Analgesic eye drops for pain control after a refractive procedure

INTERVENTION: The patients are randomized using computer‐generated randomization tables to three groups: topical nalbuphine postoperative with a concentration of 2 mg/ml (group A), topical nalbuphine with a concentration of 1 mg/ml (group B) and a control group receiving artificial tears only (group C). The patients are asked to record their pain and the number of times they use the eye drops in the first 3 days and they attend a daily examination in the first 8 days following the procedure. The last follow‐up visit is at the end of the third postoperative month to measure the final visual acuity and refractive outcome. CONDITION: Pain following photorefractive keratectomy procedure ; Surgery PRIMARY OUTCOME: Pain measured using a numeric rating scale (recording the maximum pain level) in the first 3 postoperative days SECONDARY OUTCOME: ; 1. Number of analgesic eye drops applications recorded by patients in the first 3 postoperative days; 2. Time needed for complete epithelial healing assessed by slit‐lamp examination daily in the first 8 postoperative days; 3. Best corrected visual acuity (converted to LogMAR) measured by Landolt chart at the end of the third postoperative month; 4. Refraction measured by autorefractometer at the end of the third postoperative month; INCLUSION CRITERIA: 1. Age above 20 years 2. Error of refraction is less than 4 D spherical equivalent 3. Minimum corneal thickness is more than 480 microns 4. Absence of collagen diseases 5. Absence of corneal surface abnormalities 6. Absence of ocular diseases other than the refractive error 7. No history of concurrent use of systemic or topical analgesics