Gourt > Health > Medicine > Medical Specialties > Ophthalmology > Refractive Correction > Photorefractive Keratectomy
Photorefractive keratectomy (PRK) and Laser-Assisted Sub-Epithelial Keratectomy (LASEK) are laser eye surgery procedures intended to correct a person's vision and reduce their dependency on glasses or contact lenses. The procedures permanently change 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. In LASEK the corneal epithelium is preserved with a chemical solution, peeled off, and replaced after the laser ablation is complete. With PRK the epithelium removed is discarded and allowed to regenerate. Both procedures are distinct from LASIK (Laser-Assisted in-SItu Keratomileusis), a form of laser eye surgery where 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 microkeratome or femtosecond laser used to create a 'flap' out of the outer cornea), the cornea's structural integrity is less altered by PRK, but PRK can be more painful and visual recovery is slower. The use of the anti-metabolite mitomycin can minimize the risk of post-operative haze in persons requiring larger PRK corrections. More on [ Photorefractive keratectomy ]
PRK (photorefractive keratectomy) is often recommended for people with thin corneas. Make s.. http://bit.ly/RjGzR http://bit.ly/hYIJK
nonstopdiets (nonstopdiets) Tue, 03 Nov 2009 02:01:24 -0000
PRK (photorefractive keratectomy) is often recommended for people with thin corneas. Make s.. http://bit.ly/RjGzR http://bit.ly/hYIJK
Igal Nevo PRK - Detailed description of a personal experience with PRK before, during and after the laser surgery.
My Eye Surgery - A personal account of what it was like before, during, and after the experience with PRK.
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