There are four types of hypersensitivity reaction, classified according to the way in which the ALLERGEN or ANTIGEN activates the reaction. The classic allergic reaction is the type I hypersensitivity reaction, with exposure to an external substance (the allergen) initiating the IMMUNE RESPONSE.
Flickering lights in vision, Headache and Sudden flash of lights. WebMD Symptom Checker helps you find the most common medical conditions indicated by the symptoms flickering lights in vision, headache and sudden flash of lights including Migraine headache (adult), Tension headache, and Ocular migraine.
Sudden Changes in Vision - Topic Overview. Vision changes may indicate a serious problem with the tissue that lines the back of the eyeball (retina), optic nerve, or blood vessels in the eye . Flashes of light (photopsia). Photopsia is brief but recurrent streaks, sparks, or flickers of light, particularly when you move your eyes or head.