Patient guide

LASIK Eye Surgery

A laser procedure that permanently reshapes the cornea to correct short-sightedness, long-sightedness, and astigmatism, reducing or eliminating the need for glasses or contact lenses.

What this guide covers: Who is a suitable candidate, how the procedure works, what the pre-operative assessment involves, recovery expectations, the outcomes data, risks to weigh carefully, and questions to ask before committing to a clinic.

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Quick facts

Typical stay: Day procedure (no overnight admission)
Anaesthesia: Local (numbing eye drops)
Return to work: 1–3 days for most patients
Procedure time: Around 30 minutes for both eyes
Vision stabilisation: 2–3 months

Last reviewed: June 2026

Overview

What is LASIK?

LASIK — laser-assisted in situ keratomileusis — is a surgical procedure that uses an excimer laser to reshape the cornea, the clear dome-shaped tissue at the front of the eye. In a normally sighted eye, the cornea focuses incoming light precisely onto the retina at the back. In short-sighted eyes the cornea is too steeply curved or the eyeball too long, causing light to converge in front of the retina; in long-sighted eyes the opposite applies. Astigmatism occurs when the cornea is unevenly curved, distorting focus at all distances. LASIK addresses all three by removing microscopic amounts of corneal tissue to alter its curvature and improve how light is refracted.

What distinguishes LASIK from earlier laser techniques is the flap. Rather than working on the corneal surface — as PRK (photorefractive keratectomy) does — LASIK first creates a thin hinged flap of corneal tissue, folds it aside, performs the laser treatment on the underlying stroma, then repositions the flap. Because the sensitive outer epithelium is preserved and replaced, recovery is substantially faster and the procedure is largely painless. A patient typically notices dramatically improved vision within hours.

LASIK has been performed since 1990 and has accumulated one of the largest safety datasets in elective surgery. Worldwide, tens of millions of procedures have been carried out. In 2007, NASA's ophthalmic advisory team cleared femtosecond LASIK for astronauts — a meaningful signal for a programme that is exceptionally cautious about the medical fitness of its personnel.

The procedure has evolved significantly since its introduction. The original mechanical microkeratome used to create the flap has been largely superseded in modern practice by the femtosecond laser, which uses ultrashort pulses of infrared light to separate tissue at a precisely programmed depth without a blade. Femto-LASIK produces a more uniform flap thickness, eliminates certain blade-related risks, and can be aborted partway through if suction is lost, with no lasting damage to the cornea.

LASIK is elective surgery performed on a healthy eye that functions normally with correction. The key question is not whether LASIK can improve your uncorrected vision — for most carefully selected candidates, it can — but whether the procedure is appropriate for your specific corneal anatomy, prescription stability, and lifestyle.

Who is it for?

LASIK is suitable for a defined range of prescriptions and requires a specific corneal profile. The following criteria reflect published guidelines from the German Commission for Refractive Surgery, the US FDA, and clinical standards applied across European centres.

Prescription range

The core treatment range — where results are most predictable and complication rates lowest — covers short-sightedness up to approximately −8.0 dioptres, long-sightedness up to +3.0 dioptres, and astigmatism up to 5 dioptres, provided the combined total does not exceed −6.0 dioptres.

A borderline range extends short-sightedness to −10.0 dioptres and long-sightedness to +4.0 dioptres, though complication rates are meaningfully higher at these extremes and informed consent requirements are stricter. Treatment beyond −10.0 dioptres is not considered appropriate by most regulatory bodies.

Age and prescription stability

Candidates should be at least 18 years old and have had a stable refraction — measured by an ophthalmologist or optometrist, not solely by an autorefractor — for at least two years. Significant prescription changes in recent months are a reason to wait, not to proceed.

Corneal thickness

A minimum residual corneal thickness of 250 µm must remain after the flap has been created and the laser treatment completed. Normal corneal thickness ranges from roughly 480–600 µm. The calculation — corneal thickness minus flap thickness minus maximum ablation depth — must come out above this threshold with a safety margin.

