Abstract
Abstract: :
Purpose:the aim of this study is to verify the modification of refractive and topographic parameters induced by excimer laser refractive surgery. Methods:We analysed 211 excimer laser procedures starting from Nov.1999 to Jun.2001. The mean age was 33.4 year (range: 21/58years). The mean spherical equivalent was -4.45 (range: +3.50/-13.0). Preoperatively we recorded UCVA, BVCA, manifest, automated and cycloplegic refraction, keratometric K1 and K2, topographic simK1 and K2 and I/S index, pupillometry, IOP and patient history. We used the Bausch and Lomb Technolas 217 laser. LASIK was performed in 37 eyes, using the Hansatome Keratome. Remaining 174 were treated with PRK procedure. We monitored temperature and humidity, ablation depth and expected flap thickness for lasik. Two different postoperative therapy protocols were used for lasik and prk. Patient were screened 1 week, 2 weeks, 1, 3 and 6 months after surgery: we recorded UCVA, BCVA manifest and automated refraction, keratometric K1 and K2 and topographic simK1 and K2, I/S index, re-epithelization speed, degree of haze and presence of any other complication. Longitudinal analysis based on autoregressive model of covariance was performed to evaluate the influence on variables considered. Results:at six months UCVA was 10/10 or better in 96% of the cases; 0,5% had 1 lines loss of BVCA; 97.32% achieved a spherical equivalent of +/-0,50; 36.2% had various degree of haze. We observed a correlation between preoperative and more significantly postoperative simK1 and simK2 and corneal tissue ablation as shown in the graph. Conclusion:the Chiron Technolas 217 excimer laser ablation seems to be more efficient for lower simK values and less for higher simK. This treatment algorithm could influence the corneal asphericity and therefore the out coming quality of vision.
Keywords: 547 refractive surgery: corneal topography • 550 refractive surgery: optical quality • 350 clinical (human) or epidemiologic studies: biostatistics/epidemiology methodology