LASIK for Myopia and Astigmatism: Safety and Efficacy

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Article initiated by:

David Huang, MD, PhD

All contributors:

Brad H. Feldman, M.D., David Huang, MD, PhD, Vandana Reddy, MD, Alain Saad, MD, Brian Shafer, MD

Assigned editor:

Brian Shafer, MD

Review:

Assigned status Up to Date

 by Brian Shafer, MD on August 7, 2026.

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Contributing Editors:	add

Introduction

LASIK (laser in situ keratomileusis) is a keratorefractive surgical procedure designed to correct refractive errors. LASIK involves creating a corneal flap using a microkeratome (Figure 1) or a femtosecond laser, reshaping the cornea using an excimer laser to remove tissue from the underlying stromal bed, and then replacing the flap.

LASIK is considered the reference standard of laser refractive surgery and remains the most popular refractive procedure in the United States, with approximately 800,000 procedures performed annually. A systematic review of 309 peer-reviewed LASIK articles found that, on average, 95% of patients were satisfied with their outcome.

Figure 1. Lifting of LASIK flap.

History of LASIK

LASIK evolved from a variety of techniques in refractive surgery. Keratomileusis, with both freeze and non-freeze techniques, was used in the USA in the 1970s. This procedure was followed by automated lamellar keratoplasty (ALK), in which a microkeratome was used to create either a free cap or a hinged corneal flap. Tissue from the corneal bed was removed to alter the refractive error and the flap was replaced. Keratomileusis and ALK were relatively imprecise mechanical techniques.

After its development, the excimer (excited dimer) laser was used to reshape the cornea in a technique called photorefractive keratectomy (PRK). LASIK combines the technique of creating a hinged corneal flap from ALK with excimer laser ablation from PRK (Figure 2). Potential advantages of LASIK over PRK include earlier postoperative stabilization and faster improvement of visual acuity; less postoperative patient discomfort; shorter duration of postoperative medication use; and an easier enhancement procedure.

Subsequent evolutions include the introduction of femtosecond laser flap creation (early 2000s), wavefront-guided and wavefront-optimized ablation profiles, topography-guided customized ablation, and most recently ray-tracing–based personalized ablation algorithms.

Figure 2. Illustration of excimer ablation of the stromal bed in myopic LASIK.

LASIK Indications for the Correction of Myopia and Astigmatism

LASIK is indicated for the correction of low, moderate, and high myopia with and without astigmatism. The specific dioptric limits depend on the specific laser system and the regulatory agency of each country. In the U.S.A., the approved indications can be found in the Food and Drug Administration (FDA) labeling. Representative FDA-approved ranges include myopia up to −12.00 D with astigmatism up to −6.00 D (Alcon WaveLight ALLEGRETTO WAVE), myopia ≤−7.00 D with astigmatism ≤−3.00 D (Carl Zeiss Meditec MEL 80), hyperopia up to +6.00 D with astigmatism up to +5.00 D, and mixed astigmatism up to 6.00 D at the spectacle plane.

The correction of high myopia may present a greater risk of post-LASIK ectasia and decreased quality of vision in some patients. For hyperopia, predictability and safety decline notably above 4–5 D of spherical equivalent; in FDA trial data, at least 10% of eyes with ≥4 D preoperative spherical equivalent lost ≥2 lines of BSCVA, and LASIK for hyperopia >4–5 D should be approached with caution.

The surgeon and patient should decide whether LASIK is indicated based on a full preoperative evaluation and consideration of goals and alternatives, including spectacles, contact lenses, PRK, small-incision lenticule extraction (SMILE), phakic intraocular lens implantation, and refractive lens exchange.

The following table from the JAMA review of refractive surgery in the US summarizes the technique, advantages, disadvantages, refractive range, and contraindications for the major corneal- and lens-based refractive procedures.

Figure. Common Refractive Surgical Procedures in the US

Refractive Surgery in the US in 2021. JAMA. July 5, 2021.

Content used under license from the JAMA Network® © American Medical Association

Preoperative Evaluation

Preoperative evaluation should include a complete eye examination, a full medical and ophthalmologic history, and informed consent.

