A clinical triad to diagnose paraneoplastic retinopathy. Two elderly men developed photosensitivity and light-induced glare, transient visual symptoms, and progressive visual loss several months before small cell carcinoma of the lung was discovered. Both patients had impaired visual acuity and color vision, ring scotomas, and attenuated retinal arteriole caliber. Electroretinography demonstrated abnormal cone and rod-mediated responses. Antiretinal antibodies were identified in their serum. Their visual sensory function improved following therapy with immunosuppressive agents. The triad of photosensitivity, ring scotomatous visual field loss, and attenuated retinal arteriole caliber should alert one to a paraneoplastic disorder affecting the retina. 