75 and –8,75 D and the astigmatism was between –1,25 and –3,5 D (mean –1,79D SD 0,95D). The elliptic flap could be created in all eyes without any problems and there were no postoperativ complications. The postoperative spheric refraction was between +0,5 and –0,5 D (mean -0,08 +/- 0,33 D) and the astigmatism was between 0 and –0,5 D (mean -0,23 SD 0,24). Targeted induced astigmatism was 1,79 D (SD 0,95 D) and the surgical induced astigmatism was 1,63 D (SD 1,01 D). The difference was 0,23 D (SD 0,24 D) and the magnitude of error was 0,13 D (SD 0,19 D) the mean index of success was 0,1 ( SD 0,12). Conclusion: Astigmatic LASEK with elliptic instruments is -based on a small cohort- a safe and effective method to treat astigmatism. It does not affect spherical correction. Astigmatic LASEK be superior to LASEK with round instrument, as the elliptic flap shape matches better with the actual zone of laser ablation.
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