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but they are still to be distinguished, according as the one or the other may happen to be the primary affection, and properly as they often arise from different causes.
279. The inflammation of the membranes of the eye affects especially, and most frequently, the adnata, appearing in a turgescence of its vessels; so that the red vessels which are naturally there, become not only increased in size, but there appear many more than did in a natural state. This turgescence of the vessels is attended with pain, especially upon the motion of the ball of the eye ; and this, like every other irritation applied to the surface of the eye, produces an effusion of tears, from the lachrymal glande
This inflammation commonly, and chiefly, af. fects the adnata spread on the anterior part of the bulb of the eye; but usually spreads also along the continuation of that membrane on the inside of the palpebræ ; and, as that is extended on the tarsus palpebrarum, the excretories of the sebaceous glands opening there are also frequently affected. When the affection of the adnata is considerable, it is frequently communicated to the subjacent membranes of the eye, and even to the retina itself, which thereby acquires co great a sensibility, that the slightest impression of light becomes painful.
280. The inflammation of the membranes of the eye is in different degrees, according as the adnata is more or less affected, or according as the inflammation is either of the adnata alone, or of the subjacent membranes also ; and, upon these differences, different species have been established, and different appellations given to them. But I shall not, however, prosecute the consideration of these, being of opinion that all the cases of oph. thalmia membranarum differ only in degree, and are to be cured by remedies of the same kind, more or less employed.
The remote causes of Ophthalmia are many and various; as,
1, External violence, by blows, contusions and wounds, applied to the eyes, and even very slight impulses applied, while the eye-lids are open, to the ball of the eye itself, are sometimes sufficient for the purpose.
2, Extraneous bodies introduced under the eye lids, either of an acrid quality, as smoke and other acrid vapours, or of a bulk sufficient to impede the free motion of the eye-lids upon the surface of the eye-ball.
3, The application of strong light, or even of a moderate light long continued.
4, The application of much heat, and particularly of that with moisture.
5, Much exercise of the eyes in viewing minute objects.
6, Frequent intoxication.
7, Irritation from other and various diseases of the eyes.
8, An acrimony prevailing in the mass of blood, and deposited in the sebaceous glands on the edges of the eye-lids. .
9, A change in the distribution of the blood whereby either a more than usual quantity of blood, and with more than usual force, is impelled into the vessels of the head, or whereby the free return of the venous blood from the vessels of the head is interrupted.
10, A certain consent of the eyes with the other parts of the system, whereby, from a certain state of these parts, either a simultaneous, or an alter, nating affection of the eyes, is produced,
281. The proximate cause of Ophthalmia is not different from that of inflammation in general; and the different circumstances of Ophthalmia may be explained by the difference of its remote causes, and by the different parts of the eye which it happens to effect. This may be understood from what has been already said ; and I shall now therefore proceed to consider the Cure.
282. In the cure of Ophthalmia, the first attention will be always due to the removing of the remote causes, and the various means necessary for this purpose will be directed by the consideration of these causes enumerated above.
The Ophthalmia membranarum requires the remedies proper for inflammation in general; and, when the deeper seated membranes are affected, and especially when a pyrexia is present, large general bleedings may be necessary. But this is seldom the case ; as the Ophthalmia, for the most part, is an affection purely local, accompanied with little or no pyrexia. General bleedings, therefore, from the arm or foot, have little or no effect upon it; and the cure is chiefly to be obtained by topical bleedings, that is, blood drawn from vessels near the inflamed part ; and opening the jugular vein or the temporal artery, may be considered as in some measure of this kind. It is commonly sufficient to apply a number of leeches round the eye ; and it is perhaps better still to draw blood from the temples, by cupping and scarifying. In many cases, a very effectual remedy is, that of scarifying the internal surface of the inferior eye-lid; and more so still, is cutting the turgid vessels upon the adnata itself.
283. Besides blood-letting, purging, as a remedy suited to inflammation in general, has been considered as peculiarly adapted to inflammations in any of the parts of the head, and therefore to Oph. thalmia ; and it is sometimes useful : but, for the reasons given before with respect to general bleed. ing).purging in the case of Ophthalmia does not prove useful in any degree in proportion to the evacuation excited.
284. For relaxing the spasm in the part, and taking off the determination of the fluids to it, blistering near the part has commonly been found useful.
285. Electrical sparks taken from the eye will often suddenly discuss the inflammation of the ad nata ; but the effect is seldom permanent, and even a frequent repetition seldom gives an entire cure.
286, Ophthalmia, as an external inflammation, admits of topical applications. All those, however, that increase the heat, and relax the vessels of the part, prove commonly hurtful; and the admission of cool air to the eye, the proper application of cold water immediately to the ball of the eye, and application of various cooling and astringent medicines, which at the same time do not produce much irritation, prove generally useful : even spiritous liquors, employed in moderate quantity, have often been of service.
287. In the cure of ophthalmia, much care is requisite to avoid all irritation, particularly that of light ; and the only safe and certain means of doing this is by confining the patient to a very dark chamber.
288. These are the remedies of the ophthalmia membranarum ; and, in the ophthalmia tarsi, so