Yes, halos can happen after SMILE — but the real number is under 1% of eyes.
You’re a few weeks out from SMILE, driving home after dark, and every oncoming headlight has a glowing ring around it. Google it and you’ll find the same recycled stat on page after page. Here’s what the actual research says instead — including a study that compared SMILE eyes not to LASIK, but to patients’ own natural, never-operated-on eye.
Key Takeaways
- A large 2025 case series found photopsia/halo/glare in just 0.55% of eyes within 3 months of SMILE Pro, and 0.88% beyond that.
- A randomized contralateral trial — SMILE in one eye, LASIK in the other, same patients — found no statistically significant difference in halos between the two.
- The real cause is mechanical: in dim light your pupil widens past the treated optical zone, letting untreated cornea into your line of sight.
- Halos typically peak around 1 month post-surgery and fade substantially by 3–6 months.
- Large pupils are screened for beforehand — it’s one of the standard checks before you’re cleared for surgery at all.
The Facts, Verified
Here’s what’s actually published, beyond the uncited “5% vs 10%” figure most sites repeat.
| Verified fact | Why it matters for you |
|---|---|
| A 2025 retrospective series of 916 SMILE Pro eyes recorded photopsia/halo/glare in 0.55% of eyes within 3 months, rising to 0.88% beyond 3 months | Far lower and more precise than the “~5%” figure most sites quote with no source |
| A randomized contralateral trial (SMILE in one eye, LASIK in the other, same patients) found no statistically significant difference in halos, glare, double vision, or starbursts at any visit up to 12 months | The “SMILE causes fewer halos than LASIK” claim isn’t supported by head-to-head evidence |
| A SMILE-specific study measured objective disk halo size increasing at 1 week post-op, then returning to baseline by 3 months | Gives you a realistic, SMILE-specific timeline, not one borrowed from LASIK data |
| A monocular-SMILE study comparing the operated eye against each patient’s own unoperated eye 14 months later found no significant difference in halo size — some patients saw better night vision in the SMILE eye | A stronger reassurance than “similar to LASIK”: comparable to an eye that never had surgery |
| The same 916-eye SMILE Pro series found a suction-loss rate of 0.66% and an enhancement (retreatment) rate of 1.54% | Context for how rare complications of any kind are with modern SMILE technique |
Sources: PMC (2025) SMILE Pro case series; CRSToday/PubMed Ma & Manche RCT; Graefe’s Archive disk-halo study.
What a Halo Actually is?
A halo is a bright ring or glow surrounding a light source — most noticeable around headlights, streetlamps, or a candle flame at night. It’s distinct from a starburst, where light rays spike outward from the source rather than circling it, and from glare, where the light itself just seems abnormally intense. All three fall under what ophthalmologists call photic phenomena, and SMILE, LASIK, and PRK can each produce them to varying degrees.
Why it Happens?
The mechanism is mechanical, not mysterious. SMILE reshapes a defined optical zone in the center of your cornea. In bright light your pupil stays small, so light passes only through that treated zone. In the dark, your pupil widens — and if it widens past the edge of the treated zone, light also enters through the untreated periphery, where it isn’t focused the same way. That mismatched light scatters and shows up as a ring around bright points.
A second, SMILE-specific factor: how precisely the treatment is centered. Research on optical-zone decentration found even a shift under 0.5mm off-center can introduce enough aberration to trigger halos on its own, separate from pupil size entirely — one reason precise centering matters as much as the correction itself.
Does Pupil Size Actually Predict Your Risk?
The old assumption — bigger pupils mean guaranteed halos — is being actively revised by newer, larger studies.
| What’s commonly said | What modern studies actually show | Verdict |
|---|---|---|
| “Large pupils mean you’ll definitely get halos” | A large case series found no need to reject candidates on pupil size alone, once wavefront-guided planning is used | ❌ Oversimplified |
| “Pupil size doesn’t matter at all” | Symptoms can run slightly higher in month 1 across all pupil sizes, converging by 3–6 months | ⚠️ Partly true, timing matters |
| “What predicts risk is correction strength, optical zone, and residual refractive error” | Matches findings across multiple modern wavefront-guided studies | ✅ Best-supported view |
Sources: Schallhorn case series (Ophthalmology Times); wavefront-guided LASIK pupil-size study (OCLI).
