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.

Is LASIK the Same for Every Patient?

No. LASIK should be individually planned because prescription, corneal shape, thickness, and visual needs can differ significantly—even between patients with the same refractive error.

One of the most important concepts in refractive surgery is that there is no identical treatment for every eye.

Two patients may have exactly the same glasses prescription but differ in:

• Corneal thickness.

• Corneal curvature.

• Corneal topography.

• Astigmatism.

• Ocular surface quality.

• Pupil size.

• Age.

• Professional visual demands.

• Sports activities.

• Nighttime visual requirements.

Therefore, the question should not simply be:

“Is my prescription suitable for surgery?”

A more important question is:

“Do my eyes have the characteristics required for this specific procedure?”

In a study evaluating Femto-LASIK outcomes in 254 eyes, 90% achieved uncorrected visual acuity of 20/20 or better at 12 months. However, results from a specific study population and technology platform should never be interpreted as a guarantee of individual outcomes.

Careful patient selection remains one of the most important factors in achieving appropriate refractive surgery results.

Who Is a Candidate for LASIK Eye Surgery?

A potential LASIK candidate should have a treatable refractive error and appropriate ocular characteristics, but final candidacy can only be determined after a comprehensive ophthalmic examination.

LASIK is not recommended simply because a person wants to stop wearing glasses.

The decision should be based on a medical evaluation.

Factors commonly assessed include:

• Adult age.

• Stable prescription.

• Type and degree of refractive error.

• Corneal thickness.

• Corneal shape.

• Absence of significant corneal abnormalities.

• Ocular surface health.

• Overall eye health.

• Medical history.

• Realistic visual expectations.

The FDA states that approved LASIK lasers are not indicated for patients under 18 years of age and emphasizes the importance of evaluating refractive stability, particularly when there have been recent prescription changes.

Stable vision is important because performing refractive surgery while the prescription is still changing may affect the predictability of the outcome.

However, reaching a specific age does not automatically make someone a candidate. Age is only one of several factors evaluated.

What Tests Are Performed Before LASIK Surgery?

Before recommending LASIK, an ophthalmic evaluation examines refractive error, corneal anatomy, ocular surface health, and overall eye health to determine whether the procedure is appropriate.

This evaluation is one of the most important parts of the refractive surgery process.

Tests may include:

• Refraction: determines the refractive error.

• Visual acuity testing: measures vision with and without correction.

• Corneal topography: analyzes the curvature of the cornea.

• Corneal tomography: provides three-dimensional information about corneal structure.

• Pachymetry: measures corneal thickness.

• Ocular surface evaluation: assesses tear film and surface health.

• Slit-lamp examination: evaluates the structures at the front of the eye.

• Pupil evaluation: may be included as part of an individualized optical assessment.

The FDA recommends a comprehensive eye examination before LASIK and advises reviewing ocular, medical, and medication history.

These tests are not performed simply to “approve” surgery.

They help answer essential questions:

• Is the shape of the cornea appropriate?

• Is there sufficient corneal thickness for the planned treatment?

• Is there evidence of corneal disease?

• Is the prescription stable?

• Does any condition require treatment before surgery is considered?

• Is LASIK truly the best option?

In some cases, testing may show that a patient is not an appropriate candidate for LASIK but may be evaluated for another refractive procedure.

Why Is Corneal Evaluation So Important Before LASIK?

The cornea is the tissue reshaped during LASIK, making its shape, thickness, and structural stability essential factors when determining whether the procedure can be performed safely.

Not all corneas are the same.

Corneal topography and tomography provide information that cannot be obtained simply by looking at the eye during a standard examination.

These tests can help identify irregularities and conditions that require further evaluation.

One important condition that must be considered is keratoconus (ICD-10 H18.6), a progressive disorder in which the cornea becomes structurally irregular and may progressively thin.

The FDA includes keratoconus among conditions requiring special consideration before refractive surgery and identifies thin corneas as an important factor requiring careful evaluation.

This is one reason why a proper preoperative assessment is far more important than simply knowing a patient’s glasses prescription.

Technology is important, but appropriate patient selection begins before the laser is ever activated.

What If I Am Not a Candidate for LASIK?

Not being a candidate for LASIK does not necessarily mean that no other options exist to reduce dependence on glasses, because several refractive procedures may be considered depending on the individual characteristics of the eye.

LASIK is only one of several options within refractive surgery.

Depending on the individual case, an ophthalmologist may consider alternatives such as:

• PRK (Photorefractive Keratectomy).

• SMILE and other lenticule-based procedures, when appropriate.

• Phakic intraocular lenses.

• Lens-based procedures, particularly in certain age groups.

The choice depends on factors such as corneal anatomy, refractive error, and age.

In some cases, the most appropriate medical recommendation may be not to perform surgery at that time. This is also part of responsible patient selection.

Does LASIK Eye Surgery Hurt?

LASIK is generally not painful because anesthetic eye drops are used, although patients may experience pressure or temporary sensations during and shortly after the procedure.

