SMILE vs PRK: Recovery, Suitability and the Differences Between Two Flapless Techniques

Author: Dr Val Phua
Estimated reading time: 22 minutes

SMILE and PRK are both forms of flapless laser vision correction.

Neither creates the large hinged corneal flap used in LASIK.

That similarity sometimes leads patients to assume that SMILE and PRK are essentially the same operation.

They are not.

They reshape the cornea in fundamentally different ways.

With SMILE:

A femtosecond laser creates a thin lens-shaped piece of tissue called a lenticule within the corneal stroma.
A small peripheral incision is created.
The surgeon removes the lenticule through this opening.
The corneal epithelium remains largely intact.

With PRK:

The central corneal epithelium is removed.
An excimer laser directly reshapes the anterior corneal stroma.
A bandage contact lens is placed.
The epithelium must regenerate over the following several days.

The difference explains many of the practical contrasts between the procedures.

SMILE generally offers:

Less early discomfort
Faster functional visual recovery
No large epithelial wound
No postoperative corneal-haze mechanism identical to PRK

PRK generally offers:

A very superficial treatment
No flap
No deep lenticule-dissection plane
Greater flexibility for customised excimer-laser treatments
Potential advantages in selected thinner corneas
A well-established role in surface enhancements and irregular corneal optical treatments

Modern studies show that both procedures can produce excellent final visual and refractive outcomes.

A 2026 meta-analysis comparing TransPRK with SMILE found no statistically significant difference in overall efficacy or safety, while predictability was broadly comparable. The authors concluded that procedure selection should be based more on patient characteristics, complication risk, available technology and surgeon experience than on the assumption that one technique is universally superior.

A direct randomised contralateral-eye trial comparing PRK and SMILE similarly found comparable:

Safety
Efficacy
Contrast sensitivity
Higher-order aberrations

at 18 months.

The important difference was early recovery: at one month, the PRK eyes reported worse vision and greater foreign-body sensation than the SMILE eyes.

The central message is:

SMILE and PRK can both provide excellent final vision. SMILE generally wins on comfort and speed of recovery, while PRK remains extremely valuable when a superficial, highly customisable corneal treatment is preferable.

The Quick Answer

What Is the Main Difference Between SMILE and PRK?

SMILE works inside the cornea.

PRK works from the surface of the cornea.

SMILE creates and removes an internal stromal lenticule through a small incision.

PRK removes the epithelium and uses an excimer laser directly on the anterior stromal surface.

Are Both Truly Flapless?

Yes.

Neither creates a LASIK flap.

However, “flapless” does not mean the operations affect the cornea in the same way.

SMILE creates:

An internal lenticule
An overlying corneal cap
A small access incision

PRK creates:

A large temporary epithelial defect
A superficial stromal ablation

The healing biology is therefore very different.

Which Has Faster Recovery?

SMILE.

This is probably the most obvious difference for patients.

After SMILE, many patients have useful vision by the following day.

After PRK:

The epithelium must regrow.
Pain and light sensitivity are common for several days.
A bandage contact lens is required.
Vision improves more gradually over the following weeks.

Direct comparison studies show better early visual quality after SMILE, while the difference generally diminishes with time.

Which Is More Painful?

PRK.

SMILE generally causes relatively mild:

Grittiness
Watering
Light sensitivity
Irritation

during early recovery.

PRK commonly produces:

Burning
Stinging
Significant tearing
Foreign-body sensation
Light sensitivity

particularly during the first 24 to 72 hours.

The pain improves as the epithelium closes.

Which Gives Better Final Vision?

For appropriately selected patients:

both can give excellent final vision.

A recent meta-analysis found no significant overall difference in efficacy between TransPRK and SMILE.

A 2025 study comparing low myopia treated with PRK or SMILE likewise found:

Similar refractive outcomes
Similar corrected visual acuity
Similar overall corneal higher-order aberrations

at six months.

Which Is Better for Thin Corneas?

Sometimes PRK.

But this requires careful explanation.

PRK removes tissue from the anterior surface without creating:

A LASIK flap
A relatively deep SMILE cap plane

This can make it attractive when the available corneal tissue is limited.

However:

A thin or suspicious cornea is not automatically safe for PRK.

The surgeon must still assess:

Corneal tomography
Thickness distribution
Posterior elevation
Degree of refractive correction
Ectasia risk

An eye with keratoconus or suspicious ectatic features may be unsuitable for both procedures.

Which Is Better for Contact Sports?

Both are attractive because neither leaves a LASIK flap.

For:

Boxing
Martial arts
Rugby
Military activity
High-impact occupations

both SMILE and PRK remove the concern of late traumatic LASIK flap displacement.

SMILE has the practical advantage of faster recovery.

