There is a small black spot floating in the eye, also known as flying mosquito, mainly caused by vitreous liquefaction and posterior detachment, which may be caused by physiological factors such as age, and may also be caused by pathologic factors such as uveitis, vitreous hemosiderosis, retinal tears and so on. 1. Physiological factors: when a person is born, the vitreous body presents a gel state, with age, the water in the vitreous body increases significantly, while the collagen component decreases, the patient will appear to have floating objects in front of the eyes, and some patients show that there are black dots floating when they look at something. Physiological mosquitoes generally do not affect vision, without special treatment. 2. Pathologic factors: (1) Uveitis: when uveitis involves the vitreous, it can lead to the symptom of black dots floating in the eyes when looking at something. (2) Vitreous hemorrhage: when the patient has retinal vascular disease, or when trauma causes vitreous hemorrhage, the symptom of seeing with black dots floating in front of the eyes may appear. (3) Retinal lacunae: small retinal lacunae usually have less impact, but larger lacunae may lead to retinal detachment, causing serious damage to vision, and may also combine with the symptom of seeing something with black dots fluttering in the eyes, and at the same time, there may be a decrease in visual acuity, visual field defects and other manifestations. When you find the phenomenon of seeing small black dots floating, you should go to the hospital in time for relevant examinations to clarify the cause of the disease and follow the doctor’s instructions for treatment.