Animals with disease models of human uveitis are necessary to study these complex processes. One of the most studied models is called endotoxin-induced uveitis. Endotoxin is part of the cell wall of some bacteria and is also called lipopolysaccharide. Injecting a little endotoxin under the skin of a rat will cause that rat to get uveitis. Changes in the iris blood vessels can be detected within a couple of hours after endotoxin injection and the disease is most severe after 24 hours.
Laboratory mice can also get endotoxin-induced uveitis.
Because mice are less sensitive than rats to endotoxin injected under the skin, mouse studies sometimes involve placing endotoxin directly in the eye. Despite their lower sensitivity to endotoxin, mice are often preferred subjects. Many more biological reagents are available for use in mice. Furthermore, inbred mice with mutations in critical genes allow important questions to be addressed that cannot be done otherwise. A new tool in microcirculation research is called intravital fluorescence microscopy.