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PRK (Photorefractive Keratectomy)

A flap-free laser vision correction surgery with slower recovery than LASIK but advantages for certain corneas and lifestyles.

9 min read

PRK (photorefractive keratectomy) is laser vision correction without a corneal flap. It reshapes the cornea to correct myopia, astigmatism, and on certain laser platforms hyperopia. PRK came before LASIK, then stuck around because it still solves problems LASIK does not solve as cleanly: thin-but-healthy corneas, flap-avoidance occupations, and certain surface considerations. The trade-off is the first week. PRK recovery is slower and more uncomfortable because the surface epithelium has to grow back.

Key Takeaways

  • PRK reshapes the cornea with the same excimer laser used in LASIK, but without creating a flap
  • The corneal epithelium is removed first, then the laser ablation is performed; the epithelium grows back over several days
  • Long-term visual outcomes match LASIK for most patients
  • PRK is often preferred over LASIK for thin but otherwise healthy corneas and for patients where a flap is undesirable; suspected keratoconus/ectasia or active severe dry eye usually needs stabilization or excludes elective laser vision correction
  • The trade-off is slower recovery - gritty, watery, light-sensitive days up front, with vision stabilizing over weeks to months

How PRK Works

The cornea is the clear front window of the eye and provides about two-thirds of the eye's focusing power. Most refractive errors come from the cornea being too steep (myopia), too flat (hyperopia), or unevenly curved (astigmatism). All laser refractive surgery works by reshaping the cornea to compensate.

PRK steps:

  1. Topical anesthetic drops are applied to the eye
  2. The corneal epithelium (the thin outermost layer) is removed using a brush, dilute alcohol, or a special laser; this exposes the corneal stroma
  3. An excimer laser is used to ablate the stroma, removing tiny amounts of tissue in a precise pattern that flattens, steepens, or evens out the corneal curvature
  4. A bandage contact lens is placed to protect the surface and aid epithelial healing
  5. The patient leaves the operating room the same day

The actual laser portion takes seconds to a minute. The total time in the operating room is usually 15-20 minutes for both eyes.

PRK vs. LASIK

Both procedures use the same excimer laser to reshape the corneal stroma. The difference is how access is achieved:

Feature PRK LASIK
Corneal flap None Yes - a thin hinged flap is created
Epithelium Removed and regrows over 4-7 days Lifted as part of the flap and replaced
Discomfort first week Moderate to significant Mild
Vision recovery Days to weeks Hours to days
Final visual outcome Comparable to LASIK Comparable to PRK
Risk of flap complications None (no flap) Real but low
Risk in eye trauma No flap to dislodge Flap can be displaced years later
Suitable for thin cornea Yes - preserves more stroma May not be safe
Suspected keratoconus or ectasia Generally avoided unless part of a highly selected therapeutic protocol Avoided
Cost Similar to LASIK Similar to PRK

When PRK Is Preferred Over LASIK

  • Thin corneas that cannot safely accommodate a LASIK flap and adequate residual stromal bed
  • Normal topography with a thinner cornea where LASIK would leave too little residual stromal bed
  • Selected stable superficial corneal scars where the surgeon determines surface ablation is safe
  • Dry-eye tendency after optimization - LASIK can worsen dry eye more than PRK, but active severe dry eye should be treated before any elective refractive surgery
  • High-impact occupations - military, law enforcement, certain athletes, where flap dislodgement risk would be problematic
  • Contact sports - boxing, martial arts, etc.
  • Patient preference for a flap-free procedure

What to Expect

Before the Procedure

  • A complete pre-operative evaluation including corneal topography, pachymetry, manifest refraction, and dilated retinal examination
  • Stop wearing soft contact lenses at least a week before, rigid contacts often longer (the cornea must return to its baseline shape)
  • Discussion of expected outcome, alternatives, and risks
  • Instructions on the postoperative drop regimen

During the Procedure

  • The patient lies face up under the laser
  • Topical anesthetic eliminates pain
  • The eyelids are held open with a small speculum
  • Epithelium is removed (this part may produce a faint pressure or scraping sensation, not pain)
  • The excimer laser is applied - the patient is asked to look at a fixation light
  • A bandage contact lens is placed
  • Total time per eye: typically 5-10 minutes
  • Both eyes are usually treated in the same visit

Recovery - First Week

  • The first 3-5 days are usually the most uncomfortable part of recovery
  • Significant discomfort - gritty, watery, light-sensitive
  • Vision is blurred and changes from day to day
  • Pain medication, lubricating drops, and a bandage contact lens make it manageable
  • The bandage contact lens is removed at 5-7 days when the epithelium has healed
  • Some patients describe this period as comparable to recovery after epi-off corneal cross-linking - significant but bounded

