Complete Text (Part 7)

55 lime care should be taken to carefully cleanse the lids, to remove all par- ticles of lime : a solution of boric acid may be employed for this purpose, and a 10 per cent, ointment of boric acid should be given to the patient to be stuffed into the eye at relatively frequent intervals. In addition to this, a solution of atropine maybe employed to produce dilatation of the pupil and prevent adhesion should iritis threaten. Precaution must be taken to prevent adhesions between the cornea and conjunctivae in cases where the conjunctival tissue is also injured. These may be prevented by passing a probe frequently between the conjunctiva of the globe and of the lids to break up any adhesions that may be in process of forma- tion. THE SCLEROTIC. What is the sclerotic coat of the eye ? It is the white outer membrane of the ball of the eye which, in con- nection with the cornea, forms the fibrous coat of the eye. It is very strong and inelastic, and serves to retain the form of a globe by its re- sistance to the intraocular pressure. It forms the surface of a sphere having a radius of about 12 mm. Anteriorly it is continuous with the tissues of the cornea. At this point it measures about 1 mm. in thick- ness ; 6 to 8 mm. back of the sclero-corneal margin it measures about ^ mm. in thickness. It becomes slightly thicker as it approaches the pos- terior pole of the eye, and in the vicinity of the optic nerve it reaches about l^o mm. in thickness. It gives attachment to the tendons of the extrinsic muscles of the globe. At the equator of the globe the sclerotic is pierced by four openings which give passage to the venae, vorticosce. A little to the inner side of the posterior pole^ of the globe there is a circular opening through the sclerotic which is crossed by bands of connective tissue, forming a sieve-like opening known as the lamina cribrosa. This measures about 2 mm. in diameter, and gives entrance to the nerve-bundles of the optic nerve and to the principal vessels of the retina. Encircling and near the optic nerve the sclerotic _ is pierced by small openings which give passage to the ciliary arteries and to the ciliary nerves. What is the structure of the sclerotic ? It is composed of bundles of connective tissue passing in all directions, and bound together by an interfibrillar and interfascicular cement-sub- stance. A capillary network with wide meshes passes through the entire membrane. The sclerotic is poorly supplied with nerves. A lymph- system is found resembling that of the cornea. What is the canal of Schlemm? This is a small circular canal situated about 2 mm. posterior to the sclero-corneal margin and near the inner surface of the sclerotic, which communicates with the small spaces between the fibres of the ligamen- 56 THE EYE. turn pectinatum, and is considered to be a lymph-canal aiding in the passage of fluids from the interior of the globe. It is not always single, but may be divided at times into two or three smaller canals. What is the capsule of Tenon ? This is a sac of connective tissue which surrounds the posterior part of the eye and serves as a socket in which the globe rotates. It is thin posteriorly, but becomes thicker near the equator of the globe, passes forward, is penetrated by the muscles of the globe, and is at- tached to the sclerotic about 1 line back of the sclero-corneal junction. This capsule is divided into two portions, one of which, the visceral layer, is closely adherent to the sclerotic, the other, the parietal layer, lies against the fat of the orbit, The opposed surfaces of this sac are covered with endothelium, moistened by secretion, which favors the easy movement of the globe. What inflammations is the sclerotic subject to? A form of inflammation known as episcleritis, occurring in the ante- rior segment of the sclerotic, is not infrequently met with. It consists of a deep congestion of the affected part, which presents a dark-red ap- pearance just beneath the conjunctiva. The conjunctiva becomes in- volved also, and the mass at the inflamed point is slightly elevated. The inflammation usually occurs in single patches, circumscribed and slightly nodular. It is very slow in its progress, and often includes the whole thickness of the sclerotic. It has a tendency to travel around the cor- nea, affecting at intervals the whole of the anterior segment of the globe. It is not infrequently associated with a chronic form of keratitis, and is also complicated in some cases by inflammation of the iris, ciliary body, and anterior segment of the choroid. It is then known as anterior uveitis. What is the cause of episcleritis ? It occurs most frequently in gouty individuals and in those who suffer from rheumatism. Children of a tuberculous habit are also attacked, and in these the condition known as anterior uveitis is most frequently met with. What is the treatment of episcleritis ? Local treatment alone is seldom sufficient. Hot applications may be employed with benefit. In cases where iritis exists atropine should be used, and in cases where slow ulceration of the cornea is also threatened, some stimulating application other than the hot fomentations, such as calomel or the yellow-oxide-of-mercury ointment, may be employed with benefit. The constitutional treatment consists in the giving of remedies directed against the gouty or rheumatic condition. The salicylate of sodium and also the iodide of potash, used in connection with colchicum, given for a long period of time, produces beneficial results. Since pho- 57 tophobia is often a pronounced symptom in some cases, the eye should be protected from light by the use of blue glasses or the patient may remain in a room that is partly darkened. What are the results of episcleritis ? In not a few cases where