Bleeding into the vitreous humour, the jelly-like substance that fills the back part of the eye, due to ruptured blood vessels
If blood vessels in the light-sensitive retina at the back of the eye rupture, blood leaks into the jelly-like vitreous humour. This bleeding is known as a vitreous haemorrhage. The rupture may be due to a blow to the eye; a blocked vein in the retina (see Retinal vein occlusion); or the growth of abnormally fragile blood vessels in the retina because of other disorders, such as diabetic retinopathy.
If the bleeding is minor, the only symptom may be the sudden appearance of large numbers of specks that seem to float in front of the eye (see Floaters). More severe bleeding can cause sudden loss of vision. Rarely, the blood in the vitreous humour clots, forming fibrous strands. Over a long period of time, new blood vessels may grow along these strands and pull on the retina, resulting in retinal detachment and blindness.
You should call your doctor immediately if you have sudden loss of vision or if floaters appear in your eye in large numbers. He or she will examine the eye using ophthalmoscopy. In mild cases, floaters disappear within a few days but a large haemorrhage may take several weeks to clear, and, in severe cases, an operation may be needed to remove the affected vitreous humour and seal leaking blood vessels.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.