Hypopyon is the leaking of fluids into the anterior or front chamber of the eye. This fluid, commonly referred to as pus, is a collection of white blood cells that are released from inflamed blood vessels in the iris and the tissue behind the iris. The iris is the colored part of the eye which controls the level of light inside the eye.
This inflammation, called uveitis, is typically accompanied by redness of the conjunctiva and the episclera, the outer most portion of the sclera. The conjunctiva is the mucus membrane of the eye which lines the inside of the eyelids and covers the sclera. Its main function is to produce mucus and tears to keep the eye lubricated and to help prevent microbes, or microorganisms, from entering the eye. The sclera is the white portion of the eye.
Hypopyon, also known as sterile pus, presents as a collection of yellowish exudate in the lower chamber of the eye. Exudate is a collection of fluids. It is considered sterile since the exudate occurs because of the release of toxins and not by the attack of pathogens, or infected agents. This pool of fluids can make the eye itself look cloudy or hazy.
Hypopyon stemming from uveitis or iritis, inflammation of the iris, is a reaction of the body to fight infection inside the eye. Infection can be caused by a number of infectious processes. Some infections that may cause hypopyon are tuberculosis, a deadly infection of the lungs, and herpes simplex or herpes zoster. Herpes simplex is a viral disease caused by herpes simplex viruses. Herpes zoster, commonly known as shingles, is caused by the chicken pox virus known as varicella zoster virus.
Other infections that can cause hypopyon include Lyme disease and toxicariasis. Lyme disease is an infection caused by ticks. Toxicariasis is a parasitic infection caused by roundworm in dogs and cats which infects humans.
Hypopyon can also be caused by systemic disorders. A systemic disorder is a disease or process that affects the entire body. Lyme disease, for example, is a systemic disorder caused by an infectious process. Multiple sclerosis, where the body’s autoimmune system attacks the brain and spinal cord, and psoriatic arthritis, inflammation and damage to the joints as a result of the chronic skin condition psoriasis, are also examples of systemic disorders that can cause hypopyon.