PRK has decades of use in environments where avoidance of a flap is important.

Which Causes Less Dry Eye?

Both can cause temporary dryness.

SMILE preserves the central epithelium and uses a relatively small incision, so it generally disrupts fewer superficial corneal nerves than larger-incision refractive procedures. Reviews also suggest less corneal denervation after SMILE than after PRK or LASIK, although the direct SMILE-versus-PRK dry-eye evidence is smaller than the extensive SMILE-versus-LASIK literature.

PRK initially removes:

Epithelium
Superficial nerve endings

so temporary changes in:

Corneal sensitivity
Tear-film regulation
Dry-eye symptoms

may occur during healing.

Neither procedure should be used as a substitute for treating significant pre-existing dry-eye disease.

A Note About SMILE Pro

The fundamental comparison in this article applies to both traditional SMILE and newer SMILE Pro.

SMILE Pro uses the newer ZEISS VISUMAX 800 platform.

The principle remains:

Create a lenticule within the cornea.
Remove it through a small incision.

The newer platform improves the delivery of the treatment through:

Faster lenticule creation
Centration assistance
Cyclotorsion compensation for astigmatism

Singapore National Eye Centre currently describes SMILE Pro as a small-incision, flapless treatment with lenticule creation in under approximately 10 seconds using the VISUMAX 800.

The comparison with PRK therefore remains biologically the same:

SMILE Pro = internal lenticule extraction.

PRK = surface excimer-laser ablation.

How SMILE Works

Step 1: Anaesthetic Drops

The eye is numbed using topical anaesthetic.

The patient remains awake.

Step 2: The Eye Is Docked to the Femtosecond Laser

The eye is aligned beneath the laser.

Gentle suction stabilises the cornea.

Step 3: The Lenticule Is Created

The femtosecond laser creates:

A posterior lenticule surface
An anterior lenticule surface
A lenticule edge
A small access incision

Step 4: The Surgeon Separates the Lenticule

Fine instruments are passed through the incision.

The surgeon separates the lenticule from the surrounding stromal tissue.

Step 5: The Lenticule Is Removed

The lenticule is extracted through the small incision.

This alters the curvature of the cornea.

For myopia, the central cornea becomes flatter.

Step 6: The Small Incision Heals

No stitches are normally required.

The central epithelium has not been removed, so there is no large epithelial defect requiring several days to close.

How PRK Works

Step 1: Anaesthetic Drops

The corneal surface is numbed.

Step 2: The Epithelium Is Removed

The central epithelium may be removed:

Mechanically
Using dilute alcohol
With the excimer laser in TransPRK

Step 3: The Excimer Laser Reshapes the Cornea

The laser directly ablates the anterior corneal stroma.

For myopia, the central cornea is flattened.

Step 4: Mitomycin C May Be Used

In selected cases, mitomycin C is applied briefly to reduce the postoperative wound-healing response and risk of clinically significant haze.

A meta-analysis of 3,536 eyes found strong evidence that mitomycin C reduces both early and late corneal haze after PRK.

Step 5: A Bandage Contact Lens Is Placed

The contact lens:

Protects the exposed cornea
Reduces eyelid friction
Improves comfort
Supports epithelial healing

It is normally removed after the surgeon confirms that the surface has adequately healed.

What Is TransPRK?

TransPRK is a variation of PRK in which the excimer laser removes both:

The epithelium
The underlying stromal tissue

without separate mechanical epithelial removal.

It may be called:

Transepithelial PRK
TransPRK
No-touch PRK
All-laser surface ablation

A 2025 meta-analysis involving more than 10,000 eyes found no significant difference in overall visual efficacy or safety between TransPRK and conventional PRK, although modern TransPRK may offer workflow and early-recovery advantages depending on the platform.

TransPRK is still PRK biologically.

The surface epithelium is removed and must regenerate.

SMILE vs PRK: At a Glance

Feature	SMILE / SMILE Pro	PRK / TransPRK
LASIK flap	No	No
Main mechanism	Lenticule extraction	Excimer ablation
Central epithelium removed	No	Yes
Large epithelial wound	No	Yes, temporary
Bandage contact lens	Usually no	Yes
Early pain	Usually mild	Greater
Visual recovery	Faster	Slower
Haze risk	No classic PRK haze response	Recognised risk
Mitomycin C	Not routine	Often used when indicated
Dry-eye symptoms	Possible	Possible
Customised excimer treatment	Limited	Strong advantage
Topography-guided treatment	Not in the same way	Available on suitable platforms
Contact sports	Attractive	Attractive
Enhancement strategy	Often PRK/CIRCLE	Repeat surface treatment may be possible
Hyperopia	Platform-dependent	Can be treated on appropriate excimer platforms
Ectasia	Rare but possible	Rare but possible

Recovery: The Biggest Practical Difference

Immediately After SMILE

Patients commonly notice:

Misty vision
Mild watering
Grittiness
Light sensitivity

Vision is usually already substantially improved.

