Pain perception during intravitreal injections is related to the timing of instilling anesthetic eyedrops.

Purpose: To evaluate the correlation between the timing of instilling anesthetic eyedrops prior to intravitreal injection and the patient's perception of pain associated with the injection.

Methods: A prospective observational study which included 192 eyes of 192 patients. Time interval between instillation of Oxybuprocaine-0.4% and Tetracaine-0.5% eyedrops upon checking-in and injection was measured and pain level was evaluated by the 101-point-Numeric Rating Scale.

Results: We found significant correlation between time interval from the first eyedrops to injection and injection related pain. The lowest pain score (11 ± 18) was found in the 11-15 min group, while the highest was found in the 0-6 min (26 ± 25) and in the > 35 min (31 ± 28) groups. The highest percentage of patients without pain was found in the 11-15 min (64%), followed by the 7-10 min (56%) and 16-20 min (47%) groups. 10% or 17% of the 0-6 min or > 35 min. groups, respectively, reported no pain. No patients in 11-15 min group reported severe pain versus 10% in the 0-6 min and 17% in the > 35 min groups. The highest percentage of patients with 'absent-to-mild' pain was in the 11-15 min (89%) and the 7-10 min (87%) compared to all other groups.

Conclusions: Administration of first dose of anesthetic eyedrops within 11-15 min before intravitreal injection yields the lowest levels of injection-related pain, with 7-10 min being second best. Administration of eyedrops outside of this time-window results in higher pain levels avoidable with more attention to the timing issue.