TransPRK vs LASIK vs SMILE:
real differences.

Since 1996, I have performed over 25,000 eye surgeries using different techniques and virtually every laser on the market. The comparison I present here is not theoretical: it is the result of thirty years of clinical practice, thousands of long-term follow-ups and a journey that led me to choose TransPRK SmartSurfACE as the primary protocol across the four EasyLaser clinics.

To understand the differences between these three techniques, you first need to understand what they all do the same way — and then where they diverge.

Identical goal, identical result

All three techniques — TransPRK, LASIK and SMILE — do the same thing to the cornea: they reduce its thickness or modify its curvature. In the myopic eye, the eyeball is too long: light converges in front of the retina instead of on it. By flattening the central corneal zone, the optical path is shortened and light focuses again on the retina, where it is transmitted to the brain via the optic nerve.

In the hyperopic eye, the problem is reversed: the eye is too short and light converges behind the retina. The peripheral corneal curvature is modified to increase central refractive power, with the same goal: bringing the focal point onto the retina.

If the final result is identical, the differences lie in how you get to that result — and in the consequences each path has on the corneal structure, its innervation and long-term visual quality.

How the excimer laser works: sublimation, not combustion

Before comparing the techniques, it is important to understand what the excimer laser actually does — the instrument used by both TransPRK and LASIK (but not by SMILE).

The excimer laser at 193 nm produces an ultraviolet beam that breaks the molecular bonds of corneal tissue through a process called photoablation or ablative photodecomposition. Each laser pulse removes a fraction of a micron of tissue by sublimation: the tissue passes directly from solid to gas, without passing through the liquid state and — crucially — without generating significant heat.

In other words: the excimer laser does not burn the cornea. There is no thermal heating of the surrounding tissue. The ITEC system (Intelligent Thermal Effect Control) of the AMARIS 1050RS keeps the corneal temperature below 40°C — well below the protein denaturation threshold. The ablated material is expelled as a gas plume. It is a cold, precise process, micron by micron.

This sublimation — identical in TransPRK and LASIK — produces the same corneal thickness reduction for the same dioptric correction. The same thinning, the same flattening.

The three techniques: what they actually do

TransPRK SmartSurfACE — no contact

TransPRK is the only entirely no-touch technique. The AMARIS 1050RS excimer laser first removes the epithelium (the superficial layer of approximately 55 µm, which regenerates naturally in 3-4 days) then reshapes the underlying corneal stroma — all in a single continuous pass, without any instrument ever touching the eye.

No incision, no mechanical contact, no manual instruments. The only variable is the laser, guided by the patient's diagnostic data. In our clinics, the diagnostic chain is fully integrated: the corneal tomographer MS-39 and the aberrometer Peramis acquire the complete mapping of the eye — topography, pachymetry, optical aberrations — and transmit the data directly to the planning software ORK-CAM. The predictive AI system ForeSight simulates the expected result before the procedure. The treatment plan is then transferred directly to the AMARIS 1050RS laser, with no manual intermediate step.

The entire process — from diagnosis to planning to execution — is not influenced by the operator at any point. The laser delivers the treatment, customisable at three levels: Aberration Free (optimised aspheric profile), Corneal Wavefront (guided by corneal topography) and Ocular Wavefront (guided by the aberrometry of the entire visual system). The surgeon supervises; the machine executes.

LASIK — the flap

In LASIK, the surgeon manually applies a suction ring to the eye — with a significant increase in intraocular pressure — then a femtosecond laser cuts a corneal flap of approximately 100–120 µm. The ring is removed manually, the flap is lifted manually, the excimer laser reshapes the underlying stroma by sublimation — exactly as in TransPRK — then the flap is repositioned manually.

That is 6 phases, of which 5 are operator-dependent. The excimer laser does the same work in both techniques: the same sublimation, the same thinning. But LASIK adds five manual steps that introduce as many operator-dependent variables, each with its possible consequences, and sacrifices 100–120 µm of structural tissue that does not contribute to the optical correction.

