LASIK: Suitability, Procedure, Risks and Recovery

Author: Dr Val Phua
Estimated reading time: 22 minutes

LASIK is a laser vision-correction procedure used to reduce dependence on spectacles or contact lenses.

The name stands for laser-assisted in situ keratomileusis.

During LASIK:

A thin flap is created in the cornea.
The flap is lifted.
An excimer laser precisely reshapes the underlying corneal tissue.
The flap is repositioned without stitches.

By altering the curvature of the cornea, LASIK changes how light is focused onto the retina.

It can treat selected patients with:

Myopia, or short-sightedness
Hyperopia, or long-sightedness
Astigmatism
Presbyopia using a monovision strategy in suitable patients

LASIK is generally highly effective in appropriately selected eyes. Modern studies report excellent refractive predictability and high rates of unaided distance vision, but the result depends on the prescription, corneal shape, tear film, healing response and laser platform. LASIK reduces refractive error; it does not guarantee perfect vision or freedom from spectacles under every condition.

Most patients recover functional vision rapidly. However, LASIK is still an operation on healthy corneal tissue and has genuine risks.

Possible problems include:

Dry eye symptoms
Glare, halos or starbursts
Under-correction or over-correction
Residual astigmatism
Flap-related complications
Inflammation beneath the flap
Infection
Corneal ectasia
Persistent discomfort or neuropathic pain
Rare loss of corrected vision

Careful patient selection is therefore more important than simply choosing the newest laser platform.

The Quick Answer

What Is LASIK?

LASIK is a corneal refractive procedure that changes the focusing power of the eye.

A femtosecond laser is usually used to create a thin corneal flap. An excimer laser then removes microscopic amounts of tissue from the deeper corneal layer according to the intended correction.

The flap is replaced and adheres naturally.

What Does LASIK Treat?

LASIK may correct:

Short-sightedness
Long-sightedness
Regular astigmatism
Selected residual prescriptions after previous eye surgery
Presbyopia through monovision in appropriately counselled patients

The available treatment range depends on:

The laser platform
Corneal thickness
Corneal curvature
Prescription
Optical-zone requirements
Expected residual stromal thickness
Local regulatory approval
The surgeon’s assessment

Is LASIK Painful?

Most patients feel little or no pain during the procedure.

Anaesthetic eye drops numb the cornea.

The patient may notice:

Pressure around the eye
Temporary dimming of vision
Bright lights
Clicking sounds from the laser
The smell of tissue molecules being released during laser ablation

The smell does not mean that the eye is burning.

How Long Does LASIK Take?

The complete procedure commonly takes approximately 10 to 20 minutes for both eyes.

The actual excimer-laser treatment may take only seconds, depending on the prescription and platform.

Additional time is needed for:

Preparation
Sterile cleaning
Eye alignment
Flap creation
Laser checks
Postoperative examination

How Quickly Does Vision Recover?

Many patients can see sufficiently well for basic activities by the following day.

Vision may continue to sharpen over:

Several days
Several weeks
Occasionally several months

The speed of recovery varies with:

Prescription
Dry eye
Degree of astigmatism
Healing
Treatment profile
Pre-existing visual quality

Is LASIK Permanent?

The corneal tissue removed by the excimer laser does not grow back in its original form.

However, the eye can still change because of:

Natural myopic progression
Age-related refractive change
Presbyopia
Cataract formation
Corneal biomechanical change
Diabetes-related fluctuation
Other eye disease

Long-term studies show that some patients develop gradual regression, especially after correction of higher prescriptions.

Will I Never Need Spectacles Again?

Not necessarily.

Spectacles may still be required for:

Fine print
Prolonged reading
Night driving
Very small residual refractive errors
Age-related presbyopia
Future cataract-related changes
Tasks requiring exceptionally sharp vision

The goal is usually to reduce dependence on optical correction—not to guarantee that spectacles will never be needed again.

Understanding Refractive Error

Myopia

Myopia occurs when light focuses in front of the retina.

Patients can usually see near objects more clearly than distant objects.

Myopic LASIK flattens the central cornea to reduce its focusing power.

Hyperopia

Hyperopia occurs when the eye has insufficient focusing power or is relatively short.

Hyperopic LASIK steepens the central cornea by removing tissue in a surrounding ring.

Hyperopic treatments may be more prone to:

Regression
Decentration sensitivity
Changes related to latent hyperopia
Age-related refractive change

Astigmatism

Astigmatism occurs when the cornea has different curvatures in different meridians.

The laser applies an asymmetric treatment to make the corneal focusing power more regular.

Accurate astigmatism correction depends on:

Reliable refraction
Corneal shape
Cyclotorsion compensation
Eye tracking
Treatment centration
The distinction between corneal and internal astigmatism

Presbyopia

Presbyopia is the age-related loss of the natural lens’s ability to focus at near.

Standard LASIK reshapes the cornea but does not restore the flexibility of the natural lens.

A patient with excellent distance vision after LASIK will still develop presbyopia with age.

Monovision LASIK

Monovision is a strategy in which:

One eye is corrected primarily for distance.
The other eye is left mildly short-sighted for intermediate or near vision.

The brain learns to use the clearer image from each eye according to the viewing distance.

