Primary Iris Neovascularization in Neurofibromatosis Type 1

Anterior segment neovascularization may occur in neurofibromatosis type 1 (NF1) secondary to optic nerve glioma or carotid stenosis (1,2). We report a case of primary anterior and posterior segment neovascularization and neovascular glaucoma occurring in NF1 in the absence of detectable vascular abnormality or glioma. A 14-year-old boy with NF1 presented with an episode of total loss of vision in the right eye lasting 20 minutes. Visual acuity was 20/20 in both eyes. Slit-lamp examination showed conjunctival injection, Lisch nodules, and iris neovascularization of the right eye (Fig. 1). The intraocular pressure was 45 mm Hg. Neovascular closure of the angle was confirmed by gonioscopy. There was no relative afferent pupillary defect, and color vision testing was normal. Ophthalmoscopy showed widespread arteriolar narrowing and venous dilatation with an area of vitreous hemorrhage overlying peripheral retinal neovascularization. Digital ophthalmodynamometry showed that the right central retinal arterial pressure was significantly lower than the left. Examination of the left eye was normal.FIG. 1: Iris neovascularization and Lisch nodules are evident in the right eye.Brain and orbit CT and CT angiography, including the vessels of the neck, were normal. Carotid doppler ultrasonography and cardiac examination were normal. Retinal fluorescein angiography showed peripheral retinal neovascularization. There was no evidence of retinal artery or vein occlusion. Cryotherapy was applied to the areas of peripheral retinal vascular closure. Despite regression of the anterior chamber and retinal neovascularization, an Ahmed valve was required to control the intraocular pressure. One year after the initial presentation, the visual acuity remained stable at 20/20 in each eye. Shuto and Yamamoto (3) described a case of ocular ischemia in NF1 in association with hypoplasia of the internal carotid artery. Barral and Summers (2) described a boy with NF1 and absence of the right carotid circulation who developed ocular ischemia at an age of 19 months. However, isolated ocular neovascularization in the absence of optic nerve glioma or carotid abnormality is rare. There have been 3 reports of isolated retinal ischemia occurring in young adults with NF1 (4-6) and 2 in children with NF1 (7,8). However, none had the anterior segment neovascularization and secondary glaucoma observed in this case. We acknowledge that the raised intraocular pressure might have been caused by outflow channel dysgenesis associated with NF1. Patients with NF1 have a propensity to develop aneurysms, stenoses, vascular occlusions, pseudoaneurysms, and fistulas (9). Histopathologically, small vessels may be affected by scattered nodular smooth muscle lesions that arise from the walls of the arteries and obstruct flow (10). Abnormal vascular maintenance and repair may also contribute to the pathogenesis of NF-related vasculopathy with abnormalities of neurofibromin expression leading to altered smooth muscle cell responses to endothelial signals (11). Given the absence of angiographic or ultrasonographic evidence of larger vessel occlusion in our patient, it is likely that the ocular ischemia was caused by small vessel NF-related vasculopathy.

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