Retinal Vasculitis and Perivasculitis
Active retinal vasculitis is characterized by exudates around retinal vessels resulting in white sheathing or cuffing of the affected vessels, which may be segmental (skip lesions) or confluent. The pathological data available demonstrated perivascular inflammatory cell infiltration indicating that the most accurate term for these entities probably is perivasculitis and, in most cases, periphlebitis. Although retinal arterioles or branch retinal arteries may be involved in the secondary systemic vasculitides such as systemic lupus erythematosus (SLE), as well as the primary systemic vasculitides such as Wegener’s granulomatosis, polyarteritis nodosa, Churg-Strauss syndrome, or cryoglobulinemia, this usually leads to occlusion by microthrombosis, and intraocular inflammation is often not a feature of these diseases. Therefore, this type of occlusive vasculopathy should be recognized and distinguished from other conditions characterized by active vascular sheathing or cuffing with perivascular inflammatory infiltrate. Retinal vasculitis results in leakage leading to retinal swelling, exudation, and macular edema. Occlusive retinal vasculitis affecting the retinal arterioles may cause cotton-wool spots representing microinfarcts of the retina. Occlusive periphlebitis can cause retinal edema, intraretinal hemorrhages, and hemorrhagic infarction of the retina. Late changes secondary to vascular occlusion and remodeling include telangiectasis, microaneurysms, and ischemia-induced neovascularization, with sequelae such as recurrent vitreous hemorrhage, traction retinal detachment, rubeosis iridis, and neovascular glaucoma that can lead to functional loss of the eye. Inflammatory branch retinal vein occlusions are strongly associated with Behçet’s disease and might contribute to visual loss. Characteristic features seen with fluorescein angiography in active vasculitis include leakage of dye due to breakdown of the inner blood-retinal barrier and staining of the blood vessel wall with fluorescein. Fluorescein angiography is a more sensitive technique and will frequently show that the vasculitis is more extensive than the clinical examination suggests. Fluorescein angiography is very useful to delineate areas of capillary nonperfusion, and neovascularization secondary to retinal ischemia. It is also very valuable to diagnose the presence of inflammatory branch retinal vein occlusion. The ability to identify retinal vasculitis as ischemic by fluorescein angiography has important implications for management. It is important to identify the presence of retinal ischemia in patients with retinal vasculitis because scatter laser photocoagulation should be considered when angiographic evidence of widespread retinal nonperfusion is present and before (or shortly after) the development of neovascularization. Other angiographic findings include cystoid macular edema and optic disc leakage. Leakage of dye from the optic nerve head arises from dilated capillaries that may be due to either to primary infiltration as in sarcoidosis or secondary vascular changes induced by intraocular inflammation.