LASIK and PRK

LASIK and PRK Surgery: What is the Ideal Age for Surgery?

What are LASIK and PRK?

They are laser refractive surgery techniques that correct:

Myopia

Hyperopia

Astigmatism

Ideal Age for LASIK or PRK Surgery

Optimal Range: 20 to 40 years old

Special Cases by Age:

<18 years old

No, prescription can still change.

18-21 years old

Special evaluation requires proven stability of prescription.

40+ years old

Yes, but monovision may be required if there is presbyopia ("farsightedness").

Why Not Wait Until 40?

Presbyopia (farsightedness) usually appears after 40, which may require:

Adjustments to technique (monovision).

Use of intraocular lenses instead of LASIK/PRK.

Alternatives for those over 45:

Phakic intraocular lenses (ICL) if the cornea is unsuitable.

Cataract surgery with a multifocal lens if there is already lens opacity.

Benefits of Surgery at the Right Age

Maximum independence from glasses/contact lenses during your most active years.

More stable results (lower likelihood of regression).

Faster recovery (especially with LASIK).

LASIK: The Most Popular Technique

How it works:

A corneal flap is created with a microkeratome.

Then, the excimer laser reshapes the corneal stroma (middle layer) to correct the visual defect.

Finally, the flap is repositioned without stitches.

Advantages:

Rapid recovery (visual improvement in 24-48 hours).

Minimal postoperative discomfort (mild itching, dryness).

Stable results in a short time.

Disadvantages:

Not recommended for thin or irregular corneas.

Low risk of flap complications (displacement, inflammation).

Ideal for: Patients with thick corneas and moderate refractive errors.

LASIK Treatment Animation

This video is a Zeiss animation illustrating the steps of the LASIK vision correction procedure. The typical surgical steps for this procedure are described below:

Eye Preparation:

Anesthetic drops are applied to numb the eye, and an instrument called a speculum is placed to hold the eyelids open.

Corneal Flap Creation:

The surgeon uses a microkeratome to cut a thin flap in the top layer of the cornea. This flap is carefully lifted to expose the underlying corneal tissue.

Corneal Reshaping:

With the flap lifted, an excimer laser is used to remove precise amounts of corneal tissue and reshape the cornea, thereby correcting refractive problems such as nearsightedness, farsightedness, or astigmatism. Flap repositioning:

Once the reshaping is complete, the corneal flap is returned to its original position, where it adheres naturally without the need for sutures.

This procedure typically takes less than 30 minutes and allows for rapid visual recovery in most patients.

Excimer Laser in LASIK

This image shows the corneal ablation step performed with the MEL 90 excimer laser (from Carl Zeiss Meditec), one of the most advanced systems for refractive surgery. Unlike the SCHWIND AMARIS, this device uses ultra-fast and precise laser pulse technology, displaying a characteristic pattern of multiple UV light dots that reshape the cornea.

MEL 90 Carving Process

1. Preparation and Alignment

After creating the corneal flap (with a femtosecond or microkeratome), the surgeon exposes the stroma.

The MEL 90 uses a 6D eye tracker (tracking movements in all axes, including rotations).

The laser is calibrated according to patient data (corneal topography and thickness).

2. Pulsed Laser Ablation (Pinprick Pattern)

The excimer laser (193 nm wavelength) emits microscopic pulses that remove corneal tissue without damaging adjacent structures.

Video visualization:

Rapid, sequential flashes (resembling a "shower of bright dots").

The pattern follows a customized design based on the correction:

Myopia: Flattens the center of the cornea.

Hyperopia: Sharpens the periphery to increase central curvature.

Astigmatism: Asymmetric ablation to smooth the surface.

Repetition rate: Up to 500 Hz (faster than many standard excimer lasers).

PRK: The Flap-Free Alternative

How it works:

The corneal epithelium (superficial layer) is removed with an alcohol solution or laser.

The excimer laser acts directly on the stroma to carve the correction.

The epithelium regenerates naturally within a few days (a therapeutic contact lens is placed for protection).

Advantages:

No risk of complications with the flap (best option for thin corneas).

Greater safety in patients with dry eyes or contact activities (impact sports).

Disadvantages:

Slower recovery (several days of discomfort, initial blurred vision).

Greater postoperative discomfort (burning, light sensitivity).

Ideal for: Military personnel, police officers, athletes, or those who are not LASIK candidates.

PRK Treatment Animation

This video is a Zeiss animation illustrating the procedure for photorefractive keratectomy (PRK), a laser eye surgery to correct refractive problems such as nearsightedness, farsightedness, and astigmatism. The typical surgical steps for this procedure are described below:

Eye preparation:

Anesthetic drops are administered to numb the eye, and a speculum is placed to keep the eyelids open during surgery.

Corneal epithelial removal:

Unlike LASIK, a corneal flap is not created in PRK. Instead, the surface layer of the cornea (epithelium) is removed using an alcohol solution, a mechanical device, or a laser.

