Author reply

Abstract

We would like to thank Drs Patel and Rosenberg for their comments. They raise a valid point regarding the nature of the sham injection in our study, and the implications it may have on our results.It is correct that a true sham injection in our study ideally would have involved an actual injection of a solution into the subconjunctival space, but we chose to invoke our modified sham for a number of reasons. It has been our overwhelming experience that patients, who have never had a subconjuctival injection, as was the case for our patients, almost always do not feel the injection of subconjunctival xylocaine 2% if pretreated with a topical anesthetic as we did in our study. Furthermore, since the patients were looking away at the time of injection, and could not look at their own eye until they completed the questionnaire, we felt this method of sham was reliable and the likelihood of bias was therefore small. Furthermore, we were concerned we might not get Research Ethics Board approval at our institution if we intended to inject a saline solution subconjunctivally, given the difficulty we had in gaining approval for the subconjuctival xylocaine injection. We required Health and Welfare Canada approval for this mode of xylocaine administration, since the manufacturer had not listed this method of drug delivery in their monogram. Fortunately for our study, the results were highly significant, and we feel that even if there was a small bias, it could not by itself account for the degree of significance we observed.Since the study was completed, we have used this mode of anesthesia in over 500 patients who could not tolerate topical anesthesia for the indications in our study. Almost without exception, they have all reported a significant improvement in the level of comfort with this technique. Their responses give us confidence in our results. We would like to thank Drs Patel and Rosenberg for their comments. They raise a valid point regarding the nature of the sham injection in our study, and the implications it may have on our results. It is correct that a true sham injection in our study ideally would have involved an actual injection of a solution into the subconjunctival space, but we chose to invoke our modified sham for a number of reasons. It has been our overwhelming experience that patients, who have never had a subconjuctival injection, as was the case for our patients, almost always do not feel the injection of subconjunctival xylocaine 2% if pretreated with a topical anesthetic as we did in our study. Furthermore, since the patients were looking away at the time of injection, and could not look at their own eye until they completed the questionnaire, we felt this method of sham was reliable and the likelihood of bias was therefore small. Furthermore, we were concerned we might not get Research Ethics Board approval at our institution if we intended to inject a saline solution subconjunctivally, given the difficulty we had in gaining approval for the subconjuctival xylocaine injection. We required Health and Welfare Canada approval for this mode of xylocaine administration, since the manufacturer had not listed this method of drug delivery in their monogram. Fortunately for our study, the results were highly significant, and we feel that even if there was a small bias, it could not by itself account for the degree of significance we observed. Since the study was completed, we have used this mode of anesthesia in over 500 patients who could not tolerate topical anesthesia for the indications in our study. Almost without exception, they have all reported a significant improvement in the level of comfort with this technique. Their responses give us confidence in our results. Subconjunctival Anesthesia for Laser TreatmentOphthalmologyVol. 118Issue 5PreviewWe read with great interest the study by Tesha et al1 describing the efficacy of subconjunctival 2% lidocaine in controlling pain during panretinal photocoagulation (PRP) and peripheral laser retinopexy (PLR). This randomized study found that 59% of patients experienced pain in the anesthetic group, while 97% experienced pain in the sham group, and the authors concluded that subconjunctival 2% lidocaine is effective in controlling pain during laser treatment. Full-Text PDF