To our knowledge, this report is the first to propose a new grading system for BRVO with VH. With this new grading system, we can guide surgery according to the different grades. We discussed the postoperative effect of VT combined with laser photocoagulation for different severities of VH with BRVO. Vision acuity was improved in all groups, which is in agreement with the results obtained by Hidetaka Noma et al, who described cases of BRVO. This indicates that the majority of the eyes treated with VT combined with laser photocoagulation could maintain resolution of VH and improved VA without additional treatments for an extended period of time.
However, the quality of vision depends on the macula status. It is recognized that earlier intervention probably is favourable to later to prevent macular scarring from longstanding edema. Researchers have different views on the effect of PPV with ILM peeling for ME. Kang reported that only 48.5% of patients with ERM associated with BRVO experience visual improvement after surgery, and visual decrease was observed in 9.1%. Mandelcorn  and Liang  reported that patients with ME secondary to RVO improved after PPV with ILM peeling. However, Radetzky et al.  reported no visual improvement in four patients after PPV and ILM peeling. In the present study, improved VA and reduced ME after VT were observed in the Grade I and Grade IIa groups. After VT, ME reappeared in three eyes, and CFT was reduced after IVR was performed once. We believe that the removal of the ILM is not necessary when there is no macular involvement.
Vision improvement was also observed in the Grade IIb group. ILM peeling may contribute to the complete removal of traction in the macular area. ILM peeling also improves the oxygen supply to the retina, and VT may ameliorate retinal ischemia by allowing oxygenated fluid to circulate in the vitreous cavity. Nevertheless, the degree of vision improvement in the eyes without macular membranes (the Grade I and Grade IIa groups) was much better than in the eyes with macular membranes (the Grade IIb group) in our study. Poor results may be due to the stretching effect of fibroblasts that deforms the macular structure, the underlying ischemic condition, or subtle trauma during removal of the ERM. Some study suggest that the percentage of eyes with secondary ERMs disrupted photoreceptor inner segment/outer segment (IS/OS) integrity (39.4%) and external limiting membrane (ELM) integrity (30.3%) were higher than those of idiopathic ERMs (15–28%)[32, 33]. In our study, vision improvement and ME reduction in the Grade IIb group suggest that ILM peeling is effective for ERMs with macular involvement. Ota et al. reported that substantial damage to the foveal photoreceptor layer was associated with poor VA prognosis. But Andreev et al. think a high degree of photoreceptors resistance to long-term distraction by ERM, the retina in fovea was spontaneously restored after several years of relieving tractional deformation. Therefore, we believe ERM with macular involvement affects the results of surgical treatment, but we need a long period of time to observe the development of vision.
Retinal neovascularization may lead to RD. One retrospective study reported an incidence of 3% retinal breaks in BRVO 230 eyes. VT and laser photocoagulation combined with retinal reattachment does improve vision for VH with RD. Ikuno et al. performed VT on 22 eyes with RD secondary to BRVO; 19 eyes (86%) attained total retinal reattachment and 13 eyes (59%) achieved VA better than 0.1 at the final examination. In our study, all eyes in the Grade III group attained total retinal reattachment, and 12 eyes (71%) experienced vision improvement. No statistical difference was found between the Grade III group and the other groups, which could be due to the surgery has a high success rate and not all the eyes in the Grade III group had macular involvement.
In normal circumstances, retinal laser photocoagulation is the first-line therapy for neovascular complications of RVO. In treating ME due to RVO, grid laser photocoagulation is generally considered to be the second-line therapy after anti-VEGF. Although VA results lag behind those for anti-VEGF therapy, laser photocoagulation remains a safe and effective therapy[39, 40].The Branch Vein Occlusion Study (BVOS) is the largest multicenter, randomized, controlled clinical trial to evaluate the efficacy of grid-pattern laser photocoagulation to treat ME due to BRVO[13, 41, 42]. In the research, 65% of treated eyes gained improvement of two or more lines from baseline. Until recently, this study served as the gold standard treatment for ME associated with BRVO. In the past, laser photocoagulation was performed to prevent macular damage, and it was useful to reduce ME and intraretinal fluid collection. However, VH hinders examination and treatment with laser photocoagulation. In our study, all groups were treated with laser photocoagulation therapy in combination with VT. Only 10 eyes suffered from ME again after surgery.
The retinal non-perfusion ischemic area, which accelerates the increase in intraocular VEGF, is an important underlying cause of recurrent ME in BRVO. FA can't be performed before or during surgery, so an accurate assessment of the non-perfusion ischemic area is difficult. During the 12-month follow-up,13 eyes were observed have a non-perfusion ischemic area and need further laser treatment; the percentage of patients in the four groups was 0%, 8.3%, 16.3%, and 23.5%, respectively. This indicates that the eyes in the Grade I group could maintain improvement without additional treatments for an extended period of time. VH with ERM and RD have higher rates of re-requiring laser treatment. This maybe due to hypoxia caused by ERM and RD, suggests that RD can lead to more serious hypoxia. Photoreceptor cells receive oxygen and nutritional support from the underlying retinal pigment epithelium. RD results in photoreceptor cell hypoxia and time-dependent death.
This study suggests that VT combined with laser photocoagulation is effective for BRVO with VH. Savastano et al. reported that RD developed in 1.77% of the eyes that underwent 25-G high-speed PPV. A recent large-scale study reported that the incidence of postoperative endophthalmitis was low for PPV. Except for the transient elevation of intraocular pressure that occurred in 13 eyes, no serious complications (such as RD or endophthalmitis) were found in our study.
There were some limitations to this study, such as the small sample size (especially eyes with RD), the retrospective study design, and the fact that we can't eliminate the possibility that there may have been a bias in the choice of patients. In addition, the follow-up time was short. We need a longer time to observe the development of vision and the recovery of the macular structure. Moreover, although macular status is better evaluated using OCT, we couldn't conduct this examination before surgery. Therefore, further validation of our classification scheme is warranted.
In conclusion, we proposed a new grading system for BRVO treated with PPV. BRVO with VH hindered timely and thorough evaluation and treatment. VT combined with laser photocoagulation for different severities of BRVO with VH has proven to be effective and safe. However, the VA improvement was significantly worse when EM had macular involvement (Grade IIb).