Dear Editor,

We read with interest the article “Combined treatment of intravitreal bevacizumab and intravitreal triamcinolone in patients with retinal vein occlusion: 6 months of follow-up” by Ehrlich et al. [1]. We congratulate the authors for their interesting study and offer our comments.

One major advantage we feel that the authors have not adequately highlighted is the much lower re-injection rate of 2 ± 0.81 in their patients compared to previously published reports with bevacizumab monotherapy alone where monthly injections have been proposed in order to maintain a favorable outcome [2]. We postulate that the reason that repeated administration of intravitreal bevacizumab alone could result in a progressive decrease in biological response could be attributed to tachyphylaxis. Schaal et al. [3] proposed that one solution to avoid this decrease in the biologic effect would be to combine drugs with different modes of action. They demonstrated that combining bevacizumab with triamcinolone acetonide partially alleviated the efficacy decrease observed with bevacizumab alone. We propose that this could be one of the mechanisms by which the re-injection rate would be decreased by using combination therapy, compared to monotherapy with anti-VEGF injections alone.

Also, nine out of the 16 patients studied in the article had received previous treatment and there is no data provided on whether these eyes behaved differently anatomically or functionally vis-à-vis the treatment naive eyes.

It would be of interest to know if prior monotherapy with anti-VEGF agents had any effect on the subsequent course of the disease and whether this subset of patients differed in their response to treatment, recurrence of edema, and visual recovery compared to treatment of naive eyes.