A foggy floating eye is initially considered to be caused by vitreous opacity. There are many causes of vitreous clouding, which may be vitreous liquefaction, posterior vitreous detachment, intravitreal inflammatory hemorrhage, retinal disease, etc. Therefore, if the symptom appears, it is best to go to the hospital’s outpatient ophthalmology clinic for routine examination as soon as possible. If there is no obvious abnormality in the routine examination and dilated pupil examination of the fundus, it is considered to be physiological vitreous clouding and does not need to be treated for the time being. If a huge transparent cavity is found in the posterior part of the vitreous during fundus examination, it is considered to be caused by posterior vitreous detachment. If pigment changes are found in the vitreous, be alert to the possibility of retinal fissure and retinal detachment caused by the pulling of posterior vitreous detachment. In addition, uveitis and endophthalmitis can lead to significant clouding of the vitreous, which requires timely and symptomatic treatment.