Immediately After PRK

Vision is also improved compared with unaided preoperative vision, but the eye is commonly:

Watery
Sensitive
Painful
Hazy

The bandage lens remains in place.

Day 1 After SMILE

Many patients have good functional vision.

Some can:

Work
Use screens
Perform ordinary daily tasks

although vision may still be mildly hazy.

Day 1 After PRK

The first few days are primarily about surface healing.

Patients may experience:

Significant tearing
Burning
Stinging
Photophobia
Blurred vision
Difficulty keeping the eyes open

Days 2–3 After SMILE

Vision commonly continues to sharpen.

Discomfort is usually mild.

Days 2–3 After PRK

This may still be the most uncomfortable part of recovery.

The epithelium is migrating across the treatment zone.

Days 3–5 After PRK

The epithelium commonly closes sufficiently for consideration of bandage-lens removal.

The exact timing varies.

Once epithelial closure occurs:

Pain usually improves rapidly.
Light sensitivity reduces.
Vision may remain blurred.

Week 1 After SMILE

Most patients have:

Good functional vision
Little discomfort

Possible remaining symptoms include:

Dryness
Mild glare
Halos
Slight fluctuation

Week 1 After PRK

Comfort is usually much better.

Vision may still be:

Variable
Hazy
Less crisp
Sensitive to dry eye

Weeks 2–4

The difference begins narrowing.

SMILE vision usually continues to refine.

PRK vision frequently improves substantially during this period.

A 2024 comparison of SMILE with high-frequency TransPRK found superior unaided acuity and objective optical quality with SMILE at one week and one month, but both achieved excellent visual outcomes by six months.

Three to Six Months

For uncomplicated eyes, final visual outcomes are generally much more similar than the early recovery experience suggests.

A direct 18-month randomised trial found PRK and SMILE comparable in:

Visual acuity
Efficacy
Safety
Contrast sensitivity
Wavefront aberrations

despite the more difficult early PRK recovery.

Which Should I Choose if I Need to Return to Work Quickly?

SMILE usually has the advantage.

This may matter if you:

Cannot take several days off
Drive for work
Have high screen demands
Need predictable early functional vision
Have an upcoming examination or professional commitment

PRK should not ideally be scheduled immediately before an important event where visual performance is critical.

Pain: SMILE vs PRK

Why PRK Hurts More

Corneal nerves are densely concentrated near the surface.

Removing the epithelium exposes and disturbs these superficial nerve endings.

Until the epithelium closes, this may produce substantial discomfort.

Why SMILE Is Usually More Comfortable

The central epithelial surface remains intact.

The access incision is small.

There is therefore no large exposed central wound.

Does PRK Pain Mean Something Is Wrong?

No.

Pain during the first few days can be part of normal healing.

However, seek prompt assessment for:

Increasing pain after initial improvement
Marked redness
Significant discharge
Falling vision
A visible white corneal spot

These may indicate infection or another complication.

Dry Eye

SMILE and Corneal Nerves

SMILE preserves much of the anterior corneal surface.

The small incision transects fewer anterior nerve fibres than a large LASIK flap, and the technique has generally shown favourable early corneal-sensation recovery.

PRK and Corneal Nerves

PRK directly removes the epithelial and subepithelial nerve endings across the treatment zone.

These regenerate over time.

The result may be temporary:

Reduced corneal sensitivity
Tear-film instability
Dryness
Fluctuating vision

Which Is Better for Someone with Dry Eye?

SMILE may offer a recovery advantage in some patients.

However, significant pre-existing dry-eye disease should be treated before either procedure.

The decision may also depend on:

Meibomian-gland health
Allergy
Contact-lens intolerance
Screen use
Corneal anatomy

Corneal Haze: A PRK-Specific Consideration

What Is Haze?

Corneal haze is increased light scattering within the healing anterior stroma.

It results from the corneal wound-healing response after surface ablation.

Symptoms may include:

Foggy vision
Glare
Halos
Reduced contrast
Refractive regression

Does SMILE Cause Haze?

SMILE does not produce the same surface-ablation healing response.

Classic postoperative PRK haze is therefore not a characteristic SMILE complication.

Interface-related inflammation can occur after SMILE, but this is a different process.

How Common Is Significant PRK Haze Today?

Clinically important haze is much less common than during the early years of PRK because of:

Improved laser profiles
Better postoperative treatment
More appropriate patient selection
Mitomycin C

The evidence strongly supports mitomycin C for reducing haze in appropriate PRK treatments.

