Yesterday I had Photorefractive keratectomy (PRK) surgery.
It is a laser eye surgery intended to correct a person's vision and reduce dependency on glasses or contact lenses. The procedure permanently changes the shape of the anterior central cornea using an excimer laser to ablate (burn off) a small amount of tissue from the corneal stroma at the front of the eye, just under the corneal epithelium. The outer layer of the cornea is removed prior to the ablation. A computer system tracks the patient's eye position 60 to 4,000 times per second, depending on the brand of laser used, redirecting laser pulses for precise placement. Most modern lasers will automatically center on the patient's visual axis and will pause if the eye moves out of range and then resume ablating at that point after the patient's eye is re-centered.
The outer layer of the cornea, or epithelium, is a soft, rapidly regrowing layer in contact with the air that can completely replace itself from limbal stem cells within a few days with no loss of clarity. The deeper layers of the cornea, as opposed to the outer epithelium, are laid down early in life and have very limited regenerative capacity. The deeper layers, if reshaped by a laser or cut by a microkeratome, will remain that way permanently with only limited healing or remodelling. With PRK the epithelium removed is discarded and allowed to regenerate. Both This is different from LASIK (Laser-Assisted in-SItu Keratomileusis), the most common laser eye surgery, in which the epithelium is not removed.
PRK versus LASIK
Because PRK does not involve a permanent flap in the deeper corneal layers (the LASIK procedure involves a mechanical microkeratome using a metal blade or a femtosecond laser microkeratome to create a 'flap' out of the outer cornea), the cornea's structural integrity is less altered by the procedure, but PRK can be more painful and visual recovery is slower. Bottom line, right now I can see enough to use the computer for a ten or fifteen minutes at a time, but only with LARGEST font chosen.