Part 79

Dislocation of the lens may be congenital, or acquired. In the latter case it is explained by a traumatism or a liquefaction of the vitreous and coincident softening of the suspensory ligament. In either case, if the ligament is torn through in more than one-half its circumference, the lens will hang by the remainder and move on it as on a hinge so as to change its location in the different positions of the head. This is especially so where the vitreous has become abnormally fluid as there is then no resistance to the free backward movement of the lens. The writer has seen the eye of a cow affected in this way, so that the cataractous lens advances to the pupil and recedes from it as the eye is moved. In other cases the dislocated lens, being attached below only, drops down and virtually disappears behind the lower part of the iris. In still other cases it becomes wedged into the pupil, or protrudes into the anterior chamber and lies in front of the pupil and iris. The semi-detached lens sooner or later becomes opaque. A cataract with contraction of the newly formed tissue on the capsule and undue tension on the suspensory ligament may, however, precede the dislocation which is then precipitated by some shock, as a blow, fall, sneeze, cough or emesis.

The condition leads to an apparent increase in the depth of the anterior chamber, and tremulous movement of the iris, and if illuminated the impacted condition of the lens or its changes of position can be detected. If its edge is exposed it appears as a black ring.

Treatment is useless, unless it be extraction of the lens, or iridectomy in suitable cases.

PERSISTENT ARTERIA HYALOIDEA.

In the embryo this artery occupies the central canal of the vitreous and extends from the optic papilla to the posterior pole of the lens. At times it persists after birth and even to mature life and is then detected as a gray or dark thread on ophthalmoscopic examination. Berlin records a case in an old horse and others in young cats, and Möller other cases in dogs. Treatment is manifestly hopeless.

OPACITY OF THE VITREOUS.

From inflammation of the ciliary body, choroid or retina. Pupil copperas green with white points, lines or patches, move in opposite direction from the eye, liquefied vitreous, crystals of cholesterine, scintillance, opacity. Treatment.

Opacities visible with the ophthalmoscope usually come from effusion of blood into the vitreous, or inflammation of the retina, choroid, or ciliary body. Blood thrown into the vitreous will usually leave some permanent turbidity. In choroiditis or retinitis the ophthalmoscope may reveal the changes in these structures. A turbidity appearing in the anterior portion of the vitreous, without any apparent cause, is probably due to cyclitis which cannot be seen with the ophthalmoscope, but may cause special tenderness around the sclero-corneal zone. It is common in recurrent ophthalmia of the horse and in irido-choroiditis in animals generally, and may be a distinct feature of glaucoma. The general reflection of the pupil is copperas green, but gray or white points, lines, bars or patches may often be recognized. These being back of the lens and axis of the eye, move in the opposite direction from the line of vision, thus if the eye looks upward they descend, if it looks downward they ascend, if it turns to the right, they turn to the left and vice versa. Tested by a burning candle the three reflections remain clear and distinct unless lens or cornea are affected.

Not infrequently the vitreous is found abnormally fluid, and among its solid particles in affected horses have been found crystals of cholesterin (Jacobi) and tyrosin (Möller). In the illuminated vitreous such crystals may be seen to reflect the light like a shower of sparks (synchysis scintillans). Opacity of the vitreous has been seen in cases of amaurosis in horses (Hertwig) and glaucoma in lambs (Prinz).

Treatment is rarely satisfactory, though in some recent cases, and in the absence of any other irremovable lesion, reabsorption of a slight exudate may take place, in connection with the use of mild saline laxatives and diuretics.

RETINITIS.

With choroiditis and cyclitis, albuminuria, nephritis, mellituria, leukæmia, petechial fever, contagious pneumonia. Photophobia, contracted pupil, redness around optic disc, enlarged retinal vessels, white and gray spots and radiating lines, exudates, clots, fatty degeneration. Treatment: correct primary disease.

Retinitis is usually an accompaniment of choroiditis and cyclitis, but it also occurs as a complication in a number of constitutional maladies, such as albuminuria, nephritis, mellituria, leukæmia, petechial fever, contagious pneumonia, etc. Fröhner records a case in a leukæmic horse, Peters in one suffering from petechial fever, Schindelka in cases of contagious pneumonia in the horse, and Eversbusch in recurrent ophthalmia of the horse, and under other conditions in dogs.

