Outcomes data in refractive surgery is abundant — and often misrepresented. Marketing materials cite the best numbers from the most favorable studies. Patient forums amplify negative experiences disproportionately. The truth lies in systematic, peer-reviewed evidence from large-scale studies with consistent methodology.
This page compiles the published outcomes evidence for all major vision correction procedures, explains what the numbers mean and what they don’t, and helps you understand which factors most strongly predict your individual result. It is part of the Vision Correction Procedures Compared hub.
Defining “Success” in Refractive Surgery
Before reviewing numbers, it is worth establishing what the key metrics actually measure:
Uncorrected Distance Visual Acuity (UDVA): The patient’s vision without glasses or contacts, measured on the standard Snellen chart. “20/20 or better” is the benchmark most frequently cited and most meaningful to patients.
Best Corrected Visual Acuity (BCVA): The best vision achievable with optimal glasses. Changes in BCVA post-surgery indicate whether the procedure affected the quality of correctable vision, not just the prescription. “Loss of two or more lines of BCVA” is the standard safety measure — its rate indicates how often surgery made corrected vision worse.
Refractive predictability: The percentage of patients whose final prescription fell within a defined target range — typically within ±0.50D of intended emmetropia (no glasses prescription) and within ±1.00D.
Patient satisfaction: Subjective ratings of overall satisfaction with the procedure. These are arguably the most important metrics for prospective patients.
Enhancement rate: The percentage of patients who required a second surgical procedure (within a defined follow-up period) to refine the outcome.
LASIK: Outcome Data Summary
LASIK is the most studied elective surgical procedure in history, with more than 3,000 peer-reviewed publications. The PROWL studies (Patient-Reported Outcomes With LASIK), conducted in partnership with the FDA and Department of Defense, provide some of the most rigorous US-based data available.
Visual acuity outcomes (pooled large-series data):
- UDVA 20/20 or better: 96–98% of patients
- UDVA 20/40 or better: >99% of patients
- Loss of two or more lines BCVA: <1% (approximately 0.2–0.4% in modern platforms)
Refractive predictability:
- Within ±0.50D of target: 85–92% (wavefront-guided platforms)
- Within ±1.00D of target: 97–99%
Patient satisfaction:
- Overall satisfaction: 95–96% (PROWL studies: 95.4% satisfied, 1.2% dissatisfied)
- Patients reporting visual symptoms (halos, glare, starbursts): 30–40% immediately post-procedure; decreasing to 10–20% at one year; further decreasing thereafter. Most are mild.
Enhancement rate: 2–5% within five years. Higher for hyperopia corrections and very high myopia corrections.
Dry eye: Clinically meaningful dry eye (requiring ongoing treatment beyond three months) affects approximately 5–10% of LASIK patients. Pre-existing dry eye significantly increases this rate.
PRK: Outcome Data Summary
PRK outcome data parallel LASIK over the long term, with differences concentrated in the early post-operative period.
Visual acuity outcomes (long-term, beyond 3 months):
- UDVA 20/20 or better: 95–97%
- UDVA 20/40 or better: >99%
- Loss of two or more lines BCVA: <1%
Key differences from LASIK:
- At one week and one month, PRK acuity is significantly behind LASIK due to the ongoing epithelial healing process.
- By three months, PRK outcomes are statistically equivalent to LASIK.
- Subepithelial haze (PRK haze) can affect a small percentage of patients with high corrections. Mitomycin-C prophylaxis during surgery has reduced clinically significant haze rates to less than 2–3% even in high corrections.
Patient satisfaction:
- Similar to LASIK at one year and beyond: 93–96%
- Lower satisfaction in the first 1–3 months due to the recovery burden
Enhancement rate: 2–4% within five years.
SMILE: Outcome Data Summary
SMILE was FDA-approved in 2016, and several large prospective multicenter studies and meta-analyses now provide robust US and international data.
Visual acuity outcomes:
- UDVA 20/20 or better: 96–98%
- UDVA 20/40 or better: >99%
- Loss of two or more lines BCVA: <0.5% in most large series
Comparative data vs. LASIK: Multiple head-to-head randomized controlled trials have found:
- No statistically significant difference in one-year UDVA outcomes between SMILE and LASIK for myopia within SMILE’s approved range.
