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

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.

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.

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.

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.