How would one go about forcing someone else to become blind? Something that would keep the eyes intact, but destroy the retina or optic nerve or similar, and something that is fairly direct (that is, not blunt force impact from a car accident or something). Also, for the setting of my story, I don't think high-tech things like lasers have been invented. Would you be able to go blind from seeing a bright flash of light? If so, how bright? For how long? Are there other similar ways?
Thanks in advance for any and all feedback!