Refraction and stability

Dry (manifest) and cycloplegic refraction should be performed for all patients.

Rigid contact lenses should be removed for several weeks and soft lenses for several days to weeks before examination to allow resolution of corneal warpage.

Refraction should be stable within 0.50 D for 1 year or more before LASIK surgery. Surgery is typically performed only in patients over 21 years of age owing to concern about ongoing changes in refractive error; there is no upper age limit if the eye is otherwise normal.

Corneal imaging

Measurement of corneal topography is essential and is used to screen for irregular astigmatism, keratoconus, and forme fruste keratoconus, which are associated with unpredictable refractive outcomes and progressive ectasia after LASIK. Abnormal topography is the most significant single risk factor for postoperative ectasia.

Corneal tomography and ectasia-detection software—such as the Belin-Ambrósio Enhanced Ectasia Display (BAD) on the Pentacam, epithelial thickness mapping, and the SCORE analyzer on the Orbscan—help discriminate normal corneas from ectasia-susceptible corneas.

Scheimpflug imaging and artificial intelligence algorithms have improved screening of patients at risk of ectasia and reduced its incidence to roughly 1 in 5,000 cases.

Measurement of corneal thickness is critical because of its importance in calculating anticipated residual stromal bed thickness and percent tissue altered. Normal corneal thickness ranges from approximately 490 to 650 µm. A thin cornea may also be an indication of subtle keratoconus and indicates a need for caution in tissue removal.

Ocular surface and other testing

Tear film assessment (tear breakup time, ocular surface staining, Schirmer testing, osmolarity, meibomian gland evaluation) with treatment of dry eye and blepharitis before surgery.

Slit-lamp biomicroscopy for epithelial basement membrane dystrophy, corneal scars, and lens opacity.

Dilated fundus examination, particularly in high myopes, to identify peripheral retinal pathology.

Ocular motility and binocular assessment, and corneal/ocular aberrometry.

Note on pupillometry: published studies have failed to demonstrate a relationship between pupil size and quality of postoperative vision, minimizing the importance of pupillometry in the preoperative workup.

The AAO Refractive Surgery PPP additionally recommends that patients be provided with a record listing diagnosis, preoperative keratometry readings, and refraction, as well as postoperative refraction, for use in future eye care including cataract surgery IOL calculations.

Contraindications to LASIK

The American Academy of Ophthalmology lists the following contraindications to refractive surgery:

Unstable refraction

Abnormalities of the cornea (keratoconus or other corneal ectasias, thinning, edema, interstitial or neurotrophic keratitis, extensive vascularization)

Insufficient corneal thickness for the proposed ablation depth

Visually significant cataract

Uncontrolled glaucoma

Uncontrolled external disease (blepharitis, dry eye syndrome, atopy/allergy)

Uncontrolled autoimmune or other immune-mediated disease

Uncontrolled mental illness, including anxiety or depression

Unrealistic patient expectations

Additional recognized ocular and systemic contraindications or conditions warranting caution include Fuchs corneal endothelial dystrophy, pellucid marginal degeneration, epithelial basement membrane dystrophy (EBMD), Avellino (granular type 2) corneal dystrophy, a history of herpetic keratitis, untreated peripheral retinal tears (especially in highly myopic eyes), uncontrolled diabetes, collagen vascular disease, pregnancy and lactation, severe dry eye, chronic pain syndromes, and use of amiodarone or isotretinoin.

Much of the evidence underlying systemic contraindications is derived from case reports, case series, and anecdotal experience rather than randomized trials; the safety of LASIK in well-controlled collagen vascular disease in particular remains incompletely established.

Flap Thickness and Ectasia Risk Calculation

LASIK flaps are cut with either mechanical microkeratomes or femtosecond lasers. Mechanical microkeratomes are typically labeled for nominal cut depths of between 120 and 180 µm, with a trend toward thinner flaps in newer, more precise models. Thinner flaps preserve greater stromal bed thickness and reduce the risk of ectasia. Femtosecond lasers tend to create more precise and uniform flap thickness, and settings of 100–120 µm are typically used.

