Introduction
No surgical procedure is without risk. PRK is one of the most studied and safest elective surgeries performed in modern medicine, but informed consent requires that patients understand the specific risks of the procedure, how frequently they occur, and what measures experienced surgeons take to minimize them.
Understanding PRK risks does not mean approaching the procedure with fear. It means approaching it with clarity. The risks associated with PRK are real but manageable, most complications are detectable early through structured follow-up, and the interventions available to address them are effective in the vast majority of cases. The appropriate context for PRK risk is the alternative: the long-term risk profile of contact lens dependence, which carries its own cumulative infection, surface disease, and vision-threatening complication rate that many patients underestimate.
What distinguishes top-tier PRK surgeons is not that their patients never encounter complications. It is that their protocols, selection criteria, and monitoring practices minimize the incidence and severity of complications — and their experience and clinical judgment enable rapid, effective intervention when complications do occur. For surgeons recognized for excellence in PRK safety and outcomes, consult the PRK Surgery Awards directory.
Risk 1: Corneal Haze
What It Is
Corneal haze is a proliferative healing response in the anterior stroma following PRK ablation. It is caused by abnormal keratocyte activation and myofibroblast differentiation at the ablated surface during the healing process. Haze appears as a superficial opacity when viewed under slit-lamp illumination and can, in significant cases, reduce visual clarity.
Haze is graded on a scale from trace (only visible on slit-lamp in specific illumination) to severe (visible in regular illumination, causing significant vision reduction). Most post-PRK haze is trace to mild — visible on examination but clinically insignificant. Moderate to severe haze causing meaningful vision loss is the true clinical concern.
Risk Factors
The risk of clinically significant haze increases with:
- Higher prescriptions requiring deeper ablation
- UV light exposure during the healing period (sunlight activates keratocytes)
- Failure to use or adhere to post-operative steroid drops
- Genetic predisposition (some patients have heightened healing responses)
- Dry eye conditions that impair epithelial healing quality
How Top Surgeons Mitigate It
Mitomycin-C (MMC) application: The most effective intervention. MMC, an anti-metabolite that inhibits fibroblast proliferation, is applied to the ablated stromal surface for 12 to 30 seconds at the end of PRK. At 0.02% concentration, it dramatically reduces keratocyte activation and haze formation without meaningful toxicity to surrounding tissue at the brief exposures used. With routine MMC, clinically significant haze has become rare — occurring in less than 1% of cases at most high-volume centers.
Topical steroid protocol: Post-operative steroids (prednisolone acetate or fluorometholone) modulate the inflammatory healing response. Steroids are tapered gradually over weeks to months, and the taper schedule is adjusted based on the patient’s individual healing assessment at each follow-up visit. Patients who develop early haze may have their steroid taper extended.
UV light avoidance counseling: Patients are instructed to wear UV-blocking sunglasses during the healing period (typically several months). This is a meaningful risk reduction step that some practices underemphasize.
Structured monitoring: Regular slit-lamp evaluation at every post-operative visit allows detection of early haze formation while it is still amenable to intervention with extended steroids. Haze that progresses undetected is more difficult to manage. This is one reason why adherence to the full post-operative visit schedule matters clinically, not just administratively.
Risk 2: Undercorrection and Overcorrection
What They Are
- Undercorrection: The surgical correction falls short of the intended target, leaving residual refractive error. The patient may still need glasses or contacts for some activities.
- Overcorrection: The ablation removes more tissue than planned relative to the clinical effect, pushing the patient past plano (zero refractive error) into the opposite refractive error — for example, a myope becoming mildly hyperopic.
Neither is a catastrophic complication in most cases, but both require management.
Why They Occur
Refractive surgery is not a purely mechanical procedure. The cornea’s biological healing response — including epithelial remodeling, stromal remodeling, and individual variation in tissue response — affects the final refractive outcome in ways that even the most precise laser system cannot fully anticipate. Individual variation in healing response is the primary driver of undercorrection and overcorrection.
Higher prescriptions carry higher regression risk, as the deeper ablation stimulates a more substantial healing response that can partially fill in the correction over time.
How Top Surgeons Mitigate It
Nomogram application: Experienced PRK surgeons track their outcomes data systematically and apply practice-specific nomogram adjustments to the laser system’s programmed correction. For example, if a surgeon’s outcomes data shows that patients with high myopia tend to undercorrect by approximately 5%, they may program the laser to aim for a slightly higher correction than the manifest refraction suggests, compensating for the expected healing response. Nomogram development is a mark of clinical sophistication and requires years of systematic outcome tracking.
