Cooling Anesthesia for Intravitreal Injection: Results of the Prospective Open-Label, Dose-Ranging COOL-1 Trial

To evaluate the safety and efficacy of a novel medical device to provide cooling anesthesia to the eye as local anesthesia for intravitreal injections. First in human, open-label study of 43 subjects assessed at three different doses: -10°C for 20 seconds (group 1), -15°C for 15 seconds (group 2), and -15°C for 20 seconds (group 3). Main outcome measures were safety and pain of injection using a numeric rating scale (NRS). Cooling anesthesia did not result in any serious ocular adverse events. One grade 1 adverse event was a vasovagal response during cooling administration which resolved immediately after cooling. Mean NRS scores at the time of injection for each group ranged from 2.5 to 4.3 There was a statistically significant difference between pain scores of the 3 groups at injection in aggregate but not in pairwise comparisons ( value = 0.047). There was a statistically significant decrease in pain from injection to 5 minutes post injection in all groups ( value = 0.00008, 0.003, 0.0005 for groups 1, 2, 3, respectively) as well as from 5 minutes to 24-48 hours ( value = 0.00001, 0.018, and 0.0545 for groups 1, 2, 3, respectively). The rapid cooling anesthesia device was well tolerated for achieving local anesthesia among patients receiving intravitreal injections with no serious ocular adverse events.