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.