You had laser vision correction some years ago, enjoyed a long stretch of sharp sight, and now the road signs at night or the small print on your phone have started to soften again. A reasonable question tends to follow: can the treatment simply be done a second time?
For a good number of people the answer is yes, a further correction is possible, though it is never automatic. A repeat procedure, usually called an enhancement, depends on the health and thickness of your cornea and on why your vision has changed in the first place. Understanding what makes someone suitable for a second round of LASIK helps you have a more useful conversation at your review, and sets sensible expectations about what a top-up can and cannot do.
Why vision can drift after laser correction
Laser correction reshapes the cornea, the clear dome at the front of the eye, so that light focuses more precisely on the retina. It corrects the prescription you have on the day of surgery. What it cannot do is hold your eyes still for the rest of your life.
A short-sighted prescription that was still creeping upward before surgery can carry on shifting afterwards, which is one reason surgeons ask for a settled prescription before treating in the first place. It is advised that candidates are ideally over 21, when vision is more likely to have stopped changing, and should have a prescription that has not changed much in the last year. Age plays a part too. From around the mid-forties, almost everyone develops presbyopia, the normal age-related loss of close-up focus, and laser correction does not treat it, so reading glasses at that stage reflect ageing and not a procedure that has failed.
Telling a return of short-sightedness apart from this kind of age-related change is something an assessment can clarify quickly, and understanding eye degree regression sets out how surgeons distinguish the two.
What an enhancement involves
An enhancement is a second laser treatment applied to an eye that has already been corrected. Where the first surgery created a thin corneal flap, the surgeon can sometimes lift that same flap and apply a little more laser to the tissue beneath it. The American Academy of Ophthalmology notes that some surgeons prefer not to re-lift the flap and will instead treat the surface of the cornea with a technique such as Trans PRK, which reaches a similar goal by a different route.
Whether a top-up is sensible comes down to a handful of clinical factors:
- Corneal thickness – Every laser treatment removes a small amount of tissue, and enough has to remain for the cornea to stay strong. Whether you can be treated again depends largely on whether enough thickness is left in the cornea.
- A settled prescription – A degree that is still moving will keep moving after a top-up, so surgeons usually want it stable first.
- The reason for the change – Blurring caused by something else, such as an early cataract, will not be corrected by more laser and needs its own assessment.
- Corneal shape and health – An irregular or thinning cornea can rule out further treatment altogether.
For a suitable candidate, the experience of an enhancement is broadly similar to the original surgery, with a short procedure followed by a healing period while the eye settles. As with any eye surgery it carries its own small risks, and these are weighed against the likely benefit during your consultation.
Timing and realistic expectations
There is no fixed number of times an eye can be treated. The practical limit is tissue and stability, not a set count on a chart.
Most enhancements are considered only once vision has settled after the first procedure, and sometimes years later, when a prescription has shifted. HealthHub Singapore notes that additional enhancement laser procedures may be required to reach the vision a patient is hoping for, and that a specific end result cannot always be guaranteed. That honesty is important. A top-up aims to refine vision, not to promise perfect sight for life.
Questions about long-term stability come up often here, because Singapore has one of the highest rates of short-sightedness in the world. The Singapore National Eye Centre reports that more than 80 per cent of young adults are myopic, so many people who had laser correction in their twenties are exactly the group now wondering about a second procedure a decade or two on.
Who should think twice
Not everyone who notices a change is a candidate for more laser. Thin corneas, early signs of keratoconus (weak and irregular shaped cornea), significant dry eye, or a blurring that turns out to be a cataract instead of refractive drift can each point away from a repeat procedure and towards a different solution. This is why the decision rests on examination and measurements, not on how the vision happens to feel on a given day.
Dr Lee Sao Bing, our refractive surgeon at Ava Eye Clinic, previously served as Medical Director at Shinagawa Eye Centre and as Head of the Cornea Service at the National University Hospital Eye Centre, and he assesses each eye on its own merits before advising on any further treatment.
The next step
If your vision has softened since your original laser treatment, a careful assessment is the only way to tell whether an enhancement suits you or whether something else is at work. To find out where you stand, do get in touch with our team to arrange an eye examination.