As with any surgery, infection of the corneal tissue surrounding the segments or the insertion incision site is possible. Usually this would occur within the first few weeks of the surgery and can be treated with antibiotic drops or with removal of the segments. For this reason, antibiotic drops are applied prior to the surgery and for several days afterwards. It is possible for the Intacs implants to shift from their original position, in which case they may be repositioned or permanently removed. It is also possible for the corneal tissue overlying the implants to thin, in which case the implants may require removal. During the surgery, it is possible for the tunnel or channel for the implants to be too deep or too shallow within the substance of the cornea, such that implant insertion is not possible. It is also possible for perforation of the corneal tissue to occur during insertion of the Intacs segments. Some patients experience visual symptoms including difficulty with night vision, glare, halos, blurry and fluctuating vision.