Photorefractive Keratectomy, or PRK, is a type of laser eye surgery that corrects refractive errors, including nearsightedness, farsightedness, and astigmatism. This procedure uses a highly precise excimer laser to reshape the curvature of the cornea, the clear, dome-shaped front surface of the eye. PRK is a powerful option for individuals seeking to reduce or eliminate their dependence on glasses or contact lenses, offering a permanent alteration to the eye’s focusing power.
The Mechanism of PRK
PRK is classified as a surface ablation technique because the laser is applied directly to the outer surface of the cornea. The cornea consists of multiple layers, and the outermost layer, called the epithelium, must be removed to access the underlying tissue. This removal is performed before the laser is used, exposing the next layer, known as the corneal stroma.
The excimer laser then emits cool, ultraviolet light pulses to vaporize microscopic amounts of stromal tissue with extreme precision. For correcting nearsightedness, the laser flattens the central curvature of the cornea, while for farsightedness, it steepens the periphery.
This approach fundamentally differs from Laser-Assisted In Situ Keratomileusis (LASIK) because it avoids the creation of a corneal flap. In PRK, the entire epithelial layer is removed and allowed to regenerate naturally over the next several days. Because no flap is created, the structural integrity of the cornea is maintained, which is an advantage for certain patients.
The Surgical Procedure
The PRK procedure is typically performed in an outpatient setting and takes only a short time. Upon arrival, the patient receives topical anesthetic drops to numb the eye, ensuring no pain is felt during the operation. A mild oral sedative may also be offered to help the patient relax throughout the process.
Once the patient is positioned beneath the excimer laser, a small eyelid holder, called a speculum, is placed to keep the eye open. The first surgical step involves removing the corneal epithelium, which can be accomplished using an alcohol solution, a soft brush, or a sterile surgical instrument. This process takes only a few seconds and prepares the underlying stroma for the laser treatment.
The surgeon then directs the patient to focus on a target light while the excimer laser is activated. The laser’s reshaping phase is automated and fast, often lasting between 20 to 60 seconds per eye, depending on the degree of correction needed. Modern lasers use an eye-tracking system to ensure the pulses remain precisely centered even if the eye moves slightly.
After the laser ablation is complete, the surgeon places a soft, clear bandage contact lens directly onto the treated cornea. This lens acts as a protective shield and a temporary covering for the exposed stromal tissue, not for vision correction. The bandage lens remains in place until the epithelium fully regrows, which helps manage discomfort and facilitates proper healing.
Recovery and Post-Operative Care
The initial recovery phase for PRK is characterized by discomfort and fluctuating vision. Patients commonly experience a foreign body sensation, burning, and light sensitivity for the first two to four days post-surgery. The most intense discomfort is typically reported on days two and three, just before the new epithelium fully covers the treatment area.
To manage this, patients are prescribed a regimen of medicated eye drops, including antibiotics to prevent infection and steroid drops to control inflammation and minimize the risk of corneal haze. Oral pain relievers, and sometimes even prescription-strength drops, are used to manage the initial pain.
The bandage contact lens is typically worn continuously for three to seven days and is removed by the ophthalmologist during a follow-up appointment. Once this protective lens is removed, the vision often improves immediately, becoming functional enough for driving and returning to most work activities. However, the vision may still be somewhat blurry and can fluctuate throughout the day.
While the surface epithelial healing is rapid, full visual stabilization takes significantly longer. The final visual result is often achieved over three to six months. The prolonged use of steroid drops is a major component of post-operative care, as they are gradually tapered off to guide the long-term healing of the corneal tissue. Attending all scheduled follow-up appointments is necessary to monitor the eye’s healing progression and adjust the medication schedule.
Who is a Suitable Candidate
Candidacy for PRK requires meeting general health and eye-specific standards, beginning with being at least 18 years old and having a stable vision prescription for a minimum of 12 months. Patients must also have healthy eyes, free from active infections or conditions like uncontrolled glaucoma and severe dry eye. Certain systemic conditions, such as autoimmune diseases, can also disqualify a patient from the procedure.
PRK is often the preferred choice over LASIK for individuals with corneas that are naturally too thin for safe corneal flap creation. Since PRK is a surface procedure, it preserves more of the deeper corneal tissue, which is a structural advantage for these patients.
The flap-free nature of PRK also makes it the procedure of choice for people engaged in professions or activities that carry a high risk of eye trauma. Military personnel, law enforcement officers, and contact sports athletes often select PRK because there is zero risk of a corneal flap becoming dislodged or damaged. Ultimately, a comprehensive preoperative examination determines the most appropriate procedure based on individual corneal health and lifestyle.