Comparing Vision Correction Techniques: PRK, Femto-LASIK, and ReLEx SMILE
Currently, laser vision correction—commonly referred to as LASIK—includes several techniques such as PRK, Femto-LASIK, and ReLEx SMILE. How do these techniques differ? What are their advantages, disadvantages, or risks? And which one is right for you? Khon Kaen Ram Hospital has the answers for you today.
PRK (Photorefractive Keratectomy)
PRK is the first-generation technology for laser vision correction, suitable for correcting nearsightedness up to -6.00 diopters. The ophthalmologist removes the outermost layer of the cornea (epithelium) and then uses an Excimer Laser to reshape the cornea. This method does not involve creating a corneal flap, making it suitable for patients with thin corneas. However, because the epithelium is removed, the wound resembles a circular abrasion. Consequently, patients may experience more discomfort, burning, and irritation than with other methods. Symptoms include difficulty opening the eyes, light sensitivity, and tearing. Visual recovery is slower, requiring a longer healing period and extended use of eye drops. Patients must also strictly avoid sunlight to prevent corneal haze.
Femto-LASIK
Femto-LASIK can correct nearsightedness from -1.00 to -10.00 diopters and astigmatism up to -6.00 diopters. It differs from traditional LASIK by using a laser to create the corneal flap instead of a mechanical blade, making it safer. (Khon Kaen Ram Hospital has discontinued the use of traditional blade-LASIK). The procedure involves:
- Using the first laser, a Femtosecond Laser (VisuMax), to create a corneal flap (Flap), which is then lifted.
- Using the second laser, an Excimer Laser, to reshape the cornea before closing the flap.
Since the incision is longer (nearly around the eye), patients must be careful to avoid eye trauma, as there is a risk of the flap reopening. Dry eye symptoms may persist for 6–12 months.
ReLEx SMILE (Refractive Lenticule Extraction, Small Incision Lenticule Extraction)
ReLEx SMILE is the latest innovation from Carl Zeiss Meditec, Germany, for correcting nearsightedness (-0.75 to -10.00) and astigmatism (up to -5.00). It is a "flapless" procedure that uses only one laser: the VisuMax Femtosecond Laser. The laser accurately calculates the curvature and thickness of the corneal tissue to be removed (lenticule) based on the patient's prescription. The laser creates the lenticule, which is then removed through a tiny 2–3 mm incision without creating a flap. Advantages over other methods include:
- All-laser procedure using a single machine; no blades involved.
- No epithelial removal (unlike PRK) and no corneal flap (unlike Femto-LASIK), preserving corneal structural integrity.
- Small incision and painless during the procedure.
- Highest precision in vision correction.
- Ability to return to work within 1–2 days.
- Minimal dry eye symptoms and no red eyes.
- Reduced irritation and faster wound healing.