In Germany, an additional 30 µm reserve is required for any potential future enhancement. Surgeons who cannot show you this calculation during the pre-operative assessment are not doing it properly.

Who should not have LASIK

Certain conditions rule out the procedure entirely or make outcomes unpredictable enough to recommend against it. These include keratoconus or any sign of subclinical ectasia on topography, a family history of keratoconus, corneal thickness below the safe threshold, chronic severe dry eye, autoimmune or connective tissue disorders, active inflammatory eye disease, uncontrolled glaucoma with visual field loss, and symptomatic cataracts.

Pregnancy and breastfeeding alter corneal shape and are a reason to postpone. Patients who regularly participate in contact sports carrying a significant risk of blows to the face should discuss this carefully with their surgeon, because flap displacement from direct trauma, while rare, remains a real risk years after surgery.

Pre-operative assessment

What happens before surgery

The pre-operative assessment is the most important safeguard in the entire process. Any clinic that conducts it in under an hour, or that fails to perform all of the essential measurements, should be treated with caution.

Contact lens wearers must stop wearing lenses for at least two weeks before assessment because soft lenses alter corneal shape, and the cornea must be in its natural state for the measurements to be reliable.

Corneal topography to detect irregularity, early keratoconus, or other contraindications
Pachymetry to measure corneal thickness and determine whether enough tissue exists for safe treatment
Wavefront analysis to map optical aberrations and guide personalised laser programming
Pupillometry in dim conditions, since large pupils increase the risk of halos and glare at night
Tear film assessment, because pre-existing dry eye predicts more troublesome post-operative dryness
Intraocular pressure testing to screen for glaucoma
Refraction measured at least twice, at least two weeks apart, to confirm stability
Full slit-lamp examination and dilated fundus assessment

The surgeon should also take a full medical and ocular history, review current medications, and ideally perform the refraction personally, because they carry the clinical responsibility for the treatment plan. The ablation depth, optical zone diameter, and flap thickness all flow directly from these measurements.

Treatment

What happens

01 — Preparation

Numbing eye drops are applied and a lid speculum is inserted to hold the eye open. A suction ring is then placed on the eye to stabilise it before the flap is created. During suction, patients usually feel pressure and notice their vision dimming briefly — this is temporary and expected.

02 — Flap creation

In modern femto-LASIK, an infrared femtosecond laser creates the flap by firing thousands of precisely spaced pulses within the corneal stroma at the programmed depth, typically between 100 and 160 µm below the surface. A thin margin of tissue at one edge is left intact to serve as a hinge, and the flap is then gently separated and folded back.

In older microkeratome LASIK, a motorised oscillating blade performs the cut mechanically. Both techniques can produce excellent results, but the femtosecond approach allows thinner, more uniform flaps, carries a lower risk of irregular or incomplete cuts, and allows the surgeon to stop safely if suction is lost.

03 — Excimer laser treatment

With the flap folded back, the excimer laser is applied to the exposed stromal bed. It removes tissue with extraordinary precision: approximately 15 µm of tissue corresponds to roughly 1 dioptre of correction. The patient fixates on a small light target while a real-time eye-tracking system follows involuntary eye movement and keeps the treatment centred.

The ablation itself typically lasts under 30 seconds for standard corrections. Patients often notice a faint burning odour during treatment, which is normal and reflects the laser interacting with corneal tissue.

04 — Flap repositioning

The flap is irrigated and smoothed back into position over the treated stromal bed. It adheres through surface tension and natural biological adhesion without sutures. The alignment is checked carefully, and the patient is asked to blink gently to confirm the flap has seated correctly.

If both eyes are being treated — the usual approach — the same sequence is completed for the second eye on the same day.

After surgery

Recovery timeline

Immediately after

Expect grittiness, itching, burning, and watering eyes in the first hours after surgery. Vision is blurred initially but usually improves markedly within hours. Patients are sent home with antibiotic and anti-inflammatory eye drops and are often asked to wear a protective shield overnight.

