of the mucous membrane exposed by the separation of the lids--it may be
a mere pink blush with more or less branching redness, or it may be a
deep, dark red, as from effusion of blood--and a bluish opacity of the
cornea, which is normally clear and translucent. Except when resulting
from wounds and actual extravasation of blood, however, the redness is
seen to be superficial, and if the opacity is confined to the edges, and
does not involve the entire cornea, the aqueous humor behind is seen to
be still clear and limpid. The fever is always less severe than in
internal ophthalmia, and runs high only in the worst cases. The eyelids
may be kept closed, the eyeball retracted, and the haw protruded over
one-third or one-half of the ball, but this is due to the pain only and
not to any excessive sensibility to light, as shown by the comparatively
widely dilated pupil. In internal ophthalmia, on the contrary, the
narrow, contracted pupil is the measure of the pain caused by the
falling of light on the inflamed and sensitive optic nerve (retina) and
choroid.
If the affection has resulted from a wound of the cornea, not only is
that the point of greatest opacity, forming a white speck or fleecy
cloud, but too often blood vessels begin to extend from the adjacent
vascular covering of the eye (sclerotic) to the white spot, and that
portion of the cornea is rendered permanently opaque. Again, if the
wound has been severe, though still short of cutting into the anterior
layers of the cornea, the injury may lead to ulceration that may
penetrate more or less deeply and leave a breach in the tissue which, if
filled up at all, is repaired by opaque fibrous tissue in place of the
transparent cellular structure. Pus may form, and the cornea assumes a
yellowish tinge and bursts, giving rise to a deep sore which is liable
to extend as an ulcer, and may be in its turn followed by bulging of the
cornea at that point (staphyloma). This inflammation of the conjunctiva
may be simply catarrhal, with profuse mucopurulent discharge; it may be
granular, the surface being covered with minute reddish elevations, or
it may become the seat of a false membrane (diphtheria).
_Treatment._--In treating external ophthalmia the first object is the
removal of the cause. Remove any dust, chaff, thorn, or other foreign
body from the conjunctiva, purify the stable from all sources of
ammoniacal or other irritant gas; keep the horse from dusty roads, and,
above all, from the proximity of a leading wagon and its attendant cloud
of dust; remove from pasture and feed from a rack which is neither so
high as to drop seeds, etc., into the eyes nor so low as to favor the
accumulation of blood in the head; avoid equally excess of light from a
sunny window in front of the stall and excess of darkness from the
absence of windows; preserve from cold drafts and rains and wet bedding,
and apply curative measures for inflammation of the adjacent mucous
membranes or skin. If the irritant has been of a caustic nature, remove
any remnant of it by persistent bathing with tepid water and a soft
sponge, or with water mixed with white of egg, or a glass filled with
the liquid may be inverted over the eye so that its contents may dilute
and remove the irritant. If the suffering is very severe, a lotion with
a few grains of extract of belladonna or of morphia in an ounce of water
may be applied, or, if it is available, a few drops of 4 per cent
solution of cocaine may be instilled into the eye.
In strong, vigorous patients benefit will usually be obtained from a
laxative, such as 2 tablespoonfuls of Glauber's salt daily, and if the
fever runs high from a daily dose of half an ounce of saltpeter. As
local applications, astringent solutions are usually the best, as 30
grains of borax or of sulphate of zinc in a quart of water, to be
applied constantly on a cloth, as advised under "Inflammation of the
eyelids." In the absence of anything better, cold water may serve every
purpose. Above all, adhesive and oily agents (molasses, sugar, fats) are
to be avoided, as only adding to the irritation. By way of suggesting
agents that may be used with good effect, salt and sulphate of soda may
be named, in solutions double the strength of sulphate of zinc, or 7
grains of nitrate of silver may be added to a quart of distilled water,
and will be found especially applicable in granular conjunctivitis,
diphtheria, or commencing ulceration. A cantharides blister (1 part of
Spanish fly to 4 parts lard) may be rubbed on the side of the face 3
inches below the eye, and washed off next morning with soapsuds and
oiled daily till the scabs are dropped.
WHITE SPECKS AND CLOUDINESS OF THE CORNEA.