Monovision may reduce dependence on reading spectacles, but it may also reduce:

Stereoacuity
Fine depth perception
Night-driving quality
Maximum binocular distance sharpness

Historical studies report monovision acceptance rates of approximately 70% to 90% in selected patients, but outcomes depend on the amount of anisometropia and the patient’s visual priorities.

A contact-lens monovision trial is often helpful before permanent treatment.

PresbyLASIK

PresbyLASIK uses a specialised corneal ablation profile intended to provide more than one focal range.

Different designs may create:

A central near zone
A peripheral near zone
Increased depth of focus
A multifocal corneal profile
A combination of multifocality and monovision

Current published evidence is less robust than the evidence supporting conventional myopic LASIK. A systematic review found that much of the presbyLASIK literature consisted of case series, with limited high-quality comparative evidence.

Patients considering presbyLASIK should understand the possible trade-offs between:

Near vision
Distance sharpness
Contrast
Glare
Halos
Ease of future cataract planning

Who May Be Suitable for LASIK?

A suitable patient generally has:

A stable spectacle prescription
Healthy corneas
Adequate corneal thickness
No evidence of keratoconus or ectasia
A manageable degree of refractive error
A sufficiently healthy tear film
Realistic expectations
No visually significant cataract
No uncontrolled ocular or systemic disease

Age alone does not determine suitability.

The condition of the eye and the patient’s visual goals are more important.

How Stable Must the Prescription Be?

The prescription should generally be stable for at least approximately one year.

A small change does not automatically rule out surgery, but significant ongoing progression suggests that the result may not remain stable.

Refractive instability is more likely in:

Younger adults
Progressive myopia
Pregnancy
Breastfeeding
Poorly controlled diabetes
Certain medication use
Hormonal change
Lens-related refractive change

Refractive instability is recognised as an important contraindication to elective laser vision correction.

Is There a Minimum Age?

LASIK is generally not performed below 18 years of age.

Many patients in their late teens or early twenties still have progressive myopia.

Even after the legal minimum age has been reached, surgery should be delayed if the prescription is still changing.

Is There a Maximum Age?

There is no universal maximum age.

Older patients require careful assessment for:

Presbyopia
Early cataract
Glaucoma
Macular degeneration
Dry eye
Reduced corneal endothelial reserve
Expectations regarding near vision

For a patient with early lens changes, cataract surgery or refractive lens exchange may sometimes provide a more appropriate long-term solution than LASIK.

Who May Not Be Suitable for LASIK?

LASIK may be inappropriate or require special caution in the presence of:

Keratoconus
Suspicious corneal tomography
Corneal ectasia
Inadequate corneal thickness
Unstable refraction
Significant dry eye
Active blepharitis
Recurrent corneal erosion
Epithelial basement membrane dystrophy
Previous herpetic keratitis
Active uveitis
Uncontrolled glaucoma
Visually significant cataract
Pregnancy or breastfeeding
Poorly controlled diabetes
Active autoimmune disease
Medications affecting healing or refraction
Unrealistic expectations

Reviews of current refractive-surgery guidance identify keratoconus, unstable refraction and poorly controlled ocular-surface or systemic disease among the principal contraindications.

Pregnancy and Breastfeeding

LASIK is generally postponed during pregnancy and breastfeeding.

Reasons include:

Hormonal refractive fluctuation
Corneal-curvature change
Tear-film instability
Medication considerations
The elective nature of the procedure

Measurements should be repeated after the prescription and ocular surface have stabilised.

Diabetes

Diabetes does not automatically exclude every patient.

Suitability depends on:

Quality of glucose control
Stability of the prescription
Presence of diabetic retinopathy
Corneal sensation
Wound healing
Dry eye
General health

Poorly controlled diabetes is a contraindication because it may produce refractive fluctuation and impaired healing.

Autoimmune and Connective-Tissue Disease

Active or poorly controlled autoimmune disease may increase the risk of:

Delayed epithelial healing
Severe dry eye
Inflammation
Corneal melting
Infection
Unpredictable healing

Patients with stable systemic disease require an individual risk assessment and, in selected cases, discussion with the treating physician.

Medications

The surgeon should know about all prescription and non-prescription medication.

Particular attention may be required for:

Isotretinoin
Amiodarone
Immunosuppressive medication
Steroids
Antihistamines
Antidepressants
Hormonal medication
Medication affecting tear production or refraction

Medication should not be stopped without consulting the prescribing doctor.

Contact Lenses Before Assessment

Contact lenses may temporarily alter the corneal shape.

They must usually be discontinued before final measurements.

The required interval depends on:

Soft or rigid lens
Duration of wear
Corneal warpage
Prescription
Stability of repeat maps

Rigid gas-permeable and orthokeratology lenses may require a substantially longer period of discontinuation than ordinary soft lenses.

Measurements should not be accepted until the corneal shape is stable.

The Pre-LASIK Assessment

The assessment is designed to answer three questions:

Can the prescription be treated accurately?
Can the cornea be treated safely?
Is LASIK the most appropriate procedure for this patient?

