Text book of veterinary medicine, Volume 3 (of 5)

by James Law

Other points which give circumstantial support to the microbian theory may be shortly stated:

1. The recrudescence of the disease after its various intermissions, and its preference for low, damp, cloudy localities seem to ally it to the malarial diseases of man.

2. Its appearance in certain predisposed systems, whenever an injury or debility of the eye seems to open the way for the admission of the hypothetical microbe.

3. The increased susceptibility to the malady when the system has been debilitated by disease, overwork, heating food, bad hygiene, or parasitisms, which have undermined the native power of resistance.

4. The prevalence of the affection in given localities has been supposed to imply the preservation and perhaps the multiplication of the germ in such places.

5. The increasing number of victims, year by year, when the same regiment or stud has been kept for a number of years in the same place. The theory is that with the presence of infected horses the hypothetical microbes become increasingly prevalent in the locality and above all in the stables, until even the more resistent subjects tend to succumb under the repeated infections. Thus Zundel says that in 1878, 700 army horses were stationed in Saarsburg, in 1879, 6 were attacked with recurrent ophthalmia, and in 1880, 84, Hofgeismar mentions that a dragoon regiment in Frankfort had 5 horses attacked in 1876, 12 in 1877, 11 in 1878, 14 in 1879, and 42 in 1880. We have, however, no assurance that the excessive rainfall, spoiled food or other unhygienic condition, may not have been a potent factor in the increase.

6. The obvious connection of certain cases of recurrent ophthalmia with a rheumatic condition suggests the probable operation of the same microbian cause.

Up to the present the microbian causation of this malady cannot be taken as proved, yet as a hypothesis it explains satisfactorily many of the observed morbid phenomena. That there is no such rapidly spreading infection, as would warrant us in listing this with animal plagues, is conceded, and that constitutional conditions have a potent influence is allowed, but that, in addition to these, microbian invasion is often a means of precipitating the malady is altogether probable. It may not be necessary that the microbe should in every case be of the same kind, yet the addition of a germ as the last item in the chain of causes is presumptively true.

Parasitism. Willach claims that many cases are directly due to parasites in the eye. In 19 affected eyes he found one young filaria, a number of rhabditis (?), 1 cysticercus, and a number of distomata. Leider also found round worms in such eyes. Mayer and Dexler examined a number of cases, using the centrifuge on the liquids of the eye, without in any case finding such parasites. It may be assumed that the presence of embryo worms may rouse a latent predisposition into activity, but they cannot be adduced as active causes in the vast majority of cases.

Symptoms. These vary with the severity of the attack. In some cases there is high fever while in others this may be absent, yet a lack of vigor and energy bespeaks a general constitutional disturbance. The attack is sudden with marked local irritation, photophobia and lachrymation. The eyelids are closed some times so firmly as to suggest blepharospasm, and if opened the pupil is seen to be contracted. The affected eye is retracted and appears smaller, the conjunctiva is the seat of diffuse redness and swelling, and there is a bright red peri-corneal injection, occupying the anterior portion of the sclera. The outer zone of the cornea is already the seat of a bluish white opacity, the surface appearing dull and as it were smeared with oil. The centre of the cornea may be opalescent but not so obscure as to prevent examination of the interior of the eye. In a few days the outer margin of the cornea may show vascularity, and the aqueous humor a certain degree of turbidity. The iris if still visible is seen to be swollen and rigid, and to have parted with some of its lustre, assuming a grayish or lighter color owing to congestion and exudation. The pupil is usually contracted and dilates only sluggishly and imperfectly in darkness or under the action of atropia. The iris arches forward more than is normal and may even approximate and adhere to the back of the cornea. Bayer noticed that in a partial albino (watch eye) the iris becomes sulphur yellow. The anterior chamber of the aqueous humor usually shows a grayish yellow sediment which in severe cases may fill one-third or even one-half of its depth. This may be grayish white flocculi of lymph only, or it may be colored with blood or in suppurative cases by pus. In the first day of its appearance this may be diffused through the humor, but from the fifth to the seventh day it precipitates and leaves the iris and pupil open to inspection. The pupil if not already open, may be partially dilated with atropia and then discloses the interior of the eye of a dark green, or sometimes with much exudate on the choroid, of a more yellowish green. This greenish discoloration appears to depend on opacity of the vitreous, on an exudate between the choroid and retina or on some opacity of the cornea and aqueous. At the same time under a good light some opacity of the lens or its capsule may be detected, or, with direct illumination, of the vitreous as well.