Residual stromal bed (RSB): A residual posterior stromal thickness of at least 250 µm is suggested as a safe minimum to reduce the risk of post-LASIK ectasia, although no absolute value guarantees that ectasia will not occur, since the posterior cornea exhibits weaker tensile strength than the anterior cornea. Some surgeons also believe the stromal bed should be at least half of the original corneal thickness.

Percent tissue altered (PTA): In the context of normal preoperative topography, a PTA ≥40% is associated with higher ectasia risk:

PTA=FT+ADCCTPTA = \frac{FT + AD}{CCT}

where FT = flap thickness, AD = ablation depth, and CCT = preoperative central corneal thickness. In a case-control study of eyes with normal preoperative Placido topography that developed ectasia, PTA ≥40 was the most prevalent factor (97%), followed by age <30 years (63%), RSB ≤300 µm (57%), and Ectasia Risk Score ≥3 (43%). PTA ≥40 carried the highest odds ratio (223), followed by RSB ≤300 µm (74), and was the single most significant independent variable on stepwise logistic regression.

Ectasia Risk Score System: In a comparative analysis of 171 ectasia cases, eyes developing ectasia more often had abnormal preoperative topography (35.7% vs 0%), were younger (34.4 vs 40.0 years), were more myopic (−8.53 vs −5.09 D), had thinner preoperative corneas (521.0 vs 546.5 µm), and had thinner RSB (256.3 vs 317.3 µm). The resulting weighted risk stratification scale demonstrated 91% specificity and 96% sensitivity in that series.

Intraoperative measurement: Flap thickness can be measured by intraoperative subtractive ultrasound pachymetry. Anterior segment optical coherence tomography (OCT) can be used to measure flap and stromal bed thicknesses (Figure 3). Flap thicknesses can deviate significantly from the nominal setting, and routine measurement helps the surgeon evaluate the actual range obtained.

Figure 3. Optical coherence tomography (OCT) image of a LASIK flap showing measurement of the flap and stromal bed thickness. The upper numbers represent the transverse distance from the corneal vertex in millimetres. The lower numbers represent flap thickness and residual stromal bed thickness in microns, respectively.

Surgical Technique

Before surgery, the excimer laser, suction ring, microkeratome and blade (or femtosecond laser settings) are checked by the technician and the surgeon. The surgeon also confirms that the correct treatment data are entered into the laser computer, and verifies patient identity, operative eye, and treatment plan.

1. An eyelid speculum is placed in the operative eye, which has been anesthetized with topical drops, and the fellow eye is covered.

2. The cornea is marked with ink to aid in postoperative flap alignment and to permit correct orientation in the event of a free cap.

3. A suction ring is placed on the eye to achieve fixation and elevate intraocular pressure. Adequate suction is confirmed before proceeding.

4. The microkeratome (or femtosecond laser) is used to create a hinged corneal flap.

5. After the flap has been created, it is reflected away from the cut surface and the stromal bed is dried.

6. Excimer laser ablation is performed, centered on the pupil or on the corneal vertex. Eye-tracker and iris registration technology are used to ensure a well-centered laser treatment and correct cyclotorsional alignment.

7. Following the excimer laser, the interface is irrigated and the flap is replaced, with attention to gutter symmetry and flap adherence before speculum removal.

Postoperative Care

Patients may have mild postoperative discomfort for 4 to 6 hours following LASIK treatment, during which time they should keep their eyes closed and rest or take a nap. Patients should not rub their eyes after surgery, and a protective shield is typically worn for the first 24 hours and at night for the first week.

Topical corticosteroid and antibiotic drops are used for 4 to 10 days after surgery. Preservative-free artificial tears may be used for weeks to months depending on dry eye symptoms and corneal punctate staining.

Refractive stabilization for myopes takes up to 3 months depending on the amount of treatment performed. In a recent ray-tracing LASIK study, refractive stability was achieved at 3 months, with 99.4% of eyes having ≤1.00 D change in manifest refraction spherical equivalent between 1 and 3 months.