As a result of external ophthalmia, opaque specks, clouds, or haziness
are too often left on the cornea and require for their removal that they
be daily touched with a soft feather dipped in a solution of 3 grains
nitrate of silver in 1 ounce distilled water. This should be applied
until all inflammation has subsided, and until its contact is
comparatively painless. It is rarely successful with an old, thick scar
following an ulcer, nor with an opacity having red blood vessels running
across it.
ULCERS OF THE CORNEA.
These may be treated with nitrate of silver lotion of twice the strength
used for opacities. Powdered gentian, one-half ounce, and sulphate of
iron, one-fourth ounce, daily, may improve the general health and
increase the reparatory power.
INTERNAL OPHTHALMIA (IRITIS, CHOROIDITIS, AND RETINITIS).
Although inflammations of the iris, choroid, and retina--the inner,
vascular, and nervous coats of the eye--occur to a certain extent
independently of each other, yet one usually supervenes upon the other,
and, as the symptoms are thus made to coincide, it will be best for our
present purposes to treat the three as one disease.
_Causes._--The causes of internal ophthalmia are largely those of the
external form only, acting with greater intensity or on a more
susceptible eye. Severe blows, bruises, punctures, etc., of the eye, the
penetration of foreign bodies into the eye (thorns, splinters of iron,
etc.), sudden transition from a dark stall to bright sunshine, to the
glare of snow or water, constant glare from a sunny window, abuse of the
overdraw checkrein, vivid lightning flashes, drafts of cold, damp air;
above all, when the animal is perspiring, exposure in cold rain or
snowstorms, swimming cold rivers; also certain general diseases like
rheumatism, arthritis, influenza, and disorders of the digestive
organs, may become complicated by this affection. From the close
relation between the brain and eye--alike in the blood vessels and
nerves--disorders of the first lead to affection of the second, and the
same remark applies to the persistent irritation to which the jaws are
subjected in the course of dentition. So potent is the last agency that
we dread a recurrence of ophthalmia so long as dentition is incomplete,
and hope for immunity if the animal completes its dentition without any
permanent structural change in the eye.
_Symptoms._--The symptoms will vary according to the cause. If the
attack is due to direct physical injury, the inflammation of the eyelids
and superficial structures may be quite as marked as that of the
interior of the eye. If, on the other hand, from general causes, or as a
complication of some distant disease, the affection may be largely
confined to the deeper structures, and the swelling, redness, and
tenderness of the superficial structures will be less marked. When the
external coats thus comparatively escape, the extreme anterior edge of
the white or sclerotic coat, where it overlaps the border of the
transparent cornea, is in a measure free from congestion, and, in the
absence of the obscuring dark pigment, forms a whitish ring around the
cornea. This is partly due to the fact that a series of arteries
(ciliary) passing to the inflamed iris penetrate the sclerotic coat a
short distance behind its anterior border, and there is therefore a
marked difference in color between the general sclerotic occupied
between these congested vessels and the anterior rim from which they are
absent. Unfortunately, the pigment is often so abundant in the anterior
part of the sclerotic as to hide this symptom. In internal ophthalmia
the opacity of the cornea may be confined to a zone around the outer
margin of the cornea, and even this may be a bluish haze rather than a
deep, fleecy white. In consequence it becomes impossible to see the
interior of the chamber for the aqueous humor and the condition of the
iris and pupil. The aqueous humor is usually turbid, and has numerous
yellowish-white flakes floating on its substance or deposited in the
lower part of the chamber, so as to cut off the view of the lower
portion of the iris. The still visible portion of the iris has lost its
natural, clear, dark luster, which is replaced by a brownish or
yellowish sere-leaf color. This is more marked in proportion as the iris
is inflamed, and less so as the inflammation is confined to the choroid.