Medical and Ocular History

The surgeon should ask about:

Previous eye surgery
Contact-lens wear
Dry eye
Recurrent erosions
Eye trauma
Herpetic eye disease
Glaucoma
Retinal disease
Autoimmune disease
Diabetes
Pregnancy plans
Medication
Occupational requirements
Contact sports
Night-driving needs

Visual-Acuity Testing

Both unaided and corrected vision are measured.

The corrected vision establishes the best level of clarity achieved with spectacles.

LASIK cannot be expected to produce vision substantially better than the eye’s true visual potential, although some customised treatments may improve selected measures of optical quality.

Manifest Refraction

The patient chooses between lenses to determine the subjective spectacle prescription.

The refraction may be repeated because small inconsistencies can affect the laser plan.

Cycloplegic Refraction

Dilating drops temporarily relax the eye’s focusing mechanism.

This is particularly useful for:

Younger patients
Hyperopia
Suspected accommodative spasm
A discrepancy between measurements
Avoiding excessive myopic correction

Corneal Topography

Topography maps the curvature of the front corneal surface.

It helps identify:

Regular astigmatism
Decentration
Contact-lens warpage
Irregular astigmatism
Suspicious corneal patterns
Previous refractive treatment

Corneal Tomography

Tomography assesses the three-dimensional structure of the cornea.

It may analyse:

Anterior corneal curvature
Posterior corneal curvature
Corneal thickness
Thickness distribution
Elevation maps
Ectasia-risk indices

Normal visual acuity does not exclude early keratoconus.

Tomographic screening is therefore fundamental to reducing the risk of postoperative ectasia.

Pachymetry

Pachymetry measures corneal thickness.

The surgeon considers:

Starting corneal thickness
Planned flap thickness
Estimated ablation depth
Residual stromal bed
Percentage of tissue altered
Corneal shape
Patient age
Prescription

A single minimum thickness value does not determine suitability by itself.

Epithelial Thickness Mapping

The corneal epithelium may redistribute itself to mask an underlying stromal irregularity.

Epithelial mapping can help identify:

Early keratoconus
Contact-lens warpage
Irregular corneal shape
Previous ablation patterns
Epithelial compensation

It is an additional tool rather than a replacement for topography and tomography.

Wavefront Aberrometry

Wavefront testing measures how light travels through the entire optical system of the eye.

It identifies:

Defocus
Astigmatism
Coma
Spherical aberration
Other higher-order aberrations

The information may be used for wavefront-guided treatment in selected patients.

Tear-Film and Dry-Eye Assessment

Evaluation may include:

Symptoms
Tear-break-up time
Corneal staining
Conjunctival staining
Tear meniscus
Meibomian gland function
Eyelid inflammation
Tear osmolarity
Other ocular-surface tests

Dry eye should be treated before surgery because an unstable tear film can make both the measurements and postoperative vision unreliable.

Pupil Assessment

Pupil size may be assessed under dim lighting.

A large dark-adapted pupil does not automatically rule out LASIK, but it may influence:

Optical-zone selection
Night-vision counselling
Treatment planning
Expectations regarding halos

The FDA advises that large pupils and pre-existing dry eye be considered during risk assessment.

Eye-Pressure Measurement

Eye pressure is measured to screen for glaucoma.

After LASIK, standard pressure readings may appear artificially lower because the cornea has been thinned and reshaped.

Future eye-care providers should be told about the history of LASIK.

Dilated Retinal Examination

The retina and optic nerve are examined for:

Retinal tears
Retinal degeneration
Myopic retinal disease
Macular problems
Glaucoma
Other causes of limited visual potential

LASIK corrects corneal focus but does not remove the retinal risks associated with high myopia.

How Does LASIK Work?

Step 1: Confirming the Treatment

Before surgery, the team confirms:

Patient identity
Correct eye
Prescription
Treatment plan
Laser calibration
Corneal measurements

Eye-tracking and iris-registration data may be checked.

Step 2: Anaesthetic Drops

Anaesthetic drops numb the eye.

The skin and eyelids are cleaned.

A small instrument keeps the eyelids open.

The patient does not need to worry about blinking.

Step 3: Creating the Corneal Flap

A suction ring stabilises the eye.

The patient may feel pressure, and vision may dim temporarily.

A femtosecond laser creates a thin flap within the cornea.

Older LASIK techniques used a mechanical microkeratome. Femtosecond flap creation provides programmable flap diameter, depth and architecture and is now widely used in contemporary practice.

Step 4: Lifting the Flap

The surgeon gently lifts the flap to expose the underlying corneal stroma.

The flap remains attached by a hinge.

Step 5: Excimer-Laser Reshaping

The patient looks towards a fixation light.

The excimer laser removes microscopic quantities of stromal tissue.

The laser does not cut by heat. It breaks molecular bonds through photoablation.

Modern platforms may include:

High-speed eye tracking
Cyclotorsion compensation
Pupil or limbal registration
Wavefront optimisation
Wavefront guidance
Topography guidance

Step 6: Replacing the Flap

The flap is repositioned over the treated area.

The surgeon checks:

Alignment
Smoothness
Edge position
Interface cleanliness
Flap adherence

No stitches are usually required.

Can Both Eyes Be Treated Together?

Yes.