Days 1–3

Most patients notice a significant improvement in uncorrected vision within 24 hours. A follow-up appointment is usually scheduled within one to two days to confirm healing and rule out early complications. Most patients return to desk-based work within one to three days, although light sensitivity and fluctuating vision are common during the first week.

Weeks 1–8

Dry eyes are the most frequently reported complaint in the weeks after surgery, affecting around 15–20% of patients. This happens because corneal nerve fibres are severed during flap creation, temporarily reducing the eye's ability to detect dryness and regulate tear production.

Night vision disturbance — halos, glare, and starbursts around light sources — is also common early on and usually diminishes as the cornea heals and the pupil response adapts. Patients with large pupils and higher prescriptions are more likely to experience lasting night-time symptoms, which is why honest pre-operative counselling on this point matters.

Months 1–3

Vision continues to stabilise. The final optical result is usually assessed at around three months, and decisions about enhancement or retreatment are not normally made until this point. Approximately 85% of patients achieve a residual refraction within ±0.5 dioptres of the intended target.

Long term

For the vast majority of patients, the visual result is durable. In a small percentage, regression — a gradual drift back toward the original prescription — occurs over years. This is more likely with higher initial corrections and is influenced by wound healing, hormones, and age-related lens change.

Enhancement procedures are possible in many cases, provided sufficient corneal thickness remains.

Understanding the outcomes

What the evidence shows

Over 80% of patients who undergo LASIK no longer require glasses or contact lenses for the majority of their daily activities. More than 90% achieve 20/40 vision or better — the standard required for driving without correction in the UK.

In one-year follow-up data, approximately 94% of patients had the same or better uncorrected visual acuity than they had before surgery, and only 5% reported ongoing night vision problems by twelve months, compared with a much higher proportion in the early post-operative period.

Outcomes are most predictable in patients with mild to moderate short-sightedness. Those with higher prescriptions or significant astigmatism have a wider range of possible outcomes, and a small proportion require enhancement within the first year to fine-tune the correction.

The procedure does not halt the natural ageing of the lens. Patients who have LASIK in their thirties or early forties will still develop presbyopia at the same age they would have done without surgery, and reading glasses will eventually be needed.

Warning signs

Risks and red flags

Dry eyes

This is the most common post-operative complication. Corneal nerve fibres responsible for tear production are severed during flap creation, and recovery of normal nerve function takes months. Patients with pre-existing dry eye are at heightened risk of a more significant and prolonged worsening.

Night vision disturbance

Halos, glare, and starbursts are common early on and usually resolve. A subset of patients — particularly those with large pupils or high corrections — experience persistent symptoms that materially affect quality of life, especially when driving at night.

Corneal ectasia

The most serious potential complication of LASIK. If too much tissue is removed, or if the cornea was already structurally compromised, it may progressively bulge forward under intraocular pressure. This can worsen vision in a way that cannot be corrected by further laser treatment and may ultimately require a corneal transplant.

Flap complications

Incomplete, irregular, or buttonhole flaps are more associated with microkeratome than femtosecond LASIK. Epithelial cells can also migrate beneath the repositioned flap, and the flap can theoretically be displaced by significant direct trauma years later.

Undercorrection, overcorrection, and regression

If the laser removes too little tissue, the intended correction is not fully achieved and a second procedure may be required. Overcorrection is less common but harder to address. Regression — a gradual return toward the original prescription — is more common with higher initial corrections.

Surgeon experience and urgent symptoms

Intraoperative complication rates are higher in a surgeon's earliest cases, which is why it is reasonable to ask how many LASIK procedures they have personally performed. Sudden flashes or floaters, a dark curtain in the visual field, or sudden blurring of vision after an apparently uncomplicated recovery all require prompt ophthalmic assessment.

