Macular edema is the most common cause of visual impairment in branch retinal vein occlusion (BRVO). Recently, studies using optical coherence tomography (OCT) have revealed various morphological changes associated with macular edema, including sponge-like retinal swelling, cystic changes, and serous retinal detachment.1–3 Serous retinal detachment is reported to be present in 15%–30% of patients with diabetic macular edema1,4,5 and in 15%–80.8% of patients with BRVO.6–8 Although fluid leakage from permeable macular vessels usually causes macular edema when the distribution of BRVO involves the macula, Finkelstein and Patz reported a distant effect of peripheral BRVO on the macula.9 We previously reported that the tomographic features of macular edema secondary to distant vascular disorders were caused by serous retinal detachment with slight retinal swelling.10 In that report, we speculated that the subretinal fluid in the macular area appeared to originate from a distant retinal vascular leakage because fluorescein angiography results revealed dye leakage in the extramacular area but not the macular area. Although there have been some reports about macular edema from distant BRVO,11,12 the pathogenesis remains unclear. In the present study, we investigated the tomographic changes involved in macular edema secondary to peripheral BRVO (not involving the macula) to elucidate the mechanisms of fluid movement from extramacular permeable lesions to the subretinal space at the fovea.

We retrospectively studied nine eyes from nine patients (three male and six female; median age 69 [range 49–81] years) who were followed up in our department between July 2003 and April 2012. The follow-up periods ranged from 6 to 24 (median 14) months. This retrospective study was approved by our institutional review board. We defined extramacular BRVO as occluded vessels that did not involve the macular area (5.5 mm in diameter). Inclusion criteria for this study were eyes with serous retinal detachment secondary to extramacular BRVO and a follow-up period of more than 6 months. Exclusion criteria were eyes with poor quality OCT images, serous retinal detachment caused by other etiologies, such as diabetic retinopathy, uveitis, and vitreoretinal interface disease, a history of laser photocoagulation or vitrectomy, and dense media opacity such as cataract or vitreous hemorrhage. In addition to a comprehensive ophthalmic examination, including best-corrected visual acuity, slit-lamp examination, and indirect ophthalmoscopy, time-domain or spectral-domain OCT (Stratus OCT, Cirrus HD-OCT, Carl Zeiss Meditec Inc, Dublin, CA; or Spectralis HRA/OCT, Heidelberg Engineering, Heidelberg, Germany) was performed. Six of the patients also underwent fluorescein angiography. For the OCT examination, vertical and horizontal scans (5–8 mm in length) centered on the fovea were obtained to measure the thickness of the fovea and the subretinal space. We defined foveal thickness as the distance between the inner retinal surface and the retinal pigment epithelium at the central fovea, which included the serous retinal detachment. The thickness of the subretinal space was defined as the distance between the outer surface of the detached retina and the retinal pigment epithelium at the central fovea. In six of nine eyes, laser photocoagulation was applied to the entire area of BRVO within 2 weeks of the initial examination. The other three eyes were treated with intravitreal injection of 1.25 mg bevacizumab (Avastin^®, Genentech Inc, San Francisco, CA) within 2 weeks of the first examination.

The clinical characteristics of the patients are summarized in Table 1. At the time of initial examination, visual acuity ranged from 0.03 to 0.9 (median 0.5). All nine eyes showed localized macular detachment and retinal edema which extended from extramacular BRVO to the macula. The site of occlusion was along the inferior vascular arcade in four eyes, along the superior vascular arcade in two eyes (Figure 1A), superonasal to the optic disk in two eyes (Figure 2A), and inferonasal to the optic disk in one eye (Figure 3A). In four eyes, hard exudates were seen in the macula (Figures 1A and ​and2A).2A). Fluorescein angiography in six eyes revealed dye leakage in the extramacular area but no macular leakage (Figures 1B and ​and2B).2B). Widespread nonperfusion of the retinal capillary bed was observed in three of six eyes (Figure 2B). In all nine eyes, OCT showed serous retinal detachment in the macula and outer retinal swelling of low reflectivity extending from the distant permeable lesions toward the fovea (Figures 1C, ​,2C,2C, and ​and3B).3B). On the other side across the fovea, slight retinal swelling was seen in the macula in three eyes, but no retinal swelling was found in the other six eyes. Foveal thickness was 280–575 μm (median 425 μm). The thickness of the subretinal space was 145–373 μm (median 240 μm). After treatment, serous retinal detachment and retinal swelling were resolved within 3 months in all nine eyes.