SMILE — mechanical extraction

SMILE (Small Incision Lenticule Extraction) does not use the excimer laser. The surgeon manually applies a suction ring — with a significant increase in intraocular pressure — and a femtosecond laser draws a lenticule inside the stroma. Then the surgeon makes a corneal incision of 2–4 mm with a scalpel, inserts a spatula to separate the lenticule from the surrounding tissue on both planes (anterior and posterior), and extracts it manually with forceps. Each surgical step is an operator-dependent variable.

That is 5 phases, of which 4 are operator-dependent. The mechanism is radically different from sublimation: SMILE flattens the cornea by physically removing a piece of it. No evaporation: there is cutting, manual separation and mechanical extraction. The extent of the flattening — and therefore the optical result — is the same. But the path to get there is the most invasive of the three techniques: incision, separation, forceps manipulation in an operative field of just a few millimetres.

Technical Comparison

Parameter	TransPRK	LASIK	SMILE
Operative phases	1 phase: continuous laser sublimation	6 phases: 1) suction ring manual 2) flap cut femtosecond 3) ring removal manual 4) flap lift manual 5) excimer sublimation 6) flap repositioning manual	5 phases: 1) suction ring manual 2) lenticule creation femtosecond 3) corneal incision scalpel 4) separation spatula 5) lenticule extraction forceps
Operator-dependent phases	Zero	5 of 6	4 of 5
Intraocular pressure	No increase	Significant increase	Significant increase
Instrument-eye contact	None	Ring + spatula	Ring + scalpel + spatula + forceps
Patient cooperation	Not required	Total: absolute immobility	Total: absolute immobility
Intraoperative infection risk	Zero (no contact)	Present (instrument contact)	Present (instrument contact)
Max optical zone	> 7.8 mm (up to 9 mm with blended zone)	6–6.5 mm	6–6.5 mm
Treatment profile	Customisable at 3 levels: Aberration Free, Corneal Wavefront, Ocular Wavefront	Customisable	Predetermined geometric
Corneal nerve transection	No transection	Complete circular transection	Partial transection
Chronic dryness	Rare, transient	20–55% persistent (>6 months), rare lifelong cases	Reduced vs LASIK
Visual recovery	4–5 days	2–3 days	2–3 days
PresbyMAX	Yes	Yes	No

Optical zone: why size matters

The optical zone is the area of the cornea actually treated by the laser or lenticule. It is the parameter that determines long-term visual quality — and one of the most significant differences between the three techniques.

In TransPRK, the optical zone is not limited by any cut, any flap or any lenticule to extract. The laser works on the entire exposed surface. This allows optical zones exceeding 7.8 mm — up to 9 mm including the blended zone (progressive transition zone). The scientific literature confirms that larger optical zones, achievable only with surface techniques, produce superior long-term visual quality.

In LASIK and SMILE, the optical zone is physically limited: in LASIK by the flap diameter, in SMILE by the lenticule diameter. In both cases, one typically works with optical zones of 6–6.5 mm. The SMILE lenticule has a standard diameter of 6.5 mm — not to be confused with the access incision, which measures 2-4 mm.

The real problem with the flap: the nerves

The LASIK flap is not just a simple tissue flap: its creation involves the complete circular transection of the cornea's sub-basal nerve plexus. These sensory nerves govern the tear reflex, tear production and epithelial trophism. Once transected, they never fully regenerate in their original configuration.

The consequences are documented: the literature reports that 20 to 55% of LASIK patients present persistent dry eye symptoms beyond 6 months postoperatively. What was classified as 'post-LASIK dry eye' is now increasingly recognised as a form of neuropathic corneal pain — nerve damage that produces sensations of burning, dryness, photosensitivity and chronic discomfort even in the absence of objective ocular surface changes.

This is the LASIK paradox: day-one recovery is spectacular, but long-term discomfort — when it occurs — can last months, years, or become permanent. In TransPRK, discomfort lasts 4-5 days then resolves, because the epithelium regenerates completely on an intact nerve surface.

