First Author: Y.Iida JAPAN
Co Author(s): Y. Muraoka S. Ooto K. Suzuma T. Murakami Y. Miwa A. Tsujikawa
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Branch retinal vein occlusion (BRVO) is a retinal vascular disease involving focal occlusion of the major retinal vein, and occurring most frequently at an arteriovenous (AV) crossing, which leads to development of macular pathologies. Although a common cause of branch vein occlusion has been established, the severity and prognosis of the macular lesions vary considerably and are unexplained. In this study, we used optical coherence tomography (OCT) angiography for detailed observation of the morphological and functional alterations in the affected AV crossing site and examined its association with retinal pathologies to elucidate the pathophysiology and clinical relevance of BRVO.
Observational, consecutive case series.
Forty-six consecutive patients with major BRVO involving the macular area were included. At baseline, in addition to comprehensive ophthalmic examinations, fluorescein angiography (FA) was performed in each patient using an Optos 200Tx imaging system (Optos PLC). As a treatment for macular edema, each eye received intravitreal ranibizumab injections. No eyes received any other treatment, such as scatter or grid laser photocoagulation, steroid therapy, surgical intervention, or anti-vascular endothelial growth factor agents other than ranibizumab. Morphological and functional alterations of the retinal microvasculature of the macular area, and of the affected AV crossing, were longitudinally examined by OCT-Angiography (RTVue XR Avanti). Macular non-perfusion area (NPA) was defined as the capillary dropout area within a scanning area of 3 × 3 mm sections, including the foveal avascular zone. OCT-Angiography measurement of macular NPA was performed using the manufacturer’s built-in software. Using OCT-Angiography of the affected AV crossing, we evaluated the venous diameter at the crossing site. Using FA, we also evaluated the retinal vasculature of the affected AV crossing and the peripheral NPA.
At baseline, the mean duration of symptoms was 0.7 ± 1.5 months. FA showed that the affected AV crossing pattern involved arterial overcrossing in 23 eyes (50.0%) and venous overcrossing in 11 eyes (23.9%), but the crossing pattern was not detected in 10 eyes (21.7%). OCT-Angiography clarified the AV crossing pattern in 44 eyes (95.7%), which was significantly more than that in FA (P = 0.013). The number of eyes with venous overcrossing on OCT-Angiography (20 eyes, 3.5%) was higher than on FA (P = 0.047). OCT-Angiography also showed markedly narrowed veins (25.5 ± 21.1 μm) in venous overcrossing, which was significantly narrower than that observed in arterial overcrossing (46.4 ± 23.7 μm, P = 0.005). Macular NPAs with venous overcrossing were significantly larger than those with arterial overcrossing (P = 0.011 for superficial plexus, and 0.049 for deep plexus). The peripheral NPA was 17.2 ± 24.1 in the disc area (DA) involved in arterial overcrossing, and 65.1 ± 35.3 DA in venous overcrossing, which was also significantly larger in venous overcrossing (P < 0.001). Additionally, longitudinal observation with OCT-Angiography showed that decreased retinal perfusion accompanied narrowing of both retinal veins and arteries.
OCT-Angiography is useful for detailed observation of affected AV crossings associated with BRVO. The OCT-Angiography findings suggest that the prevalence of BRVO in the venous overcrossing type is higher than previously reported, and that there is a significant association between AV crossing pattern and NPA size.