Abstract
To the Editor:
W
The optimal dosing of intravitreal bevacizumab in treating proliferative diabetic retinopathy (PDR) is still undetermined. Doses of intravitreal bevacizumab used in the literature have ranged from 1.25 to 2.5 mg. Furthermore, Arevalo et al. 2 reported a dose-dependent response that the 2.5 mg dosage is more effective than the 1.25 mg dosage to induce complete regression of retinal neovascularization (NV) in naive eyes. To maximize efficacy, we adopted the higher dose of 2.5 mg according to their observation. In addition, we chose the higher dose of 2.5 mg in this study to prolong the therapeutic effect and reduce the number of repeated injections. The average number of injections in the current study was only 1.4 in a 7.5-month follow-up period. Regarding the concern of greater risk of postoperative endophthalmitis, we believe that the risk of infection is mainly related to either poor surgical technique or aseptic preparation of operative field, but not to the higher dosing of intravitreal bevacizumab. There was no episode of ocular infection after bevacizumab injection in our study. Further study of the optimal dosing of intravitreal bevacizumab in treating PDR is indicated in the future.
In our study, the ocular or systemic adverse events were monitored after bevacizumab injection. After the injection, intraocular pressure and central retinal artery perfusion were checked, and antibiotic eye drop was applied 4 times a day for 1 week. Postinjection follow-up visit was scheduled at 1 day and 1 week, and then every 4 weeks thereafter. At each visit, complete ophthalmologic examinations, including visual acuity measurement, intraocular pressure, slit-lamp biomicroscopy, indirect ophthalmoscopy, and echography, were performed to monitor any ocular adverse events. Systemic condition was also monitored. Blood pressure was measured before bevacizumab injection and at 1 and 2 weeks after the injection. Other systemic conditions were assessed by a thorough review of system, including myocardial infarction, stroke, or other thromboembolic diseases. No systemic adverse events were observed following the injections in our study.
The retreatment criteria in the current study included: (1) fundus examination that shows no sign of decrease of vitreous hemorrhage (VH) 4 to 6 weeks after the first bevacizumab injection or (2) recurrent retinal NV associated with hemorrhage.
In the current study, the number of eyes included was too small for statistical analysis regarding the relation between the medical variables (such as the duration of diabetes, metabolic control, and systemic blood pressure) and efficacy outcome measures after bevacizumab treatment.
Laser panretinal photocoagulation (PRP) currently is the mainstay and gold standard therapy for PDR. However, NV regression may take several weeks after the completion of PRP, and NV continues to grow despite the first session of PRP in one third of patients. 3 Therefore, VH may lead to visual loss and preclude complete laser PRP in these patients. Our study demonstrated that intravitreal bevacizumab in combination with PRP showed promising short-term functional and anatomical effects in the treatment of the complication associated with high-risk PDR. In 13 eyes of high-risk PDR complicated with VH, we demonstrated that intravitreal bevacizumab achieved marked regression of retinal NV, rapid resolution of VH, and concomitant significant visual improvement in most patients. 1 Subsequent complete laser PRP destroys the ischemic retina, prevents further elevated vitreous levels of vascular endothelial growth factor (VEGF), and stops the rebleeding episodes. Nevertheless, dense persistent VH without any sign of hemorrhage absorption was also noted in 2 eyes, which required vitrectomy surgery despite intravitreal bevacizumab. In 7 eyes of high-risk PDR complicated with moderate-to-severe neovascularization on the disc (NVD), we observed the obvious resolution of NVD and concomitant diabetic macular edema after intravitreal bevacizumab, and there was modest visual improvement in this subgroup.
In conclusion, our short-term results suggest that combined anti-VEGF pharmacological therapy and PRP appears as a useful adjunctive therapeutic option for PDR. Long-term study is warranted to assess the long-term efficacy.