Recently someone I know was watching a video on her phone. She wasn’t watching it with her eyeglasses, but she’s done this in the past and nothing went wrong. So while watching the video she had sudden vision loss. All she was able to see was vague shadows and blurry figures. She used more than half of her eye drops and finally regained her vision. So I’m asking to clarify if this isn’t a neurological issue or anything serious. And if there’s a way to avoid this. Thank you in advance.