What Is LASIK Eye Surgery and How Does It Work?

LASIK is a laser refractive surgery that reshapes the cornea to correct myopia, hyperopia, and astigmatism. Its goal is to reduce dependence on glasses or contact lenses. However, eligibility depends on a comprehensive ophthalmic evaluation, including corneal characteristics, refractive stability, and individual visual needs.

Many people who wear glasses or contact lenses wonder whether laser vision correction could reduce their dependence on corrective eyewear. LASIK is one of the best-known refractive surgery procedures, but understanding how it works—and how candidacy is determined—is essential before making a decision.

What Exactly Is LASIK Eye Surgery?

LASIK is a refractive surgery procedure that precisely reshapes the cornea using laser technology to correct certain refractive errors and reduce dependence on glasses or contact lenses.

LASIK stands for Laser-Assisted In Situ Keratomileusis.

To understand how the procedure works, it is helpful to understand the role of the cornea. The cornea is the clear structure located at the front of the eye. Together with the crystalline lens, it plays an essential role in focusing light onto the retina.

The U.S. Food and Drug Administration (FDA) describes LASIK as a procedure that permanently changes the shape of the cornea using an excimer laser to reduce dependence on glasses or contact lenses.

When the shape of the cornea and the length of the eye prevent light from focusing properly on the retina, a refractive error occurs. LASIK changes the curvature of the cornea to improve the way light is focused.

It is important to understand that LASIK does not modify the retina, optic nerve, or natural lens. The procedure works primarily by reshaping the cornea.

In a worldwide review of scientific literature involving 2,198 patients, overall patient satisfaction after LASIK was reported at 95.4%. This figure reflects outcomes across clinical studies and should not be interpreted as a guarantee of an identical result for every individual patient.

Which Vision Problems Can LASIK Correct?

LASIK may be used to correct certain cases of myopia, hyperopia, and astigmatism, provided that the patient's ocular anatomy and clinical characteristics are appropriate for the procedure.

The main refractive errors that may be evaluated for laser vision correction include:

What Is Myopia? (ICD-10 H52.1)

Myopia, commonly known as nearsightedness, occurs when light focuses in front of the retina, making distant objects appear blurry.

In myopic eyes, LASIK reshapes the central cornea to reduce its optical power and move the focal point closer to the retina.

What Is Hyperopia? (ICD-10 H52.0)

Hyperopia, or farsightedness, occurs when the optical system of the eye does not focus light appropriately on the retina.

LASIK uses a different corneal reshaping pattern to increase the optical power needed to improve focusing.

What Is Astigmatism? (ICD-10 H52.2)

Astigmatism occurs when the curvature of the cornea or optical system is not uniform across different meridians, potentially causing blurred or distorted vision.

The FDA recognizes myopia, hyperopia, and astigmatism as the main refractive errors treated with laser vision correction procedures such as LASIK.

Not every prescription or type of refractive error is treated in the same way. Knowing the prescription of a patient's glasses alone is not enough to determine whether LASIK is appropriate.

How Does LASIK Eye Surgery Work?

LASIK works by microscopically reshaping the cornea to change how light enters the eye and improve the accuracy of its focus on the retina.

The procedure generally involves two main surgical steps.

First, a thin layer of corneal tissue called a flap is created. An excimer laser is then applied to the inner layer of the cornea, known as the stroma.

The laser removes microscopic amounts of tissue according to a carefully calculated treatment pattern.

Once the laser treatment is completed, the flap is repositioned.

The FDA describes LASIK as a controlled reshaping of corneal tissue using computer-guided laser pulses after a corneal flap has been temporarily lifted.

The amount and pattern of tissue reshaping depend on several factors, not simply the patient's glasses prescription.

These may include:

• Type of refractive error.

• Degree of refractive error.

• Amount of astigmatism.

• Corneal thickness.

• Corneal shape and regularity.

• Planned optical zone.

• Individual optical characteristics.

For this reason, two patients with the same prescription may require different treatment plans—or may not be candidates for the same procedure.

What Happens During LASIK Surgery Step by Step?

During LASIK, the eye is prepared with topical anesthetic drops, a corneal flap is created, an excimer laser reshapes the cornea, and the flap is repositioned without the need for stitches in most cases.

Although every procedure is individualized, LASIK generally follows several stages.

How Is the Eye Prepared Before LASIK?

Before the procedure begins, anesthetic eye drops are applied to numb the surface of the eye.

The patient remains awake throughout the procedure and receives instructions from the surgical team.

General anesthesia is not required.

Before surgery, patients should also have completed a comprehensive evaluation and discussed visual expectations, benefits, and alternatives. The FDA recommends that patients have the opportunity to ask questions and understand the procedure before making their decision.

How Is the Corneal Flap Created?

The corneal flap is a thin layer of tissue that allows temporary access to the corneal stroma, where the laser reshaping is performed.

Depending on the technique and technology used, the flap may be created with:

• A mechanical microkeratome.

• A femtosecond laser.

When the flap is created with a femtosecond laser, the procedure is often referred to as Femto-LASIK or All-Laser LASIK.

The FDA explains that one of the primary differences between conventional LASIK and All-Laser LASIK is the technology used to create the corneal flap.

What Does the Excimer Laser Do?

The excimer laser reshapes corneal tissue using computer-controlled pulses of energy.

The treatment pattern is calculated from measurements obtained during the preoperative evaluation.

After the laser treatment is completed, the corneal flap is carefully repositioned.

The goal is to modify the geometry of the cornea so that the eye's optical system can focus light more accurately.

Why is modern LASIK safer than it was two decades ago?

Due to the combination of three-dimensional corneal diagnostics that screen out non-eligible candidates and lasers equipped with automated Eye-Tracking that enhance treatment accuracy.

Is everyone with myopia or astigmatism a candidate for LASIK?

No. The decision requires evaluating corneal thickness, refractive stability, and structural eye health during a thorough consultation[cite: 1, 2].

Why is modern LASIK safer than it was two decades ago?

Due to the combination of three-dimensional corneal diagnostics that screen out non-eligible candidates and lasers equipped with automated Eye-Tracking that enhance treatment accuracy.

Is everyone with myopia or astigmatism a candidate for LASIK?

No. The decision requires evaluating corneal thickness, refractive stability, and structural eye health during a thorough consultation[cite: 1, 2].

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Dr. Enrique Barragán Garza

Oftalmólogo Certificado por el Consejo Mexicano de Oftalmología – Cirugía LASIK en Monterrey

Cédula Profesional: UDEM 1750253

Cédula de Especialidad: IMSS 3392272

📍 Hidalgo 2040, Col. Obispado, Monterrey, N.L.

📞 +52 81 1365 0303 | WhatsApp +52 81 2660 1641

Medical Review:

Content clinically reviewed and validated by Dr. Enrique Barragán Garza, Specialist in Ophthalmology and Refractive Surgery in Monterrey. Practice located in the Obispado area. [cite: 1, 2]

El contenido de este sitio no sustituye una valoración médica profesional ni equivale a diagnóstico, pronóstico, tratamiento o prescripción por parte de un especialista certificado.
Los tratamientos pueden tener efectos secundarios. Consulta siempre con un médico u oftalmólogo calificado antes de tomar decisiones sobre tu salud visual.
En caso de presentar una emergencia médica, busca atención inmediata en un servicio de urgencias.