Bilateral same-day treatment is common because:

The prescription is usually bilateral.
Recovery can occur simultaneously.
Binocular imbalance is reduced.
The patient needs only one main recovery period.

Each eye still requires independent checks and treatment planning.

Wavefront-Optimised LASIK

Wavefront-optimised treatment is designed to reduce the induction of spherical aberration by adjusting laser delivery across the cornea.

It does not use a fully individualised map of every higher-order aberration.

Wavefront-Guided LASIK

Wavefront-guided treatment incorporates measurements from the entire optical system of the eye.

It may be useful when:

Measurements are reliable
Higher-order aberrations are significant
The pupil and iris registration are suitable
The treatment platform supports the correction

Topography-Guided LASIK

Topography-guided treatment is based primarily on corneal surface shape.

It may aim to:

Regularise corneal optics
Improve treatment centration
Reduce corneal asymmetry
Correct refractive error

Randomised studies show that modern wavefront-guided, topography-guided and wavefront-optimised treatments can all produce excellent results. No single profile is consistently superior for every normal untreated cornea, and the relative advantages vary according to the platform, planning method and outcome being measured.

Does the Surgeon or the Laser Matter More?

Both matter.

The laser platform affects:

Ablation speed
Eye tracking
Treatment profiles
Optical-zone options
Energy delivery

The surgeon and clinical team determine:

Whether the patient should undergo LASIK at all
The quality of the measurements
Treatment selection
Flap planning
Management of the ocular surface
Identification and treatment of complications

Advanced technology cannot compensate for poor patient selection.

What Happens Immediately After LASIK?

The patient may notice:

Hazy or misty vision
Watering
Light sensitivity
Burning
Grittiness
Difficulty keeping the eyes open
Halos around lights

The discomfort is usually most noticeable during the first several hours.

The patient should go home and rest with the eyes closed when possible.

Eye Drops After LASIK

Medication may include:

Antibiotic drops
Steroid drops
Preservative-free lubricants
Other dry-eye treatment

The exact regimen varies.

Patients should:

Wash their hands
Avoid touching the bottle tip to the eye
Use the drops as prescribed
Space different drops apart
Avoid stopping steroid medication without advice

The First Night

Protective shields may be worn during sleep.

The patient should avoid:

Eye rubbing
Pressing the eyelids
Sleeping face-down
Allowing a child or pet to strike the eye

The First Day

Vision is often significantly improved.

Temporary symptoms may still include:

Haze
Glare
Halos
Fluctuation
Dryness
Light sensitivity

A postoperative examination checks:

Flap position
Corneal surface
Inflammation
Infection
Visual acuity

The First Week

Vision usually stabilises progressively.

Fluctuation may be more noticeable:

Late in the day
During prolonged screen use
In air-conditioned environments
When the tear film is unstable
At night

The First Month

Dryness, glare and intermittent blur usually continue to improve.

The refractive result is often close to its intended target, but small changes may continue.

How Soon Can Normal Activities Resume?

Individual instructions take priority.

Many patients can return to desk work within a few days.

Temporary precautions commonly include avoiding:

Eye rubbing
Eye makeup
Dusty environments
Dirty water
Swimming
Contact sports
Activities with risk of facial trauma

Can I Use a Computer or Phone?

Yes.

Screens do not damage the flap or reverse the laser correction.

However, prolonged screen use reduces blinking and may worsen:

Dryness
Burning
Fluctuating vision
Eye fatigue

Patients should take regular breaks and use lubricants when advised.

When Can I Drive?

Driving should resume only when:

Vision is legally adequate
The patient feels comfortable
Glare is manageable
Depth perception is satisfactory
Sedative effects have resolved
The surgeon has not advised otherwise

Patients should not drive themselves home after surgery.

When Can I Exercise?

Light walking is usually possible early.

Strenuous exercise may need to be avoided temporarily.

Activities with a risk of eye impact require greater caution.

When Can I Swim?

Swimming is generally avoided during the early healing period because pool, sea and spa water may contain organisms or irritants.

The surgeon will provide a specific timeline.

When Can I Wear Eye Makeup?

Eye makeup is usually avoided during the early postoperative period.

Old mascara or eye products may be contaminated and should not be used near a healing eye.

When Can I Fly?

Uncomplicated LASIK does not place a gas bubble inside the eye and usually does not prohibit flying.

Aircraft cabins may worsen dryness, so lubricating drops may be helpful.

Patients should consider the timing of postoperative appointments.

Expected Visual Results

Modern LASIK can produce excellent unaided distance vision in appropriately selected patients.

A recent prospective study of topography-guided LASIK reported 20/20 or better unaided distance vision in 97% of treated eyes at one year, while a contemporary randomised trial found similarly strong results with wavefront-guided and topography-guided treatments. These figures describe selected study populations and should not be treated as a guarantee for every patient.

A large Singapore clinical audit involving 37,932 eyes found that outcomes improved substantially over a decade as technology, nomograms and clinical governance evolved. In the later years of that audit, more than 93% of eyes were within one dioptre of the intended target.

Is 20/20 the Same as Perfect Vision?

No.

