The ciliary body is highly vascular, and is engaged in the secretion of the humours of the eye. Being very active it is peculiarly liable to acute inflammations, more especially as it is related anatomically both to iris and choroid, and is apt to partake in the inflammations of either.

The choroid is also a vascular structure, containing a layer of pigment cells on its inner or retinal surface. Inflammation of it is not usually acute, except in sympathetic ophthalmia (see further on), and, when chronic, it causes disturbances of the pigment, which produce alterations in the ophthalmoscopic appearances. Sometime-a formation of true bone occurs in the choroid in chronic iuflanima tion, and such an ossification seems a usual occurrence when the eye has undergone atrophy from injury.