What are the risks and complications of photorefractive keratectomy (PRK)?

Risks and Complications of Photorefractive Keratectomy (PRK)

PRK carries uncommon but potentially permanent complications including loss of best-corrected visual acuity, corneal haze, infectious keratitis, and corneal ectasia, though the procedure is generally safe with proper patient selection. 1

Common Side Effects and Complications

Refractive Outcomes

• Symptomatic undercorrection or overcorrection occurs in a minority of patients, with undercorrection rates of 7.4% in low myopia and 38.7% in high myopia requiring retreatment 2
• Partial regression of effect is common, particularly with higher degrees of myopia, causing gradual return of refractive error over months 1
• Induced regular or irregular astigmatism can develop from improper axis alignment during surgery or healing irregularities 1
• Induced anisometropia may occur between eyes 1

Visual Quality Issues

• Visual aberrations including glare, starburst, or halo effects occur especially at night, with 3.6% of patients reporting these symptoms 1, 3
• Decreased contrast sensitivity can persist after surgery 1
• Loss of best-corrected visual acuity (BCVA) occurs in approximately 0.7% of eyes at one year, with 2.7% losing one or more lines 1, 2, 3

Corneal Complications

• Corneal haze or scarring (early or delayed onset) develops from subepithelial fibrosis and is more common with higher corrections, with severe haze present in only 0.6% of eyes at one year 1, 2
• Corneal infiltrates, ulceration, melting, or perforation (sterile or microbial) can occur and require urgent evaluation 1
• Corneal ectasia (progressive corneal steepening) is a rare but serious complication that can develop months to years after surgery 1
• Central toxic keratopathy causes acute vision loss with characteristic corneal findings 1

Ocular Surface and Nerve-Related Issues

• Development or exacerbation of dry eye symptoms is extremely common after PRK, causing fluctuating vision particularly with blinking 1, 4
• Decreased corneal sensitivity occurs due to nerve disruption 1
• Corneal neuralgia can manifest as chronic pain requiring multimodal treatment beyond standard dry eye therapies 1
• Recurrent corneal erosion may develop in susceptible patients 1

Infectious and Inflammatory Complications

• Reactivation of HSV keratitis can occur in patients with prior herpes simplex virus infection, warranting perioperative antiviral prophylaxis 1
• Microbial keratitis must be considered whenever a corneal infiltrate is seen, particularly with delayed epithelial healing 1

Medication-Related Complications

• Corticosteroid-induced complications including ocular hypertension (3.5% of patients), glaucoma, and cataract can develop from postoperative steroid use 1, 3
• Complications related to mitomycin-C (used off-label to reduce haze) include endothelial cell decrease 1

Other Complications

• Adverse effect on ocular alignment may occur 1
• Ptosis develops in 0.4% of eyes 1, 3
• Artifactual reduction of measured IOP occurs due to corneal thinning 1

Important Clinical Considerations

Postoperative Course

• Vision is typically poor for weeks after PRK, with activities like driving potentially impossible during this period due to ongoing epithelial healing 1, 4
• Epithelialization usually completes within 5 days, but stable vision and refraction may not be achieved for many months 1

Risk Mitigation

• Proper patient selection is critical to minimize complications, with 82.5% of eyes developing no complications when appropriately selected 3
• Retreatments should not be performed until refraction, corneal haze, and topography have stabilized, usually requiring at least 6 months 1
• Off-label mitomycin-C application at the time of retreatment reduces recurrence of haze but carries risks of endothelial damage 1

Common Pitfalls

• Anesthetic and NSAID drops may delay corneal epithelialization and should be prescribed judiciously, though they provide improved pain control 1
• Sterile corneal infiltrates associated with NSAID drops without concomitant corticosteroids have been described, but microbial keratitis must always be ruled out 1
• Retreatment in the presence of anything more than mild corneal haze should be carefully considered 1