The quantity of flocculent deposit in the chamber of the aqueous humor
is also in direct ratio to the inflammation of the iris. Perhaps the
most marked feature of internal ophthalmia is the extreme and painful
sensitiveness to light. On this account the lids are usually closed, but
when opened the pupil is seen to be narrowly closed, even if the animal
has been kept in a darkened stall. Exceptions to this are seen when
inflammatory effusion has overfilled the globe of the eye, and by
pressure on the retina has paralyzed it, or when the exudation into the
substance of the retina itself has similarly led to its paralysis. Then
the pupil may be dilated, and frequently its margin loses its regular,
ovoid outline and becomes uneven by reason of the adhesions which it has
contracted with the capsule of the lens, through its inflammatory
exudations. In the case of excessive effusion into the globe of the eye
that is found to have become tense and hard so that it can not be
indented with the tip of the finger, paralysis of the retina is liable
to result. With such paralysis of the retina, vision is heavily clouded
or entirely lost; hence, in spite of the open pupil, the finger may be
approached to the eye without the animal's becoming conscious of it
until it touches the surface, and if the nose on the affected side is
gently struck and a feint made to repeat the blow the patient makes no
effort to evade it. Sometimes the edges of the contracted pupil become
adherent to each other by an intervening plastic exudation, and the
opening becomes virtually abolished. In severe inflammations pus may
form in the choroid or iris, and escaping into the cavity of the aqueous
humor show as a yellowish-white stratum below. In nearly all cases there
is resulting exudation into the lens or its capsule, constituting a
cloudiness or opacity (cataract), which in severe and old-standing cases
appears as a white, fleecy mass behind a widely dilated pupil. In the
slighter cases cataract is to be recognized by examination of the eye in
a dark chamber, with an oblique side light, as described in the
introduction to this article. Cataracts that appear as a simple haze or
indefinite, fleecy cloud are usually on the capsule (capsular), while
those that show a radiating arrangement are in the lens (lenticular),
the radiating fibers of which the exudate follows. Black cataracts are
formed by the adhesion of the pigment on the back of the iris to the
front of the lens, and by the subsequent tearing loose of the iris,
leaving a portion of its pigment adherent to the capsule of the lens. If
the pupil is so contracted that it is impossible to see the lens, it may
be dilated by applying to the front of the eye with a feather some drops
of a solution of 4 grains of atropia in an ounce of water.
_Treatment._--The treatment of internal ophthalmia should embrace,
first, the removal of all existing causes or sources of aggravation of
the disease, which need not be repeated here. Special care to protect
the patient against strong light, cold, wet weather, and active exertion
must, however, be insisted on. A dark stall and a cloth hung over the
eye are important, while cleanliness, warmth, dryness, and rest are
equally demanded. If the patient is strong and vigorous, a dose of 4
drams of Barbados aloes may be given, and if there is any reason to
suspect a rheumatic origin one-half a dram powdered colchicum and
one-half ounce salicylate of soda may be given daily. Locally the
astringent lotions advised for external ophthalmia may be resorted to,
especially when the superficial inflammation is well marked. More
important, however, is to instill into the eye, a few drops at a time, a
solution of 4 grains of atropia in 1 ounce of distilled water. This may
be effected with the aid of a soft feather, and may be repeated at
intervals of 10 minutes until the pupil is widely dilated. As the horse
is to be kept in a dark stall, the consequent admission of light will be
harmless, and the dilation of the pupil prevents adhesion between the
iris and lens, relieves the constant tension of the eye in the effort to
adapt the pupil to the light, and solicits the contraction of the blood
vessels of the eye and the lessening of congestion, exudation, and
intraocular pressure. Should atropia not agree with the case, it may be
replaced by morphia (same strength) or cocaine in 4 per cent solution.
Another local measure is a blister, which can usually be applied to
advantage on the side of the nose or beneath the ear. Spanish flies may
be used as for external ophthalmia. In very severe cases the parts
beneath the eye may be shaved and three or four leeches applied. Setons
are sometimes beneficial, and even puncture of the eyeball, but these
should be reserved for professional hands.
The diet throughout should be easily digestible and moderate in
quantity--bran mash, middlings, grass, steamed hay, etc.
Even after the active inflammation has subsided the atropia lotion
should be continued for several weeks to keep the eye in a state of rest
in its still weak and irritable condition, and during this period the
patient should be kept in semidarkness, or taken out only with a dark
shade over the eye. For the same reason heavy drafts and, rapid paces,
which would cause congestion of the head, should be carefully avoided.