Residual refractive error can be corrected after stabilization, typically by relifting the flap and ablating the stromal bed in a retreatment procedure (enhancement). Before retreatment, refractive stability must be documented, other causes of residual refractive error (accommodative spasm, cataract, ectasia) excluded, and repeat topography/tomography obtained. To ensure preservation of at least 250 µm of residual bed thickness after laser retreatment, preoperative OCT or intraoperative ultrasound pachymetry should be performed. Surface ablation may be preferred over flap lift in eyes at higher risk of epithelial ingrowth or with marginal residual stroma.

Outcomes of LASIK for Myopia and Astigmatism

Efficacy, Predictability, and Safety

A systematic review of 64 LASIK studies published since 2000 reported that 75% to 100% (median, 92%) of eyes with myopia or myopic astigmatism were within 1.00 D of the intended correction, with low to moderate myopia corrected more predictably than higher degrees. Uncorrected visual acuity of 20/40 or better was achieved in 94% to 100% (median, 98%) of eyes with low to moderate myopia and 76% to 97% (median, 89%) of eyes with high myopia. Across 25 studies, a median of 0.6% (range, 0%–3%) of eyes lost two or more lines of BCVA.

An 18-year prospective audit of 53,731 myopic LASIK eyes provides among the most robust real-world data available:

Overall efficacy index 0.91, with >99% of eyes achieving UCVA ≥20/40 and >70% achieving 20/20 since 2010

95.43% of eyes had no loss of vision; 4.2% lost 1 line and 0.37% lost ≥2 lines of BCVA

Safety index >1.05 since 2010

>94.0% of eyes within ±1.00 D of target and ≥70% within ±0.50 D from 2010 onward

Retreatment rate 2.55%; overall complication rate 0.98%, with annual rates <0.8% since 2010

A 2016 review cited by JAMA found that 99.5% of patients who undergo LASIK achieve spectacle independence and 98.6% are within ±1.0 D of the attempted correction.

High Myopia

Results in high myopia are more variable. Reinstein et al. reported that postoperative spherical equivalent was within ±0.50 D in 55% and ±1.00 D in 83% of eyes after primary treatment for high myopia and astigmatism from −8.00 to −14.25 D; after retreatment, 69% were within ±0.50 D and 95% within ±1.00 D. The AAO similarly notes that results of LASIK are more variable in eyes with moderate-to-high myopia (>6.0 D).

Contemporary Platform Outcomes

Platform / Approach · Key Outcomes · References

Teneo 317 M2 aspheric profile (FDA trial, 333 eyes) · 97.8% UDVA ≥20/25 at 9 months; 92.7% within ±0.50 D; no eyes lost ≥2 lines CDVA; satisfaction rose from 27.7% to 98.1% · [2]

Ray tracing–guided LASIK (326 eyes, 12 months) · 92.0% within ±0.50 D, 98.5% within ±1.00 D; 94.4% UDVA ≥20/20; no eyes lost ≥2 lines; 98% very/completely satisfied; OSDI improved 14.9 → 7.7 · [3]

Topography-guided FS-LASIK (60 eyes, 12 months) · Mean UDVA −0.09 logMAR; 26.9% gained ≥1 line of UDVA over baseline CDVA; stable to 12 months · [4]

18-year audit, mixed platforms (53,731 eyes) · Efficacy index 0.91; 0.37% lost ≥2 lines BCVA; complication rate 0.98% · [5]

LASIK Complications

Complications occur in LASIK as in any other surgical procedure. Serious adverse complications leading to significant permanent visual loss occur rarely. Less serious side effects such as dry eyes, night-time starbursts, and/or reduced contrast sensitivity occur relatively frequently. A detailed discussion is available in the LASIK Complications article.

Dry eye is the most common complication or side effect following LASIK. It usually resolves over 6 to 12 months but persists in up to 20% of patients and may in part represent a corneal neuropathy.

Flap complications include free, incomplete, or buttonholed flaps, striae/folds, and slipped/displaced flaps. If the flap created during the LASIK procedure is irregular, incomplete, or buttonholed, laser treatment cannot safely be performed in the same session; after a healing period, a secondary LASIK or PRK procedure may be performed in some cases. Flap-related complications are markedly less common when the flap is prepared using a femtosecond laser.

