Complete Text (Part 9)

smaller than normal and the tension much reduced, in which condition it remains. The reflex from the interior is of a whitish -yellow color, and may readily be mistaken for the reflex produced by glioma of the retina. What is the treatment of suppurative and metastatic choroiditis ? If the pain is intense or if the globe is ruptured, enucleation is ad- visable. If, however, the condition occurs in childhood and is not pain- ful, the eye may be permitted to remain and the patient may be treated simply for the purpose of relieving pain. What is tubercular choroiditis? It is a form of choroiditis in which miliary tubercles form in its THE IRIS, CILIARY BODY, AND CHOROID. 69 tissues. The tubercles usually appear near the posterior pole of the eye and affect the choroid in preference to any other tunic. They always appear in connection with tuberculosis of other parts of the body. Their occurrence in cases which come before the oculist is very rare. With the ophthalmoscope a reddish point in the fundus of the eye is the first thing observable. Shortly afterward the points present a whitish ap- pearance at their centres and are distinctly elevated. Vision is disturbed only at the points covered by the tubercle. _ They advance slowly, and usually produce so little disturbance that it is unnecessary to direct the treatment to them particularly during the life of the patient. At times they become large, and the surgeon finds it necessary to enucleate the eye. What are the microscopical appearances of tubercle of the choroid ? The tumor is usually located in the anterior layers of the choroid, apparently springing from the choriocapillaris. They are surrounded by small infiltration-cells, and are composed of small and giant cells, usually breaking down in their centres. They contain tubercle bacilli which are easily demonstrated on section. What is the condition to which the name sclero- choroiditis pos- terior or posterior staphyloma is given ? This is usually a passive condition, due to enlargement of the globe of the eye from the influence of the intraocular pressure on the pre- viously weakened sclerotic coat of the eye. The gradual bulging of the eye backward, the process taking place at the posterior pole of the eye, puts the choroid on the stretch and produces atrophy, usually in that part immediately surrounding the optic nerve. In the early stage of this condition a whitish patch, crescentic in shape, usually shows itself to the temporal side of the optic disk, and is known as a myopic crescent. As the process advances atrophy of the choroid becomes more marked, and a large, irregular patch is formed about the optic disk. The devel- opment of this condition takes place in many cases about the age of puberty, and becomes stationary when the individual has reached adult life. What is the treatment for sclero-choroiditis posterior? Errors of refraction must be corrected. The eyes must not be used to excess and the general health of the individual must be improved. What are the characteristic appearances of rupture of the cho- roid? and what are its causes? This condition presents at first the evidences of hemorrhage from the choroid, which consists of a reddish patch, indicating the position of a clot of blood, and an indistinct whitish haziness associated with it, which marks the position of exudation not containing blood-corpuscles. As the blood and serous exudation are absorbed, a whitish patch is found to 70 THE EYE. occupy the fundus back of the clot, and when the absorption is complete a white line, usually somewhat curved, with its concave border toward the optic disk, is found to be present. It is clearly seen to be posterior to the retina, as the retinal vessels pass over it in an uninterrupted course. The white appearance is due to the showing through of the sclerotic. The cause of rupture of the choroid is contusion, usually from a blow. The blow is received on the front or anterior portion of the eye, producing rupture of the choroid nearly opposite to the point on which the blow was received, the rupture being by contrecoup. No treatment can be employed to benefit the condition. What is coloboma of the choroid ? It is a congenital condition resulting from an arrest in the development of the eye at a stage before the retinal fissure has become entirely closed. It also implies coloboma of the posterior layers of the retina, and is due to non-closure of the retinal tissue, and not to any original defect in the formation of the choroid. The condition is often associated with con- genital coloboma of the iris and with micro-ophthahnus. The defect in the choroid is always in a downward direction from the optic disk. The borders of the defect are deeply pigmented. The defect itself has a white background, because of the showing through of the sclerotic. Over this defect pass a few retinal vessels, indicating that a portion of the layers of the retina are present over at least a part of the defect. A blind spot, corresponding very nearly in size to the coloboma, is always present in the visual fields. To what forms of tumors are the choroid, ciliary body, and iris subject ? The tumor most frequently met with is sarcoma. It may be pig- mented or devoid of pigment, and originate from any part of the cho- roid, ciliary body, or iris. Sarcoma is most frequently met with in the choroid, where it is pigmented in almost every case. Carcinoma also affects the choroid, usually secondary to carcinoma in some other part of the body. Primary carcinoma is impossible in the choroid, but may occur in the ciliary body. In this last-named part of the vascular tract carcinoma, if it develops, must develop from the epithelial cells supplied by its retinal portion. Tubercles and gummata may also form in these membranes. Cystic formations sometimes occur in the iris, but are very rare. Cavernoma of the choroid has been observed. What are the symptoms of sarcoma of the choroid ? The patient's attention is usually first called to the trouble in the ejTe from a defect in vision. In the early stage of the growth no pain is ex- perienced, but as the growth advances a stage is reached in which there is distinct increase in the tension of the eye, with pain referable usually to the side of the head. On examining the eye with the ophthalmo- scope detachment of the retina is found, and a reddish nodular mass is THE RETINA. 