If it is a sudden onset of blindness, it depends on the duration of the attack and the symptoms at the time of onset. If it is transient, it may be due to insufficient blood supply to the fundus of the eye, such as in elderly people, patients with low blood pressure, or when standing up suddenly, it feels like a layer of hooded matter in front of the eyes, or even a feeling of black hoodedness, which belongs to insufficient perfusion of the fundus of the eye. Or there may be inflammation of the conjunctiva, with a lot of discharge from the eye, and a sudden lack of clarity when blinking, which may improve after flushing the conjunctival sac and applying medication. Internal inflammation of the eye, such as uveitis, can lead to a feeling of blindness and even pain, photophobia, and loss of vision. If the eye pressure is high, it may be accompanied by ipsilateral eye swelling, head swelling, headache, soreness at the root of the nose, and a cloudy, hazy feeling when looking at things, but it will improve over time and disappear. In case of cloudy sensation, if the vision does not recover after the attack, it is considered to be a problem of blood circulation in the retina of the eye or a lesion in the macula.