Interface complications include diffuse lamellar keratitis (DLK), infectious keratitis, epithelial ingrowth, pressure-induced stromal keratitis, and central toxic keratopathy. Persistent DLK unresponsive to corticosteroids should prompt consideration of microbial keratitis or interlamellar fluid due to increased IOP—which must be measured peripheral to the LASIK flap—as well as intraocular inflammation or endothelial decompensation.

Post-LASIK ectasia may occur when the biomechanical stability of the cornea is altered; contemporary screening has reduced its incidence to approximately 1 in 5,000 cases.

It is uncertain whether there is any relationship between LASIK and an increased incidence of postoperative retinal detachment. Ischemic optic neuropathy is a rare reported complication.

Patient-Reported Outcomes

The FDA-sponsored PROWL-1 (262 active-duty Navy personnel) and PROWL-2 (312 civilians) studies systematically assessed symptoms and satisfaction using validated questionnaires:

At 3 months, 99% (PROWL-1) and 96% (PROWL-2) of patients had binocular UCVA of 20/20 or better.

Overall prevalence of visual and dry eye symptoms decreased after surgery, but 43% (PROWL-1) and 46% (PROWL-2) of participants without preoperative symptoms developed at least one new visual symptom at 3 months.

Of participants with normal baseline Ocular Surface Disease Index scores, approximately 28% had mild, moderate, or severe dry eye symptoms at 3 months.

Rates of dissatisfaction with vision ranged from 1% to 4%, and dissatisfaction with surgery from 1% to 2%.

Less than 1% of participants reported difficulty performing usual activities due to symptoms.

Participants were more likely to report visual symptoms on the questionnaire than to their clinicians, supporting systematic questionnaire use.

The following table from the PROWL studies details the prevalence, development, resolution, and functional impact of visual symptoms before and after LASIK.

Table 3. Visual Symptoms Reported on the Questionnaire by Participants in the Analytical Cohorts in the PROWL-1 and -2 Studies

Symptoms and Satisfaction of Patients in the Patient-Reported Outcomes With Laser In Situ Keratomileusis (PROWL) Studies. JAMA Ophthalmol. December 31, 2016.

Content used under license from the JAMA Network® © American Medical Association

The Patient-Reported Outcomes with LASIK Symptoms and Satisfaction (PROWL-SS) questionnaire and scoring guide are available from the Academy.

Customized Ablation Profiles

Wavefront-Guided LASIK

Wavefront-guided LASIK (WFG), also called custom LASIK, is a variation of LASIK in which the excimer laser ablates a sophisticated pattern based on measurements from a wavefront aberrometer (Figure 4). The goal is a more optically ideal ablation based on all measured optical aberrations, not just spherical and cylindrical refractive errors.

WFG LASIK is safe and effective. A Cochrane review of 33 RCTs (1,499 participants, 2,797 eyes) found no evidence of a difference between wavefront and corresponding conventional procedures for UCVA 20/20 or better, loss of ≥1 line of BSCVA, or refraction within ±0.50 D of target, with low certainty of evidence. Comparing wavefront-optimized with wavefront-guided procedures at 12 months, there was likewise no difference in these outcomes or in mean higher-order aberrations, although wavefront-optimized LASIK may modestly improve mean spherical equivalent relative to wavefront-guided LASIK (MD −0.14 D).

In a randomized contralateral-eye trial of 200 eyes, both wavefront-optimized and high-resolution wavefront-guided LASIK achieved excellent UDVA without significant difference, but WFG eyes had a significantly greater mean gain in lines of CDVA, better low-contrast visual acuity, lower trefoil, and closer proximity to emmetropia.

Figure 4. Schematic of wavefront technology, showing a wavefront pattern.

Topography-Guided LASIK

Topography-guided customized ablation treatment (TCAT) uses corneal topographic data—rather than whole-eye wavefront data—to design the ablation profile, addressing corneal irregularity directly.

