There are two common forms of tumour, sarcoma and glioma.

Sarcoma springs in the majority of cases from the choroid, but may take origin in the ciliary body or iris. It is usually a spindle-celled tumour, and in the large majority of cases is pigmented. The unpig-mented forms are usually round-celled. The sarcoma in its growth usually detaches the retina and encroaches on the vitreous humour. The eyeball is occupied by the tumour mass, which generally in course of time also extends into and through the sclerotic. The sarcoma is prone to generalization, and tumours, frequently pigmented, spring up in various organs.

Glioma takes origin in the retina. It consists of round cells in a fine reticulum. The cells may be so abundant as to make the tumour approach to the structure of the sarcoma. Two forms are described under the designations exophytum and endophytum, according as the tumour originates in the external or internal granular layer of the retina. The tumour retains the characters of the layer from which it has originated. It grows for a time in the retina, gradually enlarging and filling the globe. After a time it may involve the coats of the eyeball and extend through the sclerotic. Occasionally it extends by metastasis to distant organs. It is characterized by a bright yellow reflection seen through the pupil.

Epithelioma sometimes occurs in the eyeball, usually originating at the junction of cornea and conjunctiva. It may also originate in the conjunctiva. Cancer sometimes takes origin in the lachrymal glands.

The conjunctiva is also liable to simple growths, the commonest being the papilloma, whose most frequent seat is the junction of the cornea and conjunctiva.