Excimer Laser Treatment for Myopia, Hyperopia, and Astigmatism

Excimer laser is a method used to treat refractive errors such as myopia, hyperopia, and astigmatism. While eyeglasses and contact lenses correct vision, they do not structurally treat refractive errors. Excimer laser permanently reshapes the cornea, correcting these errors at a structural level. For successful treatment, it is essential to clearly explain the advantages and disadvantages of the method and for the doctor to understand the patient’s expectations.

What is Excimer Laser?

The term Excimer is derived from the words “excited dimer (gas)”. In laser treatment, argon fluoride gas is electrically stimulated to produce a homogeneous laser beam with a wavelength of 193 nm. The laser beam is directed through lenses and mirrors within the device to reshape the cornea. The procedure is fully computer-controlled.

Advanced excimer laser devices include an eye-tracking system to prevent unintended movements from causing side effects during treatment.

Excimer Laser Treatment Methods

Different types of excimer laser treatments include:

• Photorefractive Keratectomy (PRK)
• Laser-Assisted In Situ Keratomileusis (LASIK)
• LASEK
• SMILE ReLEx

These techniques differ mainly in how the corneal tissue is prepared, but the laser correction process itself is the same for PRK, LASIK, and LASEK. The SMILE technique follows a different procedure.

Excimer laser reshapes different parts of the cornea depending on the refractive error:

• Myopia: The central cornea is flattened.
• Hyperopia: The outer cornea is steepened.
• Astigmatism: The cornea is reshaped at the appropriate angle to correct irregular curvature.

PRK: What Is It and Who Is It For?

The cornea, the eye’s outermost transparent structure, is responsible for refracting light. PRK involves removing the epithelium (outermost layer) with alcohol or mechanical methods. The underlying stromal tissue is reshaped with laser, correcting the refractive error.

After treatment, a protective contact lens is placed over the eye and removed within 2-5 days.

LASIK: What Is It and Who Is It For?

LASIK is one of the most commonly performed refractive surgeries. It involves:

1. Creating a thin flap (90-150 microns thick) on the cornea using either:
   • A microkeratome (automated blade)
   • A femtosecond laser (preferred for precision and reduced complications)
2. The flap remains attached via a hinge, usually positioned near the nasal root to reduce dry eye risk.
3. The underlying stromal tissue is reshaped with an excimer laser.
4. The flap is repositioned without the need for stitches.

Recovery:

• Minimal discomfort compared to PRK.
• Temporary burning or stinging for 5-6 hours after surgery.
• Vision improves within 24 hours.

What is LASEK?

LASEK is similar to LASIK but:

• Uses alcohol to loosen the epithelial layer instead of creating a flap.
• The epithelial sheet is lifted, laser is applied, and then the sheet is repositioned.
• A contact lens is placed for protection during healing.

Advantages:

• Preferred for thin corneas, where LASIK may not be safe.
• Reduces flap-related complications compared to LASIK.

What is SMILE ReLEx Laser?

SMILE (Small Incision Lenticule Extraction) is a minimally invasive procedure where:

1. A femtosecond laser creates a disc-shaped lenticule within the corneal stroma.
2. The lenticule is extracted through a small (2 mm) incision, reshaping the cornea.

Advantages:

• Suitable for high myopia and astigmatism.
• Ideal for patients with dry eyes.
• Preserves corneal biomechanics, making it preferred for athletes and certain professionals.

Why Is LASIK Preferred Over PRK and LASEK?

• Less pain and discomfort compared to PRK.
• Faster healing and quicker visual recovery.
• Less likelihood of corneal haze in high prescriptions.
• Effective for low, moderate, and high myopia, whereas PRK is mainly used for low-to-moderate cases (up to -5.0 D).

Who Can Have Laser Eye Surgery?

✔️ Eligible Candidates:

• Over 18 years old.
• Stable prescription (≤0.50 D change in the last year).
• No eye or systemic diseases that may interfere with healing.
• Psychologically stable individuals.

❌ Not Suitable for:

• Unrealistic expectations.
• Individuals with only one functional eye.
• Corneal diseases (congenital or acquired).
• Active eye infections.
• Autoimmune diseases (e.g., vasculitis, connective tissue diseases).
• Herpes eye infections.
• Severe dry eye syndrome.
• Glaucoma (high eye pressure).
• Cataracts or diabetes-related retinal diseases.
• Advanced keratoconus.
• Pregnant or breastfeeding women.
• Patients taking medications like Accutane or Imitrex.

Pre-Laser Preparation & Procedure

Before Surgery

• Contact lenses must be removed:
  • Hard lenses: 3-4 weeks before surgery.
  • Soft lenses: 10 days before surgery.
• Aspirin and blood-thinning medications should be stopped 2-3 weeks before surgery.
• Eye examination includes:
  • Visual acuity assessment.
  • Corneal thickness (pachymetry) and topography.
  • Intraocular pressure measurement.
  • Retinal health evaluation.

Procedure

1. Patient details are entered into the laser computer.
2. Anesthetic eye drops are applied.
3. The eye is sterilized, and a lid speculum keeps the eyelids open.
4. The patient is instructed to focus on a green laser light.
5. The laser procedure varies depending on the method (PRK, LASIK, LASEK, SMILE).
6. Antibiotic and corticosteroid drops are applied post-surgery.

Post-Laser Care

• First 30 minutes: Immediate check-up for flap positioning and debris removal.
• Medications:
  • Artificial tears
  • Antibiotic and steroid drops
• Protective Measures:
  • Wear sunglasses at night after surgery.
  • Avoid rubbing the eyes.
  • Avoid water exposure for:
    • 1 day after LASIK
    • 3 days after PRK

Complications of Laser Surgery

• Under- or over-correction
• Infection (rare)
• Regression of correction (more common in PRK)
• Flap issues (LASIK-specific)
• Corneal haze (PRK-specific)
• Halos around lights (temporary, more common in hyperopia)
• Night vision reduction (usually resolves within 6 months – 1 year)
• Presbyopia onset (natural aging process, more noticeable after 40 years)

Frequently Asked Questions

🔹 Can laser surgery be repeated?
Yes, if the cornea is thick enough.

🔹 Can irregular astigmatism be corrected with laser?
Yes, with specialized laser programs.

🔹 Can contact lenses be worn if correction is inadequate?
Yes.

🔹 Does laser surgery cause blindness?
No, but a thorough preoperative evaluation is essential to minimize risks.

🔹 Does every eye surgery carry a risk of blindness?
Yes, but laser eye surgery has an extremely low risk when performed correctly.