A large black shadow fluttering in front of the eyes may be retinal detachment, and may also be caused by other diseases, such as uveitis, retinal tear, vitreous clouding, and so on. 1. Retinal detachment: retinal detachment is mainly related to retinal tear, vitreous pull, inflammation and infection, usually patients will not be accompanied by pain, but the discomfort of black shadow will suddenly appear in front of the eyes, but also accompanied by blurring of vision, visual field defects and other symptoms. 2. Uveitis: Uveitis may be related to eye infections, autoimmune diseases, eye trauma, etc. Uveitis will cause some patients to have symptoms of large black shadows in front of their eyes, accompanied by blurred vision, eye pain, photophobia, tearing and other symptoms. 3. Retinal tear: retinal tear is related to retinal degeneration, vitreous detachment and other factors, early patients may have no obvious symptoms, with the progress of the disease can appear before the eyes of a large black shadow fluttering, flashing sensation, vision loss and other uncomfortable symptoms. 4. Vitreous clouding: Vitreous clouding is related to ageing, hemorrhage, trauma and other factors, which can cause some patients to have large black shadows in front of their eyes, and there will also be vision loss and other uncomfortable symptoms. It is recommended that patients with large dark shadows in front of their eyes should consult a doctor in time to evaluate their condition and follow the doctor’s instructions for treatment.