ARTICLE Evaluation of early postoperative ocular pain after photorefractive keratectomy and corneal crosslinking Siamak Zarei-Ghanavati, MD, MS, FICO, Soheyla Jafarpour, MD, FICO, Alireza Radyn-Majd, MD, Hamed Hosseinikhah-Manshadi, MD Purpose: To evaluate and compare early postoperative pain after photorefractive keratectomy (PRK) and corneal crosslinking (CXL). Setting: Khatam-al-Anbia Eye Hospital, Mashhad, Iran. Design: Prospective case series. Methods: The PRK group included patients with simple refractive errors whereas the CXL group included patients with clinical ker- atoconus. The groups were compared regarding the level of pain based on the visual analogue scale (VAS), verbal rating scale (VRS), and Wong-Baker FACES pain rating scale immediately after surgery, 6 hours postoperatively, and 1, 3, and 7 days postoperatively. The epithelial defect size was measured at 6 hours after surgery and 1 day and 3 days after surgery in both groups. Results: The study comprised 68 patients (34 patients in the PRK group and 34 patients in the CXL group). The epithelial defect size was significantly smaller in the CXL group than in the PRK group (P < .001); however, the amount of pain was significantly higher after CXL than after PRK based on VAS and VRS (P Z .04 and P Z .019, respectively). In the FACES scaling system, the pain score was also higher in the CXL group than in the PRK group. However, the differ- ence was not statistically significant. No intraoperative or postoper- ative complications were observed during follow-up. Conclusions: The epithelial defect healing rate was statistically significantly faster in the CXL group than in the PRK group. Howev- er, the level of pain was greater in the CXL group, suggesting that postsurgical pain might be influenced by other factors than the epithelial defect. J Cataract Refract Surg 2018; -:-–- Q 2018 ASCRS and ESCRS T he cornea has the densest small fiber innervation in the body. The corneal nerve density is estimated to be 300 to 400 times higher than that of human skin. 1,2 Corneal sensory nerve fibers containing myelinated Ad and unmyelinated C fibers, which are derived from the ophthalmic branch of the trigeminal nerve, penetrate the limbus and form a rich subepithelial nerve plexus in the anterior third of the stroma. 2–5 This nerve plexus brings the pain signals to the central nervous system. Several mechanisms might be involved in cornea-related pain, including stimulation of the corneal nerve endings from an epithelial defect, ablation of corneal nerves, and chemoactivation of nerves by neuromediators and chemi- cals. 6–9 The exact mechanism of cornea-related pain is still unclear and patients might experience intensive pain after corneal procedures. Since the introduction of corneal crosslinking (CXL) and photorefractive keratectomy (PRK) procedures, postopera- tive pain management has been a major challenge for both the patient and the surgeon. Corneal crosslinking is a promising procedure to halt the progression of keratoconus. 6,9,10 Corneal crosslinking uses ultraviolet-A (UVA) light and riboflavin (a photosensi- tizer), which strengthens the cornea by releasing oxygen radicals that lead to covalent crosslinking of the collagen fi- bers. 9–12 The postoperative pain can be intense, in partic- ular in the first 3 days, even with an aggressive pain control regimen. 13,14 Corneal surface ablation, in the form of PRK, has long been a mainstay for the treatment of refractive errors such as myopia. 7 A considerable portion of the anterior cornea containing heavy innervation is removed in this Submitted: September 30, 2016 | Final revision submitted: January 27, 2018 | Accepted: February 17, 2018 From the Eye Research Center (Zarei-Ghanavati, Jafarpour, Hosseinikhah-Manshadi), Mashhad University of Medical Sciences, Mashhad, and Shahid Beheshti University of Medical Sciences (Radyn-Majd), Tehran, Iran. Corresponding author: Soheyla Jafarpour, MD, Eye Research Center, Mashhad University of Medical Sciences, Khatam-al-Anbia Eye Hospital, Abootaleb Boulevard, Mashhad, Iran. Email: soheylajafarpour@gmail.com. Q 2018 ASCRS and ESCRS Published by Elsevier Inc. 0886-3350/$ - see frontmatter https://doi.org/10.1016/j.jcrs.2018.02.019 1