A high-contrast visual-acuity chart does not fully measure:

Contrast sensitivity
Glare
Night vision
Tear-film fluctuation
Halos
Starbursts
Double images
Visual comfort
Quality of vision

A patient may read 20/20 but still notice visual symptoms.

Conversely, a patient with a small residual prescription may be highly satisfied if spectacles are rarely needed.

Patient Satisfaction

Most appropriately selected LASIK patients report high satisfaction.

In the FDA-associated PROWL studies, dissatisfaction with the surgery was approximately 1% to 2%, although some patients developed new visual or dry-eye symptoms. Among participants without a particular symptom before surgery, 43% to 46% reported at least one new visual symptom at three months. Most symptoms did not prevent ordinary activities, but the findings highlight the importance of counselling beyond the visual-acuity result.

More recent studies using modern treatment profiles also report high satisfaction, although individual outcomes remain dependent on patient selection and study design.

Night-Vision Symptoms

Possible symptoms include:

Halos
Glare
Starbursts
Ghost images
Reduced contrast
Smearing around headlights

These may be related to:

Tear-film instability
Residual refractive error
Higher-order aberrations
Large pupils
Treatment centration
Optical-zone transition
Healing

Symptoms often improve over the first several months.

Persistent or severe symptoms require evaluation.

Dry Eye After LASIK

Dry eye is one of the most common postoperative concerns.

LASIK temporarily disrupts corneal nerves that contribute to:

Corneal sensation
Reflex tearing
Blinking
Tear-film regulation
Epithelial health

Possible symptoms include:

Burning
Grittiness
Fluctuating vision
Redness
Light sensitivity
Tired eyes
Excessive tearing
Contact-lens intolerance

A systematic review identified pre-existing ocular-surface disease, meibomian gland dysfunction, deeper ablation and LASIK-related nerve disruption among the factors associated with post-refractive dry eye.

How Long Does Dry Eye Last?

For many patients, symptoms improve substantially within:

Several weeks
Three to six months
Occasionally up to one year

A minority develop persistent symptoms.

The PROWL studies found that approximately 28% of participants with normal preoperative dry-eye scores reported some degree of dry-eye symptoms at three months, while overall dry-eye prevalence within the study populations decreased because many participants had symptoms before surgery.

Treating Dry Eye

Management may include:

Preservative-free artificial tears
Lubricating gel
Warm compresses
Lid hygiene
Treatment of meibomian gland dysfunction
Anti-inflammatory eye drops
Punctal plugs
Autologous serum
Scleral lenses
Other specialised therapy

Severe pain that appears disproportionate to the surface findings may require assessment for neuropathic corneal pain.

Under-Correction and Over-Correction

The achieved result may differ from the intended target.

Possible causes include:

Biological healing
Measurement variation
Laser-tissue interaction
Tear-film instability
Treatment centration
Higher prescriptions
Hyperopic regression
Astigmatic-axis error

Management may include:

Observation
Spectacles
Contact lenses
Enhancement surgery
Treatment of dry eye

Regression

Regression means that part of the refractive error returns after an initially successful result.

It may be influenced by:

High preoperative prescription
Corneal healing
Epithelial remodelling
Residual stromal thickness
Age-related lens change
Continuing axial myopia
Hyperopic treatment

Older ten-year LASIK studies show gradual myopic drift in some eyes, particularly after higher corrections. The results of historical treatments should not be assumed to represent current lasers exactly, but they demonstrate that the eye can continue changing after surgery.

Enhancement Surgery

An enhancement may be considered when:

A meaningful residual prescription remains
The prescription is stable
The cornea remains suitable
The visual problem is explained by the residual error
The patient is significantly affected
The expected benefit exceeds the additional risk

Options may include:

Lifting the original flap
Surface ablation over the flap
Spectacle or contact-lens correction
An intraocular procedure in selected patients

An enhancement is not automatically indicated for every small residual refractive error.

Flap Displacement

The LASIK flap does not regain the same structural strength as untouched cornea.

Early displacement may occur after:

Eye rubbing
Direct trauma
Accidental contact
Poor flap adherence

Symptoms may include:

Sudden blur
Pain
Watering
Light sensitivity
A foreign-body sensation

Prompt repositioning generally produces a good result.

Late traumatic flap displacement is uncommon but can occur years after surgery following significant direct eye trauma.

Protective eyewear is important for contact sports and hazardous occupations.

Flap Striae

Striae are folds within the flap.

Fine peripheral folds may not affect vision.

Central or significant folds may cause:

Blur
Ghosting
Irregular astigmatism
Reduced corrected vision

Treatment may include flap lifting, stretching and repositioning.

Epithelial Ingrowth

Surface epithelial cells may grow beneath the edge of the flap.

It is more common after:

Flap lifting for enhancement
Flap trauma
Epithelial defects
Older age
Previous ingrowth

Most small peripheral areas can be observed.

Treatment may be needed when ingrowth:

Progresses
Approaches the visual axis
Causes flap melting
Produces irregular astigmatism
Reduces vision

Diffuse Lamellar Keratitis

Diffuse lamellar keratitis, or DLK, is sterile inflammation within the flap interface.

It may appear as fine white inflammatory cells beneath the flap.

