INTERNAL OPHTHALMIA.
Diagnosis of internal ophthalmias difficult. Causes: as in conjunctivitis, extension of conjunctivitis or keratitis to iris, choroid, ciliary circle, retina; Lymphatic constitution, damp soil, air and stable, pit life, dentition, grain feeding, training. Symptoms: ophthalmic symptoms generally, enlarged ciliary vessels in sclera not movable; white zone around corneal margin; iris dull, brownish, sluggish; intraocular tension increased: flocculi in aqueous humor: photophobia: oblique focal illumination: sudden change from darkness to light: synechia: ophthalmoscope. Cyclitis. Diagnosis: from keratitis, recurrent ophthalmia. Lesions: according to chief seat of the disease: inflammation of Descemet’s membrane, iris, choroid, ciliary circle, lens, vitreous and retina in variable degree. Opacity of aqueous, lens, capsules, or vitreous. Prognosis: always grave, often vision impaired or lost. Treatment: rest, pure air, apart from strong sunshine, removal of causes, local bleeding or cupping, derivation, purgative, cooling diuretics: locally astringent antiseptic lotions, cocaine, homatropine, blister, undue tension antiseptic puncture, mercury oxide ointment; in rheumatic cases salicin or sodium salicylate.
In the domestic animals it is not always possible to distinguish between inflammations affecting different portions of the inner and middle coats of the eye (iritis, cyclitis, choroiditis, retinitis), so that it is convenient to give in general terms the phenomena and treatment of the class known as ophthalmia internus. This is all the more appropriate that inflammation of one of these divisions so frequently extends to the others producing panophthalmitis, that the disease in one usually implies an early implication of all.
Causes. Many of the causes of conjunctivitis, when acting with special intensity, or for too long a time, may cause internal ophthalmia. Severe blows, bruises, punctures, lacerations, sand, cinders, dust, lime, foreign bodies inducing traumas, sudden transitions from darkness to bright sunshine, habitual exposure to sunshine or to the reflection from snow, ice or water, through a window in front of the stall, the abuse of the overdraw check rein, the glare of electric light or of lightning flashes, draughts of cold damp air between windows or doors, the beating of cold storms on the eyes and skin, a sudden chill from plunging in water or standing in a cold draught when perspiring, blows with branches, pine cones or needles in the eye, the constant irritation from entropion, trichiases, burdocks or thistles in the forelock, irritant gases, etc., are among the factors which coöperate in setting up the disease. Again diseases of the digestive organs, rheumatism, influenza, canine distemper, brust-seuche, petechial fever, variola, eczema, and aphthous fever may be direct causes. Conjunctivitis and keratitis are liable to merge into irido-choroiditis by extension, and above all when owing to perforation of the cornea a direct channel is opened for the easy entrance of infective, pathogenic microbes. A lymphatic constitution, connected with low breeding, or living in a low, damp, cloudy region, or in dark, damp, impure stables, has a strongly predisposing influence. The period of dentition, connected as it usually is with domestication, stabling, grain feeding, and training is often a potent accessory cause.
Symptoms. With the general phenomena of superficial or external ophthalmia there are some indications which may be called pathognomonic. These may be summarized as follows: in eyes devoid of pigment the enlarged ciliary vessels run deeply and are not tortuous, nor mobile when rubbed; the scleral redness increases toward the margin of the cornea, but leaves a white zone in front of the penetration of the ciliary vessels; the iris has lost its clear reflection, appearing dull or brownish; the pupil is contracted and sluggish in response to light and darkness, it may be fixed or may show marked unevenness in its margin: the tension of the eye ball is often increased, flocculi of lymph may be seen in the aqueous humor settling into the lower part of the anterior chamber. This deposit may be white or yellowish or it may even be reddened by extravasated blood especially in traumatic injuries. In traumas, too, the cornea and even the aqueous or vitreous humor may be opaque. In cases resulting from exposure to cold or from internal causes, the media of the eye are at first clear and transparent. The condition of the interior of the eye is usually to be learned by examining the patient as he stands facing the light from a dark back ground. A stable door or window will afford the requisite amount of rays falling from above and from each side upon the interior of the eye. The observer looks indirectly or obliquely and under favorable conditions can see the iris and through the pupil. If the pupil is unduly closed it may often be dilated by instilling a few drops of a 5 per cent. solution of atropia and waiting for fifteen or twenty minutes.
The examination is made more satisfactorily with a candle or other single source of light in a dark chamber. If this light is surrounded by a chimney opaque except at one side which is directed toward the eye, the results are much more satisfactory. Focal illumination with a biconvex lens, or oblique illumination will show a swollen condition of the iris with uneven bulging swellings at different points, and generally a lack of the clear dark surface which marks the healthy iris. It may be yellowish or brownish, rather than dark, or blue, or yellow, but is always duller than normal. The pupil may be contracted or dilated, but is always uneven at the margin according to the degree of congestion of the different portions. It may be quite immovable under the stimulus of light and darkness, and is always sluggish as compared with the healthy condition. To test this reflex action, the one eye may be bandaged, and the other eye covered with the palm of the hand for one or two minutes. When exposed the pupil will be found to be widely dilated, and in the healthy eye it will rapidly contract and dilate alternately until it has reached a condition of adaptation to the intensity of the light when it will remain immovable. With the inflamed iris these contractions and dilatations will be lacking altogether, or they will be sluggish and imperfect in various degrees according to the intensity of the inflammation, the degree of congestion or the tension of the liquid media of the eye. Restricted movement may also be due to adhesion to the cornea, (synechia anterior) or to the capsule of the lens (synechia posterior).
