Author: Claude (AI), from PubMed abstracts · Reviewed by: Dr Mina Abdelmseih · Reviewed: 2026-11-15 · Review due: 2027-11-15

Educational content only. Not personalised medical advice. Clinical decisions remain the responsibility of the treating clinician.

Laser refractive surgery: LASIK, SMILE and PRK

Laser refractive surgery reshapes the cornea to correct myopia and astigmatism, by surface ablation (PRK, LASEK, transepithelial PRK), by a flap and excimer ablation (LASIK), or by lenticule extraction through a small incision (SMILE, also called KLEx) [S1] [S10]. Randomised evidence shows broadly similar efficacy and safety across the main techniques [S2] [S7]. For eye-care workers outside refractive centres, the key tasks are appropriate referral and recognising complications after surgery [S8] [S10].

Key points - A network meta-analysis of 48 RCTs found no significant differences in efficacy, safety or visual quality between the main laser techniques for myopia; femtosecond LASIK had the best predictability [S2]. - SMILE and LASIK gave comparable safety and efficacy in a meta-analysis of 11 RCTs; LASIK was more predictable and SMILE induced less spherical aberration [S7]. - Wavefront-guided or wavefront-optimised ablation showed no important difference from conventional ablation at 12 months (low-certainty evidence) [S6]. - LASIK significantly reduced tear production and tear break-up time; reductions after SMILE and PRK were not significant [S4]. - A 2025 international guideline on lenticule extraction emphasises screening for keratoconus and managing infection and intraoperative complications [S10].

Evidence last checked: 2026-10-17 (PubMed abstracts).

Red flags

• Pain, redness or reduced vision after surgery. Perioperative infection is a complication requiring management strategies in the KLEx guideline [S10]. Treat as an emergency.
• Blurred vision with raised intraocular pressure after LASIK. Interface fluid syndrome is a fluid pocket in the stroma that reduces visual acuity; 33.3% of reported patients needed surgery [S8].
• Undiagnosed keratoconus before surgery. Preoperative screening for keratoconus is a key recommendation [S10].

Recognise it: who is a candidate

• Cochrane trials included adults aged 18 to 60 years with myopia up to 12 D [S1]; the Cochrane wavefront review included adults aged 18 or over [S6].
• Refractive accuracy depends on corneal thickness, degree of myopia, nomogram and optical zone [S10].
• PRK is used for myopia, astigmatism and hyperopia; a very small percentage have corneal haze or regression [S5].

Confirm it: preoperative assessment

• The KLEx guideline gives recommendations for preoperative screening, candidate selection, intraoperative quality control, postoperative monitoring and complication management [S10].
• Corneal biomechanical measures may improve safety and predictability but need further validation [S10].

Manage it

Before acting on this section, check the national and local guidelines, product information and regulatory approvals that apply where you practise. See the medical disclaimer.

Tier A (primary care / no specialist)

• Laser refractive surgery is not available or needed at this level. Spectacles and contact lenses remain alternatives [S1].
• After someone has had refractive surgery, ask about pain, redness and reduced vision and refer as below.

Tier B (general eye clinic)

• Counselling. Explain that outcomes are similar between techniques [S2], and that LASIK carries more dry-eye signs than SMILE or PRK [S4].
• Post-operative review. Measure intraocular pressure in a LASIK patient with blurred vision: higher presenting IOP and duration of 1 month or less were associated with better final acuity in interface fluid syndrome [S8].

Tier C (specialist centre)

1. Choice of technique. - In a paired-eye RCT of 70 Asian patients (mean -5.3 D), SMILE and femtosecond LASIK achieved 85% vs 83% uncorrected acuity of 20/20 or better and 99% vs 99% within ±1.0 D at 12 months [S3]. - Pooled RCTs: LASIK more often within ±0.5 D (RR 0.91 favouring LASIK) [S7]. - LASEK vs LASIK: uncertain difference in uncorrected acuity; regression was reported only after LASEK (8 of 37 eyes) and flap striae and over-correction only after LASIK (5 of 39 eyes), very low to low certainty [S1].
2. Surface ablation. Transepithelial PRK and mechanical or alcohol-assisted PRK showed no significant differences in efficacy or safety in 20 studies (10 204 eyes); conventional PRK remains reliable where advanced technology is not affordable [S11].
3. Ablation profile. Wavefront-optimised LASIK may slightly improve mean spherical equivalent versus wavefront-guided LASIK (MD -0.14 D, low certainty) [S6].
4. Prophylactic crosslinking. Adding CXL reduced central corneal thickness and safety and efficacy indices, with no difference in 20/20 uncorrected acuity at 12 months or more [S9]. Routine use is not supported by these sources [S9].
5. Complication protocols. Have strategies for wrong-plane dissection, difficult lenticule removal, suction loss and infection [S10].

Refer when

Pitfalls

• Promising a specific technique is superior: differences in efficacy and safety are not significant [S2] [S7].
• Missing interface fluid syndrome in a LASIK patient with blurred vision and raised pressure [S8].
• Assuming prophylactic CXL adds safety [S9].
• Ignoring dry eye after LASIK [S4].

Evidence notes

• Many trials had unclear risk of bias and did not account for paired eyes [S1] [S6].
• The interface fluid syndrome data come from a small pooled case series [S8].
• The PRK practice pattern abstract gives no quantitative data [S5].
• The search returned many off-topic records (dental "smile" aesthetics and others), which were excluded.
• Not covered by these sources: rates of ectasia and infectious keratitis, hyperopic outcomes, cost and access in low-income settings.

Related articles

• Phakic intraocular lenses
• Keratoconus and corneal cross-linking

References

See the numbered source list below. Each marker [S#] links to its PubMed and DOI record.