RECURRENT OPHTHALMIA (PERIODIC OPHTHALMIA, OR MOON-BLINDNESS).
This is an inflammatory affection of the interior of the eye, intimately
related to certain soils, climates, and systems, showing a strong
tendency to recur again and again, and usually ending in blindness from
cataract or other serious injury.
_Causes._--Its causes may be fundamentally attributed to soil. On damp
clays and marshy grounds, on the frequently overflowed river bottoms and
deltas, on the coasts of seas and lakes alternately submerged and
exposed, this disease prevails extensively, and in many instances in
France (Reynal), Belgium, Alsace (Zundel, Miltenberger), Germany, and
England it has very largely decreased under land drainage and improved
methods of culture. Other influences, more or less associated with such
soil, are potent causative factors. Thus damp air and a cloudy, wet
climate, so constantly associated with wet lands, are universally
charged with causing the disease. These act on the animal body to
produce a lymphatic constitution with an excess of connective tissue,
bones, and muscles of coarse, open texture, thick skins, and gummy legs
covered with a profusion of long hair. Hence the heavy horses of Belgium
and southwestern France have suffered severely from the affection, while
high, dry lands adjacent, like Catalonia, in Spain, and Dauphiny,
Provence, and Languedoc; in France, have in the main escaped.
The rank, aqueous fodders grown on such soils are other causes, but
these again are calculated to undermine the character of the nervous and
sanguineous temperament and to superinduce the lymphatic. Other feeds
act by leading to constipation and other disorders of the digestive
organs, thus impairing the general health. Hence in any animal
predisposed to this disease, heating, starchy feeds, such as maize,
wheat, and buckwheat, are to be carefully avoided. It has been widely
charged that beans, peas, vetches, and other Leguminosae are dangerous,
but a fuller inquiry contradicts the statement. If these feeds are well
grown, they invigorate and fortify the system, while, like any other
fodder, if grown rank; aqueous, and deficient in assimilable principles,
they tend to lower the health and open the way for the disease.
The period of dentition and training is a fertile exciting cause, for
though the malady may appear at any time from birth to old age, yet the
great majority of victims are from 2 to 6 years old, and if a horse
escapes the affection till after 6 there is a reasonable hope that he
will continue to resist it. The irritation about the head during the
eruption of the teeth, and while fretting in the unwonted bridle and
collar, the stimulating grain diet and the close air of the stable all
combine to rouse the latent tendency to disease in the eye, while direct
injuries by bridle, whip, or hay seeds are not without their influence.
In the same way local irritants, like dust, severe rain and snow storms,
smoke, and acrid vapors are contributing causes.
It is evident, however, that no one of these is sufficient of itself to
produce the disease, and it has been alleged that the true cause is a
microbe, or the irritant products of a microbe, which is harbored in the
marshy soil. The prevalence of the disease on the same damp soils which
produce ague in man and anthrax in cattle has been quoted in support of
this doctrine, as also the fact that, other things being equal, the
malady is always more prevalent in basins surrounded by hills where the
air is still and such products are concentrated, and that a forest or
simple belt of trees will, as in ague, at times limit the area of its
prevalence. Another argument for the same view is found in the fact that
on certain farms irrigated by town sewage this malady has become
extremely prevalent, the sewage being assumed to form a suitable nidus
for the growth of the germ. But on these sewage farms a fresh crop may
be cut every fortnight, and the product is precisely that aqueous
material which contributes to a lymphatic structure and a low tone of
health. The presence of a definite germ in the system has not yet been
proved, and in the present state of our knowledge we are only warranted
in charging the disease to the deleterious emanations from the marshy
soil in which bacterial ferments are constantly producing them.