Pupil size is still measured as part of your workup — see what counts as large for your case — but it’s one factor among several, not a solo predictor.
SMILE vs LASIK: Setting the Record Straight
The claim that SMILE causes meaningfully fewer halos than LASIK is repeated constantly, but the strongest evidence available — a randomized trial with SMILE in one eye and LASIK in the other, same patients — found no significant difference in halos, glare, double vision, or starbursts through 12 months. More patients did prefer their LASIK eye overall by month 12 (46% vs 19%), but that tracked with sharpness of vision, not halos. None of this makes SMILE the worse choice — it means the “fewer halos” marketing point doesn’t hold up against head-to-head data.
Halo, Glare, Starburst or Rainbow Glare?
These terms get used interchangeably, but they point to different things — one is specific to LASIK, not SMILE.
| What you’re seeing | Likely cause | Typical path |
|---|---|---|
| Faint ring around lights, fading over weeks | Normal pupil/optical-zone mismatch in dim light | ✅ Expected; monitor and follow up as scheduled |
| Rays spiking outward from lights (starburst) | Same mechanism as halos, different visual pattern | ⚠️ Usually resolves alongside halos |
| Rainbow-coloured streaks around lights | A flap-related diffraction effect specific to femtosecond LASIK | ⚠️ Not a SMILE phenomenon at all — flag it to your surgeon |
| Halos that worsen or persist well past 6 months | Possibly an atypical healing pattern | ❌ Needs an in-person evaluation, not more waiting |
Source: photic-phenomena classification per refractive surgery literature.
How Long It Lasts?
SMILE-specific measurements back this up: one study tracking objective disk halo size found it rose at 1 week post-op, then returned to baseline by 3 months. A more telling study followed patients with SMILE in only one eye, comparing it against their own unoperated eye 14 months later — no significant difference in halo size, and some patients reported better night vision in the SMILE eye. That’s stronger reassurance than “comparable to LASIK” — comparable to an eye that never had surgery. Improvement tracks alongside broader night vision recovery after SMILE generally.
What You Can Do?
- Limit night driving during the first few weeks while your cornea is still settling.
- Use lubricating drops as directed — untreated dryness can worsen glare on its own; see which drops actually help.
- Keep your follow-up appointments so your surgeon can track whether your timeline matches the expected curve.
- Ask about topography-guided planning if you’re still deciding on a procedure — how the treatment zone is mapped can influence photic-phenomena risk.
If symptoms are still significant well past the expected recovery window, or if you’re comparing SMILE against other options like Contoura Vision or SMILE Pro, that’s a conversation for your surgeon, not a symptom to just wait out.
Bottom Line
Halos after SMILE are real, but recent data puts them well under 1% of eyes — and the “SMILE beats LASIK on halos” claim doesn’t survive head-to-head comparison. Most cases fade within months as your pupil-to-optical-zone relationship stabilises. Book a consultation if your symptoms feel outside the normal pattern described here.
FAQs
Is SMILE really better than LASIK for avoiding halos?
Not according to the best available evidence. A randomized trial comparing both procedures in the same patients found no significant difference in halo rates.
How common are halos after SMILE, really?
A large 2025 case series put photopsia/halo/glare at 0.55% of eyes within 3 months, and 0.88% beyond that — much lower than the commonly quoted 5%.
Will halos go away on their own?
For most patients, yes. Studies show symptoms peak around 1 month and decline steadily through 3–6 months as the cornea settles.
What’s the difference between a halo and rainbow glare?
A halo is a plain ring of light around a bright source. Rainbow glare shows distinct colors and is a flap-related effect specific to LASIK — it isn’t something SMILE patients experience.
Does having large pupils mean I’ll definitely get halos?
No — that’s an oversimplified, outdated belief. Modern studies show correction strength and optical zone design predict risk better than pupil size alone, though it’s still measured as part of your workup.
