Pain perception, aqueous humour cytokines, and miosis response following first and second eye femtosecond laser-assisted cataract surgery: A randomised, prospective, intraindividual study.

Background: To compare pain perception, pupil behaviours, and cytokine levels during first-eye and second-eye femtosecond laser-assisted cataract surgery (FLACS) and determine which is better regarding a short or long interval for bilateral FLACS.

Methods: Notably, 96 eyes of 48 patients with bilateral cataracts underwent the first surgeries in the left or right eye, according to a random sequence. They were further randomised into 2- and 6-week subgroups based on surgery intervals. Pupil size was measured from captured images, and pain perception was assessed using a visual analog scale (VAS). Aqueous humour prostaglandin E2 (PGE2), monocyte chemoattractant protein-1 (MCP-1), interleukin (IL)-6, and IL-8 levels were also quantitatively analysed. All patients were followed for 1 week to evaluate changes in endothelial cell density (ECD), central corneal thickness (CCT), and macular central subfield thickness (CST).

Results: Ocular pain was significantly higher in patients who underwent second-eye FLACS. First tear break-up time was negatively correlated with VAS score. MCP-1 levels were significantly higher in patients who underwent second-eye FLACS, and VAS scores were positively correlated with MCP-1 levels across all patients. There were no differences between sequential FLACS in miosis, PGE2, IL-6, IL-8 levels and changes in postoperative ECD, CCT, and CST. Patients who underwent second-eye FLACS after 6 weeks showed more CCT, CST, and MCP-1 changes than baseline.

Conclusion: Second-eye FLACS causes more pain and upregulated MCP-1. There was no difference between sequential FLACS in PGE2 levels, miosis, and postoperative inflammation. Furthermore, first-eye FLACS triggered a sympathetic irritation, particularly after a 6-week interval.