the sclerotic is deeply involved, the inflam- mation results in thinning the sclerotic in its anterior segment, and the intraocular pressure subsequeptly leads to bulging of the sclerotic at the weak point and to the production of scleral staphyloma. How should wounds of the sclerotic be treated ? Rupture of the sclerotic by blows on the eye occur almost always without an accompanying opening through the conjunctiva, and por- tions of the vitreous, with at times the lens, escape beneath the con- junctiva. If the le'ns alone is found beneath the conjunctiva, it may be permitted to escape by incision through this membrane, the wound thoroughly cleansed with an antiseptic, a compress bandage applied, and the eye left to recover. If there is an escape of a considerable amount of the contents of the globe, it becomes necessary to remove the globe ; and this should be done early. If the rupture is slight and the interior of the eye is clouded by the occurrence of hemorrhages, it is well to apply a compress bandage and let nature proceed to a clear- ing up of the media before any operative measure is undertaken, as after this operative procedure may be unnecessary. Should the wound occur through the anterior portion of the sclerotic, involving the attach- ment of the ciliary body, the danger to vision by slow inflammation and to affection of the fellow-eye through sympathy may be very great. It is in such cases sometimes necessary to remove the globe to prevent fur- ther injury. Cleanly incised wounds, even if quite extensive, if they do not involve the ciliary body, usually heal kindly and favorably under the influence of a compress bandage. Wounds in the anterior fourth of the sclerotic — that portion known as the ciliary region — are particularly dangerous, because of the effect liable to ensue from infection of the ciliary body and from irritation to this part through cicatricial contraction. Such eyes, if they are not immediately removed, should be carefully watched, and on the first sign of sympathetic inflammation to the fellow-eye or of the appearance of glaucomatous symptoms to the injured eye they should be removed. THE IRIS, CILIARY BODY, AND CHOROID. What is the second membrane of the eye ? It is composed of the iris, ciliary body, and choroid, and is known as the vascular membrane, tunica vasculosa, or uveal tract. It is very rich in vessels and nerves, and is pigmented throughout except in albinoes. 58 (For description, see p. 59.) 59 What is an albino ? An individual whose tissues throughout the body are without pig- ment. What is the iris? The iris is a circular membrane perforated in its centre, which hangs as a curtain in the anterior portion of the eye and serves to regulate the amount of light admitted to the interior of the eye. It measures about 11 mm. in diameter. It springs from a root which is attached to the ciliary body and to the ligamentum pectinatum. Its free margin rests against the anterior capsule of the crystalline lens when the pupil is con- tracted or moderately dilated. In a state of maximum dilatation it hangs free in the aqueous humor. The iris serves to separate the ante- rior from the posterior chamber of the eye. From before backward the iris is compose^ of a layer of endothelium, posterior to which is the stroma of the iris, composed of a framework of connective tissue con- taining bundles of radiating fibres and of interlacing fibres. In the stroma of the iris are found the blood-vessels and nerves, and in colored irides pigment-cells more or less numerous are deposited. Near the pupillary margin of the iris, extending for a distance of from 1 to 1| mm., and being about ^ mm. in thickness, is the circular muscle known as the sphincter iridis. Posterior to the stroma of the iris is the uveal layer, which consists of two layers of deeply-pigmented cells. The pig- ment consists of minute granules placed in cells having indistinct nuclei. What is the structure of the sphincter of the iris ? and what is its nerve-supply? The sphincter of the iris is composed, of non-striated muscle-fibres, and receives its nerve-supply from a third or motor oculi. From what source is the vascular and nerve-supply to the iris derived ? The vessels to the iris come from the long ciliary arteries, which are two in number. They pierce the sclerotic near the optic-nerve entrance, pass forward between the sclerotic and choroid in the horizontal merid- ian, and just before reaching the root of the iris in the ciliary body divide and send one branch above and one branch below, encircling the iris. These branches meet in the perpendicular meridian and anasto- Fig. 9.— Diagrammatic Representation of the Course of the Vessels in the Eye (hori- zontal section, after Leber). The veins are represented black, the arteries clear, a, arteriae ciliares posteriores breves ; b, arteriae ciliares posteriores longs ; c'c, arteriae et vena? ciliares anteriores; dd', arteriae et venae conjunct! vales posteriores; e'e, arte- riae et venae centrales retinae ; /, vessels of the internal, and g, of the external optic sheath ; //, venae vorticosa ; i, venae ciliares posteriores breves ; k, branch of the pos- terior short ciliary artery to the optic nerve : /, anastomoses of the choroidal vessels with those of the optic nerve ; m, choriocapillaris ; n, episcleral branches ; o, arteria recurrens choroidalis ; p, circulus arteriosus iridis major ; q, vessels of iris ; r, of the ciliary processes ; s, branch to the vena vorticalis from the ciliary muscle ; u, cir- culus venosus ; v, marginal loop plexus of the cornea ; w, arteria et vena conjuncti- valis anterior. 