###Human: Can excess screen viewing lead to flash blindness kind of visual disturbance? ###Assistant: Hello. I understand your concern. There are not many conditions which can give rise to the feeling of being blinded by a camera flash for 24 hours. A few of the conditions which can give rise to periodic flashes of light are retinal detachment, posterior vitreous detachment, ocular migraine and aura of migraine. None of these conditions can cause a flash of blinding light for 24 hours. But in case you are referring to episodic blindness, there are several causes like prodromal stages of retinal blood vessel disorder, migraine, Raynaud's disease, intermittent glaucoma and carotid artery stenosis (for which the ultrasound neck is done). I feel that the cause may be neurological and related to the blood supply. In case you need further information, please send me a scanned copy of your doctors records or tests reports. I will do my best to help you.