PRESBYOND Side Effects and Risks

How to read risk information

Risk writing fails in two directions. Marketing stops at how many patients are delighted, which can be true and incomplete. Patient forums collect the worst outcomes, which are real and unrepresentative. Neither tells you where your own eye sits.

Two questions make any risk description more useful. What kind of event is this: something most patients experience, something uncommon, or a rare serious event? And could it have been anticipated: was it visible in the measurements, in the tear film, or in the lens?

A third question is specific to this treatment. Is the risk one of the surgery, or one of the plan? A corneal flap, dry eye and infection belong to LASIK. The experience of having two eyes doing different jobs belongs to the blended strategy, and it is the risk patients most often underestimate.

What most patients notice

These are the effects patients describe most often in the first days and weeks. They are consequences of reshaping the cornea and of asking the brain to combine two different images, not signs that something has gone wrong.

• Dryness and grittiness. The most frequently reported symptom after any LASIK procedure.
• Glare and halos. Rings or flare around lights, usually most noticeable at night.
• Light sensitivity. Bright light and screens feeling uncomfortable early on.
• Fluctuating sharpness. Vision varying through the day or between the two eyes.
• A sense of imbalance between the eyes. One eye feeling dominant, or closer work feeling easier on one side.
• Headache or eye strain during close work. Often reported while the brain is adjusting.

Most of these improve as the surface settles and adaptation progresses. A minority of patients report some persisting, and the honest position is that the published series follow patients for six to twelve months, which is long enough to describe early outcomes and not long enough to describe a lifetime.

Dry eye

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

Refractive surgery cuts corneal nerves, which are part of the feedback loop that keeps the surface moist and comfortable. LASIK creates a flap, and the nerves that cross it are interrupted. The surface usually recovers, but recovery is measured in months, and pre-existing dry eye is the largest single predictor of trouble afterwards.

The practical consequence is that a dry eye problem should be identified and treated before surgery, not discovered at the first post-operative visit. Ask what your tear film assessment showed, and what the clinic wants done about it before a date is set.

Glare, halos and night driving

Night vision symptoms are among the most discussed trade-offs of laser correction for presbyopia, partly because the plan deliberately gives the eyes different focus and partly because a larger pupil in low light exposes more of the transition zone in a corneal ablation.

An earlier one-year series of 20 patients reported night vision disturbance as its most common complaint, alongside near vision that was relatively weaker than the patients had hoped. That is a small study, and it is still the most specific statement the PRESBYOND literature offers on this point.

What can be said without inventing a figure: halos and glare are commonly reported early, often settle, and can persist at a level some patients notice. How much they matter depends on the person as much as the eye. A professional night driver and someone who rarely drives after dark are not making the same decision.

If night driving is central to your work, say so at the assessment and ask what the plan would do about it. That is a legitimate reason to choose a more conservative target, a different procedure, or no surgery.

When adaptation does not happen

This is the risk that belongs to blended vision specifically, and the one to discuss most carefully. The plan assumes the brain will combine an eye focused for distance with an eye left short-sighted. Most people do adjust. Some do not, or adjust only partly, and report persistent imbalance, headache, or dissatisfaction with one range of vision.

There is no scan that predicts this. The available signals are indirect: a contact lens trial, a history of monovision lens wear, and a careful conversation about what the person does all day.

The important question is not whether adaptation usually happens, which the published series suggest it does, but what the clinic does when it does not. Reasonable answers include a period of observation with review, glasses for specific tasks, a contact lens on one eye, or in selected cases a further procedure to reduce the difference. A clinic that has no answer has not thought about it.

Residual vision and enhancement

Refractive surgery aims at a target, and not every eye lands exactly on it. A small residual can be left alone, corrected with glasses for chosen tasks, or refined with a further procedure once refraction has stabilised.

Enhancement after LASIK usually means lifting the original flap and treating again, which is technically simpler than a second procedure after SMILE. It still requires corneal tissue, still carries risk, and is not always possible or advisable. The published PRESBYOND series report retreatment in a minority of patients, more often in long-sighted than in short-sighted eyes.

Before treatment, establish three things in writing: whether refinement is included, discounted or charged in full; whether there is a time limit on that policy; and what happens if your cornea cannot support another treatment.

Rare and serious complications

These are uncommon. They are listed plainly because a person making a permanent decision about their eyes is entitled to know they exist, and because the assessment is largely designed to reduce them.

• Corneal ectasia. A rare weakening and bulging of the cornea, associated with removing too much tissue from a cornea that was too thin or abnormal to begin with. Topography and pachymetry screening exist to detect exactly that.
• Infection. Uncommon and serious when it occurs. It is the reason for the restrictions on water, swimming, eye makeup and rubbing in the early period.
• Inflammation at the interface. The plane under the flap where the laser worked. Usually managed with anti-inflammatory drops and monitoring.
• Flap complications. Displacement, folds or epithelial ingrowth. More likely with trauma or rubbing in the early weeks, which is why the instructions matter.
• Persistent dry eye or persistent night vision symptoms at a level that affects daily life.

Symptoms that need prompt review

What screening can and cannot prevent