Heredity is one of the most potent causes. The lymphatic constitution is
of course transmitted and with it the proclivity to recurring
ophthalmia. This is notorious in the case of both parents, male and
female. The tendency appears to be stronger, however, if either parent
has already suffered. Thus a mare may have borne a number of sound
foals, and then fallen a victim to the malady, and all foals
subsequently borne have likewise suffered. So it is in the case of the
stallion. Reynal even quotes the appearance of the disease in alternate
generations, the stallion offspring of blind parents remaining sound
through life and yet producing foals which furnish numerous victims of
recurrent ophthalmia. On the contrary, the offspring of diseased parents
removed to high, dry regions and furnished with wholesome, nourishing
rations will nearly all escape. Hence the dealers take colts that are
still sound or have had but one attack from the affected low Pyrenees
(France) to the unaffected Catalonia (Spain), with confidence that they
will escape, and from the Jura Valley to Dauphiny with the same result.
Yet the hereditary taint is so strong and pernicious that intelligent
horsemen everywhere refuse to breed from either horse or mare that has
once suffered from recurrent ophthalmia, and the French Government studs
not only reject all unsound stallions, but refuse service to any mare
which has suffered with her eyes. It is this avoidance of the hereditary
predisposition more than anything else that has reduced the formerly
wide prevalence of this disease in the European countries generally. A
consideration for the future of our horses would demand the disuse of
all sires that are unlicensed, and the refusal of a license to any sire
which has suffered from this or any other communicable constitutional
disease.
Other contributing causes deserve passing mention. Unwholesome feed and
a faulty method of feeding undoubtedly predisposes to the disease, and
in the same district the carefully fed will escape in far larger
proportion than the badly fed; it is so also with every other condition
which undermines the general health. The presence of worms in the
intestines, overwork, and debilitating diseases and causes of every kind
weaken the vitality and lay the system more open to attack. Thierry long
ago showed that the improvement of close, low, dark, damp stables, where
the disease had previously prevailed, practically banished the
affection. Whatever contributes to strength and vigor is protective;
whatever contributes to weakness and poor health is provocative of the
disease in the predisposed subject.
_Symptoms._--The symptoms vary according to the severity of the attack.
In some cases there is marked fever, and in some slighter cases it may
be almost altogether wanting, but there is always a lack of vigor and
energy, bespeaking general disorder. The local symptoms are in the main
those of internal ophthalmia, in many cases with an increased hardness
of the eyeball from effusion into its cavity. The contracted pupil does
not expand much in darkness, nor even under the action of belladonna.
Opacity advances from the margin, over a part or whole of the cornea,
but so long as it is transparent there may be seen the turbid, aqueous
humor with or without flocculi, the dingy iris robbed of its clear,
black aspect, the slightly clouded lens, and a greenish-yellow
reflection from the depth of the eye. From the fifth to the seventh day
the flocculi precipitate in the lower part of the chamber, exposing more
clearly the iris and lens, and absorption commences, so that the eye may
be cleared up in ten or fifteen days.
The characteristic of the disease is, however, its recurrence again and
again in the same eye until blindness results. The attacks may follow
one another after intervals of a month, more or less, but they show no
relation to any particular phase of the moon, as might be inferred from
the familiar name, but are determined rather by the weather, the health,
the feed, or by some periodicity of the system. From five to seven
attacks usually result in blindness, and then the second eye is liable
to be attacked until it also is ruined.
In the intervals between the attacks some remaining symptoms betray the
condition, and they become more marked after each successive access of
disease. Even after the first attack there is a bluish ring around the
margin of the transparent cornea. The eye seems smaller than the other,
at first because it is retracted in its socket, and often after several
attacks because of actual shrinkage (atrophy). The upper eyelid, in
place of presenting a uniform, continuous arch, has, about one-third
from its inner angle, an abrupt bend, caused by the contraction of the
levator muscle. The front of the iris has exchanged some of its dark,
clear brilliancy for a lusterless yellow, and the depth of the eye
presents more or less of the greenish-yellow shade. The pupil remains a
little contracted, except in advanced and aggravated cases, when, with
opaque lens, it is widely dilated. If, as is common, one eye only has
suffered, the contrast in these respects with the sound eye is all the
more characteristic. Another feature is the erect, attentive carriage of
the ear, to compensate to some extent for the waning vision.
The attacks vary greatly in severity in different cases, but the
recurrence is characteristic, and all alike lead to cataract and
intraocular effusion, with pressure on the retina and abolition of
sight.