The first-in-human feasibility trial comparing non-pharmacologic, ultra-rapid focal cooling and standard-of-care pharmacological anaesthesia showed the novel method was quicker, was well-tolerated by patients and resulted in similar patient-reported pain scores, according to a speaker American Society of Retina Specialists annual meeting in Vancouver, Canada.

“Ultra-rapid cooling of the eye was well-tolerated and provided effective non-pharmacologic anaesthesia, Dr Cagri Besirli, MD, PhD, said.

“This first-in-human proof-of-concept study indicates that ultra-rapid cooling may be useful for ocular anaesthesia, and we believe that this novel method may be an improved way of delivering anaesthesia and improve patient care of intravitreal delivery,” DrBesirli said.

Current methods have drawbacks

“Thecurrent methods of ocular anaesthesia have a variety of drawbacks, including patient risk for corneal toxicity and subconjunctival haemorrhage. Additionally, surgeons must wait between three and 10 minutes for the anaesthesia to take adequate effect, he said.

Dr Besirli and colleagues created a focal cooling device to provide patients with ocular anaesthesia.

“You put the device about 3 mm to 4 mm from the limbus … activate the cooling and the cold temperatures rapidly penetrate the deep tissue, block the nerve conduction, and once you have this within 10 to 20 seconds, you perform intravitreal injection using standard technique,” he said.

To test the feasibility and efficacy of the technique, 22 patients were included in a single-centre, randomised, unmasked, controlled trial comparing focal cooling and standard-of-care pharmacologic anaesthesia.

Standard of care

Patients were randomly assigned to one of five cooling groups, ranging from –5°C for 10 seconds to –10°C for 20 seconds. The second eye of each patient underwent the standard of care.

“We found that the effect of the pain control was better in increasing treatment duration and decreasing temperatures,” Dr Besirli said.

Patients in the –10°C for 10 seconds and –10°C for 20 seconds groups reported similar pain scores as patients who received traditional anaesthesia. Also, ultra-rapid anesthesia via cooling reduced patient wait times for intravitreal delivery, about a 4.5-minute savings when compared with the standard of care.

Additionally, at four hours after injection, pain scores were similar between the target temperature of –10°C and the standard of care, Dr Besirli said.