Who Has Greater Haze Risk?

Risk tends to increase with:

Greater ablation depth
Higher myopic correction
Strong wound-healing response
Significant UV exposure
Certain treatment parameters

This is one reason very high myopic corrections are not automatically ideal for PRK.

Corneal Biomechanics: Which Is Stronger?

This is more complicated than marketing slogans suggest.

Because SMILE has no LASIK flap, it is often described as biomechanically strong.

That comparison is most intuitive when SMILE is compared with LASIK.

The comparison with PRK is different.

PRK Is Also Flapless

PRK does not create:

A LASIK flap
A deep corneal cap

It removes tissue from the anterior surface.

What Do Direct Studies Show?

A 2025 randomised comparison of PRK and SMILE in low-to-moderate myopia found:

Comparable visual outcomes
Comparable epithelial remodelling
Comparable higher-order aberrations

but several measured biomechanical indices changed more after SMILE.

The authors concluded that PRK demonstrated greater biomechanical stability in their study population.

A separate matched one-year study likewise found a greater residual stromal-bed proportion after PRK and smaller changes in several biomechanical measurements.

Other experimental work has found no significant difference in measured elastic properties between PRK and SMILE.

The responsible conclusion is therefore:

There is no justification for claiming that SMILE is universally biomechanically superior to PRK.

The structural effect depends on:

Treatment depth
Cap depth
Optical zone
Prescription
Corneal thickness
Individual anatomy

Which Removes More Tissue?

This cannot be answered simply from the name of the operation.

The amount and distribution of tissue affected depend on:

Prescription
Optical zone
Transition zone
SMILE cap parameters
Minimum lenticule thickness
Excimer ablation profile

For a particular patient, the surgeon should calculate the actual expected tissue architecture rather than assuming one procedure is automatically more tissue-saving.

Thin Corneas

PRK is often considered when the cornea is too thin for LASIK because it avoids flap creation.

It may also be preferable to SMILE for certain low-to-moderate corrections when a more superficial structural approach is advantageous.

However:

Corneal thickness alone is never enough to establish safety.

A thin cornea with:

Abnormal posterior elevation
Inferior steepening
Abnormal pachymetric progression
Keratoconus features

may be unsuitable for all routine corneal refractive surgery.

Keratoconus and Ectasia

Can SMILE Cause Ectasia?

Yes, rarely.

Can PRK Cause Ectasia?

Yes, rarely.

A systematic review estimated reported ectasia rates in eyes without identifiable preoperative risk factors at approximately:

20 per 100,000 PRK eyes
11 per 100,000 SMILE eyes

However, these numbers were calculated from reported cases and estimated surgical volumes rather than a prospective registry, and SMILE had substantially less historical follow-up at the time.

These figures should therefore not be treated as exact individual probabilities.

The most important determinant is good preoperative screening.

Can PRK Be Done if LASIK or SMILE Is Unsafe Because of Keratoconus?

Not simply because it is surface surgery.

Untreated keratoconus is a corneal structural disorder.

Removing tissue from a biomechanically abnormal cornea may worsen instability.

Selected specialised procedures combining topography-guided treatment and cross-linking are a different clinical situation and should not be confused with routine refractive PRK.

Visual Quality

Is One Procedure Sharper?

Not universally.

Visual quality depends on:

Residual prescription
Astigmatism
Treatment centration
Tear film
Optical zone
Pupil size
Higher-order aberrations

Higher-Order Aberrations

A 2025 comparison of low-myopia PRK and SMILE found no significant difference in overall postoperative corneal aberrations.

In moderate-to-high myopia, a 2024 study found:

Better early optical quality after SMILE
Less coma after TransPRK later in follow-up
Less spherical aberration after SMILE at some later time points

demonstrating that each technique can have different optical strengths.

A separate 2025 study found TransPRK had lower total higher-order aberrations and better low-light contrast than SMILE at six months, although differences in optical-zone design may have contributed.

Therefore:

There is no credible basis for claiming that either SMILE or PRK universally produces better night vision.

Astigmatism

Both can correct myopic astigmatism.

PRK

Modern excimer-laser platforms may incorporate:

Eye tracking
Cyclotorsion compensation
Wavefront optimisation
Wavefront guidance
Topography guidance

This can provide considerable flexibility.

SMILE

Astigmatism is incorporated into lenticule geometry.

First-generation SMILE showed some tendency towards astigmatic under-correction in pooled studies, particularly with higher cylinder.

Modern SMILE Pro addresses this through:

OcuLign cyclotorsion compensation
CentraLign-assisted positioning

so older SMILE astigmatism studies may underestimate current performance.

Customisation: An Important PRK Advantage

This is one of PRK’s major strengths.

