This disease is of very rare occurrence in the horse. It consists of an increased tension within the eyeball in consequence of an excessive secretion of the aqueous and vitreous humours. As a result of this the eyeball is rendered full and unyielding to the touch, and somewhat elongated from before to behind. By this change of form the animal becomes myopic or short-sighted. One or both eyes may be affected, but it is usually the case that the disease attacks each in succession, and unless combated by treatment results in serious derangement of the internal structures, of which cataract is not an uncommon consequence. The symptoms of glaucoma are variable, but it will be generally found that the pupils are dilated and sluggish in their contraction. The anterior choroidal veins are large and visible, and the globe is hard and resisting to pressure. The media are quite transparent, but the movements of the animal indicate defective vision. When examined by the ophthalmoscope the surface of the optic disc is found to be more or less concave and pallid, and the veins are remarkably increased in size, while the arteries are diminished. The remedy in these cases consists in the operation of iridectomy, or removal of a portion of the iris.