Alternatives to LASIK

LASIK is not the only refractive surgical option, and it is not the right choice for everyone. The alternatives are worth understanding before committing to a consultation.

PRK (photorefractive keratectomy)

PRK treats the corneal surface directly, without creating a flap. Recovery is slower and the early post-operative period is more uncomfortable, but there is no flap to displace or develop complications, and slightly more corneal tissue is preserved.

PRK is often preferred for patients with thin corneas, those who participate in contact sports, and candidates whose topography raises concern about ectasia risk.

SMILE (small incision lenticule extraction)

SMILE uses a femtosecond laser to create a small lens-shaped disc of tissue within the cornea which is then extracted through a tiny incision, without creating a full flap. Because no flap is involved, displacement risk is eliminated and corneal nerve integrity may be better preserved, which can translate into less dry eye.

Long-term outcome data is accumulating but is still less extensive than for LASIK or PRK.

Phakic intraocular lens implantation

This involves placing an artificial lens inside the eye without removing corneal tissue. It is particularly suited to patients whose prescriptions lie beyond the safe laser-treatment range, or whose corneas are too thin for the required ablation.

It is reversible, but it carries the risks of intraocular surgery, including cataract formation over time.

A clinic that offers only one technique and does not explain why it is preferable to the alternatives for your specific eye is not giving you the full picture.

Before you commit

Questions to ask

How many LASIK procedures have you personally performed, and what is your intraoperative complication rate?
Will wavefront-guided treatment be used, and what does my wavefront map show?
What is my calculated residual stromal thickness after flap and ablation, and how does that compare with the minimum threshold?
Does my topography show any sign of irregularity that could indicate early keratoconus or ectasia risk?
Given my pupil size, what is the planned optical zone diameter, and what is the likelihood of persistent night vision symptoms?
Am I a better candidate for LASIK, PRK, or SMILE, and what is the specific reasoning for the recommendation you are making?
If I require an enhancement procedure, is there sufficient corneal thickness to perform one, and what would that cost?
What is your protocol if I develop a complication after returning home, particularly if I am travelling from outside Turkey?

LASIK in Turkey

Turkey, and Istanbul in particular, has a well-established refractive surgery sector. The city has been part of the international LASIK community since the early 1990s, and several Turkish clinics are equipped with the same femtosecond and wavefront-guided laser platforms found in leading UK and German units.

Prices are considerably lower than in the UK, where LASIK typically costs between £1,500 and £3,000 per eye privately, making Turkey attractive to patients who have done their research.

The critical variable is not the laser hardware — which is broadly standardised internationally — but the quality of the pre-operative assessment and the experience of the surgeon. Most avoidable complications trace back to inadequate topography review or failure to respect corneal thickness thresholds.

Patients travelling for LASIK should also establish in advance who they will see at home if they experience a complication after returning. Most issues such as dry eye, undercorrection, or mild regression are manageable at distance with good communication between the Turkish clinic and a local provider, but serious complications such as ectasia are best handled close to home.

Global Doctor Review

How Global Doctor Review can help

Global Doctor Review is an independent research and rankings organisation covering Turkey's medical tourism sector. It does not accept commercial sponsorship, does not take referral fees, and does not allow providers to purchase placement in its rankings or directory.

The platform has assessed over 400 hospitals, 150 medical centres, 300 private practices, and 800 medical tourism agencies — all licensed by the Turkish Department of Health. Its ophthalmology ranking is currently in progress, covering LASIK and refractive surgery centres, cataract surgery providers, retinal specialists and comprehensive eye hospitals, applying the same documented research methodology used across its other speciality rankings.

For patients considering LASIK or eye surgery in Turkey, Global Doctor Review offers three things of practical value. First, a directory of verified, licensed providers across Turkey's major cities, allowing patients to confirm that a clinic they are considering holds the required government authorisation. Second, independent rankings — when published — based on documented criteria rather than advertising relationships or patient review volume. Third, a published research methodology, allowing patients to understand the basis on which assessments are made.

Next steps

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