Because PRK uses an excimer laser directly on the corneal surface, treatment can potentially be:

Wavefront-optimised
Wavefront-guided
Topography-guided

depending on the laser platform.

When Might Topography-Guided PRK Be Useful?

Selected situations include:

Irregular corneal optics
Previous refractive-surgery problems
Decentered ablations
Selected enhancement cases

Topography-guided PRK has even been used to treat symptomatic irregularity following previous SMILE, although haze prevention becomes important.

SMILE does not currently provide the same point-by-point corneal-surface ablation flexibility.

High Myopia

Both procedures can treat substantial myopia in appropriately selected eyes.

However, increasing correction changes the risk-benefit calculation.

High Myopia and PRK

Larger excimer ablations may increase:

Haze risk
Regression
Tissue removal
Healing variability

Historical 10-year PRK studies found substantially greater regression and retreatment after treatment of myopia above -6.00 D than after lower corrections.

Those studies used older laser technology, so the exact numbers should not be applied directly to modern PRK.

The biological principle remains relevant.

High Myopia and SMILE

SMILE can treat high myopia in suitable corneas.

Long-term studies have demonstrated favourable results up to approximately -10.00 D, with a 10-year study finding 81% within ±0.50 D and 94% within ±1.00 D of target among the eyes reviewed.

However, higher SMILE correction requires a thicker lenticule.

Should ICL Be Considered?

Yes.

As myopia increases, ICL deserves increasingly serious consideration because it:

Preserves corneal stromal tissue
Avoids large corneal curvature changes
Can provide excellent optical quality in high myopia

The question should therefore not be:

“SMILE or PRK?”

when a third option may be anatomically more suitable.

Low Myopia

Both PRK and SMILE can perform extremely well for low myopia.

A 2025 direct comparison of eyes between approximately -1.00 and -2.00 D found both procedures safe and effective with comparable six-month visual quality.

For low myopia, procedure choice may depend more on:

Recovery expectations
Corneal thickness
Customisation needs
Cost
Surgeon preference

than on final visual acuity.

Hyperopia

PRK can treat selected hyperopic prescriptions using appropriate excimer-laser platforms.

Traditional SMILE was primarily used for:

Myopia
Myopic astigmatism

The newer VISUMAX 800 platform now supports hyperopic lenticule extraction in some jurisdictions, but availability and regulatory approval vary.

PRK remains the more historically established surface-laser option for hyperopic treatment.

Contact and Combat Sports

Both procedures are flapless.

This removes the specific concern of traumatic LASIK flap displacement.

SMILE may be attractive when:

Rapid return to daily function matters.
Contact sports are part of the patient’s lifestyle.

PRK may be attractive when:

Maximum flap avoidance is desired.
A superficial treatment is anatomically preferable.
Longer recovery is acceptable.

Neither operation eliminates the need for protective eyewear.

Military and High-Impact Occupations

PRK has historically been widely used in military and aviation refractive programmes because it creates no flap.

SMILE offers another flapless approach with:

Less postoperative pain
Faster functional recovery

Current occupational standards vary.

Patients should check the medical requirements of their military, aviation or professional authority before surgery.

Enhancement After SMILE

If meaningful residual refractive error remains after SMILE, enhancement options may include:

PRK
CIRCLE
LASIK-type strategies in selected cases

PRK is therefore a common way to perform a surface enhancement after SMILE.

Enhancement After PRK

Repeat surface ablation may sometimes be possible after PRK.

Suitability depends on:

Remaining corneal thickness
Tomography
Residual prescription
Previous haze response
Stability

Repeated corneal surgery should never be automatic simply because some small prescription remains.

Is Enhancement Easier After PRK?

Not necessarily.

The strategy depends on:

What surgery was performed first
Corneal anatomy
Residual prescription
Time since surgery

SMILE does not have a conventional LASIK flap available for straightforward relifting.

PRK does not have a flap either.

Both therefore require individualised retreatment planning.

Infection

Infection is rare after both procedures.

PRK

The early infection concern is particularly relevant while:

The epithelium remains open
A bandage contact lens is present

SMILE

The epithelial barrier remains largely intact, but infection can still occur within the small incision or interface.

Seek prompt assessment after either procedure for:

Increasing pain
Increasing redness
Light sensitivity
Discharge
Falling vision
A white corneal spot

Returning to Exercise

SMILE

Light exercise may resume relatively quickly once the surgeon is satisfied.

PRK

More caution is required during the first few days while:

The surface is healing
The bandage contact lens remains in place

Swimming

Avoid swimming after either procedure during early healing.

This includes:

Pools
Sea water
Hot tubs

The risk is particularly important after PRK while the epithelial barrier remains incomplete.