Treatment planning refinement: Modern planning software integrates topographic, wavefront, and refractive data to optimize ablation profiles. Surgeons who use all available data rather than relying solely on manifest refraction produce more predictable outcomes.
Enhancement policy: Leading practices offer enhancement — a repeat surface ablation — for patients with clinically significant residual refractive error after the eye has stabilized (typically at six months or later). Enhancement policy transparency, including eligibility criteria and cost structure, should be discussed before primary surgery.
For complete data on PRK accuracy outcomes, see PRK Surgery Safety and Long-Term Outcomes.
Risk 3: Corneal Regression
What It Is
Regression refers to a gradual return toward the pre-operative prescription over months to years following surgery. It is distinct from undercorrection (which refers to the immediate surgical result) and represents the cornea’s long-term biological tendency to partially compensate for the altered curvature.
Regression is more common with:
- Higher initial prescriptions
- Younger patients (whose corneas may have more biological plasticity)
- Hyperopic corrections (which regress more than myopic corrections)
How Top Surgeons Mitigate It
Prescription selection: Surgeons who understand regression risk manage patient expectations proactively, explaining that long-term visual stability may require monitoring and possibly enhancement in patients with higher prescriptions.
Long-term follow-up: Detecting regression requires monitoring refraction over time. Practices with structured long-term follow-up — including six-month and one-year refraction checks — identify regression early and can offer enhancement when it reaches clinical significance.
Enhancement availability: A practice’s enhancement policy directly influences how regression is managed. Patients who know that enhancement is available at no additional charge (within the guarantee period) experience less anxiety about the possibility of regression.
Risk 4: Dry Eye and Reduced Corneal Sensitivity
What It Is
PRK removes the corneal epithelium and ablates the anterior stroma, affecting the sub-epithelial nerve plexus — the dense network of corneal nerves responsible for corneal sensitivity and tear reflex stimulation. Temporary reduction in corneal sensitivity following PRK can impair the neuro-reflex that drives tear production, contributing to dry eye symptoms during the healing period.
PRK affects a smaller nerve population than LASIK (which severs nerves over a wider area with the lamellar flap), so the post-PRK dry eye impact is generally milder. However, patients with pre-existing dry eye are at elevated risk of significant post-operative symptoms.
How Top Surgeons Mitigate It
Pre-operative dry eye screening and treatment: Identifying and treating dry eye before surgery is the most effective intervention. Practices that include tear film assessment in every refractive evaluation — and that delay surgery until dry eye is optimized — have better post-operative dry eye outcomes. See PRK and Contact Lens Wearers: What You Should Know for a discussion of contact lens-related dry eye in this context.
Proactive post-operative lubrication: Preservative-free artificial tears, used generously in the post-operative period, support epithelial healing and corneal surface hydration. Practices that emphasize lubricant use as part of the post-operative drop regimen — not just antibiotics and steroids — demonstrate awareness of this risk.
Omega-3 supplementation: Evidence supports the use of high-dose omega-3 fatty acid supplementation (EPA + DHA) for meibomian gland function and tear film quality. Some surgeons recommend starting omega-3 supplementation weeks before PRK.
Punctal plugs: Temporary collagen or permanent silicone punctal plugs, which reduce tear drainage and increase tear volume, can be used pre-operatively in dry eye patients and post-operatively in those who develop significant dry eye after PRK.
Risk 5: Infection (Microbial Keratitis)
What It Is
During the three-to-five-day period when the corneal epithelium has been removed and the bandage contact lens is in place, the stromal surface is exposed. While the risk of infection during this period is very low, it is a recognized complication of PRK that can cause corneal scarring if not promptly identified and treated.
Published infection rates after PRK are approximately 1 in 2,000 to 1 in 5,000 cases. Severe infections causing permanent vision loss are exceedingly rare in patients who receive standard post-operative antibiotic prophylaxis and attend their scheduled follow-up visits.
How Top Surgeons Mitigate It
Prophylactic antibiotic drops: All PRK patients receive topical antibiotic drops for the first week post-operatively, covering the period of maximum infection risk. The specific antibiotic regimen varies by practice preference and local pathogen resistance patterns.
Proper bandage contact lens management: The bandage lens should not be disturbed, rubbed, or removed except by the surgeon at the scheduled removal visit. Patients are instructed to contact the practice immediately if the lens appears to have shifted or been removed prematurely.
