The purpose of this study was to evaluate possible treatments to decrease the probability of RVH in patients who received PPV for nonabsorbent VH due to PDR. In this study, we intravitreally injected VA and TA at the end of the surgery. Although not statistically significant, the incidence in VA and TA group was lower than BSS group, especially the incidence of early RVH.
The causes of RVH are different according to the VH time. Early RVH was defined as VH occurring within 1 month after surgery while late RVH was defined as VH occurring between 4 weeks and 12 months after surgery. As we know, the causes of early RVH appeared to be dispersion of remnant blood clots from the vitreous base, bleeding from remnant fibrovascular tissues spontaneously or after coagula attached to the vessels falled off [3,17,18]. The etiology of late RVH is considered to involve sclerotomy sites neovascularization, along with anterior hyaloidal fibrovascular proliferation [11,19,20].
In this study, for the first time, we intravitreally injected 1ml VA at the end of surgery and we prefer to use it when there was bleeding of retinal vessels in fibrovascular tissue which was controlled by temporarily raising the intraocular pressure and pressing the bleeding site with the tip of the cutter directly, or applying endodiathermy during the operation. That is to say we tend to use VA in the eyes that prone to bleed. However, of 18 eyes in VA group, there was only one severe RVH case at 3 month after surgery and especially no early RVH was identified. The integral incidence was 5.6%, lower than BSS group and also some previous results[2,3,11]. It implied that VA was to a extent prevent RVH especially early RVH. As we all know, VA was commonly and safely used in ocular surgery. It is viscous and can occupy the space which somewhat likes the silicon oil. The characteristic may help to reduce the fluidity of vitreous humor and reduce the dispersion of remaining blood. It might also buffer the shear or scouring force of vitreous liquid on retina vessels when there was eye movement and the relative motion of vitrous liquid and retina would produce. And thus VA might reduce the risk of rebleeding of vascular stumps and falling off of coagula attached to the vessels. Meanwhile the VA would take several days to hydrate completely or being discharged. During this time, the IOP would be higher than normal as the VA was discharged through the trabecular meshwork and somewhat block the passage. Besides, VA occupied the vitreous cavity, but aqueous humor constantly produced, so the volume would beyond the normal and thus resulted in high IOP. Early postoperative hypotony after PPV has been suspected to be associated with an increment of RVH [4,21]. Lee et al [3] had showed that patients who experienced postoperative hypotony had an 11.20-fold increased risk of immediate PVH. Soto-Pedre et al [22] suggested early peaks of RVH occurs at the end of the first week. So, to the contrary, higher IOP in the early stage after PPV may be a protect factor. In this study, the IOP averaged at 21.67±10.39 at 1wk in VA group. The IOP elevation of VA group mostly began at 3 or 4 day and continued during the first week after surgery. And most of the IOP decreased to normal in the 2nd week under ocular hypotensive treatment. So we believed that VA probably could prevent immediate or early RVH.