Showering

You may usually shower carefully.

Avoid:

Direct water spray into the eyes
Shampoo
Soap
Rubbing

during early recovery.

Screens

Screens do not damage either laser correction.

After PRK, screen use may simply be uncomfortable during the first few days.

After SMILE, many people resume screen use quickly.

For both:

Blink frequently.
Use prescribed lubricants.
Take breaks.

Driving

Do not decide based simply on the number of days after surgery.

Drive when:

Visual acuity is adequate.
Glare is acceptable.
Vision feels stable.
You are confident.
The postoperative examination is satisfactory.

SMILE patients often reach this stage sooner than PRK patients.

Does Either Procedure Prevent Presbyopia?

No.

Presbyopia results from ageing of the natural crystalline lens.

A patient with excellent distance vision after SMILE or PRK may still need reading glasses later.

Does Either Procedure Prevent Cataract?

No.

Both affect the cornea.

Neither prevents the natural lens from ageing.

Does Either Procedure Affect Future Cataract Surgery?

Yes.

Both alter corneal curvature.

Future cataract-surgery calculations therefore need to account for previous corneal refractive surgery.

Tell your cataract surgeon whether you previously underwent:

PRK
TransPRK
SMILE
SMILE Pro

Retaining old refractive records may be useful.

Does Either Procedure Remove the Retinal Risks of High Myopia?

No.

This is extremely important.

A patient may have been:

-8.00 D before surgery

and see:

6/6 without glasses afterwards.

The eyeball may still remain elongated.

The patient still has increased lifetime risk of:

Retinal tear
Retinal detachment
Myopic macular degeneration
Myopic choroidal neovascularisation

Laser surgery corrects the optics.

It does not shorten the eye.

Long-Term Results

Both procedures have reassuring long-term data.

PRK

PRK has been performed for several decades.

Ten-year studies confirm durable safety, although higher corrections show greater long-term regression than lower corrections.

SMILE

SMILE now also has follow-up extending to ten years.

Long-term cohorts report:

Good efficacy
Good safety
Relatively small average regression

over a decade.

SMILE Pro itself is newer.

The long-term biological evidence comes from established SMILE, while the newer platform improves the way the procedure is delivered.

Common Myths

“SMILE and PRK Are the Same Because Both Are Flapless”

False.

SMILE is an intrastromal lenticule-extraction procedure.

PRK is a surface-ablation procedure.

“Flapless Means No Corneal Wound”

False.

PRK intentionally creates a large temporary epithelial wound.

SMILE creates a small incision and internal stromal planes.

“SMILE Has No Recovery Time”

False.

Recovery is rapid, but vision still requires time to stabilise.

“PRK Takes Six Months Before You Can See”

False.

Useful vision generally returns far sooner.

Fine stabilisation may continue for months.

“PRK Is Old Technology”

False.

The original principle is older, but modern PRK may use:

Advanced excimer profiles
High-speed eye tracking
TransPRK
SmartPulse or similar surface optimisation
Wavefront guidance
Topography guidance

“SMILE Is Automatically Better Because It Is Newer”

False.

“SMILE Is Always Stronger Than PRK”

Not supported.

Modern direct biomechanical studies show that PRK may preserve several measured biomechanical parameters at least as well as—and sometimes better than—SMILE.

“PRK Is Always Better for Thin Corneas”

False.

Corneal tomography matters as much as thickness.

“SMILE Cannot Cause Ectasia”

False.

“PRK Cannot Cause Ectasia”

False.

Both require proper keratoconus screening.

“PRK Always Causes Haze”

False.

Clinically significant haze is uncommon with modern treatment and appropriate mitomycin C use.

“SMILE Causes No Dry Eye”

False.

“PRK Permanently Damages Corneal Nerves”

False.

Corneal nerves regenerate gradually after surgery.

“SMILE Always Gives Better Night Vision”

False.

Optical studies show advantages and disadvantages for each procedure depending on:

Treatment profile
Optical zone
Prescription
Pupil size

“PRK Is Better for Every Athlete”

Not necessarily.

SMILE is also flapless and offers much faster early recovery.

“Once the Surgery Is Done, My Myopia Cannot Return”

False.

Regression or natural refractive progression may occur.

“Laser Surgery Removes the Risks of High Myopia”

False.

Retinal risks remain.

Frequently Asked Questions

Which Is Safer: SMILE or PRK?

Both have excellent safety records in properly selected patients.

Their risks differ.

SMILE avoids:

Large epithelial defects
PRK-type haze

PRK avoids:

Lenticule-dissection complications
A deeper internal cap/lenticule architecture

Patient selection matters more than declaring one universally safer.

Which Gives Better 6/6 Vision?

