Photorefractive Keratectomy

Excerpt

Photorefractive keratectomy (PRK) is a laser-based eye surgery used to correct visual refractive errors, including myopia, hyperopia, and astigmatism. PRK was developed in 1983 by Dr Steven Trokel and colleagues and first performed in 1987 by Dr Theo Seiler in Berlin. After receiving approval from the US Food and Drug Administration (FDA) in 1996, PRK became the preferred surgical treatment for ametropia, as it provided more predictable and stable results than incisional keratotomy. However, the number of PRK procedures fell in the late 1990s with the growing popularity of laser in situ keratomileusis (LASIK). Today, LASIK remains the most commonly performed visual refractive surgery; nonetheless, there remain select situations in which PRK may be preferable.

PRK is a widely recognized and time-tested laser vision correction procedure that has played a pivotal role in the evolution of refractive surgery. Developed in the late 1980s, PRK was the first laser-based surgical technique to correct refractive errors, particularly myopia, hyperopia, and astigmatism. Since its FDA approval in the 1990s, it has offered a safe and effective alternative to glasses and contact lenses, laying the groundwork for subsequent innovations such as LASIK and small incision lenticule extraction (SMILE).

PRK operates on the principle of reshaping the anterior corneal stroma using an excimer laser to alter the cornea's refractive power. Unlike LASIK, which involves creating a corneal flap, PRK involves the mechanical or chemical removal of the corneal epithelium, followed by laser ablation of the underlying stromal tissue. This approach eliminates flap-related complications and preserves more of the corneal tissue, making PRK particularly suitable for individuals with thinner corneas, irregular corneal topographies, or those at a higher risk of trauma (eg, military personnel and athletes involved in contact sports).

The indications for PRK have expanded over the years with advancements in diagnostic technologies, laser platforms, and postoperative management. PRK is primarily recommended for patients with stable refractive errors, adequate corneal thickness, and no corneal ectatic disorders, such as keratoconus. PRK is also considered a safer option in patients with occupational or lifestyle considerations that pose a risk to corneal flap integrity. Additionally, PRK has found applications in the treatment of residual refractive errors after cataract surgery or corneal transplantation, as well as in therapeutic refractive surgery for anterior stromal scars and epithelial basement membrane dystrophies.

The role of corneal wound healing is one of the key physiological considerations in PRK. After epithelial removal and stromal ablation, re-epithelialization occurs over 3 to 5 days, during which a bandage contact lens is typically placed for patient comfort. Unlike LASIK, PRK is associated with a more extended visual recovery period and greater early postoperative discomfort. However, with the use of modern techniques, medications, and adjunctive therapies such as mitomycin C, the risks of haze formation, regression, and delayed healing have significantly declined.

The efficacy of PRK in achieving excellent uncorrected visual acuity and reducing refractive errors has been well documented in numerous randomized controlled trials and long-term follow-up studies. Clinical outcomes demonstrate that the refractive accuracy and visual acuity achieved with PRK are comparable to those of LASIK, particularly in patients with low-to-moderate degrees of myopia. Furthermore, the risk of postoperative dry eye may be reduced in PRK due to the absence of corneal flap creation, preserving more of the sub-basal nerve plexus.

Technological advancements have played a transformative role in enhancing PRK outcomes. The introduction of wavefront-guided and topography-guided ablation profiles has improved the quality of vision by addressing higher-order aberrations and irregular astigmatism. Additionally, newer generation excimer lasers with faster ablation rates and enhanced eye-tracking systems have minimized treatment times, reduced thermal damage, and improved centration accuracy.

From a patient-centered care perspective, PRK requires thorough preoperative counseling and shared decision-making. Patients must be informed about the initial discomfort, slower recovery, and potential need for temporary spectacles during the healing period. However, for appropriate candidates, the long-term satisfaction with PRK is high due to the procedure's safety, predictability, and durability. Postoperative care typically involves the use of corticosteroid eye drops for 4 to 6 weeks or longer to mitigate inflammation and haze, along with regular follow-up to monitor healing and refractive stability.

In the broader scope of refractive surgery, PRK remains relevant despite the popularity of LASIK and SMILE. PRK is a preferred option in patients with relative contraindications to LASIK, such as borderline corneal thickness, anterior basement membrane dystrophy, epithelial irregularities, or superficial corneal opacities. Moreover, PRK is less likely to induce ectasia in susceptible eyes due to the absence of biomechanical weakening from flap creation. In cases of retreatment or enhancement where flap re-lifting may pose a risk, surface ablation techniques, such as PRK, are often the technique of choice.

The interprofessional team, including ophthalmologists, optometrists, nurses, and technicians, plays a crucial role in the success of PRK. A comprehensive preoperative evaluation by optometrists and ophthalmic technicians ensures the appropriate selection of patients for surgery. Intraoperative precision by surgeons and postoperative care by the nursing team contribute significantly to the overall outcome and patient satisfaction. Interprofessional collaboration also enhances patient education, medication adherence, and management of expectations, thereby improving the patient experience and reducing complication rates.

Recent literature continues to support PRK as a viable and valuable refractive surgical option. Meta-analyses and registry-based studies have confirmed its safety and effectiveness even in complex scenarios, such as post-keratoplasty eyes or those with minor anterior stromal irregularities. The desire for biomechanical preservation and long-term corneal stability also drives the resurgence in interest in surface ablation techniques. In conclusion, PRK stands as a cornerstone of refractive surgical practice, offering a safe, predictable, and effective method for vision correction. With continued technological improvements and expanding indications, PRK remains a vital tool in the armamentarium of refractive surgeons. The importance of PRK lies not only in its historical legacy but also in its ongoing relevance in the era of individualized, tissue-preserving refractive surgery.