See Pleura. - Hypopyon, (from under, and pus).

Pyosis, and abscessus oculi. The disease has been considered to arise from a collection of pus under the cornea; but this idea is, at least, imperfect, if not erroneous. The matter is not confined to the anterior chamber of the eye, nor is it purulent. It sometimes collects in the posterior chamber, and is never truly pus, but that kind of sebaceous mucus which is found between the eye lids of diseased eyes, or of a consistence between this and what is found effused on inflamed membranes after death. The hypopyon is, at least, never the consequence of the real ulceration which takes place between the laminae of the cornea.

It is the exudation of the gluten, in consequence of inflammation, which first falls to the bottom of the aqueous humour, appearing there in the form of a crescent, from the capillary attraction of the sides of the coats. It gradually fills both chambers, passing through the pupil, and conceals the iris; but, after the active period of inflammation ends, seems to increase no further. After this period, also, it gives little pain; and common people, as well as children, bear it as an unavoidable effect of ophthalmia, with little uneasiness, and as little complaint.

As the hypopyon is with difficulty removed, it should be with the utmost care prevented. When therefore it is threatened, the remedies of ophthalmia should be employed with augmented rigour and activity, to prevent its occurrence or increase. When it has taken place, friction has been employed to promote its absorption, or we have been directed to puncture the cornea to discharge it. It is easy to direct both; and the surgeon, after he has given these directions, seems to rest in security. Nothing is more fallacious than such indiscriminate advice.

Friction, in a supine posture, as recommended, is often injurious by increasing the inflammation, and consequently the exudation. It is at the same time highly painful, and cannot be continued.

The division of the cornea to discharge the matter is a more obvious measure. Many inconveniences, however, attend this operation; and not the least is the inflammation which the operation excites, by which the disease is exasperated. If, according to Richter's advice, the aperture is small, the time required for the discharge of the viscid fluid is so long, that the edges of the wound suppurate, the iris is prolapsed, and the crystalline often discharged. At best, we substitute an ulceration of the cornea to the hypopyon. There is, indeed, one case in which the operation may be risked, with all its inconveniences, where the distention is so great as to bring on inflammation, and destroy the organ. In general, it is better to trust to absorption, which Janin supposed to be accelerated by decoction of mallows, and others by an infusion of sage; but these act as emollients only.

Other practitioners have employed, to promote absorption, bags of tepid mallows, with some camphor, or the vitriolic collyrium, with mucilage of quince seeds, varying the proportions according to the degree of sensibility; for, though it should be always felt to irritate, the irritation should not be so considerable as to produce inflammation.

When the distention is so great as to destroy the organ, and to be near bursting, it may be opened, the crystalline suffered to escape, and the ball of the eye to sink, so as to admit of an artificial one. In this case the sight cannot be recovered: the pain may be relieved, and deformity prevented. When a natural opening occurs at an earlier period, so as to admit of a discharge, it may be allowed to proceed; for natural openings are not so injurious as artificial ones. In such cases, when the matter is evacuated the ulcer may be healed by touching its edges with the argentum nitratum in a diluted state.

See St. Yves on the Diseases of the Eye; Heister's Surgery; Bell's Surgery, vol. iii. p. 313, &c; White's Surgery, p. 232; Scarpa on Diseases of the Eye; Richter Observationum Chirurgicarum, fasciculus i. cap. 12; Janin Memoirs, etc. sur loeil 99, p. 405.