This retrospective study assessed variables associated with patients’ self-assessed postoperative pain after photorefractive keratectomy (PRK).
Study design
Researchers evaluated 231 patients undergoing standard PRK surgery which included epithelial debridement performed with an Amoils brush, followed by laser ablation with either the CustomVue VISX Star S4 or Wavelight EX500 excimer laser. After ablation, the eye was rinsed with chilled balanced salt solution and received a bandage contact lens. All patients received a prescription for oral analgesics along with a bottle of topical tetracaine to be used only in cases of severe pain.
Patient gender, age, season at the time of surgery, ablation depth, surgeon status (attending vs. resident), topical tetracaine use, and subjective pain scores at postoperative days 1 and 7 were recorded. For each variable, researchers analyzed average pain scores (10-point scale) and amount of pain medication taken.
Outcomes
Mean pain scores were 0.78 and 0.03 on postoperative day 1 and 7, respectively. Patients who used topical tetracaine reported significantly higher pain on both days compared with patients who did not use it (P<0.001 and P=0.038, respectively). Similarly, patients using topical tetracaine took more oral pain medication (9.4 vs. 7.0, P=0.022). No significant differences in pain scores were seen based on surgeon status, ablation depth, gender and season. Although men reported a higher amount of oral pain medication use than women, the difference was not statistically significant (7.8 vs. 6.6, P=0.086). There were no delays in epithelial healing or adverse effects to medications.
Limitations
Since patients did not record a log of pain scores, pain experienced between postoperative day 1 and 7 was not captured. Considering that pain peaks between these postoperative timepoints, this is especially important to note. Any differences in pain scores present during these days would not have been captured by study investigators, potentially impacting the ability to detect any associations, or lack thereof, between pain and the independent variables assessed. Patients using topical tetracaine were found to have taken significantly more pain tablets as well. Although this might suggest that oral medications did not completely control pain, further investigation would be necessary to confirm causality. On average, men took 1 more pain pill compared with women. Despite not reaching statistical significance, it is tempting to assign this difference solely to sex. However, other explanations should be considered, including the fact that weight-based dosing adjustments for these oral medications were not performed for men and women.
Clinical significance
As expected, patients who used tetracaine also reported higher pain scores on postoperative day 1 and 7. This is useful to know because it suggests that patients followed instructions to only use the drop when experiencing severe pain. In addition, no delayed epithelial healing was seen indicating that no topical anesthetic-induced epithelial toxicity occurred, further reaffirming that patients used appropriate doses and quantities of medication. Patients taking tetracaine are also more likely to take oral pain medication. Based on these results, perhaps an improved regimen of either topical or oral medication could obviate the need for using both treatments.