Both commonly achieve excellent unaided vision.

Current comparative evidence does not demonstrate a meaningful universal difference in final efficacy.

Which Recovers Faster?

SMILE.

Which Hurts More?

PRK.

How Long Does PRK Hurt?

Discomfort is usually greatest during the first 24 to 72 hours and improves substantially as the epithelium closes.

How Long Does SMILE Hurt?

Most patients experience only mild discomfort during the first day.

Which Is Better for Dry Eye?

SMILE may offer an early nerve-preservation advantage.

Significant dry-eye disease should be treated before either operation.

Which Is Better for Night Vision?

Neither universally.

Optical-zone design, centration, pupil size and residual refractive error may matter more.

Which Is Better for High Astigmatism?

Modern excimer PRK offers excellent astigmatic flexibility.

Modern SMILE Pro has improved astigmatic alignment through cyclotorsion compensation.

The individual cylinder and axis should guide the decision.

Can PRK Correct a Prescription SMILE Cannot?

Depending on the laser platform, PRK may offer greater flexibility for:

Hyperopia
Customised treatments
Certain irregular optical patterns

Which Is Better for -2.00 D?

Both may work extremely well.

Recovery preferences and anatomy may drive the decision.

Which Is Better for -5.00 D?

Both remain reasonable in many normal corneas.

Which Is Better for -9.00 D?

SMILE may be preferable to PRK in some suitable corneas because of:

Faster recovery
Lower haze concern

but ICL should also be considered because the correction is high.

Can I Have PRK After SMILE?

Yes in selected cases.

Surface ablation is a recognised enhancement strategy after SMILE.

Can I Have SMILE After PRK?

This is less routine and requires careful assessment of:

Existing corneal thickness
Prior ablation
Tomography
Residual refractive error

Another enhancement strategy may be preferable.

Can I Have Cataract Surgery Later?

Yes after either procedure.

Does PRK Affect Eye-Pressure Measurements?

Yes.

Does SMILE Affect Eye-Pressure Measurements?

Yes.

Both change corneal:

Thickness
Curvature
Biomechanics

and may cause applanation-based eye-pressure readings to underestimate the true physiological pressure.

Can I Wear Contact Lenses Again?

Yes if needed after complete healing.

Previous corneal reshaping may affect the ideal lens design.

Which Is Better for Boxing?

Both avoid a LASIK flap.

SMILE may offer faster recovery.

PRK has a long history of use in high-impact populations.

Which Is Better for Military Service?

This depends on current military policy.

Check occupational standards before surgery.

Can I Swim Earlier After SMILE?

Usually yes compared with PRK, although swimming should still be avoided during the early postoperative period until the surgeon permits it.

Can I Work the Day After SMILE?

Some patients can.

Can I Work the Day After PRK?

It is generally unrealistic to plan on comfortable full-time work the following day.

Can PRK Vision Become Better Than SMILE Vision Eventually?

Both can achieve excellent final corrected and unaided acuity.

The difference is usually not best described as one becoming “better”.

Does TransPRK Recover as Fast as SMILE?

Usually not.

Modern TransPRK may improve early recovery compared with conventional PRK, but it still requires epithelial regeneration.

Warning Signs After SMILE

Contact the treating clinic promptly for:

Increasing pain
Increasing redness
Significant light sensitivity
Falling vision
Discharge
A white corneal spot

Warning Signs After PRK

The same warning signs apply.

Particular attention is warranted when symptoms:

improve and then become significantly worse.

This may indicate:

Infection
Epithelial breakdown
Significant inflammation

Retinal Warning Signs After Either Procedure

Seek urgent retinal assessment for:

New flashes
A sudden shower of floaters
A curtain or shadow
Sudden peripheral-field loss

These are especially important if you were highly myopic before surgery.

A SMILE vs PRK Decision Checklist

Your Prescription

How much myopia do I have?
How much astigmatism?
Is the prescription stable?
Is it sufficiently high that ICL should also be considered?

Your Cornea

Is my tomography completely normal?
How thick is the cornea?
What is the posterior corneal elevation?
Is there any ectasia concern?
How much tissue would each procedure affect?

Your Ocular Surface

Do I have dry eye?
Do I have meibomian-gland dysfunction?
Do I have allergy?
Do I rub my eyes?

Your Recovery Needs

How many days can I take off work?
Do I need to drive quickly?
Can I tolerate several uncomfortable days?
Do I have an important event soon?

Your Lifestyle

Do I participate in contact sports?
Do I work in dust or water?
Do I have military or aviation requirements?
Is night vision particularly important?

Your Optical Needs

Would I benefit from topography-guided treatment?
Do I have significant corneal aberrations?
Is a customised excimer treatment advantageous?