LASIK is performed using topical anesthetic eye drops.

The patient remains awake and is instructed to focus on a fixation target.

After surgery, temporary sensations may include:

• A foreign-body sensation.

• Tearing.

• Mild burning.

• Light sensitivity.

• Initially blurred vision.

The FDA notes that temporary discomfort and blurred vision may occur during the early recovery period.

Individual experiences vary, but the surgical procedure itself is generally brief.

How Long Does Recovery Take After LASIK?

Vision often improves quickly after LASIK, although complete recovery and visual stabilization vary between patients and may continue over days, weeks, or, in some aspects, several months.

It is important to distinguish between seeing better and having completed the entire healing process.

Many patients experience significant visual improvement relatively soon after surgery. However, some visual fluctuation may occur during the first days or weeks.

Recovery includes:

1. Initial visual improvement.

2. Ocular surface adaptation.

3. Corneal healing and stabilization.

4. Postoperative follow-up.

The FDA recommends a postoperative examination within the first 24 to 48 hours and continued follow-up according to clinical progress. Visual stabilization may continue during the first months after surgery.

During recovery, patients should follow the specific instructions provided by their ophthalmologist.

What Care Is Needed After LASIK?

After LASIK, postoperative instructions should be followed carefully to protect the eye during recovery and support proper healing.

Recommendations vary by patient but commonly include:

• Using prescribed medications.

• Avoiding rubbing the eyes.

• Attending scheduled follow-up appointments.

• Protecting the eyes as instructed.

• Avoiding eye makeup for the recommended period.

• Avoiding contaminated water exposure.

• Temporarily limiting certain sports activities when recommended.

The FDA advises patients not to rub their eyes after surgery and notes that activities such as swimming and contact sports may require temporary restrictions during recovery.

General recommendations should not replace the specific postoperative instructions provided by the treating ophthalmologist.

What Visual Results Can I Expect After LASIK?

Many patients significantly reduce their dependence on glasses after LASIK, but individual visual outcomes depend on ocular characteristics, the initial refractive error, the technique used, and each patient’s biological healing response.

The goal of LASIK is to improve uncorrected vision.

However, absolute promises should be avoided.

Even when refractive surgery is appropriately indicated, not every patient will achieve exactly the same level of visual acuity.

A review of 19 studies involving 2,198 patients reported an overall satisfaction rate of 95.4% after LASIK.

In another study involving a specific Femto-LASIK platform, 90% of eyes achieved uncorrected 20/20 vision or better at 12 months. However, results depend on the study population, range of prescriptions, and technology used.

For this reason, published percentages should help patients understand general outcomes—not serve as a guarantee of an individual result.

An important question before surgery is:

“What is a realistic visual outcome for my eyes?”

Does LASIK Permanently Eliminate the Need for Glasses?

LASIK can significantly reduce dependence on glasses for certain refractive errors, but it does not stop natural age-related changes in the eye or guarantee that a person will never need vision correction again.

This is one of the most important concepts to understand before refractive surgery.

LASIK changes the cornea, but the eye continues to undergo natural changes over time.

These may include:

• Presbyopia.

• Age-related optical changes.

• Changes in the natural lens.

• Cataract.

• Additional refractive changes.

The FDA notes that some patients may continue to need glasses or contact lenses after surgery, depending on their visual outcome and specific needs.

Therefore, a realistic goal is not necessarily to promise that someone will “never wear glasses again,” but rather to evaluate how much dependence on corrective eyewear may reasonably be reduced.

What Happens If I Am Over 40 and Considering LASIK?

After age 40, presbyopia may affect the ability to focus on near objects, and conventional LASIK for distance vision does not necessarily prevent this natural age-related change.

Presbyopia (ICD-10 H52.4) is primarily related to progressive changes in the eye’s ability to accommodate and focus at close distances.

As a result, a patient may achieve excellent distance vision after LASIK but eventually require reading glasses.

In selected patients, different visual strategies may be considered.

One option is SUPRACOR surgery, or you can also consider monovision, in which one eye is optimized primarily for distance vision and the other for near vision.

The FDA describes monovision as an approach that may help address presbyopia-related visual needs, while emphasizing that adaptation and individual suitability should be evaluated carefully.

Age should therefore be part of refractive surgery planning.

Planning refractive surgery for a 25-year-old is not necessarily the same as planning surgery for a 45- or 55-year-old with different visual requirements.

Does LASIK Have Risks?

Like any surgical procedure, LASIK has potential risks and limitations, although the goal in appropriately selected patients is to achieve good visual quality with a favorable balance between expected benefits and safety.

Risks should be discussed openly without allowing them to become the sole focus of the decision or minimizing their importance.

Temporary effects may occur during recovery, and less commonly, complications may require additional treatment.

The FDA recommends that patients understand the benefits, limitations, and potential complications before deciding to undergo refractive surgery.

Topics that should be discussed individually include:

• The possibility of residual refractive error.

• The possible need for glasses for certain activities.

• Age-related visual changes.

• The importance of postoperative follow-up.

