Undergoing LASIK a second time, known as an enhancement or retreatment, is often safe and effective for individuals who experience a shift in vision after the initial procedure. However, this secondary procedure is only suitable for patients who meet specific medical criteria. An enhancement is a specialized technique used to fine-tune visual correction, typically when the initial result was imperfect or the eye has changed slightly over time. This approach differs from the original surgery because the cornea’s anatomy has already been permanently altered.
Understanding Vision Regression After LASIK
The need for a second procedure is usually prompted by vision regression, which is the subtle return of a small amount of refractive error. This does not mean the first surgery failed, but rather that the eye continued to change or healed differently than anticipated. Early regression, occurring within the first few months, is often due to the eye’s natural healing response, where the corneal tissue attempts to remodel back toward its original shape.
A high initial prescription increases the likelihood of needing a touch-up because more corneal tissue was removed initially. Vision changes can also occur years later due to the progression of the eye’s underlying refractive error or hormonal shifts. It is important to distinguish true regression from age-related changes like presbyopia, which LASIK does not treat and requires reading glasses later in life.
Critical Factors for Retreatment Eligibility
The determination of safety for a LASIK enhancement depends on a meticulous re-evaluation of the eye’s structure and overall health. The most important factor is the remaining thickness of the corneal tissue. Since LASIK removes tissue from the cornea’s middle layer, the stroma, a retreatment requires removing an additional amount.
A safety threshold known as the residual stromal bed thickness must be maintained to prevent the cornea from weakening. Most surgeons require a minimum of 250 to 300 microns of tissue to remain underneath the original flap after the enhancement. Failure to meet this requirement increases the risk of a severe complication called corneal ectasia.
Other Eligibility Requirements
Beyond corneal thickness, a patient’s prescription must have remained stable for at least six months to one year. Good overall eye health is also necessary, meaning the absence of uncontrolled autoimmune disorders, active eye infections, or severe, unmanaged dry eye disease.
Methods Used for a Second LASIK Procedure
The technical approach to a LASIK enhancement differs from the original surgery because a flap already exists. Surgeons use two primary methods to perform the retreatment.
Flap Lift
The most common technique is the flap lift, where the surgeon carefully re-lifts the original corneal flap, applies the laser correction to the underlying tissue, and then repositions the flap. This method is preferred for retreatments performed within the first few years, as it allows for a faster visual recovery time compared to surface ablation.
Surface Ablation
The alternative method is surface ablation, such as Photorefractive Keratectomy (PRK) or LASEK, performed on top of the original LASIK flap. This is typically chosen if the flap cannot be safely lifted or if the remaining corneal tissue is too thin. Surface ablation avoids the structural risks associated with re-lifting a flap but involves a longer, more uncomfortable healing period and a slower return to clear vision. The choice between these two methods is based on the patient’s corneal measurements and the integrity of the existing flap.
Specific Risks Associated with LASIK Enhancement
While enhancements are safe for eligible patients, they carry specific risks heightened compared to the primary procedure. The most serious concern is the risk of developing corneal ectasia, a condition where the cornea weakens and bulges forward, causing significant vision distortion. This risk is directly tied to the amount of tissue removed, making the residual stromal bed thickness the primary safety measure.
Flap-related complications are also a unique concern during a retreatment. Re-lifting the existing flap can increase the potential for epithelial ingrowth, where surface cells grow underneath the flap, sometimes requiring a further procedure to resolve. Additionally, an enhancement can exacerbate dry eye symptoms, a common side effect of any corneal surgery. Patients may also experience visual disturbances such as halos, glare, or irregular astigmatism.