Video: PKR (surface laser) step-by-step
The PKR (to sight refractive procedures) is an eye operation and a technique called "surface" used for low and medium myopia correction, associated or not to of theastigmatism. The correction of myopia and astigmatism is done jointly (laser photoablation). The PKR is particularly suitable for thin corneas, which the topographic characteristics (corneal topography) suggest that a maximum preservation of corneal Biomechanics is indicated. The absence of cutting of the flap (unlike the) LASIK) preserves a largest cornea thickness.
It starts with a stage of preparation of the corneal surface, intended to remove soft and precise central corneal epithelium. Firstly, the cornea is anesthetized by eye drops (drops). Once the patient has been installed under the microscope of the laser, and after local disinfection, one cylindrical applicator specifically designed for the PKR to apply a solution of medicinal alcohol diluted to 20 ° on the only central part of corneal epithelium, for 20 seconds. This diluted solution allows to cleave cell junctions between epithelium and superficial corneal stroma; the epithelium can be detached more easily. The centering of the applicator is made on the position of the pupil.
A small sponge to absorb the solution diluted in the applicator before withdrawal of it. The withdrawal of epithelium is exposed to the solution is made by preserving the ocular surface and the adjacent epithelium. The removal of the epithelium is done in a gentle manner, and applies only to the area required for exposure of the corneal stroma excimer laser.
Once the epithelium is removed, the surface of the superficial corneal stroma is exposed and ready to receive the laser radiation. The patient sets a green focus flashing, coaxial with optical laser beam. The start-up of the eye tracker allows to compensate the micro eye movements, and centered treatment during the delivery of laser radiation. The eye tracker is a complex system which films the eye to the frequency of 1024 frames per second! The high frequency of the excimer laser used (Wavelight Alcon EX 500 for 500 Hz or 500 shots per second) to reduce the duration of the photoablatif treatment. After rinsing with saline and application of antibiotic eye drops, a (non-corrective) bandage soft contact lens is placed on the cornea and left about 5 days.
PKR, the two eyes are usually made the same day successively.
CONSULT: the main page on the PKR