PRK and Other Laser Vision Correction Procedures

Roughly 700,000 LASIK procedures are performed annually in the United States, but LASIK is not the only — or even always the best — option for laser vision correction (American Academy of Ophthalmology). Photorefractive keratectomy (PRK), the original surface ablation technique approved by the FDA in 1995, remains a first-line choice for patients with thin corneas, certain corneal irregularities, or occupations that carry a higher risk of eye trauma. Understanding how PRK fits alongside LASIK, SMILE, and newer approaches helps patients and referring clinicians match the procedure to the eye — not the other way around.

How PRK Works

PRK reshapes the corneal stroma using an excimer laser, the same ultraviolet 193 nm wavelength instrument used in LASIK. The critical difference is access. Rather than creating a hinged corneal flap, the surgeon removes the thin outer epithelial layer — roughly 50 micrometers thick — either manually, with a dilute alcohol solution, or with a specialized brush. The excimer laser then ablates a precise amount of stromal tissue to correct the refractive error (myopia, hyperopia, or astigmatism). Because no flap is created, PRK eliminates flap-related complications such as displacement, striae, or epithelial ingrowth.

Recovery takes longer than LASIK. The epithelium regenerates over three to five days, during which a bandage contact lens protects the corneal surface. Visual acuity often stabilizes within one to three months, compared with roughly 24 hours for LASIK. That tradeoff matters — but for the right candidate, the structural integrity of a flap-free cornea is worth the wait.

LASIK: The Comparison Everyone Makes

LASIK (Laser-Assisted in Situ Keratomileusis), FDA-approved in 1999, dominates the refractive surgery conversation largely because of its rapid visual recovery and minimal post-operative discomfort. A femtosecond laser or microkeratome creates a corneal flap approximately 100–120 micrometers thick, under which the excimer laser performs the ablation. The flap is repositioned, and it adheres without sutures.

A large meta-analysis published in the Journal of Cataract & Refractive Surgery found that 99.5% of modern LASIK patients achieved 20/40 or better uncorrected visual acuity, and over 90% achieved 20/20 (FDA LASIK Quality of Life Study). Patient satisfaction rates consistently land between 96% and 98%.

The catch: LASIK requires sufficient corneal thickness to accommodate both the flap and the ablation. Patients with corneas thinner than approximately 500 micrometers, or those with corneal ectasia risk factors identified on topography, are generally steered toward PRK.

SMILE: The Newer Arrival

Small Incision Lenticule Extraction (SMILE) received FDA approval in 2016 for myopia correction and in 2024 expanded to include myopic astigmatism. Instead of ablating tissue with an excimer laser, SMILE uses a femtosecond laser to create a small lens-shaped piece of tissue (a lenticule) within the cornea, which the surgeon removes through an incision of roughly 2–4 mm (FDA Premarket Approval Database). No flap, no surface ablation.

SMILE's appeal lies in its small incision, which preserves more corneal nerve fibers than a full LASIK flap. Early data suggests lower rates of dry eye symptoms in the first six months compared to LASIK. The limitation: SMILE does not yet treat hyperopia in the U.S., and enhancement procedures after SMILE are technically more complex than after LASIK or PRK.

Who Gets PRK — and Why

PRK remains the procedure of choice in specific clinical scenarios:

• Thin corneas — Pachymetry readings below 500 µm, where flap creation would leave insufficient residual stromal bed (the generally accepted minimum is 250 µm).
• High-risk occupations — Military personnel, law enforcement officers, and contact sport athletes face elevated risk of flap dislocation. The U.S. Department of Defense has historically favored PRK for active-duty service members (Military Health System).
• Prior corneal scarring or dystrophies — Surface ablation can sometimes address superficial irregularities simultaneously.
• Patients with large pupils or borderline topography — Wavefront-guided PRK allows customized treatment profiles without the biomechanical compromise of a flap.

Post-operative mitochondrial suppression with mitomycin-C (MMC), applied briefly during surgery, has reduced the historic risk of corneal haze — once the primary disadvantage of PRK — to below 2–3% in most published series.

What About TransPRK and Other Surface Variants?

TransPRK (transepithelial PRK) streamlines the procedure by using the excimer laser itself to remove the epithelium and reshape the stroma in a single step. This "no-touch" approach reduces operative time and may improve surface smoothness. LASEK, a close cousin of PRK, preserves the epithelial sheet by loosening it with alcohol before ablation and repositioning it afterward — though most large centers have moved away from LASEK, finding its recovery profile similar to PRK without meaningful clinical advantage.

Risks Common Across All Procedures

No refractive procedure is without risk. Across PRK, LASIK, and SMILE, potential complications include:

• Dry eye — particularly common in the first three to six months; tends to be more persistent after LASIK than PRK in some studies.
• Undercorrection or overcorrection — enhancement rates hover around 5–10% depending on the initial refractive error and patient age.
• Night vision disturbances — halos, glare, and starbursts, most common with larger pupil sizes relative to treatment zone diameter.
• Regression — gradual return of mild refractive error, more frequently observed in higher corrections (above −6.00 diopters).

The FDA's LASIK Quality of Life Collaboration Project found that fewer than 1% of patients experienced significant difficulty with daily activities due to visual symptoms post-operatively (FDA).

Choosing Between Procedures

The decision tree is less about which procedure is "best" and more about which procedure fits a given cornea, refractive error, lifestyle, and risk tolerance. A thorough preoperative evaluation — including corneal topography, pachymetry, wavefront aberrometry, tear film assessment, and pupillometry — provides the data needed for an informed recommendation. The best refractive outcome starts not with the laser, but with the measurement.

References

• American Academy of Ophthalmology — LASIK
• FDA — LASIK Quality of Life Collaboration Project
• FDA — Premarket Approvals (PMA) Database
• Military Health System — Eye Care and Refractive Surgery
• National Eye Institute — Refractive Errors

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