The patient may notice:

Blur
Light sensitivity
Discomfort
Haze

Early treatment commonly involves intensive steroid drops.

More severe cases may require the flap to be lifted and irrigated.

A recent review distinguishes DLK from other uncommon non-infectious inflammatory conditions such as central toxic keratopathy and transient light-sensitivity syndrome.

Infection

Infectious keratitis after LASIK is rare but potentially sight-threatening.

A large study reported microbial keratitis after approximately 0.0046% of LASIK procedures—about one case per 21,700 treated eyes.

Warning signs include:

Increasing pain
Increasing redness
Worsening vision
Discharge
Marked light sensitivity
A white corneal spot

Urgent examination and antimicrobial treatment are required.

Corneal Ectasia

Corneal ectasia is progressive thinning and bulging of the cornea after refractive surgery.

It may cause:

Increasing astigmatism
Progressive short-sightedness
Ghosting
Reduced corrected vision
Irregular corneal shape
Contact-lens dependence

Risk factors include:

Undiagnosed keratoconus
Suspicious tomography
Inadequate residual stromal tissue
High percentage of tissue altered
Young age
Abnormal corneal shape
Eye rubbing
Genetic predisposition

A systematic review confirmed that post-refractive ectasia is uncommon but can occur after LASIK, PRK and SMILE, including occasionally in eyes without an obvious preoperative risk factor.

Treatment may involve:

Corneal cross-linking
Spectacles
Rigid or scleral contact lenses
Intracorneal ring segments
Specialised laser treatment
Corneal transplantation in advanced disease

Loss of Corrected Vision

Rarely, an eye may not see as clearly with spectacles after LASIK as it did before surgery.

Possible causes include:

Irregular astigmatism
Corneal scarring
Infection
Severe dry eye
Ectasia
Central flap folds
Decentration
Interface inflammation

Large modern series show that clinically significant loss of corrected vision is uncommon, but it cannot be reduced to zero.

Chronic Ocular Pain

A small number of patients develop persistent burning, aching or light sensitivity despite limited visible surface damage.

This may reflect:

Severe dry eye
Corneal nerve dysfunction
Neuropathic corneal pain
Central pain sensitisation

Risk may be more relevant in patients with:

Pre-existing chronic pain
Migraine
Fibromyalgia
Anxiety or depression
Severe dry-eye symptoms
Contact-lens intolerance

Persistent pain deserves specialist assessment and should not be dismissed merely because the cornea appears relatively normal.

Does LASIK Cause Cataracts?

LASIK reshapes the cornea and does not directly remove or replace the natural lens.

It does not prevent age-related cataract formation.

A patient who undergoes LASIK may still require cataract surgery later.

Cataract Surgery After LASIK

Previous LASIK changes the relationship between the front and back surfaces of the cornea.

This can make intraocular lens power calculation more challenging.

Patients should keep:

Their original spectacle prescription
Pre-LASIK corneal measurements
Operative records
Laser treatment details

Modern post-refractive formulas and tomography improve accuracy, but refractive prediction remains less straightforward than in an untreated cornea.

Eye-Pressure Measurement After LASIK

LASIK makes the central cornea thinner and flatter in myopic treatments.

Conventional applanation pressure readings may therefore underestimate true intraocular pressure.

This is particularly important in:

Glaucoma suspects
Patients with a strong family history
High myopes
Patients requiring steroid treatment

Future eye-care providers should be informed about the refractive surgery history.

Does LASIK Cause Retinal Detachment?

LASIK treats the cornea, not the retina.

Patients with high myopia may already have an increased lifetime risk of:

Retinal tears
Retinal detachment
Myopic macular degeneration
Other retinal complications

Correcting the spectacle prescription does not remove the underlying retinal risk.

New flashes, floaters or a curtain-like shadow require urgent retinal assessment whether or not LASIK has been performed.

LASIK Versus PRK

PRK removes the surface epithelium and applies the excimer laser without creating a permanent stromal flap.

Advantages of LASIK

Faster visual recovery
Less early discomfort
Lower risk of corneal haze
Rapid return to work

Advantages of PRK

No flap-related complications
More residual stromal tissue in selected eyes
May be preferred for certain corneas or occupations
May be preferable when trauma risk is high

Limitations of PRK

More discomfort during early healing
Slower visual recovery
Risk of haze
Longer medication course
Greater early fluctuation

Comparative studies generally find that both procedures can produce effective long-term vision in appropriately selected patients, with LASIK offering faster recovery.

LASIK Versus SMILE

SMILE removes a laser-created stromal lenticule through a small incision without creating a LASIK flap.

Randomised-trial meta-analysis found similar overall efficacy, safety and predictability between SMILE and femtosecond LASIK for myopia.

Possible Advantages of LASIK

Faster initial visual recovery
Flexible customised excimer profiles
Established eye tracking and cyclotorsion compensation
Straightforward treatment of selected residual errors

Possible Advantages of SMILE

No flap
Smaller corneal incision
Better early preservation of corneal sensitivity
Less disruption of some corneal nerves
Potentially fewer early dry-eye effects

Recent meta-analysis found better tear stability and corneal-sensitivity preservation after lenticule extraction than after femtosecond LASIK, although both procedures may cause temporary dry eye.

