Introduction
Refractive surgeries, such as laser-assisted in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK), are widely performed procedures that correct refractive errors.1 While both surgeries have proven effective in achieving excellent visual outcomes, the occurrence of pain and discomfort after surgery remain a concern, both in the acute period and chronically.2 3 In LASIK, a hinged corneal epithelial flap is created to expose the corneal stroma, photoablation is performed to reshape the cornea under the flap, and the flap is repositioned. In PRK, the corneal epithelium is removed centrally and photoablation is performed directly on the anterior stroma.4 The frequency of postoperative pain after PRK has been examined in prior studies. In one study that quantified pain on a numeric rating scale (NRS, 0–10 scale), ocular pain ≥2 was present in 97% (n=71) of individuals in the postoperative period (mean NRS of 6.3±2.5). In fact, a high proportion of individuals (52%, n=38) reported a pain intensity higher than 7.5 Unfortunately, less data are available on the incidence of acute pain after LASIK.
Information on the incidence and factors associated with acute pain after refractive surgery (eg, PRK and LASIK) could improve targeting and choice of prophylactic and therapeutic algorithms. Oral non-steroidal anti-inflammatory drugs (NSAIDs) and opioids, topical NSAIDs, topical anaesthetics, cold patches and bandage soft contact lenses have all been used to mitigate acute pain after PRK.6 In a prospective study of 157 individuals, peak pain scores within 5 days of PRK (rated on a 0–10 NRS) were significantly lower in individuals who received topical (0.4% ketorolac) compared with oral (naproxen 220 mg) NSAIDs every 12 hours for 72 hours after surgery (4.2±2.19 vs 5.82±1.94, p<0.0001, respectively).7 Similar studies are lacking with respect to management of acute pain after LASIK.
It is important to understand which patients are at risk for acute pain after refractive surgery as the presence of acute postsurgical pain has been identified as a risk factor for chronic pain development in ocular surgeries. In a retrospective study of 119 individuals who underwent cataract surgery, recall of higher acute postoperative pain during the first week after surgery (NRS 0–10) was a risk factor for persistent postoperative pain (OR 1.30, 95% CI 1.06 to 1.60).8 Acute pain has similarly been identified as a risk factor for chronic pain after refractive surgery.9 In our prospective study of individuals who underwent refractive surgery (n=109), ocular pain before surgery (OR 1.9, 95% CI 1.1 to 3.3, NRS 0–10) and ocular pain 1 day after surgery (OR 1.6, 95% CI 1.2 to 2.2, p=0.005, NRS 0–10) increased the risk of persistent pain after surgery (defined as NRS ≥3 at both 3 and 6 months).9 As such, understanding and addressing acute pain after refractive surgery may improve management of patients and long-term outcomes.
More information is thus needed on the frequency and risk factors for acute pain development after refractive surgery. Several studies have examined this question after surgeries outside the eye. In a retrospective study of 1041 unilateral total knee arthroplasty procedures, female gender (OR 1.76, 95% CI 1.31 to 2.36, p<0.001) and higher body mass index (OR 1.06, 95% CI 1.02 to 1.09, p<0.001) predicted ‘major pain’ 1 day after surgery (NRS ≥5, 0–10 scale).10 Similar factors were identified in a prospective study of 466 individuals undergoing cataract surgery, with female gender (β=0.21, p<0.001), younger age (β=−0.13, p=0.005) and higher education level (β=0.14, p=0.003) predicting pain report 1 day after surgery (0–10 scale).11 Our current study investigates the incidence, severity and risk factors for acute pain following both PRK and LASIK.