71 visible, usually either by examination with the ophthalmoscope or by oblique illumination, over the surface of which blood-vessels may be seen. Sarcoma of the ciliary body has much the same character. Oc- curring in the iris, it is usually deeply pigmented and produces a spherical tumor. It is of course easily recognized when it appears on this mem- brane. Flat sarcoma is of rare occurrence. Carcinoma of the choroid is usually flat, covering a considerable area. It affects the vision, but does not readily present any marked pathological condition in the inte- rior of the eye, the diagnosis being made from the history of carcinoma in other parts of the body, the failure in vision, and the occurrence of an apparently exaggerated hypermetropia evident on ophthalmoscopic examination. What are the symptoms of gumma of the uveal tract ? Gumma of the choroid is exceedingly rare. It is met with more fre- quently in the ciliary body and in the iris. It is usually accompanied by more acute inflammatory symptoms than is the case in carcinoma or sar- coma. In the ciliary body the differential diagnosis is made with diffi- culty. In the iris its color differs markedly from sarcoma. It is usually of a yellowish-white color, with blood-vessels crossing over its apex and with an inflamed base. The history and the conduct of the growth, and the treatment with mercury and potassium, will determine the diagnosis. What is the treatment of sarcoma of the choroid or of the cili- ary body? The globe should be removed at the earliest possible moment to pre- vent, as far as possible, metastatic processes from taking place. What is the treatment of sarcoma of the iris ? When the growth is small and occupies a portion of the iris near the pupillary margin, it is sometimes possible to remove the growth by mak- iug an iridectomy without sacrificing the eye. Where the growth has attained large dimensions a removal of the eye is necessary. THE RETINA. What is the retina ? The retina is the percipient membrane of the eye. It covers the whole of the interior of the eye in its posterior portion forward to a point about two lines anterior to the equator of the globe. It is an ex- pansion of the nerve-tissue of the brain held together by a connective- tissue framework. What is the structure of the retina ? Microscopical examination shows it to be composed of ten different layers, which from within outward are as follows : Lying next to the 72 THE EYE. vitreous is the membrana Umltans interna. This membrane is formed by the close apposition of the expanded heads of Midler's fibres ; it is very thin. Next to this layer we have the nerve-fibre layer of the retina, in which the nerve-fibres coming from the optic nerve are distributed. External to this layer is the ganglion-cell layer, composed of large branching nerve-cells disposed in rows four or five deep in the region of the fovea centralis, becoming very much scattered at the periphery of the retina. The nerve-fibres are connected with the ganglion- cells, and the cells send processes to each other and into the deeper layers of the retina. Directly beneath this layer is the inner granular layer. It con- sists of very fine connective-tissue fibres, which anastomose very freely. Posterior to this layer is the inner layer of nuclei, the inner molecular layer of some authors. It is composed of numerous round cells asso- ciated closely together. External to this layer is the external granular layer, resembling in structure the internal granular layer. Next to this comes the external nuclear layer, composed of round nuclei, resembling the inner nuclear layer ; the external nuclear layer is somewhat thicker than the internal. Exterior to this layer is the membrana limitans ex- terna, also apparently made up from the expanded ends of Midler s fibres. Springing from this layer is the percipient layer of the retina, the rods and cones. The rods consist of long rod-like processes, being- attached to the external limiting membrane and fixed by the extremities into the outer layer of the retina. The cones are composed of two parts — a base, which is conical in shape and extends about one-third of the distance between the external limiting membrane and the outer layer of the retina ; it is granular in structure. The outer limb is very thin and narrow, and is attached to the external layer of the retina. At certain portions of the retina the rods are greatly in excess of the cones, but near the entrance of the optic nerve the cones are more plentiful. At the fovea centralis they are much narrower than in other parts, and are present to the exclusion of the rods. Posterior to the layer of rods and cones is a single layer of large hexagonal pigmented cells, which are known as the epithelium of the choroid, but more properly as the pig- ment-layer of the retina. At the optic-nerve entrance the retina is pierced by a circular opening. The retina is limited anteriorly, or rather its functional layers are limited anteriorly, by what is known as the ora serrata, an irregular or serrated border where the retina suddenly be- comes thinner and loses its nerve-elements. What is the appearance of the retina when viewed by the oph- thalmoscope ? It is perfectly transparent in nearly all its parts, and the reflex obtained by looking into the eye with the ophthalmoscope is derived from other tissues. Blood-vessels belonging to it course over it anterior to the cho- roid. At the fovea centralis a circular whitish ring may sometimes be observed, which marks the border of this depression. THE RETINA. 