LASIK and PRK are established procedures used to correct refractive errors by reshaping the cornea. While LASIK is the more common choice due to its rapid recovery, a small percentage of patients experience a gradual return of their original vision defect, known as regression, years after the initial surgery. When this occurs, an enhancement procedure is often recommended to restore optimal clarity. For patients who have previously undergone LASIK, PRK is frequently the chosen method for this secondary treatment. This surface ablation technique is a safe strategy to fine-tune vision after the initial LASIK results have diminished over time.
Why PRK is the Preferred Enhancement Method
The decision to use PRK for a LASIK enhancement is primarily driven by the need to protect the structural integrity of the cornea. During the original LASIK procedure, a thin flap of corneal tissue is created and lifted to allow the excimer laser to treat the underlying stromal bed. Re-lifting this original flap for a second time carries several risks that surgeons prefer to avoid, especially if the enhancement is needed several years later.
One of the most significant concerns is the risk of epithelial ingrowth, where the surface cells grow underneath the flap rather than over the incision line. This complication can cause irregular astigmatism and vision loss. The risk of it occurring increases substantially when re-lifting a flap that has been in place for more than two or three years. Performing PRK, which involves treating the surface of the cornea and the existing flap, completely bypasses the need for flap manipulation.
PRK preserves the existing stable bond between the flap and the underlying tissue. By avoiding a second flap procedure, the structural stability of the cornea is maintained, minimizing the potential for weakening the eye’s architecture. This technique also allows the surgeon to address minor irregularities on the flap surface. The PRK enhancement prioritizes long-term corneal health and stability over the faster recovery offered by a flap re-lift.
Essential Screening and Eligibility Criteria
Before a surgeon approves a PRK enhancement after LASIK, a thorough clinical evaluation is required to confirm safety and eligibility. The most critical measurement is the thickness of the residual stromal bed (RSB), which is the remaining tissue underneath the original LASIK flap. Surgeons must ensure that the total corneal tissue remaining after the PRK treatment meets a minimum safety threshold, typically at least 250 micrometers, to maintain biomechanical stability and prevent a condition called ectasia.
The surgeon will also perform detailed corneal mapping, known as topography, to assess the shape and curvature of the cornea. This mapping helps identify any pre-existing or developing corneal irregularities, which could indicate a risk of ectasia or an unstable correction. The patient’s refractive error must also be stable, meaning their prescription has not changed significantly for at least one year, confirming that the regression has stopped. Additionally, the surgeon will evaluate the overall health of the eye, checking for conditions like severe dry eye or cataract formation, which could affect the outcome of the procedure.
The Post-LASIK PRK Procedure
The PRK enhancement procedure is performed directly on the surface of the existing LASIK flap. After the eye is numbed with topical anesthetic drops, the surgeon carefully removes the corneal epithelium, the outermost layer of cells, a process called debridement. This is typically done either mechanically with a surgical brush or blade, chemically with an alcohol solution, or sometimes with the laser itself.
Once the underlying flap surface is exposed, the excimer laser is used to precisely reshape the tissue based on the patient’s current refractive error. Because the treatment is applied to the surface of the flap, the depth of the ablation is minimal, further preserving the integrity of the deeper stromal bed. To minimize the risk of postoperative haze, a medication called Mitomycin C is often applied to the treated area for a short period. Finally, a clear, non-prescription bandage contact lens is placed on the eye to act as a protective layer, allowing the epithelial cells to regrow comfortably underneath.
Recovery Timeline and Visual Expectations
Patients should anticipate that the recovery from a PRK enhancement is different from the rapid healing experienced after the initial LASIK surgery. Since the outer layer of the cornea is removed, it must fully regenerate, which causes temporary discomfort, light sensitivity, and blurred vision for the first few days. The bandage contact lens usually remains in place for three to seven days until the new epithelial layer has completely closed the wound.
Functional vision, which is often sufficient for driving and returning to work, typically begins to stabilize within one to two weeks after the procedure. However, the final visual clarity improves gradually as the new epithelial cells mature and the underlying cornea fully heals. It is common for vision to fluctuate for the first month, and final, stable vision may not be achieved until three to six months post-procedure. Patients are advised to use prescribed anti-inflammatory and antibiotic eye drops diligently during this extended period to manage healing and reduce the risk of complications like corneal haze.