The two cavernous sinuses are large veins lying within the skull cavity, immediately behind each eye socket (orbit) and on either side of the pituitary gland. They connect with the veins of the face and those of the brain. As well as containing blood, the cavernous sinuses also contain the nerves running forward to control the eye-moving muscles and to provide sensation to part of the face, and a large artery, the internal carotid artery.

The network of veins that runs back to join the cavernous sinuses carries blood mainly from a triangular area centred around the nose. Any infection in this area, as from a pimple or boil in the nostril or on the upper lip or nose, may cause a local tissue inflammation known as cellulitis. From this local inflammation, infection may spread backwards by way of the veins to reach, and involve, one of the cavernous sinuses. If this happens, the blood in the sinus may turn to an infected clot, with potentially very serious consequences. This is a cavernous sinus thrombosis.

Treatment

The condition can be easily treated with antibiotic drugs.

Symptoms

Symptoms include:

• high fever;
• severe pain behind and around the eye;
• paralysis of eye movement;
• forward protrusion of the eyeball (proptosis);
• severe blurring or loss of vision;and;
• gross swelling of the lids and of the membrane covering the white of the eye (the conjunctiva).

Cataract never causes complete blindness in the sense of total absence of the ability to see light. People with dense cataracts can still usually distinguish an open from a closed door and will always see windows in daytime. But as the transparency of the lenses is gradually lost, image clarity slowly declines. Perception of detail becomes less and less until eventually the vision is completely clouded.

Contrary to what many people think, cataracts are not usually visible by other people. It is only the occasional and exceptionally mature cataract that shows as a white pupil.