A small quantity of limpid water. The term is applied to the pellucid water which distends the capsule of the crystalline lens, and the lens itself; and to a disorder of the eye lids. P, AEgineta, in lib. vi. cap. xiv. says, that it is a pinguinous substance under the skin of the eye lid, also called hydatis. It is the hor-deolumhydalidosum of Sauvages; hydatidous, or watery stian. In children it is sometimes so troublesome as to produce much uneasiness. The upper eye lid appears watery, and cannot be elevated; the eyes are very tender, distilling a fluid, especially in a morning, if exposed to the light. In order to the cure, an incision is made through the skin of the eye lid, and the cyst is to be dissected out, if it cannot be eradicated by gently pulling it.

Mr. St. Yves takes notice of a complaint on the edge of the eye lids, or on the tunica conjunctiva, which resembles the bladders that appear on the skin after a burn; he calls these also hydatids. The method of cure which he proposes, is to open the tumour with the point of a lancet. But if all the circumference of the globe is covered with water, the conjunctiva will be inflamed; and in this case bleeding, purging, and a collyrium of aq. calcis, will be necessary. See Wallis's Nos. Meth. Oculor. Bell's Surgery, vol. i. p. 264.