SMILE Pro Risks and Side Effects: A Balanced Guide

How to read risk information

Risk writing fails in two directions. Industry material tends to stop at “most patients are delighted”, which is true and incomplete. Patient forums tend to collect the worst outcomes, which are real and unrepresentative. Neither gives you a sense of your own position.

Two habits make the material you read more useful. First, ask what kind of event it is: a side effect most patients experience to some degree, a complication that is uncommon, or a rare serious event. Second, ask whether the risk was knowable in advance. That is the category you can actually act on, because it is what the preoperative assessment exists to detect.

Commonly reported side effects

These are the effects patients describe most often. Most improve over the first weeks and months, though a minority of people report some persisting longer. They are consequences of cutting and reshaping the cornea, not signs that something has gone wrong.

Dry eye

Dry eye is the side effect most worth understanding before surgery, because it is the most common, the most persistent when it does persist, and the most influenced by factors that are measurable beforehand.

Every refractive procedure cuts corneal nerves. Those nerves are part of the feedback loop that keeps the ocular surface comfortable and moist, so disrupting them reduces tear production and changes blink behaviour. In a small-incision procedure fewer nerves are cut than in a flap-based one, which is why pooled analyses and reviews generally report more favourable early corneal sensation and dry-eye measures after SMILE than after femtosecond LASIK.

Three caveats matter as much as the finding:

• The literature is not unanimous. Individual studies disagree, and a favourable pooled result does not mean a favourable individual one.
• SMILE can still cause dry eye. A reduced risk relative to another procedure is not the same as no risk.
• Pre-existing dry eye is the biggest predictor. If your ocular surface is already compromised, the relevant question is not which procedure is gentler but whether to proceed at all, and in what order.

Most people who develop dryness after surgery find it improves over the first months. For a minority it persists, and for those people it can be more intrusive than they anticipated. Standard treatment is lubricants and management of the ocular surface, and your clinic should be able to describe how they would manage it.

Dry eye, explained by an ophthalmologist

Michael Chua, MD · Named clinician How to Treat Dry Eyes Like an Ophthalmologist

Third-party video Presented by Michael Chua, a named practising ophthalmologist, for a general audience. It covers how dry eye is assessed and managed. It is not surgical advice and it is not about SMILE specifically: dry eye matters here because it is one of the factors assessed before any refractive surgery. Watch on YouTube (opens in a new tab)

Glare, halos and night vision

Rings, starbursts and glare around lights: car headlights at night being the classic example are commonly reported in the early weeks. They are usually described as diminishing as healing settles, although some patients report residual night vision symptoms at a level they notice.

Several factors influence how much this affects you: how much tissue was removed, the size of the treatment zone relative to your pupil in low light, your own visual sensitivity, and how much night driving you do. If you drive at night professionally, or the idea of halos around headlights would be genuinely intolerable, that is worth saying explicitly at your assessment.

Under-correction and over-correction

Refractive surgery aims at a target prescription, and not every eye lands exactly on it.

• Under-correction leaves some of the original error uncorrected, so distance vision is better than before but not as sharp as intended.
• Over-correction overshoots, which can leave you slightly long-sighted and makes close work harder.

A small residual is common and often tolerated easily. Which direction is more troublesome depends on your age, your work and your other eye. This is why asking “what will you do if I have a residual” is a more useful question at the assessment than asking about success rates.

Residual prescription and enhancement

If refraction settles with a meaningful residual, a further procedure (an enhancement) may be considered. This is normally discussed after refraction has stabilised, which is why a decision should not be made in the first weeks however impatient the wait feels.

The enhancement conversation after SMILE is structurally different from after LASIK. There is no flap to lift, so options may involve a surface treatment or creating a flap in a second procedure, depending on your cornea and the residual. Not every residual is treatable, and a considered surgeon will say so rather than promise a top-up.

Before surgery, establish three things in writing: whether enhancements are included, discounted or charged in full; whether there is a time limit on that policy; and what happens if an enhancement is not possible for your cornea. The quote checklist covers this.

Inflammation

Postoperative inflammation at the interface: the plane inside the cornea where the laser worked: is a recognised finding after lenticule extraction. It is usually managed with anti-inflammatory drops and monitoring, and most cases resolve with treatment. It is one reason the early follow-up appointment exists and one reason postoperative drops should be used exactly as prescribed rather than stopped when the eye feels fine.

Infection

Infection after refractive surgery is uncommon, but it is a serious event when it occurs, and it is the reason behind several restrictions that patients find inconvenient: no water, no swimming, no eye makeup, no rubbing. Those restrictions are not arbitrary caution. They are the mechanism by which this particular risk is kept low.

Contact your clinic promptly (not at the next scheduled visit) if you develop increasing pain, increasing redness, discharge, or vision that worsens rather than fluctuates.

Rare and serious complications

These are uncommon, and they are the events the preoperative assessment is largely designed to prevent. They are listed plainly rather than buried, because a reader making a permanent decision about their eyes is entitled to know they exist.

• Corneal ectasia. A rare complication in which the cornea weakens and bulges, affecting vision and sometimes requiring further treatment. It is associated with removing too much tissue from a cornea that was too thin or abnormal to begin with, which is precisely what pachymetry and topography screening exist to detect.
• Epithelial ingrowth. Surface cells growing into the interface. More associated with flap-based surgery, but possible after any corneal incision.
• Suction loss during the laser phase. The suction holding the eye against the laser interface can be released, which may mean pausing, stopping or rescheduling the treatment. It is a technical event rather than a complication of the eye, but it is worth asking your surgeon how they handle it.
• Persistent dry eye or persistent night vision symptoms at a level that affects daily life.

Risk factors you can and cannot change

Sorting risks by whether they are modifiable is the most practical thing you can do with this page.

Questions to ask your surgeon about risk

These are drawn from the printable list on the procedure page. The ones about complications are the ones that produce the most information, and the ones patients most often skip.