Lesions. Besides the general congestion of the mucosa, there are liable to be special lesions in the depth of the conjunctival sac at the point where the mucosa passes from the eyelid to the sclerotic, causing uneven swellings from infiltration in this region. The lymph bodies or follicles in this part are swollen and project as small red or grayish nodules visible when the eyelid is everted, and at other times the whole infiltrated conjunctiva projects between the lids constituting the condition known as chemosis. The papillæ conjunctivæ are also hypertrophied, so as to become visible to the naked eye, and ulcers may be present on the mucosa. The cornea is often clouded blue or milky, or it may have become in part vascular and reddish, or even ulcerated. A more or less abundant muco-purulent discharge is always present.
Symptoms. The inflammation is usually moderate in degree, the eyes water without being habitually closed, the hairs are lost from the cheek, which is habitually wet, the lids are swollen, and like the cilia tend to stick together after sleep, and the whole mucosa is visibly infiltrated and congested, but usually especially at given points, as in the cul de sac, on the lids or membrana nictitans. Unless the animal has been treated with irritant dressings, there is much less pain on manipulation than in acute conjunctivitis. On everting the lids the folliculitis in the cul de sac and the circumscribed swellings become apparent. The membrana nictitans is partly projected over the cornea, and the eyeball usually appears smaller by reason of its retraction within the orbit.
In cases of eczema, or demodectic mange, the lesions of the skin of the eyelids will furnish the key to the trouble.
Treatment. The first object must be to remove the cause which tends to keep up the malady. Foreign bodies, musty hay fed from high racks, dusty roads, excess of light, windows in unsuitable places, damp stalls or pastures, and local parasitism must be corrected. In case of persistent chemosis keeping up the inflammation, and which will not subside under the usual astringent lotions, the hernial mucosa may be excised. (See chemosis.)
The usual astringent lotions may be employed, sulphate of zinc (2:100), sulphate of copper (1:200), alum (5:100), tannin (10:100) to which may be added sulphate of atropia. In place of being simply applied to the surface of the lids, or the cornea, it is usually desirable to inject it into all parts of the cul de sac beneath the upper and lower lids and beneath the nictitating membrane. Alum 4 grs. and boric acid 3 grains, in water 1 oz. make a good combination. As the mucosa becomes accustomed to one agent, we may change for another. Thus in addition to the above, silver nitrate (2:100), and lead acetate (2:100) are often useful as alternates. In obstinate cases red or yellowish oxide of mercury in vaseline (5:100) may be applied inside the lids and on their margins.
Counter-irritation is often desirable, in the horse a blister of cantharides or mercury biniodide to cover a spot as large as a silver dollar above the anterior end of the maxillary spine (zygomatic), or a stout silk thread as a seton inserted in the same place. In the dog the blister may be applied on the temporal region.
Cupping or leeching beneath the eye, or phlebotomy from the angular vein of the eye may prove useful. Great care should be taken to prevent further injury by rubbing.
PURULENT CONJUNCTIVITIS. BLENNORRHŒA.
More purulent and more infective through dust, tongues, rubbing posts, kennels, swill; a class due to different microbes. Prevalence in dogs, swine, horses, sheep, goats, cats. Symptoms: acute conjunctivitis with excess of pus, follicular swelling and enlarged lymph bodies in cul de sac. Diagnosis. Treatment: Astringent and antiseptic lotions, injected often: silver nitrate: pyoktannin.
The forms of conjunctivitis in which there is an abundant production of pus are usually relatively more inoculable and therefore more liable to pass from animal to animal in a casual manner. Infection takes place through the dried up discharges floating as dust, but more directly by means of the tongue when the animals lick each other, and through posts against which they rub the head. Animals smelling or licking the infected genital organs and then the eyes of their fellows may convey it readily. Dogs occupying the same kennel successively, contract the disease (Guilmot). Swine feeding from the same trough and plunging the face into swill up to the eyes are especially subject to infection. In speaking of such infections one must be understood to refer to a group and not to one specific disease, as that will vary with the particular pus microbe present, and with the virulency of such microbe in the particular case. In keeping with the greater fertility of microbes in the warm season, these affections have been more commonly met with in summer than in winter, and where the animals are kept in filthy surroundings rather than otherwise. This is above all true of swine. Möller records a wide spread epizootic of gonorrhœal ophthalmia in dogs in Berlin and environs in 1883. In different cases, however, he failed to induce disease in the eyes by direct inoculation with the preputial secretion. Heinman equally failed with the gonococcus of man in inoculations on the eyes of rabbits, and dogs. Fröhner, however, succeeded in infecting the eye of the dog by applying the gonorrhœal discharge of man.