Questions to Ask the Surgeon

Why do you recommend SMILE rather than PRK for me?
Why PRK rather than SMILE?
Is my cornea structurally normal?
Which procedure leaves the better tissue profile in my particular cornea?
What is my haze risk?
Will mitomycin C be used with PRK?
How long should I take off work?
How quickly can I drive?
How would you enhance the result if some prescription remains?
Should I consider ICL instead?

Which Procedure Often Makes More Sense?

SMILE May Be Particularly Attractive When

Rapid recovery is important
Myopia is within an appropriate range
Corneal tomography is normal
Corneal thickness is suitable
The patient wants a flapless procedure
Contact sports are important
Several uncomfortable postoperative days would be difficult

PRK May Be Particularly Attractive When

A highly superficial treatment is advantageous
The cornea is unsuitable for a deeper flap/cap approach but still otherwise safe for surface ablation
Topography-guided treatment is needed
Wavefront-guided treatment is desirable
A previous refractive procedure requires surface enhancement
The patient accepts a slower recovery

Neither May Be Best When

Tomography is abnormal
Keratoconus is present
Severe uncontrolled dry eye is present
Cataract is developing
The prescription is unstable
High myopia makes ICL a better anatomical choice

The Bottom Line

SMILE and PRK are both flapless refractive-surgery procedures, but they are very different operations.

SMILE:

Creates an internal stromal lenticule
Removes it through a small incision
Preserves the central epithelium
Usually causes mild early discomfort
Provides rapid functional visual recovery
Does not produce the classic surface-ablation haze response
Can still cause dryness, residual prescription and rare ectasia

PRK:

Removes the central epithelium
Uses an excimer laser to reshape the anterior stroma
Requires a bandage contact lens
Causes more discomfort during the first several days
Has slower early visual recovery
Can produce corneal haze
Allows sophisticated excimer-laser customisation
May provide an advantageous tissue strategy in selected corneas

Modern comparative evidence shows that final visual outcomes are generally similar.

A 2026 meta-analysis found no significant overall difference in efficacy between TransPRK and SMILE.

A direct 18-month randomised trial likewise found comparable:

Safety
Efficacy
Contrast sensitivity
Higher-order aberrations

while SMILE provided a more comfortable and visually functional early recovery.

SMILE therefore has a clear practical advantage when the patient values:

Faster recovery
Less early pain
No bandage contact lens

PRK retains important advantages when the surgeon wants:

A superficial treatment
Topography-guided correction
Wavefront-guided treatment
A surface enhancement strategy

The biomechanical comparison is more nuanced than commonly assumed.

Recent direct studies suggest that PRK may preserve several biomechanical parameters at least as well as SMILE, so the phrase “SMILE is stronger because it is flapless” should not be used when comparing SMILE with another flapless procedure such as PRK.

Both procedures can rarely be followed by ectasia, which is why careful corneal tomography remains essential.

PRK carries a unique haze risk, but modern mitomycin-C protocols substantially reduce that risk.

Both procedures have reassuring long-term evidence extending to approximately a decade or more.

The most important message is:

Choose SMILE when its small-incision approach and faster recovery best match the eye and lifestyle. Choose PRK when a superficial or highly customised excimer treatment offers a better anatomical or optical strategy. Being flapless is only the beginning of the comparison—the best procedure is the one that leaves the safest cornea while delivering the visual result the patient actually needs.

References

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Damgaard IB, et al. Eighteen-month outcomes of a contralateral randomised prospective clinical trial comparing PRK and SMILE for myopia. PMID: 36892242.
Joshi S, Bari A, Shakkarwal C, et al. Visual outcomes and corneal biomechanical properties after PRK and SMILE in low-to-moderate myopia. Indian J Ophthalmol. 2025;73:128–133. PMID: 39446853.
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Guo H, et al. Corneal biomechanical properties after SMILE versus FLEX, LASIK, LASEK or PRK: systematic review and meta-analysis. PMID: 31370817.
Chang YM, Liang CM, Weng TH, et al. Mitomycin C for prevention of corneal haze in PRK: meta-analysis and trial sequential analysis. Acta Ophthalmol. 2021;99:652–662. PMID: 33326173.
Moshirfar M, et al. Ectasia after corneal refractive surgery: a systematic review. Ophthalmol Ther. 2021. PMID: 34417707.
Blum M, et al. Ten-year results of small-incision lenticule extraction. J Refract Surg. 2019. PMID: 31610002.
Xia F, Chen Z, Miao H, et al. Ten-year outcomes following SMILE for myopia up to -10 D. 2024. PMID: 37194118.
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Singapore National Eye Centre. SMILE Pro clinical information and VISUMAX 800 treatment description. Current August 2026 information.