Background: Vitreoretinal complications are rare in laser in situ keratomileusis (LASIK). Increase in intraocular pressure caused by intraoperative suction with subsequent deforming of the ocular globe and excimer laser shock during the ablation have been discussed as possible causes. The purpose of this study was to determine the effect of LASIK on the vitreous body. Patients and methods: In a prospective study we performed ocular ultrasonography (B scan) immediately before and 1 week after LASIK procedure in 103 myopic or myopic astigmatic eyes (53 patients, mean age 36.3 years, 32 women, 21 men). In particular, the prevalence, localization, and extent of posterior vitreous detachment (PVD) were determined. Results: The mean spherical equivalent was- 4.85 D (range- 1.25 to- 8.38) and the mean anteroposterior ocular globe length was 25.13 mm (range 23.31- 27.65). Ninety-five eyes (92.2% ) had no PVD preoperatively. Nine eyes out of this group (seven patients, 9.5% ) developed incomplete PVD as assessed 1 week postoperatively. Eight eyes (7.8% ) had a partial PVD preoperatively and in only one eye was an extension of vitreous detachment observed after the surgery. None of the preoperatively measured parameters could predict the occurrence of PVD by LASIK. Conclusions: LASIK may in rare cases lead to new occurrence of PVD or extension of a previously existing partial PVD. Background: Vitreoretinal complications are rare in laser in situ keratomileusis (LASIK). Increase in intraocular pressure caused by intraoperative suction with subsequent deforming of the ocular globe and excimer laser shock during the ablation have been discussed as possible causes. The purpose of this study was Patients and methods: In a prospective study we performed ocular ultrasonography (B scan) immediately before and 1 week after LASIK procedure in 103 myopic or myopic astigmatic eyes (53 patients, mean age 36.3 years , 32 women, 21 men). In particular, the prevalence, localization, and extent of posterior vitreous detachment (PVD) were determined. Results: The mean spherical equivalent was- 4.85 D (range- 1.25 to 8.38) and the mean anteroposterior Ninety-five eyes (92.2%) had no PVD preoperatively. Nine eyes out of this group (seven patients, 9.5%) developed incomple Eight eyes (7.8%) had a partial PVD preoperatively and in only one eye was an extension of vitreous detachment observed after the surgery. None of the preoperatively measured parameters could predict the occurrence of PVD by LASIK. Conclusions: LASIK may in rare cases lead to new occurrence of PVD or extension of a previously existing partial PVD.