When viewed with the ophthalmoscope properly focused the choroid may show a lack of its normal lustre and an unevenness due to the formation of small rounded elevations in connection with congestion, or exudation, and patches of yellowish red or whitish discoloration together with lines of the same color following the course of the blood-vessels. It may also reveal dark spots of opacity in the lens (cataract) or clouds in the anterior region of the vitreous, the result of exudations. The blood-vessels may appear enlarged and tortuous.
In some cases the exudate may form a false membrane which completely closes the pupil.
A special tenderness around the margin of the cornea is suggestive of cyclitis. Internal ophthalmia is usually accompanied by a variable amount of fever.
Diagnosis. From simple keratitis, it is distinguished by the thickening, discoloration and sluggishness of the iris, by the absence, in many cases, of corneal opacity, and of free lachrymation, and in some instances by increased tension of the eyeball.
Recurring ophthalmia, which is usually also an internal inflammation, appears more abruptly and often at first with greater severity, and accompanied by more hyperthermia. There is almost always a bluish white opacity around the margin of the cornea, the eye is retracted in its sheath so as to appear smaller, and the upper lid usually shows a marked angle between its inner and middle thirds in place of the evenly curved arch of the healthy palpebra. It usually appears for the first time in the young and in those that have inherited the susceptibility and have been kept on damp soils, in cloudy districts, or dark buildings.
Lesions. These are necessarily varied according as the inflammation is concentrated on particular parts of the interior of the eye. The secreting membrane of the aqueous humor is nearly always inflamed giving rise to an exudate and a milky opacity of the aqueous humor. The iris is the seat of congestion exudation, thickening, cell proliferation and investment by false membranes. The capsule of the lens is early clouded, may be covered by exudate and is rendered vascular in some cases. The choroid is also the seat of congestion, exudation and discoloration with the covering up at points of its pigmentary layer. The vitreous and lens finally become the seat of exudation and opacity which is liable to prove permanent.
Prognosis. The internal ophthalmias are always to be dreaded. In other organs exudates may take place and become organized as permanent structures without abolishing the function or rendering the organ physiologically useless, but in the delicate and transparent tissues of the eye, any such permanent product almost infallibly causes opacity and loss, or serious impairment of vision. In the retina the displacement, derangement, or covering up of the cones and rods necessarily interferes with or abolishes sight, the opacity of the cornea, lens, capsule, or vitreous interrupts the rays of light, and the destruction, or coating over of the pigment of the choroid leads to undue reflection and destroys vision. Beside this the destruction or impairment of one part of the eye, changes the refraction and blurs the vision, or interferes with accommodation and destroys the utility of the organ. Unless therefore the disease can be cut short in its early stages and a complete resolution effected it is likely to leave the patient very much deteriorated in value. Fortunately it is only in the most violent cases or in very susceptible animals that the disease in the one eye is transmitted to the other by sympathy and leads to destruction of that eye as well.
In the treatment of internal ophthalmia, rest in pure air and moderate warmth, away from a fierce glare of light is imperative. The causes should as far as possible be removed. Next, it is desirable to establish derivation. Leblanc and Trasbot attach great importance to phlebotomy from the jugular on the same side. A more direct local action with less loss of blood may be obtained from opening the angular vein of the eye or applying a leech beneath the lower lid. In most cases a sufficient derivative action can be secured by an active purgative which may be followed by daily doses of cooling diuretics. Locally astringent lotions (lead acetate or zinc sulphate 1 dr. to 1 qt. water; mercuric chloride, 1 ∶ 5000; boric acid, 2 ∶ 100; pyoktannin, 1 ∶ 1000) in combination with cocaine hydrochlorate, homatropin, atropia sulphate, duboisia or hyoscyamin (1 ∶ 1000) would be appropriate. These may be applied over the eye on a soft cloth, and in cases of infective inflammation the more antiseptic agents may be injected under the lids. When the inflammation is very severe the atropia or other sedative agent may be made of the strength of 1 ∶ 100 and a drop or two placed inside the lids with a dropper every two or three hours.
A blister of biniodide of mercury may be applied to a space the size of a dollar above the anterior end of the zygomatic ridge, or in dogs back of the ear on the side of the neck: or a seton may be passed through the skin in the same situation.
When the eyeball is unduly tense, puncture through the margin of the cornea with a fine aseptic lancet will relieve the tension and in some cases induce a more healthy action. Assiduous antisepsis is needful until the wound has healed.
In other cases benefit can be obtained from the use of an ointment of yellow oxide of mercury 1 part, in vaseline 10 parts, or of iodoform of the same strength. A small portion the size of a grain of wheat is put under the lid, and the latter manipulated with the finger to bring it in contact with all parts of the surface. In case of a rheumatic origin salicin and salicylate of soda are demanded.