To investigate changes in the pain-suppressing potency of 2 preoperatively applied topical nonsteroidal antiinflammatory drugs (NSAIDs) after photorefractive keratectomy (PRK) using a time-serial pain-scoring system.Saeyan Eye Center, Seoul, South Korea.Comparative case series.Ninety-four patients were randomly assigned to 2 groups: ketorolac group (ketorolac 0.5% in 1 eye and ofloxacin 0.3% in the other eye) and diclofenac group (diclofenac 0.1% in 1 eye and ofloxacin 0.3% in the other eye). One drop of each ophthalmic drug was applied 3 times to each eye 30 minutes before PRK. No other NSAID or steroid was prescribed until 4 days after PRK. The patients were asked to score the postoperative pain in each eye with a visual analog scale at 6, 18, 24, 36, 48, 72, and 96 hours.The natural peak of pain was located between 24 and 36 hours. Initially, the degree of pain reduction was constant for both NSAIDs; it dropped after 24 hours and 36 hours in the ketorolac group and the diclofenac group, respectively. The postoperative time-serial pattern of the pain score changed in the diclofenac group but not in the ketorolac group compared with the pattern in the ofloxacin-treated eye. The visual outcome was not affected by either NSAID, and significant complications were not noticed for a mean of 7 months.The duration and pattern of the action may vary according to types of NSAIDs. Preemptive topical diclofenac 0.1% was a safe and effective method for post-PRK pain control.No author has a financial or proprietary interest in any material or method mentioned.