SIMPLE ACUTE CATARRHAL CONJUNCTIVITIS.
Causes: irritant gases, smoke, dry air, dust, pollen, microbes, insects, seeds, chaff, awns, sand, dust, quicklime, coal dust, hairs, whips, canes, branches, stubble, fences, nails, claws, teeth, iodine, chlorine, bromine, formalin, turpentine, rain, hail, sleet, glare of sun, ice, snow, white sand or clay, filaria, acari, infectious diseases. Symptoms: closed lids, epiphora, redness diffuse on lids, ramified on sclera, projected nictitans, milky flocculent discharge, later purulent, matted lashes or tarsi. No photophobia. Fever variable. Lesions: exudate: cell proliferation: papillæ enlarged: desquamation: swollen lymphoid bodies: hyperplasia: abscess: ulcer. Treatment: remove cause, sterilized syringing, antiseptic and astringent collyria, sublimate, zinc sulphate, lead acetate, pyoktannin, silver nitrate, morphia, atropia, cocaine, vaseline, cupping, leeching.
Under this head may be noted the simple forms of conjunctival inflammation, which result from direct injuries, irritant gases from manure, smoke, very dry air, dust, pollen, and in which no specific nor contagious element is a prominent feature. Strictly speaking, all purulent conjunctivitis are probably infecting, as all may be held to be associated with the presence of pus microbes. As early as 1864, de Graefe said every inflammation of the conjunctiva which “secretes, is inoculable and therefore transmissible,” and Warlomont concurs, saying that “conjunctival ophthalmias have one character in common: all can produce a secretory product which, when brought in contact with a sound conjunctiva, is capable of provoking the different affections of this mucosa.” The exposure of the conjunctiva of man and beast alike, to the germs borne on the dust or carried in liquids or on solids, renders this structure preëminently susceptible to infection, while the lachrymal and mucous secretions furnish a favorable culture medium. Fortunately in the lower animal the danger of infection is greatly reduced, since there are comparatively few opportunities for the transference of the germ through water, soap, sponge or towel, to which man is exposed, not only in public lavatories but even in private families. Thus in the animal the single case remains isolated and in a sense sporadic, only because there have not been the means of transferring and inoculating the morbid product.
Causes. The contact of mechanical and chemical irritants of all kinds, insects, seeds of gramineæ, chaff, particles of fodders, barley and other awns and spikes, grains of sand, dust, quicklime, coal dust, smoke, hairs, blows with whips, canes, branches, stubble, fences, etc. Also erosions caused by nails, claws, teeth, and by falls must be considered.
Irritant gases and vapors whether from accumulation of manure in the stables, or from chemical products of fires and factories are direct causes. The mere exposure for some time to the warm, dry air from a furnace is injurious to the mucosa, and the emanations from certain medicines, iodine, chlorine, bromine, formaline, turpentine are strongly irritant.
Exposure in a cold draught, or in a blast of cold rain or hail, or even to a cold dry wind, in the case of hunting dogs working much in water, are potent factors.
The glare of the sun through a window at the front of a stall, or from a white surface of snow, ice or water or even from white sand, lime or clay is an active cause. The overdraw check exposing the eyes directly to the sun is often injurious. We must include the irritations caused by the filaria lachrymalis and by various lesions already described—trichiasis, entropion, ectropion, stenosis of the lachrymal duct, etc.
In certain animals a distinct predisposition exists, often as the result of a previous attack, and such are readily attacked under slight disturbing causes.
It should not be forgotten that hyperæmia and even inflammation of the conjunctiva, often accompanies different infective diseases—strangles, influenza, contagious pneumonia, rinderpest, canine distemper, etc.
Symptoms. The discharge of tears and the closure more or less complete of the eyelids are among the earliest and most marked symptoms. The general conjunctiva is congested and that on the inner side of the lids especially, so as often to hide the individual vessels, while on the sclerotic portion they usually remain distinct, tortuous and freely movable with the mucosa upon the sclera beneath. The membrane is more or less infiltrated, swollen and opaque. In two or three days this has increased so that the lids are visibly swollen, and completely closed, or the paw is projected over the cornea. The discharge has become milky or flocculent, and mats the cilia together, or holds the eyelids closed. Unless the cornea has been directly injured it usually remains clear, and there is no photophobia nor contraction of the pupil. The lids, however, are tender and nervous animals show active resistance to any attempt to examine the eye. In aggravated cases a free muco-purulent discharge takes place, and the red, swollen mucosa projects between the eye and the tarsus, constituting chemosis. In such circumstances the inflammation may extend to the cornea causing opacity and photophobia or to the iris and choroid or other deep-seated parts.