Weeks 2-4

  • Vision continues to improve and clear
  • Mild glare and halos are common, particularly at night
  • Light sensitivity gradually improves
  • Most patients can return to desk work within a week and most other activities within 2 weeks

Months 1-3

  • Vision continues to refine and stabilize
  • Glare and halos diminish
  • Postoperative steroid drop course (typically 1-3 months) protects against haze formation

Long-Term

  • Most patients reach final stable vision by 3-6 months
  • Visual outcomes are comparable to LASIK at 6+ months postoperatively
  • Need for reading glasses with age (presbyopia) is not affected - PRK does not prevent presbyopia from developing

Risks

PRK has a strong safety record. Possible complications, mostly uncommon:

  • Pain and discomfort during epithelial healing - universal but transient
  • Corneal haze - diffuse haziness that develops in the weeks after surgery; usually mild and resolves with topical steroids. Persistent dense haze is rare but more common with high-correction PRK and was historically common before mitomycin-C was added to the procedure.
  • Undercorrection or overcorrection - the achieved correction is slightly different from intended; sometimes addressed by an enhancement procedure later
  • Regression - gradual return of refractive error over months to years
  • Glare and halos at night - most common in the first months; usually improves
  • Dry eye - usually less severe than after LASIK but can occur
  • Corneal infection - rare; risk is in the days to weeks while the epithelium heals
  • Persistent epithelial defect - slow healing, manageable with extended bandage contact lens and lubrication
  • Loss of best-corrected vision - extremely uncommon with modern technique

Mitomycin-C

After the excimer ablation, a sponge soaked in mitomycin-C 0.02% (a topical anti-fibrotic) is applied to the corneal stroma for typically 12-30 seconds, then thoroughly rinsed. This significantly reduces the risk of post-PRK haze, particularly for corrections greater than approximately −6 D. Many U.S. surgeons now use mitomycin-C routinely for all PRK regardless of correction depth.

Outcomes

For typical refractive errors:

  • >95% of patients achieve 20/40 uncorrected vision or better - a common legal driving threshold without glasses, though rules vary by state
  • >80% reach 20/20 or better
  • Outcomes are comparable to LASIK at 6+ months out for appropriate candidates
  • A small minority require enhancement (touch-up) procedures

Frequently Asked Questions

Is PRK better or worse than LASIK?

Neither is universally better. LASIK is more comfortable in the first week and gives faster visual recovery; PRK avoids a flap and may fit thin corneas or high-impact lifestyles better. Long-term outcomes are comparable in appropriate candidates. The right choice depends on corneal measurements, prescription, tear film, occupational needs, and risk tolerance.

Why is PRK so much more uncomfortable than LASIK?

LASIK preserves the corneal epithelium by lifting it as part of the flap and replacing it. PRK removes the epithelium entirely, leaving an open wound on the surface of the cornea that has to heal over 4-7 days. Healing this wound produces gritty, watery, light-sensitive eyes for several days. Pain medication, lubricating drops, and a bandage contact lens manage this period.

Will I see well right away?

No. Vision is significantly blurred for the first 3-5 days, somewhat blurred for the first 1-2 weeks, and gradually clears over weeks. Many patients can drive once vision is legal, comfortable, and cleared by the surgeon, often around a week. Final stable vision is reached at 3-6 months. This contrasts with LASIK, where many patients see well within 24 hours.

The most common reasons are thin but otherwise healthy corneas, an occupation or sport in which a corneal flap would be undesirable, or dry-eye risk after the ocular surface has been optimized. If topography suggests keratoconus or ectasia, elective laser vision correction is usually avoided unless the surgeon is using a special therapeutic protocol. Your eye doctor decides based on the full pre-operative evaluation.

Does PRK eliminate the need for glasses forever?

Not necessarily. For distance vision, most patients are glasses-free for many years. As age progresses, presbyopia develops in everyone - the eye's lens loses its ability to focus at near - and reading glasses or progressives are usually needed in your 40s and beyond. PRK corrects the cornea but does not prevent age-related lens changes.

Can PRK be repeated?

A small enhancement (touch-up) procedure can be performed if the initial result is undercorrected. Repeat full PRK is uncommon but possible in selected eyes. For age-related changes (cataracts, presbyopia), other procedures are typically more appropriate than additional laser refractive surgery.

References

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