The VISX STAR S2 Excimer Laser System is approved for photorefractive keratectomy (PRK) for the reduction or elimination of nearsightedness (0 to -12.0 D) with up to -4.0 D of astigmatism, and hyperopia (farsightedness) between +1.0 and +6.0 D. Alternatives to PRK include eyeglasses, contact lenses, radial keratotomy or automated lamellar keratectomy. The following are the results of the clinical studies in patients who are mildly nearsighted (MN), mildly nearsighted with astigmatism (MNA), highly nearsighted with or without astigmatism (HN) and moderately farsighted (MF) at approximately 1 year after surgery: eyes could see 20/40 or better without the help of glasses; (MN=94%; MNA=91%; HN=90%; MF=95%), eyes could see 20/20 or better with glasses before surgery and could see 20/40 or better after surgery with the help of glasses (MN=99%; MNA=98%; HN=99%; MF=99%); increase in intraocular pressure (MN=1.8%, MNA=2.2%; HM=0.7%; MF=0.9%), corneal haze (MN=0.6%; MNA=4.3%; HM=1.3%; MF=0.9%).. The following is a list of adverse events and complications that occurred in patients at approximately 1 year after treatment: worsening of best spectacle corrected vision with a loss of more than 2 lines of vision (MN=0.4%; MNA=3.5%; HN=2.5%; MF=0%), overcorrection by more than 1 diopter (MN=1.2%, MNA=1.2%; HN=5.1%; MF=2.6%), overcorrection by more than 2 diopters (MN=0.2%; MNA=1.2%; HN=1.9%; MF=0%); increase in astigmatism (MN=3.1%; MNA and HN - not available; MF=0.9%). The following assessments were judged by the patient after surgery compared to the vision before surgery: Double vision as somewhat worse: MN=0.6%; MNA=1.1%, HN-not available; MF=5.2%; Double vision as much worse: MN=1.0%; MNA=4.3%; HN - not available; MF=0.9%. Sensitivity to bright lights as somewhat worse: MN=3.7%; MNA=6.5%; HN-not available; MF=6.1%; Sensitivity to bright lights as much worse: MN=1.6%; MNA=6.5%; HN - not available; MF=0.9%. Difficulty with night vision as somewhat worse: MN=2.7%; MNA=9.8%; HN-not available; MF=4.3%; Difficulty with night vision as much worse: MN=2.5%; MNA=8.7%; HN - not available; MF=1.7%. The long term risks of PRK have not been studied.