How the LASIK Procedure Works: A Step-by-Step Guide

LASIK Procedure Overview

LASIK (Laser-Assisted In Situ Keratomileusis) is an outpatient refractive surgery that permanently corrects vision by reshaping the cornea — the clear front surface of the eye. The procedure addresses the root cause of blurry vision: a corneal shape that prevents light from focusing precisely on the retina. By removing microscopic amounts of corneal tissue with an ultraviolet excimer laser, LASIK changes how light bends as it enters the eye.

The entire procedure takes approximately 15 minutes for both eyes combined. The actual laser treatment lasts only 20 to 60 seconds per eye, depending on your prescription. Most patients experience dramatic vision improvement within hours of surgery and return to most normal activities within 24 to 48 hours. Since FDA approval in 1999, LASIK has become the most-performed elective surgical procedure in the United States, with over 700,000 procedures annually.

Pre-Operative Evaluation: The Foundation of Safe LASIK

A thorough pre-operative evaluation is the most important step in determining whether LASIK is safe and appropriate for your eyes. This evaluation goes far beyond a standard glasses prescription check and typically takes 60 to 90 minutes. The goal is to build a complete picture of your corneal anatomy, visual system, and tear film quality before any surgical planning begins.

The evaluation includes corneal topography — a detailed map of the corneal surface that identifies irregularities or early keratoconus that would disqualify a patient from LASIK. Pachymetry measures corneal thickness at multiple points; most surgeons require at least 500 microns with sufficient residual tissue after the planned treatment. Wavefront aberrometry captures higher-order optical imperfections unique to your visual system. Tear film testing evaluates dry eye risk, and a dilated fundus exam checks retinal health.

If you wear contact lenses, you must stop wearing them before the evaluation: at least 2 weeks for soft lenses, 3 weeks for toric soft lenses, and 4 to 8 weeks for rigid gas permeable (RGP) lenses. Contacts temporarily change corneal shape, and measurements must reflect your cornea's natural form.

What Happens on LASIK Surgery Day

On the day of surgery, you will arrive without contact lenses and without eye makeup or perfume. Arrange for someone to drive you home — you will not be able to drive immediately after the procedure. The surgical team will review your measurements, confirm your prescription, and answer any remaining questions.

Numbing eye drops (topical anesthesia) are applied to both eyes, making the procedure essentially painless. You may feel mild pressure during flap creation, but there is no cutting sensation. A lid speculum holds your eye open gently so you do not need to worry about blinking. You will be asked to look at a target light — typically a blinking green dot — throughout the treatment.

Creating the Corneal Flap

The first step of LASIK is creating a thin, hinged flap in the outer corneal tissue (the epithelium and anterior stroma). This flap is folded back to expose the underlying corneal bed where laser reshaping occurs. There are two methods for flap creation:

Method	Technology	Flap Thickness	Advantages
Microkeratome	Oscillating blade	130–160 microns	Faster, lower cost, decades of data
Femtosecond laser	Infrared laser pulses	90–110 microns	More precise, thinner flap, bladeless

The bladeless (femtosecond) approach has become the standard of care at most modern LASIK centers because it allows more precise control over flap dimensions, reducing the risk of flap-related complications. The traditional microkeratome approach remains effective and is still used successfully at many centers. Your surgeon will recommend the best approach based on your corneal characteristics.

The Excimer Laser Treatment

Once the flap is lifted, the excimer laser — a cool ultraviolet laser operating at 193 nm wavelength — removes precise amounts of stromal tissue to reshape the cornea. For myopia (nearsightedness), the laser flattens the central cornea. For hyperopia, it steepens the central cornea. For astigmatism, it creates a more uniform, spherical surface.

The excimer laser removes approximately 0.25 microns of tissue per pulse, and each pulse takes about 12 nanoseconds. Modern laser platforms use eye-tracking systems that monitor eye position up to 1,000 times per second, automatically pausing and adjusting if the eye moves. This tracking technology has substantially improved accuracy and safety compared to early-generation systems.

After laser treatment, the surgeon carefully repositions the corneal flap. No stitches are needed — the flap adheres through natural surface tension and begins bonding within minutes. The eye is inspected to confirm proper flap position, and antibiotic and anti-inflammatory drops are instilled.

Types of LASIK Procedures Available

Modern LASIK encompasses several variations distinguished by how the flap is created and how the laser treatment is customized:

• Traditional LASIK — microkeratome flap with standard excimer treatment based on glasses prescription.
• Bladeless/All-Laser LASIK — femtosecond laser flap creation for greater precision.
• Wavefront-Guided LASIK — custom treatment addressing higher-order aberrations beyond standard refraction.
• Topography-Guided LASIK — uses corneal surface maps to treat irregularities, potentially achieving supernormal vision.
• Custom LASIK — a broad term for any personalized treatment using wavefront or topography data.
• Monovision LASIK — corrects one eye for distance and one for near to address presbyopia after age 40.

Immediately After LASIK Surgery

In the first minutes after surgery, your vision will be blurry or hazy — this is normal and expected. You may feel a mild burning or foreign body sensation as the numbing drops wear off. Most patients rest for 2 to 4 hours after surgery, with eye shields taped in place to prevent accidental rubbing.

By the evening of surgery day, many patients already notice dramatically improved vision. For the complete timeline of what to expect, see our LASIK recovery guide. Your surgeon will schedule a follow-up appointment for the next morning to confirm flap position and measure initial visual acuity.

Understanding LASIK risks and complications and candidacy requirements will help you have a productive consultation conversation with your surgeon.