Patients usually refer to the white part of the eye below the black eye as the fundus, where capillary dilation and redness occur, often mistakenly called fundus congestion by the general public, but in fact it is conjunctival congestion, usually caused by conjunctivitis, keratitis, iridocyclitis, allergies, sclerositis, etc. Depending on the cause, anti-infection or hormonal suppression of immune response and other medications are needed to eliminate congestion. The fundus, which is usually referred to as the retina, cannot be observed by the patient himself and requires a professional fundoscopic examination to see if congestion has occurred. Common causes include optic neuritis and optic disc vasculitis, which can lead to congestion of the tissue around the optic disc in the fundus and require oral or intravenous hormone medication. Diseases such as diabetic retinopathy and retinal vein embolism can induce retinal neovascularization, which can also manifest as congestion in the fundus and require fundus laser treatment.