Corneal reshaping:

Once the underlying corneal tissue is exposed, an excimer laser is used to remove precise amounts of tissue and reshape the cornea, thereby correcting refractive errors.

Therapeutic contact lens placement:

After reshaping, a soft contact lens is placed on the cornea to protect the eye and facilitate epithelial regeneration during the healing process.

Visual recovery with PRK is typically slower than with LASIK, as the epithelium needs time to fully regenerate. However, PRK is a viable option for patients with thin corneas or certain corneal irregularities where LASIK is not recommended.

Patient Experience on the Day of Surgery

This video presents the features of the SCHWIND AMARIS excimer laser used in refractive surgery. The following describes a typical patient experience on the day of surgery with this type of laser:

Pre-Preparation:

The patient should follow medical instructions, such as avoiding makeup, perfume, or hair products on the day of surgery. Additionally, they may be prescribed antibiotic eye drops to use before the procedure.

Arrival at the Clinic:

Upon arrival, the medical staff will perform a final evaluation and answer any questions. Anesthetic drops will be administered to numb the eye and ensure a painless procedure.

During Surgery:

The patient lies on a table under the excimer laser. An instrument is used to hold the eyelids open. The patient will be asked to focus on a specific light to ensure the laser's precision. The SCHWIND AMARIS laser, known for its high precision and speed, reshapes the cornea in a matter of seconds.

Immediate Postoperative Care:

After surgery, it is common to experience blurred vision, a foreign body sensation, or mild irritation, which usually disappears within a few hours. Rest and avoiding rubbing your eyes are recommended.

Recovery: Most patients notice a significant improvement in their vision the next day. However, full recovery may vary by individual.

Excimer Laser Calibration

The Importance of Proper Excimer Laser Calibration in Refractive Surgery

Although excimer lasers are extremely precise and advanced instruments, their proper calibration is critical to ensuring the safety and effectiveness of refractive surgery (such as LASIK or PRK). Here are the main reasons:

Corneal Ablation Precision

The excimer laser reshapes the cornea with micron-level (millionths of a meter) accuracy. Improper calibration could lead to:

Overtreatment or undertreatment, leaving the patient with residual refractive errors (uncorrected nearsightedness, farsightedness, or astigmatism).

Irregularities in the corneal surface, causing visual aberrations (halos, flare, or blurred vision).

Patient Safety

Improper calibration can lead to:

Excessive corneal tissue loss, weakening the structure of the eye.

Damage to adjacent tissues (such as the corneal endothelium).

Consistency of the result

Each eye has unique characteristics. The laser must be perfectly adjusted to accommodate:

Ambient humidity and temperature (factors that affect laser energy).

The type of correction (myopia vs. hyperopia, for example).

Compliance with medical protocols

International standards (such as those of the FDA or CE) require periodic verification of the laser to maintain its certification.

Why can't all patients undergo LASIK or PRK?

LASIK and PRK refractive surgeries are safe and effective, but they are not suitable for everyone. Their feasibility depends on anatomical, ophthalmological, and general health factors. Here are the main reasons:

Corneal Conditions

Cornea that is too thin

LASIK requires creating a corneal flap (minimum 480–500 µm thick).

If the cornea is very thin (<480 µm), there is a risk of corneal ectasia (deformation).

Alternative: PRK (no flap required) or intraocular lenses (ICL).

Keratoconus or Irregular Cornea

LASIK/PRK can weaken the cornea and worsen keratoconus.

Solution: Perform cross-linking first (to strengthen the cornea) and then evaluate other options.

1.Corneal Scarring

If there are opacities from previous infections (e.g., ocular herpes), the laser cannot work evenly.

2. Unstable Prescription

Myopia, hyperopia, or astigmatism must be stable for at least 1–2 years.

Patients under 21 years of age: Your eyes can still change.

3. Severe Dry Eye

Both LASIK and PRK can temporarily worsen dry eye.

If you already have severe, uncontrolled dry eye, it is better to opt for ICL (it does not affect the cornea).

4. Very Large Pupil (Nyctalopia)

If your pupil dilates >7 mm in the dark, LASIK can cause severe halos at night.

5. Eye Diseases

Advanced Glaucoma: Increased intraocular pressure during LASIK is risky.

Cataracts: If the lens is already opacified, it is best to perform cataract surgery with an intraocular lens.

Diabetic retinopathy: Risk of postoperative macular edema.

6. Pregnancy or Breastfeeding

Hormonal changes alter corneal shape and prescription.

It is recommended to wait 3–6 months after breastfeeding.

7. Autoimmune Diseases

Lupus, rheumatoid arthritis, or Sjögren's syndrome: These can affect corneal healing.

Alternatives if you are not a candidate for LASIK/PRK

Intraocular lenses (ICL): For high myopia or thin corneas.

Cross-linking + PRK: For early keratoconus.

Specialty contact lenses.