The choice depends on the eye, prescription, available platform, surgeon experience and patient priorities.

LASIK Versus ICL

An implantable collamer lens is placed inside the eye without removing the natural lens.

It may be considered for:

High myopia
Thin corneas
Corneas unsuitable for laser ablation
Patients seeking high optical quality
Prescriptions outside an appropriate LASIK range

Advantages of LASIK

No intraocular implant
Rapid recovery
No risk of intraocular lens-related cataract or vault problems
No intraocular surgery

Advantages of ICL

No removal of corneal stromal tissue
Suitable for higher prescriptions
Potentially better optical quality in selected high myopes
Removable or exchangeable

Randomised-trial reviews have found phakic lenses to be competitive with, and in selected moderate-to-high myopia safer than, excimer-laser correction over short-term follow-up. However, ICL introduces separate intraocular risks and requires long-term monitoring.

Is LASIK Suitable for Athletes?

LASIK may be suitable for many athletes.

However, patients involved in:

Boxing
Martial arts
Rugby
Combat sports
Activities involving facial impact

should discuss the permanent flap and alternative flap-free procedures such as PRK or SMILE.

Protective eyewear remains important after any refractive procedure.

Is LASIK Suitable for Pilots or Military Personnel?

Occupational standards vary.

Patients should confirm the requirements of their:

Employer
Licensing body
Military service
Aviation authority
Professional organisation

before surgery.

The FDA specifically advises patients to ensure that refractive surgery will not jeopardise occupational eligibility.

Can LASIK Be Reversed?

LASIK is not considered fully reversible.

The flap can be lifted, but the corneal tissue removed by the excimer laser cannot simply be replaced.

Residual refractive error may sometimes be adjusted through:

Additional laser treatment
Spectacles
Contact lenses
Intraocular procedures

The original untreated cornea cannot be completely restored.

Can LASIK Treat Very High Myopia?

Technically treating a prescription does not necessarily mean that doing so is the best option.

Higher corrections require:

More tissue removal
A larger biomechanical effect
Greater concern about regression
More careful optical-zone planning
More stringent ectasia screening

Historical studies of very high myopia showed substantial long-term regression and higher enhancement rates. Modern practice often considers an ICL rather than LASIK when the prescription is high or the cornea is not ideal.

Common Myths

“LASIK Guarantees Perfect Vision”

False.

Most suitable patients achieve good unaided vision, but residual prescription and optical symptoms remain possible.

“LASIK Prevents Presbyopia”

False.

The natural lens continues ageing.

Reading spectacles or monovision may eventually be needed.

“The Laser Can Slip if I Move”

Modern lasers use rapid eye tracking.

The laser can pause when alignment is lost.

The patient should still cooperate with fixation instructions.

“The Eye Can Be Accidentally Burned”

False.

The excimer laser reshapes tissue through photoablation rather than thermal burning.

“LASIK Wears Off After Ten Years”

Not exactly.

The removed tissue does not simply return, but the eye may change because of ageing, myopic progression, regression or cataract.

“Anyone with a Thin Cornea Should Have SMILE Instead”

False.

SMILE also alters corneal tissue and biomechanics.

A thin or suspicious cornea requires a complete assessment rather than automatic substitution of one procedure for another.

“LASIK Is Safer Than Contact Lenses for Everyone”

Not necessarily.

Both contact lenses and surgery have risks.

The comparison depends on contact-lens hygiene, wear duration, ocular surface, prescription and surgical suitability.

“Dry Eye Always Goes Away”

False.

Most cases improve, but persistent dry eye or neuropathic symptoms can occur.

“A Newer Laser Guarantees a Better Result”

False.

Outcomes depend on:

Patient selection
Measurements
Treatment planning
Surgeon experience
Ocular-surface management
Postoperative care

Frequently Asked Questions

Am I Too Short-Sighted for LASIK?

Suitability depends on more than the spectacle number.

The surgeon must consider:

Corneal thickness
Corneal shape
Optical-zone size
Residual stromal bed
Age
Retinal health
Alternative treatments

Can Astigmatism Be Fully Corrected?

Regular astigmatism can often be treated effectively.

A small residual amount may remain.

Irregular astigmatism may require a different approach.

Can Both Eyes Have Different Treatments?

Yes.

In selected patients, one eye may undergo a different treatment profile or even a different procedure because of differences in:

Corneal shape
Prescription
Thickness
Visual target
Ocular health

Can I Have LASIK Again?

An enhancement may be possible if:

The residual error is stable
The cornea remains suitable
The flap and ocular surface are healthy
The benefit justifies the risk

Surface ablation may be preferred to lifting an old flap in selected patients.

How Long Should I Wait Before an Enhancement?

The prescription should be stable.

This often requires at least several months and sometimes longer, depending on:

Type of correction
Healing
Dry eye
Degree of residual error
Corneal thickness

Will LASIK Change My Eye Colour?

No.

The laser reshapes the transparent cornea and does not change iris pigmentation.

Will I See the Laser?

The patient sees fixation lights and brightness but does not usually see the surgical detail clearly.

What Happens if I Blink?

An eyelid holder prevents blinking during the critical part of the procedure.