73 What are opaque nerve-fibres occuring on the retina? They are fibres passing from the optic disk on to the retina which still retain the medullary substance common to nerve-fibres in other parts of the body, especially those which go to make up large nerve-trunks. The fibres are spread out oyer the retina, usually near the optic disk, and form white patches which obscure all details of the portion of the fun- dus which they occupy. They are congenital and do not change through life. What disease-processes affect the retina? Some of the most common are syphilitic retinitis, albuminuric retinitis, hemorrhagic retinitis, and retinitis pigmentosa. What is congestion of the retina ? It is a condition that may occur, but is very difficult of diagnosis. It is seldom possible to say that a retina is congested. It must pass into a condition of retinitis with exudation to make the diagnosis positive. What is albuminuric retinitis ? It is a condition of the retina dependent on the depraved condition of the blood, brought about by disease of the kidneys and an excessive waste of albuminoids from the blood. What is the appearance of albuminuric retinitis ? In the beginning there is a slight congestion of the disk with haziness Fig. 11. Renal Retinitis at a Late Stage (Wecker and Jaeger). 74 THE EYE. of the retina, particularly noticeable at the posterior pole of the eye. Soon whitish patches appear in the retina in the vicinity of the fovea centralis. These patches have usually somewhat of a symmetrical ar- rangement, radiating from the fovea centralis and spreading out in the shape of a fan. White spots, also due to exudation and diffuse in cha- racter, are found in the vicinity of the disk and along the blood-vessels. It not infrequently occurs that hemorrhages take place in the retina, often as forerunners of the retinal exudation. The whitish patches are due to the escape of the plasma of the blood into the various layers of the retina. When diffuse patches occur the exudation has taken place in the nerve-fibre layer. It obscures the blood-vessels and underlying structures. The sharply-cut, well-defined patches are due to the pres- ence of exudation in the deep layers of the retina, where they occupy spaces formed between MiiUer's fibres. As the disease progresses the ex- udation becomes more plentiful until a stage is reached when the exuda- tion ceases and absorption begins. Hemorrhages usually come from the capillaries and small veins. What are the causes of albuminuric retinitis ? Nephritis, whether acute or chronic, may cause this condition. In the acute form of nephritis the retinitis occurring is of the exudative variety. In chronic nephritis the retinitis following is of the hemorrhagic variety. The treatment is directed to the condition of the kidneys. What is retinitis pigmentosa? This is a disease characterized by the formation of small stellate pig- ment-patches, occurring first in the peripheral portions of the retina. It is essentially a degenerative process, affecting the choroid as well as the retina. It usually commences in early life and extends over a long period of time, gradually increasing in intensity, and eventually producing almost complete blindness. The pigmentation consists in the hypertrophy of the retinal pigment, which advances into the substance of the retina in the form of minute prolongations, and reaches and follows the course of the smaller retinal vessels. The retinal vessels become much reduced in size and the disk takes on a smoky, pale appearance. The visual fields narrow concentrically. However, when they comprise an angle of not more than thirty or forty degrees the patient's central vision is usually acute. Gradually the disease encroaches upon the remaining retina, and vision is almost if not entirely abolished. Individuals affected with this malady have great difficulty in seeing at night, because of the small area of retina capable of receiving impressions, and because of the slug- gish condition of the remaining approximately normal portion. In rare cases the disease begins at the posterior part. It is then termed retinitis pigmentosa centralis. What is the treatment of retinitis pigmentosa ? Treatment is of but little avail, and may be ignored. The health of THE RETINA. 75 the patient and the maintenance of good hygienic surroundings should be the physician's greatest care. Associated with retinitis pigmentosa we sometimes have a form of cataract known as posterior polar cataract. In many cases the optic nerve is more or less atrophied. What is hemorrhagic retinitis ? This is a form of retinitis dependent upon the condition of the blood- vessels. Occurring in old people, it almost always accompanies chronic interstitial nephritis, and is the expression of systemic disease of the arteries. The arterial walls become much thickened and the blood- current is interfered with. Because of stagnation produced from in- sufficient blood-supply to certain portions of the retina the walls of capillaries and veins become weakened and permit of the escape of blood. What is syphilitic retinitis? This form of retinitis is characterized by excessive exudation, and by hemorrhages more or less profuse occurring in the retina, and not infre- quently also passing into the vitreous. The condition is almost always accompanied with a thickening of the walls of the vessels, a veritable syphilitic peri- and endarteritis. The disturbance to vision is very marked. The disease is not infrequently accompanied with more or less affection of the choroid. As it progresses toward recovery the exudation and hemorrhages gradually disappear, leaving the arteries reduced in size, atrophic patches in the choroid, and strings of connective tissue in various parts of the vitreous. What is the treatment of this form of retinitis