• The potential need for additional treatment in selected cases.

One of the most important ways to reduce avoidable risks is through appropriate patient selection and a comprehensive preoperative evaluation.

Not every eye should undergo surgery, and not every patient should receive the same procedure.

How Can I Know Whether LASIK Is the Best Option for Me?

The only way to determine whether LASIK is appropriate is through a comprehensive ophthalmic evaluation that analyzes eye health, corneal characteristics, refractive stability, and individual visual needs.

A refractive surgery consultation should answer much more than a simple “yes” or “no.”

Ideally, it should help the patient understand:

• Whether refractive surgery is medically appropriate.

• Whether LASIK is a suitable option.

• Whether another procedure may be more appropriate.

• What visual results may reasonably be expected.

• What limitations exist.

• How age influences the decision.

• What postoperative care will be required.

The FDA recommends that patients have sufficient time to discuss benefits, risks, and alternatives before making a decision and signing informed consent.

Refractive surgery should be an informed and individualized decision.

The question is not simply:

“Do I want to stop wearing glasses?”

It should also be:

“Which option is most appropriate for my eyes and my visual needs?”

Frequently Asked Questions About LASIK

How Long Does LASIK Surgery Take?

The laser treatment itself is brief, although the total procedure includes patient preparation, flap creation, laser treatment, and repositioning of the corneal tissue.

The exact duration varies depending on the technology used and the planned treatment.

Do I Have to Be Awake During LASIK?

Yes. LASIK is generally performed using topical anesthetic eye drops, and the patient remains awake throughout the procedure.

The patient receives instructions and is asked to maintain fixation during specific stages of surgery.

Can I Move My Eyes During LASIK?

Modern laser systems may incorporate eye-tracking technology, while patients are also instructed to maintain their gaze in the appropriate position.

The technology used may vary depending on the surgical platform.

Can Everyone With Myopia Have LASIK?

No. Having myopia does not automatically make someone a candidate for LASIK.

Corneal shape and thickness, refractive stability, and overall eye health are among the factors that must be evaluated.

What Happens If I Am Not a Candidate for LASIK?

Depending on the characteristics of the eye, other refractive procedures may be considered, or continuing with glasses or contact lenses may be the most appropriate option.

Not being a candidate for one specific technique does not necessarily mean that no other alternatives exist.

How Can I Find Out If I Am a Candidate for LASIK in Monterrey?

If you are considering laser vision correction and want to reduce your dependence on glasses or contact lenses, a comprehensive ophthalmic evaluation is the first step in determining whether LASIK is appropriate for your eyes.

During the evaluation, factors such as refractive stability, corneal shape and thickness, ocular surface health, and individual visual needs are assessed. These studies help determine not only whether you may be a candidate for LASIK, but also whether another refractive surgery option may be more appropriate.

Dr. Enrique Barragán Garza, Ophthalmologist in Monterrey, Mexico, provides individualized ophthalmic evaluations to help patients understand their options for laser vision correction and refractive surgery.

The decision to undergo refractive surgery should be based on the individual characteristics of each patient’s eyes and on realistic visual expectations.

Schedule an ophthalmic evaluation in Monterrey to determine whether LASIK or another refractive surgery option may be appropriate for you.

Clinical Conclusion: What Should I Know Before Considering LASIK?

LASIK is a laser refractive surgery technique that reshapes the cornea to correct selected cases of myopia, hyperopia, and astigmatism.

Its primary goal is to reduce dependence on glasses or contact lenses.

However, the decision to undergo refractive surgery should not be based solely on a glasses prescription or the desire to stop wearing corrective lenses.

The most important part of the process begins before surgery. A comprehensive ophthalmic evaluation allows the ophthalmologist to study the cornea, confirm refractive stability, assess overall eye health, and determine whether LASIK is truly the most appropriate procedure.

Published research has shown high levels of patient satisfaction in appropriately selected LASIK candidates, including an overall satisfaction rate of 95.4% in a review involving 2,198 patients.

But every eye is different.

For this reason, a good refractive surgery consultation should not simply answer:

“Can I have surgery?”

It should help determine:

“Which option offers the best balance between safety, visual quality, and my individual needs?”

Authorship and Medical Review

Written by:

Dr. Enrique Barragán Garza, Ophthalmologist

Professional License: UDEM 1750253

Specialty License: IMSS 3392272

Certified by the Mexican Board of Ophthalmology

Medically reviewed by:

Dr. Enrique Barragán Garza, Ophthalmologist

Date of last medical review: September 4, 2026

COFEPRIS Advertising Authorization: 2419012002A00337

Medical References

1. U.S. Food and Drug Administration (FDA). Patient information regarding LASIK, candidate selection, recovery, and preoperative considerations.

2. Solomon KD, Fernández de Castro LE, Sandoval HP, et al. LASIK world literature review: quality of life and patient satisfaction. Ophthalmology. 2009;116(4):691-701.

3. Clinical studies indexed in PubMed evaluating Femto-LASIK outcomes and laser refractive correction of myopia and astigmatism.

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