You are unable to see the fundus and see what is pictured below on eye exam. What does the patient have?
Our patient had mutton fat precipitateson the inside of the cornea. It was impossible to see the fundus, not because of a vitreous hemorrhage but because the deposits did not allow light through. She had pronounced photophobia which is a key finding in uveitis.
Uveitis is inflammation of the pigmented layer that lies between the retina and the outer fibrous layer which is made up of thesclera and cornea. It includes the iris, ciliary body and choroid. Uveitis is classified anatomically by the part of the eye involved into anterior chamber which is similar to iritis (occurring frequently with a corneal abrasion), intermediate involving thevitreous, or posterior uveitis (chorioretinitis) involving the retina. 90% of uveitis is anterior.
Mutton fat precipitates are white blood cells deposited on the endothelium of the cornea which occur because of inflammation of the iris or ciliary body. They are “greasy” in appearance; hence, the name mutton fat. They can occur in uveitis caused by herpes, sarcoid, syphilis, tuberculosis HLA-B27, and autoimmune diseases.
T cells must normally be suppressed by dendritic cells in the eye which produce TGF beta . If T cells proliferatesystemically, they can migrate to the eye and cause release of cytokines and inflammation.
Globally, many infectious diseases also result in uveitis including Lyme disese, syphilis, parasitic disease and even Zika virus. Our patient was felt to have uveitis from a previous herpes infection.
Teaching point: Consider the causes of uveitis when evaluating the red eye.
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Ruggieri S, Frassanito MA, Dammacco R. Treg lymphocytes in autoimmune uveitis. 2012 Ocular immunology and inflammation 20(4): 255-61.