A meta-analysis of 7 RCTs (1,168 eyes) comparing TCAT-LASIK with wavefront-optimized LASIK found no difference in the proportion achieving UDVA 20/20 or better, but TCAT achieved a higher proportion within ±0.50 D of target (RR 1.06, 95% CI 1.02–1.11, P = .003) and less surgically induced higher-order aberration, spherical aberration, and coma. No patient in either group lost ≥2 lines of CDVA.

Head-to-head comparisons of topography-guided versus wavefront-guided LASIK have shown broadly equivalent results:

In a randomized contralateral-eye trial of 100 eyes at 12 months, there were no significant differences in spherical equivalent, higher-order aberrations, or low-contrast acuity; however, significantly more WFG eyes achieved UDVA of 20/12.5 (P = .003).

In a prospective double-blind randomized trial of 66 participants at 6 months, TG-LASIK showed a higher efficiency index (1.08 vs 1.02; P = .03) and better mean spherical equivalent (0.04 vs 0.13 D; P = .04), while WFG-LASIK had superior low-contrast UDVA and CDVA. Safety indices, residual HOAs, and dry eye symptoms were similar.

In eyes with oblique astigmatism, topography-guided LASIK planned with the Phorcides Analytic Engine produced lower residual refractive cylinder, better UDVA and CDVA, a higher proportion within ±0.50 D of plano, and fewer enhancements than wavefront-optimized treatment.

Ray-Tracing–Guided LASIK

Ray tracing–based treatment planning constructs a 3D virtual model of the individual eye and derives a personalized ablation profile. In a prospective FDA-registered study of 326 eyes with myopia up to −10.00 D, 92.0% achieved MRSE within ±0.50 D and 98.5% within ±1.00 D; 94.4% achieved UDVA of 20/20 or better at 12 months; no eyes lost ≥2 lines of CDVA; and 98% of patients reported being very or completely satisfied. Dry eye symptoms improved from baseline (OSDI 14.90 → 7.69).

Femtosecond LASIK

The femtosecond laser creates a corneal incision by delivering laser pulses at a predetermined depth in the cornea. These pulses cause microphotodisruption, generating an expanding bubble of gas (CO₂) and water that cleaves the tissue and creates a plane of separation (Figure 5).

Compared to conventional mechanical microkeratomes, femtosecond lasers create LASIK flaps with more predictable and uniform thickness, and fewer flap complications; the transition from mechanical to femtosecond flaps has reduced the risk of complications overall. Femtosecond LASIK has been shown to provide better predictability of refractive outcomes and lower enhancement rates than microkeratome LASIK.

However, side effects unique to the femtosecond laser have been reported, particularly with earlier-generation platforms and higher energy settings, including transient light sensitivity syndrome, rainbow glare, opaque bubble layer, vertical gas breakthrough, and anterior chamber gas bubbles.

Figure 5. Illustration of a femtosecond laser cutting a LASIK flap.

LASIK Versus SMILE

Small-incision lenticule extraction (SMILE) creates an intrastromal lenticule with a femtosecond laser that is removed through a small peripheral incision, avoiding flap creation entirely. By avoiding a corneal flap, SMILE is hypothesized to better preserve corneal biomechanical strength—the anterior stroma accounts for approximately 60% of total corneal tensile strength—and to reduce dry eye by preserving the sub-basal nerve plexus.

Visual and refractive outcomes

In a prospective, randomized, paired-eye, single-masked trial of 70 patients (mean preoperative SE ≈ −5.3 D), SMILE and femtosecond LASIK were equivalent at 12 months for efficacy (85% vs 83% UDVA ≥20/20; P = .81), predictability (99% vs 99% within ±1.00 D; P = 1.0), and safety (safety index 1.15 vs 1.15; P = .93).

A Cochrane-methodology systematic review of 11 RCTs (1,101 eyes) found no significant difference in final spherical equivalent (P = .72), proportion achieving UDVA 20/20 or better (P = .35), or proportion within ±1.00 D of target (P = .70). Ocular surface signs and symptoms were less frequent after SMILE.

A meta-analysis of 12 studies (1,076 eyes) similarly found no differences in loss of ≥1 line of BSCVA, UCVA 20/20 or better, mean logMAR UCVA, postoperative spherical equivalent, or refraction within ±1.00 D at 3–6 months.