The question of pain and recovery

TransPRK's critics focus on two points: postoperative pain and slower recovery. Both deserve an honest answer.

Recovery

The TransPRK result is immediate — the cornea already has its new shape at the end of the laser. But visual recovery takes 4-5 days: the time needed for corneal epithelium regeneration. It is a natural biological process: the superficial layer removed by the laser reforms completely, restoring the smooth corneal surface. With therapeutic contact lenses and the pharmacological protocol we use, discomfort is manageable.

Recovery speed depends on several factors: the patient's age, the extent of the initial correction and the type of defect. Recovery is faster in myopes, more gradual in hyperopes. In astigmatic and amblyopic patients, visual perception also depends on neuronal adaptation — the time the brain needs to adjust to the new optics. This applies to all techniques, not just TransPRK. At two weeks, the visual result is identical regardless of the technique used.

Pain

Postoperative discomfort in TransPRK is real but brief: 2-3 days of foreign body sensation, eased by therapeutic lenses and the pharmacological protocol. It resolves completely with epithelium regeneration.

In LASIK, immediate discomfort is minimal — but the problem is what comes after. The flap cut transects the corneal nerve fibres, causing chronic dryness in a significant percentage of patients that can last months or years. This persistent discomfort — burning, photosensitivity, gritty sensation — has nothing to do with the excimer laser. It is a direct and documented consequence of the nerve transection caused by flap creation.

SMILE: operator-dependent variables

SMILE is often presented as a 'flap-free' alternative to LASIK. It is true there is no flap in the traditional sense — but the degree of manual surgical manipulation is even greater.

The SMILE procedure requires: a scalpel incision into the cornea, insertion of a spatula to separate the lenticule from the surrounding tissue on two separate planes (anterior and posterior), and extraction of the lenticule with forceps through an opening of a few millimetres. Every step is manual, every step is operator-dependent, and the literature documents a significant learning curve with more frequent complications in the initial phases.

Furthermore, the SMILE correction profile is geometrically predetermined — a disc of variable thickness calculated by the software — without the ability to customise the ablation based on the patient's individual aberrometry. Eye-tracking during treatment is not available with the same precision as excimer systems.

Why TransPRK reduces haze and regression

Corneal haze — a postoperative opacification — is historically associated with surface techniques. But modern TransPRK with SmartPulse Technology has changed the picture: the stromal surface left by the AMARIS laser is significantly smoother than conventional ablations, reducing the scarring response.

There is a fundamental distinction: in TransPRK, any haze is superficial and subepithelial — it resolves spontaneously with the maturation of the regenerated epithelium. In LASIK and SMILE, haze or fibrosis occurs at the deep stromal level, beneath the flap or in the lenticule separation zone. These deep opacities are often irreversible, because scar tissue forms in a zone with no access to the epithelium's regenerative processes.

The larger optical zone contributes directly: a more progressive transition between treated and untreated zones reduces the asymmetric biomechanical forces that stimulate haze formation and regression over time.

When TransPRK is not the best choice

No technique is universal. TransPRK is not indicated for very high myopia (beyond -10 dioptres), where the amount of tissue to remove exceeds the biomechanical safety margin. In these cases, implantable phakic lenses (ICL) are the safest alternative.

For high hyperopia, the comparison between techniques must be made on a case-by-case basis using real diagnostic data.

Why we chose TransPRK as our standard

The choice is not commercial. It is clinical. After thirty years of experience with different techniques and virtually every laser on the market, TransPRK SmartSurfACE with the AMARIS 1050RS offers the best overall balance: zero mechanical manipulation, zero operator-dependent variables, larger optical zone, preserved corneal innervation, personalised ablation profile, and the same final visual result as any other technique — with fewer consequences for the cornea's structure and biology.

Recovery is slower by a few days. That is the only real disadvantage. And for my patients — to whom I explain exactly what I have written here — it is a compromise they willingly accept in exchange for a stronger, more stable and healthier cornea for the decades to come.