floater [AS, flotian, to float] , a spot that appears to drift in front of the eye, caused by a shadow cast on the retina by vitreous debris. Most floaters are benign and represent remnants of a network of blood vessels that existed prenatally in the vitreous cavity. The sudden onset of several floaters may indicate serious disease. Hemorrhage into the vitreous humor may cause a large number of big and little shadows and a red discoloration of vision. The cause is often traumatic injury, but spontaneous intraocular hemorrhage is observed in proliferative diabetic retinopathy, hypertension, or increased intracranial pressure. Cancer, detachment of the retina, occlusion of a retinal vein, and other purely ocular diseases may also cause hemorrhage into the vitreous cavity. Inflammation of the retina resulting from chorioretinitis may cause entry of inflammatory cells into the vitreous humor. Inflammatory debris may adhere to the vitreous framework in netlike masses that are very disruptive of normal vision. Retinal detachment also causes a sudden appearance of flashes of light and/or floaters and a diminished field of vision as a shower of red cells and pigment is released into the vitreous humor. Careful ophthalmological examination through a well-dilated pupil is recommended for all people who experience a sudden occurrence of floaters because each of the pathological causes can be treated in the early stages and loss of vision can usually be prevented. Also called musca volitans, musca volitantes.