60 THE EYE. mose, but not very freely. This circle is termed the circuhs iridis major. From it radial branches are sent into the iris to the pupillary margin, where they break up into a capillary network and form the cir- culus in'th's minor. The venous blood from the iris is conducted to the ciliary body, and finds exit from the globe principally through the ante- rior ciliary veins. The iris is richly supplied with nerves of sensation, derived from the ciliary nerves, which are .branches of the ophthalmic ganglion and of the nasal division of the fifth. These nerves enter the iris from the ciliary body at its root in relatively large trunks, ten to twelve in number, and pass into the stroma of the iris, where they form a rich plexus from which terminal filaments are given off. What is the hyaline membrane of the iris ? This is a thin membrane found between the uvea and the stroma of the iris, which is continuous with the lamina vitrea of the ciliary body and the choroid. On what are the contraction and dilatation of the pupil dependent ? These movements are very complex. The contraction of the pupil is brought about by nervous impulse to the sphincter papillae through the third or motor oculi. This motion is not under control of the will, but is dominated by certain stimuli. Contraction of the pupil is brought about by light being reflected into the eye, by the effort of accom- modation, etc. Dilatation of the pupil depends on stimulation of the sympathetic through its vaso-motor branches and the removal of stimuli to the filaments of the third. It cannot be demonstrated that radiating muscular fibres exist in the human iris. It is therefore thought that dilatation of the iris is brought about by contraction of the walls of the blood-vessels, and consequent diminution in their, lumen. The removal of so much blood from the iris lessens the amount of its bulk, and neces- sitates the removal of the remaining substance of the iris toward its root. Division of the third nerve alone produces but moderate dilatation of the pupil, proving that some other influence must be operative to produce the maximum dilatation. Paralysis of the sympathetic pro- duces maximum contraction of the pupil, demonstrating the fact that dilatation of the blood-vessels exerts a strong influence in reducing the pupil to a minimum size. What is the ciliary body? This is a portion of the vascular tract of the eye which is composed of a connective-tissue framework containing non-striated muscle-fibre, blood-vessels, and nerves. It measures about 1 mm. in thickness in its thickest portion, and is about 4 mm. in length. It is attached to the sclerotic by an annular band of connective-tissue filaments at a point about 2 mm. back of the clear margin of the cornea. It contains the muscle of accommodation, which is composed of non-striated fibres ar- ranged in bundles. Some of these pass meridianly ; others of these BODY, AKD CHOROID. 61 bundles pass equatorially. This muscle serves to change the curvature of the crystalline lens in such a manner that the focus of rays of light for objects at different distances may fall upon the retina at the will of the observer. Depending from the inner surface of the ciliary body are the ciliary processes. They are about seventy in number, are very vas- cular, and serve to secrete the nutrient fluids in the interior of the eye which go to sustain the vitality of a portion of the vitreous, the lens, and the cornea. The nerve-supply to the ciliary body is plentiful and is derived from the ciliary nerves. The ciliary body is continuous with the choroid in its deeper layers. The inner layers of the ciliary body are the lamina vitrea and the uveal layer. These correspond in struc- ture to the same layers in the iris, and are continuous with them. Pos- teriorly these layers are continuous with the lamina vitrea of the choroid, with the pigment-layer of the retina, and with the framework of the retina. In the anterior portion of the ciliary body the pigmented layer is composed of a double layer of pigmented cells ; in its posterior portion back of the apices of the ciliary processes the inner layer of cells is not pigmented. What is the choroid ? The choroid is a pigmented membrane which covers the inner poste- rior two-thirds of the surface of the sclerotic. It is composed from with- out inward of— first, a thin pigmented layer which is attached to the sclerotic and is known as the lamina fnsca (by some regarded as part of the sclerotic). It is composed mostly of branching pigmented cells, and is almost entirely devoid of blood-vessels. Between this and the next layer of the choroid is a space known as the perichoroidal lymph-space, the walls of which are lined with endothelial cells. The next layer is the so-called lamina suprachoroidce. This membrane contains the large vessels of the choroid, of which the arteries are derived from the short ciliary arteries, eight or ten in number, which pierce the sclerotic in the region of the optic nerve. They break up into a network, and send radial branches into the inner layer of the choroid, which is known as the clioriocapillaris. The veins in this layer gradually converge and form the trunks of four large veins which pass out of the eye at the equator and are known as the venae vorticosse. These large vessels are held in position by a framework of connected tissue, which is interspersed in the brunette by numerous branching pigment-cells. Interior to this layer is a thin membrane composed of connective-tissue fibres, elastic and non-elastic, termed the elastic membrane of Sattler. This layer ex- tends from the optic nerve to the ora serrata of the retina. The lamina suprachoroidae does not stop at this point, but is_ continuous with the ciliary body. Finally is the last layer of the choroid, the lamina vitrea. This is a hyaline membrane, and is closely connected with the outer layer of the retina. The choroid is richly supplied with nerves, the