Astigmatism correction

A meta-analysis of 17 studies (1,985 eyes) found generally equivalent outcomes for astigmatism correction, but with a tendency toward undercorrection with SMILE. For low-to-moderate astigmatism (≤2.00 D), SMILE showed a smaller correction index (MD −0.08; P = .008) and larger difference vector (MD 0.18; P < .0001) than LASIK, whereas LASIK induced greater spherical aberration (MD −0.12; P = .04).

Dry eye and corneal innervation

A meta-analysis of 12 studies found greater OSDI scores (MD −6.68; P = .006) and lower corneal sensitivity (MD 12.40; P < .00001) at 6 months in the FS-LASIK group.

A 2025 meta-analysis of 18 studies found significantly longer tear breakup time after lenticule extraction at 3 months (MD 3.27 s; P < .0001) and 6 months (MD 3.32 s; P < .0001), better Schirmer results (MD 0.82 mm; P = .0001), and better corneal sensitivity preservation at 1 and 6 months, though OSDI differences were not statistically significant.

In a prospective randomized contralateral-eye trial of 80 eyes, LASIK produced greater corneal denervation than SMILE at 1, 3, and 6 months, but both returned to baseline sensitivity at 12 months, and there was no difference in patient-reported OSDI at any visit; OSDI improved from baseline in both groups.

Procedure selection

Current evidence supports the following considerations:

Favoring SMILE: High myopia (smaller decrease in functional optical zone, less induced spherical aberration and mesopic HOAs), preexisting dry eye, contact/collision sport participation or occupational trauma risk (no flap), and concern for long-term myopic regression.

Favoring FS-LASIK: Hyperopia (SMILE lacks FDA/CE approval for hyperopic correction), low-to-moderate myopic astigmatism (less undercorrection), need for rapid visual recovery, need for customized wavefront- or topography-guided treatment, and ease of enhancement.

FS-LASIK remains the reference-standard refractive procedure owing to rapid recovery and predictable results, while customized (wavefront- and topography-guided) FS-LASIK outperforms SMILE on some visual quality metrics.

Special Considerations

Monovision and Presbyopia

LASIK monovision, in which the nondominant eye is targeted for low myopia, is an option for presbyopic patients. A preoperative contact lens trial is recommended to confirm tolerance of anisometropia, as a minority of patients cannot adapt because of reduced stereopsis and intermediate blur. Presbyopia-correcting ablation profiles (PresbyLASIK) using multifocal or increased-depth-of-focus corneal profiles are available in some jurisdictions but involve trade-offs in contrast sensitivity.

LASIK in the Setting of Prior or Future Ocular Surgery

Patients who have undergone LASIK require modified intraocular lens power calculation formulas at the time of future cataract surgery, as standard keratometry-based formulas overestimate corneal power and result in hyperopic surprise. Preoperative records—diagnosis, preoperative keratometry, and pre- and postoperative refraction—should be provided to patients for this purpose.

Intraocular Pressure Measurement

LASIK reduces central corneal thickness and alters corneal biomechanics, artifactually lowering Goldmann applanation IOP readings, with implications for future glaucoma screening. In the setting of suspected interface fluid syndrome, IOP must be measured peripheral to the flap.

Conclusions

LASIK is an excellent procedure for most patients with myopia and astigmatism, with an efficacy index of approximately 0.91 and loss of ≥2 lines of BCVA in only about 0.37% of eyes in large contemporary series. Proper preoperative screening—particularly corneal tomography to exclude ectasia-susceptible corneas, calculation of residual stromal bed and percent tissue altered, and optimization of the ocular surface—is the single most important determinant of a safe outcome. While surgical complications are rare, good postoperative care and systematic assessment of patient-reported symptoms are important, since new visual and dry eye symptoms occur in a substantial minority of patients even after technically uncomplicated surgery.

Additional Resources

American Academy of Ophthalmology. LASIK. EyeSmart/Eye Health.

American Academy of Ophthalmology. Refractive Surgery Preferred Practice Pattern.

U.S. Food and Drug Administration. LASIK.