Topical anesthetics may be favored to reduce pain of intravitreal injection

While various anesthetic methods may be equally effective in lessening pain, topical anesthetics may be more convenient for patients.

While many anesthetics are effective in reducing pain caused by intravitreal injection, application of topical anesthetic drops may be a preferable method, a study suggested.

“[Intravitreal injection] is so common and yet, there is no consensus on the best way to make the patient comfortable,” Gregory R. Blaha, MD, PhD, one of the study’s authors, said in an interview with Ocular Surgery News. “We had been using topical [anesthetics], and we felt that they were working well and wanted to make sure that we were doing the best thing for our patients.”

The prospective, masked study used a randomized block design to assign each of 24 patients to a unique schedule of anesthetic agents. Patients received four intravitreal injections that were preceded by one of four types of anesthesia, including 0.5% proparacaine, 0.5% tetracaine, a pledget of 4% lidocaine and a subconjunctival injection of 2% lidocaine.

As part of the inclusion criteria, all patients had received at least one prior intravitreal injection.

“Usually when patients get a first injection, it can be scary, and we did not want that increased anxiety to affect their perception of pain,” Dr. Blaha said.

Study results

Immediately following intravitreal injection, patients graded their pain on a scale of zero to 10 for each of the two portions of the procedure, anesthesia and injection. Combined pain scores were also calculated to determine total discomfort.

The average pain score for anesthesia was 0.7 for topical proparacaine, 1.0 for topical tetracaine, 1.4 for lidocaine pledget and 1.6 for subconjunctival injection of lidocaine. The differences between these scores were not statistically significant.

The slightly higher score reported for subconjunctival lidocaine may have been due to more manipulation of the conjunctiva and discomfort caused by needle use, Dr. Blaha said. He added that a stinging sensation may also occur during injection of lidocaine.

The average pain score for intravitreal injection was 2.8 with proparacaine, 3.1 with tetracaine, 3.0 with lidocaine pledget and 2.8 with subconjunctival lidocaine. The differences between these scores were not statistically significant, nor were the differences between the four combined pain scores.

Of eyes that received subconjunctival lidocaine, 54% experienced subconjunctival hemorrhage. None of the other anesthetic methods were associated with any complications.

While patients received a mean of 12.9 intravitreal injections prior to the study, no correlation was demonstrated between the number of previous injections and reported pain scores.

Preference for topical anesthetics

Dr. Blaha said that it is easy to nick a blood vessel during subconjunctival injection, which explains the high percentage of patients who experienced hemorrhage.

“Many of the [reported hemorrhages] were small, but we still counted them, because patients do not like the way they look. … So, if we can find a different way of doing anesthesia that does not cause them, then that is a benefit,” he said.

In support of the study authors’ preference for topical anesthetics, they found that adding a drop of topical proparacaine before application of the pledget lidocaine and subconjunctival injection of lidocaine did not result in any significant difference in pain score.

“This would be expected to give even better anesthesia in these two groups, and thus, the lack of significant difference between the groups gives further support for topical anesthesia alone,” the study authors wrote.

Dr. Blaha noted that the study did not assess a topical anesthetic gel because there is concern that this agent may block iodine from preventing infection. The study authors also acknowledged that pain was not evaluated after the immediate post-injection period and suggested that the effect of anesthetics on delayed pain be assessed in future studies.

“Based on our study, I feel that topical anesthesia is safe, effective, quick and cost-effective, and it is the anesthetic method that I use,” Dr. Blaha said. – by Michelle Pagnani

Reference:

• Blaha GR, Tilton EP, Barouch FC, Marx JL. Randomized trial of anesthetic methods for intravitreal injections. Retina. 2011;31(3):535-539.

• Gregory R. Blaha, MD, PhD, can be reached at the Lahey Clinic, Department of Ophthalmology, 1 Essex Center Drive, Peabody, MA 01960; 978-538-4400; email: gregory.r.blaha@lahey.org.
• Disclosure: Dr. Blaha has no relevant financial disclosures.

With proper technique, intravitreal injections can be almost painless, yet only a few small studies have attempted to assess patient perceptions of discomfort associated with common methods of ocular anesthesia. Dr. Blaha and his colleagues report the results of a prospective, masked, randomized trial of four common approaches to anesthesia for intravitreal injection. The significance of this study is the finding that, while each method comes with benefits and drawbacks, the overall pain experience is very similar.

Currently there is a limited amount of published literature that can be used to help direct clinical practice patterns concerning anesthesia for intravitreal injection. This study supports the notion that any of the common anesthesia techniques is reasonable and effective and that the choice of anesthesia should be tailored to the particular desires of the physician and patient.

– Jonathan L. Prenner, MD
Clinical Assistant Professor, Robert Wood Johnson Medical School
Disclosure: No products or companies are mentioned that would require financial disclosure.