- SMILE patients report significantly less dry eye at 3 months, 6 months, and 1 year.
- Some studies report slightly lower higher-order aberration induction with SMILE compared to LASIK, though clinical significance is modest.
Patient satisfaction: 95–97%
Enhancement rate: 2–5% within five years.
EVO ICL: Outcome Data Summary
EVO ICL is the newest major procedure reviewed here to achieve large-scale US adoption, and its outcome data are impressive — consistently showing the highest patient satisfaction rates of any reviewed procedure.
Visual acuity outcomes:
- UDVA 20/20 or better: 96–99%
- UDVA 20/40 or better: >99%
- Loss of two or more lines BCVA: <0.5%
Refractive predictability:
- Within ±0.50D of target: 88–93% (the slightly lower rate compared to LASIK reflects the complexity of achieving precision in phakic IOL placement and the custom-ordering nature of the lens)
- Within ±1.00D of target: 96–99%
Patient satisfaction:
- 97–99% overall satisfaction in large clinical series (FDA clinical trial data: 99.4% of patients reported they would have the procedure again)
- EVO ICL satisfaction rates are consistently the highest reported in comparative refractive surgery literature
Why EVO ICL satisfaction is highest: Multiple publications attribute this to the optical quality of the Collamer lens material. Unlike laser procedures, EVO ICL adds optical correction without removing corneal tissue or altering the natural corneal surface optics. This produces particularly high-quality vision in low-light conditions — reducing halos and starbursts compared to equivalent laser corrections.
Enhancement rate: Less than 1% require lens exchange. A small percentage (approximately 2–5%) require supplemental laser correction (PRK or LASIK over the ICL) to address residual refractive error.
Serious complications:
- Cataract formation: historically a concern with older ICL generations; the EVO+ generation’s central port design has reduced cataract formation to rates approaching background age-matched rates in large post-market studies.
- Elevated intraocular pressure: managed with topical medications or laser iridotomy if needed; rare with modern EVO ICL design.
What the Averages Don’t Tell You
Population averages are a necessary starting point, but they can be misleading for individual decision-making. Three factors produce significant deviation from average outcomes:
1. Candidate selection quality. The published success rates above apply to appropriately selected candidates. Patients who underwent LASIK with corneas too thin for safe ablation, or who had undetected keratoconus at the time of surgery, produce outcomes far worse than these averages. Rigorous pre-operative screening is what separates practices with 97% satisfaction from practices with 88% satisfaction.
2. Surgeon experience and volume. The correlation between surgeon volume and refractive outcomes is well-established. High-volume, experienced surgeons consistently deliver tighter refractive predictability — more patients within ±0.25D of target — than lower-volume surgeons. This translates to fewer enhancements and higher satisfaction.
3. Technology generation. Wavefront-guided LASIK on a current-generation platform produces substantially better refractive predictability than standard LASIK on an older platform. Comparing outcome percentages between different technology tiers requires caution.
This is why independent recognition programs — such as our LASIK Surgery Awards and EVO ICL Awards — provide value beyond what published averages can convey. They identify the practices operating at the high end of these outcome curves, not just at the average.
Enhancement and Long-Term Stability
All major vision correction procedures can experience some degree of long-term prescription change:
LASIK regression: More common for high myopia and hyperopia corrections. Typically small in magnitude (-0.25D to -0.75D over 5–10 years). Enhancement can be performed if the corneal thickness permits.
PRK regression: Similar profile to LASIK. Generally well-managed with standard enhancement protocols.
EVO ICL stability: Excellent — the Collamer lens does not change its power over time. Apparent “regression” after ICL surgery is more typically caused by natural myopia progression in younger patients, not the lens itself.
RLE stability: Excellent for the distance prescription (IOL power is fixed). PCO (posterior capsule opacification) can cause apparent blurring that is easily treated with a YAG laser capsulotomy.
Related Resources
- LASIK vs PRK vs EVO ICL: Complete Comparison
- Vision Correction Procedures Compared
- Which Vision Correction Is Safest?
- What Is the Best Vision Correction Surgery?
- What Happens If My Vision Changes After a Procedure?
- Is Vision Correction Surgery Worth the Money?
*This content is educational and does not constitute medical advice. Outcome data reflect published peer-reviewed literature and should be interpreted with guidance from a qualified ophthalmologist during a personalized consultation.*