PRK surgery or Photo Refractive Keratectomy is the medical term where through a surgical process, a thin flap is created on the corneal tissue, folding the flap to remodel the tissue beneath with a laser. Finally, this flap is repositioned and the eye heals on its own during the recovery or postoperative period. In common parlance PRK surgery is known as laser surgery.
Variations of LASIK Surgery: PRK surgery
The acronym LASIK can be expanded to laser assisted in situ (in the place) keratomileusis is a refractive surgery for correcting the cornea. It involves making an incision using a laser below a corneal flap (in situ) to modify the shape of the cornea (keratomileusis). LASIK surgery is different from PRK Surgery as it utilizes a highly specialized excimer laser to correct refractive errors, improving vision, and reduces and/or eliminates the requirement to use spectacles or contact lenses.
LASIK surgery – History and Process
This surgery modifies the shape of the cornea, which is a transparent layer on top of the eye. The Excimer laser had been used for decades; the real breakthrough in LASIK is attributed to Loannis Pallikaris from Greece who first used it in 1991.
LASIK surgery is a three stage process:
i.Create a flap of corneal tissue.
ii.Remodel of the cornea below the flap with a laser beam.
iii.Reposition the flap
1. Flap creation
A corneal suction ring is placed on the eye, to keep the eye in place. It is common during this step for small blood vessels to burst and subsequent bleeding (subconjunctival hemorrhage) where blood oozes into the white (sclera) of the eye. It is a relatively a harmless side effect that cures itself in a few weeks. The heightened suction causes a temporary blurring and dimming of in the eye being treated. Once the eye is ‘rendered unconscious’, the flap is created. This step is carried out with a metal blade (mechanical microkeratome), or a femtosecond laser microkeratome (also known as Intra LASIK). This creates a bundle of tiny bubbles within the cornea. These bubbles are closely huddled. One end of this flap is folded to leave a ‘hinge’. The flap is folded back, revealing the ’stroma’, or the middle section of the cornea is pulled and folded back. This is a relatively painful part of the procedure.
2. Laser remodeling
The corneal stroma is remodeled using an Excimer laser (193 nm). Tissue is melted and vaporized in a controlled environment ensuring no damage is caused to the adjacent stroma. The most important aspect is there is no requirement of heat or burning or incision is required to ablate the tissue. The tissue is removed in layers and barely a fraction of a micrometre in thickness. Use of the laser helps in much more speedier recovery than PRK Surgery. Once the flap is lifted, patient suffers from a hazy vision. The only light visible is white light surrounding the laser’s orange light. This does tend to a mild disorientation of the patient.
3. Repositioning of flap
Once the stromal layer is reshaped by the laser, the flap (LASIK flap) is carefully restored around the treatment area by the doctor. Air bubbles, leftover tissues and debris are removed; Adhesives are used to keep the flap in place till complete healing.
Since PRK surgery is a variation of LASIK surgery, the procedure in PRK is slightly different from the classic LASIK surgery!
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