To compare the role of VA with other existing tamponade, we also intravitreally injected 2mg TA at the end of the surgery. There was only one RVH case at 1 month after surgery, and the VH was absorbed spontaneously. TA is a water-insoluble and long-acting steroid hormone that has been commonly and safely used to assist vitrectomy for PDR, anti-inflammation or macular edema in eyes for many years [23-25]. During the study, we prefer to use TA in the cases that had prominent macular edema or much exudation during the operation. Previously, intravitreal injection of TA in PPV sugery at different time for PDR patients has been evaluated for preventing RVH, but the results were different. Liao et al [15] reported that intravitreally injection of 4mg TA after posterior vitreous detachment (PVD) during PPV for PDR could prevent RVH. The incidence of early RVH after PPV was significantly lower in the TA group (1.7%) than in the non-TA group (9.9%).They also indicated that TA injection immediately after PVD led to improved haemostasis. They found that retinal bleeding was obviously reduced or stopped after TA intravitreal injection during PPV. TA particles could cover the bleeding area and form a thin layer with red blood cells to manage intraoperative active bleeding [26]. Besides, TA was able to stabilise the blood-retinal barrier by inhibiting prostaglandins and inflammatory adhesion molecules as well as by reducing VEGF levels [27-29]. TA can maintain its effect for 2–3 weeks or even longer in the vitreous cavity as it is slowly absorbed and difficult to dissolve in liquid [30-31]. These might explain why TA reduce the incidence of early RVH after PPV. Faghihi et al [29] reported rate of early RVH and reoperation were significantly lower in patients taking intravitreal injection of 4mg TA compared with other group (13.2% in TA group and 45.5% in control group); and no reoperation in TA group and 11.8% in the control, respectively. However, negative results were also reported previously. Takamura et al [32] reported that RVH after PPV for patients with VH due to PDR occurred in 2 (4.8%) cases in TA-injection group and 3 (7.1%) cases in the non-TA injection group. The difference of the ratio was insignificant between the groups. Hu et al [23] evaluated treatment efficacy of postoperative intravitreal 2mg TA at the basis of preoperative intravitreal ranibizumab (IVR) in patients undergoing PPV for PDR. Patients received PPV with preoperative IVR or underwent PPV combined preoperative IVR and postoperative IV of TA. No significant difference of RVH was observed between the two groups. In our study, the overall incidence of RVH of TA group was 5.6% with no early RVH or any reoperation. The results was comparative with the previous studies. Compared with BSS group, although not significant, the incidence was lower, especially the early RVH. So we should not ingnore that possibility that TA might help to inhibit early RVH.
In this study, the postoperative IOP did not show significant differences between the TA and BSS groups at 1wk. Actually, some patients had transient higher postoperative IOP in the TA group within the first week. However, most patients with high IOP drop to normal after ocular hypotensive treatment. This was similar to the previous studies[23,29]. And the duration was aligned with the pharmacokinetics of triamcinolone acetonide after a single intravitreal injection. Beer et al [33] reported that the half-life of TA in the aqueous humour was 18.6 days in the non-vitrectomised eyes, whereas it was only 3.2 days in the vitrectomised eyes.
Every group had one late RVH case. Previously, the cause of late RVH was believed to be the fibrovascular ingrowth at the sclerotomy sites[4, 34]. However, in the patients undergoing reoperation in our study, we found no neovascularization at the sclerostomy sites through scleral indentation. And we just perform simple vitreous cavity washout and retinal laser photocoagulation supplement. After the second surgery, no one has VH again during the follow up. We believed that reasons for late RVH was complicated. BCVA of three goups did not show significant difference at the end of follow-up. It seemed that there was no advantage or disadvantage in VA and TA application with respect to BCVA.
The present study had some limitations. This was a prospective, single-center study, in which all vitrectomies were performed by a single surgeon. A major limitation of this study was the presence of a selection bias because our study was not a randomised prospective study. Patients who received VA or TA injections usually had bleeding-prone lesions or inflammation indications in the fundus. BSS cases usually had relatively mild lesion based on the judgement of the surgeon. However, VA and TA group still have lower incidency of RVH within 1 month which indicates VA and TA injections had positive effects in this study. Besides, In this study we only calculate the severe RVH that we considered to have clinically significance. Nevertheless, further randomised case-controlled studies on this topic are recommended.
In conclusion, we for the first time studies the effects of IV VA on RVH after vitrectomy for PDR and found the overall incidence of RVH in VA group was lower than in BSS group, especially the early incidence of RVH. Although the integral incidence is not statistically significant, we could not ignore the trend. Besides, we evaluated the role of TA simutaneously, and VA seemed to have a comparative role with TA, wherase may avoid the side effects of TA such as promoting cataract formation. The temporary increased IOP in VA group might be one of the effective cause or a disadvantage which should be assessed further. In all, VA may be a potential tamponade agent that can be used to prevent RVH in PDR patients especially the ones that prone to bleed during the operation. Randomised case-controlled studies with a larger number of cases would be required to confirm our findings.