What Happens if I Look Away?

The eye tracker follows small eye movements.

The laser pauses if alignment is outside the permitted range.

Can I Rub My Eyes After LASIK?

Eye rubbing should be avoided during early recovery.

Long-term vigorous eye rubbing should also be discouraged because it can:

Injure the flap
Worsen allergy-related inflammation
Stress the cornea
Contribute to ectatic change in susceptible eyes

When Can I Wash My Face?

Gentle facial washing is generally possible, but water, soap and pressure should be kept away from the eyes during the early postoperative period.

Follow the surgeon’s specific instructions.

When Can I Resume Contact Sports?

This depends on the sport and healing.

Sports involving direct eye or facial trauma require a longer precautionary period and protective eyewear.

Can LASIK Cause Blindness?

Severe permanent visual loss is very rare.

It may result from complications such as:

Infection
Severe ectasia
Corneal scarring
Uncontrolled inflammation
Other unrelated ocular disease

The possibility is small but not zero.

Will I Need Reading Glasses?

Patients approaching or beyond the presbyopic age should expect near vision to become an issue unless monovision or another presbyopia strategy is selected.

Even with monovision, spectacles may be needed for fine print or prolonged near work.

Is LASIK Better Before or After Pregnancy?

It is generally better performed when the patient is not pregnant or breastfeeding and the prescription has stabilised.

Can I Have Cataract Surgery Later?

Yes.

The cataract surgeon should know that LASIK was performed and should use appropriate post-refractive lens-calculation methods.

Does LASIK Affect Future Glaucoma Testing?

It may affect interpretation of eye-pressure readings and certain corneal biomechanical measurements.

Optic-nerve imaging and visual-field testing remain important.

Can LASIK Correct Lazy Eye?

No.

LASIK can correct the optical prescription, but it does not reverse amblyopia that developed during childhood.

The final vision is limited by the eye’s established visual potential.

When to Seek Urgent Eye Care After LASIK

Seek urgent assessment for:

Increasing pain
Increasing redness
Rapidly worsening vision
Thick discharge
Marked light sensitivity
A white spot on the cornea
Sudden flap displacement
Trauma to the eye
Vision that becomes worse after initially improving
New flashes or floaters
A curtain or shadow

Severe pain or worsening vision should never be assumed to be normal dry eye.

A LASIK Assessment Checklist

Visual Goals to Discuss

Distance vision
Near vision
Computer distance
Night driving
Sports
Occupational requirements
Spectacle independence
Monovision
Tolerance of glare or halos

Medical Information to Report

Diabetes
Autoimmune disease
Thyroid disease
Pregnancy or breastfeeding
Migraine
Chronic pain
Allergies
Medication
Previous healing problems

Eye History to Report

Dry eye
Contact-lens intolerance
Eye rubbing
Keratoconus in the family
Herpetic eye disease
Glaucoma
Retinal tears
Eye trauma
Previous eye surgery
Recurrent corneal erosion

Tests That May Be Used

Unaided and corrected vision
Manifest refraction
Cycloplegic refraction
Corneal topography
Corneal tomography
Pachymetry
Epithelial mapping
Wavefront aberrometry
Tear-film testing
Pupil measurement
Eye-pressure measurement
Dilated retinal examination

Questions to Ask the Surgeon

Am I genuinely suitable for LASIK?
Is my corneal tomography completely normal?
Is the prescription stable?
How much corneal tissue will remain?
Would PRK, SMILE or ICL be safer?
Which treatment profile will be used?
What visual result is realistic?
How likely am I to need reading spectacles?
Should I consider monovision?
What is my risk of dry eye?
What is my risk of ectasia?
What happens if residual prescription remains?
What symptoms require urgent review?
How frequently will I be examined afterwards?

The Bottom Line

LASIK uses a femtosecond laser and an excimer laser to reshape the cornea and reduce refractive error.

It may treat:

Myopia
Hyperopia
Astigmatism
Presbyopia through monovision in selected patients

The procedure usually:

Takes only several minutes per eye
Causes little pain
Allows rapid visual recovery
Reduces dependence on spectacles or contact lenses

However, LASIK does not guarantee perfect vision.

Possible limitations include:

Residual refractive error
Future spectacle use
Presbyopia
Regression
Dry eye
Night-vision symptoms
Need for enhancement

Possible complications include:

Flap displacement
Flap folds
Epithelial ingrowth
Diffuse lamellar keratitis
Infection
Corneal ectasia
Rare loss of corrected vision
Persistent ocular pain

The quality of the result depends on:

Stable refraction
Healthy corneal shape
Adequate corneal thickness
A healthy ocular surface
Accurate measurements
Appropriate treatment selection
Realistic expectations
Careful postoperative follow-up

LASIK may not be the best procedure for every patient.

PRK may be preferable when avoiding a flap is important.

SMILE may offer advantages for selected myopic patients concerned about flap-related issues or early dry eye.

ICL may be more appropriate for high prescriptions or corneas unsuitable for laser treatment.

The most important message is:

The success of LASIK begins before the laser is used. A thorough assessment should determine not only whether LASIK is technically possible, but whether it is the safest and most appropriate vision-correction option for that individual eye.

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