Prompt evaluation of red flags: Patients are given clear instructions about symptoms that warrant urgent evaluation: increasing redness, pain, discharge, or sudden vision decline during the first week. Practices with accessible after-hours lines for post-operative concerns enable early intervention.
Risk 6: Glare, Halos, and Night Vision Disturbance
What It Is
Some patients experience increased awareness of halos, starbursts, or glare around lights — particularly at night — after PRK. These symptoms are most common in the first one to three months of recovery and diminish significantly with neuroadaptation.
Risk factors include large pupil diameter (the pupil expands to a diameter larger than the optical treatment zone in dim light, creating a peripheral zone of uncorrected tissue), high prescriptions, and pre-existing higher-order aberrations.
How Top Surgeons Mitigate It
Large optical zone selection: Modern excimer platforms allow surgeons to select larger optical zones and smooth transition zones that reduce the risk of pupil-edge effects. Surgeons who optimize optical zone diameter based on the patient’s pupil size reduce night vision complication risk.
Wavefront-guided treatment: Wavefront-guided PRK corrects the full aberration profile of the eye, reducing both pre-existing aberrations and the aberrations that can be induced by surgery itself. This results in better night vision quality compared to conventional ablation. See PRK Technology and Surgical Advancements for a detailed discussion.
Patient selection and counseling: Patients with very large pupils in dim light are counseled specifically about night vision risk before surgery and may be offered larger optical zone profiles or alternative procedures where the risk can be better managed.
The Rare but Serious Risk: Post-PRK Ectasia
Post-operative ectasia — progressive corneal thinning and bulging after refractive surgery — is a rare but potentially serious complication. In PRK, ectasia risk is substantially lower than in LASIK because no lamellar cut is made. The most significant ectasia risk factor is unrecognized pre-existing keratoconus or forme fruste keratoconus — a subclinical ectatic condition not detected on topography alone.
Top surgeons mitigate ectasia risk through:
- Comprehensive pre-operative screening using both topography and tomography (Scheimpflug imaging)
- Epithelial thickness mapping with OCT to identify patterns inconsistent with simple astigmatism
- Conservative exclusion of borderline cases where clinical uncertainty exists
- Detailed clinical judgment that integrates all diagnostic data rather than relying on any single measurement
For a full discussion of PRK safety, see PRK Surgery Safety and Long-Term Outcomes.
What Patients Should Ask About Risk Management
“What specific steps do you take to prevent corneal haze?” — The surgeon should mention MMC protocol specifically.
“How do you handle patients who undercorrect or regress?” — The surgeon should explain their enhancement policy clearly.
“What is your post-operative monitoring schedule?” — Look for structured follow-up through six to twelve months, not just a brief post-op check.
“How do I contact you if I have concerns between visits?” — Accessible after-hours communication is a safety feature, not just a convenience.
For guidance on evaluating overall surgeon quality relative to these risk management standards, see How PRK Surgeons Are Evaluated for Awards and PRK Surgeon Credentials and Qualifications.
Frequently Asked Questions
How common are serious complications from PRK? Vision-threatening complications from PRK in appropriately selected patients are very rare — estimated at less than 1 in 50,000 cases in experienced hands. The more common complications (mild haze, undercorrection, temporary dry eye) are manageable and typically resolve with appropriate treatment.
Is PRK riskier than LASIK? They carry different risk profiles, not universally higher or lower risk. PRK eliminates flap-related complications but carries slightly higher short-term risks of haze and prolonged visual recovery. For appropriately selected patients, neither procedure has a clearly superior overall safety profile.
What happens if I develop significant haze? Mild to moderate haze often responds to extended topical steroid treatment. In cases where haze causes significant vision reduction and does not respond to steroids, phototherapeutic keratectomy (PTK) — a laser procedure that smooths the anterior surface — may be used to remove the haze layer.
Can PRK be redone if the results are unsatisfactory? Yes, in most cases. Enhancement PRK is performed once the eye has fully stabilized and sufficient corneal tissue remains. The enhancement procedure is essentially a repeat PRK with MMC and follows the same recovery trajectory as the primary procedure.
Next Steps
PRK is a procedure with a well-characterized risk profile and effective mitigation strategies for every known complication. Understanding these risks — and verifying that your surgeon has protocols to address them — is the most important step you can take before surgery. Start your surgeon search with PRK Surgery Awards, where recognized surgeons have been evaluated for the clinical and safety protocols described throughout this page.