The attack is accompanied at the outset with much photophobia and contraction of the pupil. When this is dilated and the fundus of the eye examined with the ophthalmoscope, the retina is seen to be reddened for some distance around the optic disc and the blood-vessels are materially enlarged. Later, white or gray spots and lines are seen in and around the disc, tending to assume a radiating direction, and the retina at large, on careful examination may have a distinctly striped appearance. Brownish, reddish or light colored exudates and hæmorrhages may be made out in certain cases between retina and hyaloid, or between the retina and choroid. Fatty degeneration of the fibrous tissue is common.

Treatment must be first that for the primary disease of which the retinitis is a complication, and the result will depend on how amenable that affection is to therapeutic measures. In advanced albuminuria or mellituria, the retinitis, which is usually double, is hopeless, while in contagious pneumonia, petechial fever, leukæmia and other less fatal affections, retinitis in its initial stages may recover. In cases of advanced disease with serious structural changes in the retina, recovery cannot be looked for.

DETACHMENT OF THE RETINA.

This may occur in any case of retinitis or choroiditis. It is especially common in recurrent ophthalmia in horses. It may also occur through the dragging by contracting inflammatory products in organization. Spontaneous recoveries have taken place through reabsorption, and attempts have been made by the injection of iodide lotion to hasten this, or more safely by rest and diaphoresis. Puncture and aspiration have also been tried with most varied results. As a rule in the lower animals the treatment of the inflammation, with rest, a pressure bandage, and pilocarpin will be indicated.

RETINAL HEMORRHAGE.

This occurs in inflammations of the retina or choroid, also in degenerations of the vascular walls and as a result of traumas, or poisons. Schindelka quotes a case in a dog from ptomaines, Eversbusch, one from scurvy in the dog, Appenroth, one in a calf from a blow with a cow’s horn, and others in cats and horses from traumas. It is present to a slight extent in all inflammations of the retina. With the ophthalmoscope the recent lesion appears as a bluish red blotch on a bright red ground, and the older lesion of a brownish red. Rest and a pressure bandage may be employed after subsidence of the inflammation.

TUMORS OF THE RETINA.

Eversbusch found subretinal cysts in a 24 year old horse, Merkel and others have found similar bodies in old dogs and cattle. Sarcomata and melanosarcoma are found on the surface of the choroid in gray horses, implicating the retina. The only remedy is enucleation of the bulb.

INFLAMMATION OF THE OPTIC NERVE. PAPILLITIS.

Choked disc. Neuro-retinitis. Papillo-retinitis. Nerve swelling blocks veins. Causes: lead, tumors in brain bilateral, in orbit unilateral, influenza, petechial fever. Symptoms: redness of optic disc, retinal arteries contracted, veins gorged, papilla swollen (woolly), vitreous opacity. Treatment.

This is also known as choked disc from the obstruction of the return of blood by the veins of the retina which pass out at the cribriform lamina. The swelling of the nerve ending and papilla compress the veins, causing stagnation and venous congestion in the retina. When the retina is thus involved the term neuro-retinitis or papillo-retinitis is often applied.

Causes. The condition has been traced to lead poisoning, brain or orbital tumors, and various infectious diseases. Except in orbital tumor the disease is usually bilateral. In horses Schindelka has seen the condition in influenza and Peters in petechial fever, heart failure and dyspnœa. In a necropsy on a horse the writer found complete cataract, atrophy of the bulb to less than two-thirds the size of its fellow, thickening and furrowing of the sclera, the presence of an extensive old blood clot in the seat of the vitreous, cupping of the disc, retro-ocular neuritis with exudate inside the sheath, and a considerable reddish brown tumor of the choroid plexus on the same side. The trouble was attributed to the blow of a rope on the eye a considerable time before. The blood in the vitreous retained its dark hue and showed no evidence of microbian invasion.

Symptoms. To the phenomena of retinitis there is added violent injection of the capillary plexus of the papilla. The arteries of the retina are contracted while the veins are dilated and tortuous. The papilla is swollen and is said to have a woolly appearance. The vitreous may be opaque by reason of exudation or blood extravasation into its substance. Retro-ocular neuritis is usually present, and brain tumor in certain cases. Möller calls attention to the fact that with atrophy of the bulb the elliptical outline of the papilla gradually lessens and it becomes more nearly round. In dogs, too, the form of the papilla is also changed and the same author has found it distinctly triangular. The pupil may be at first strongly contracted and later freely dilated.

Treatment is usually of little avail and does not differ materially from that adopted in retinitis. In tumor of the orbit pressing on the optic nerve it may sometimes be reached through the temporal fossa, but usually in all such cases enucleation of the eyeball is demanded.

RETRO-BULBAR OPTIC NEURITIS.