Complete Text (Part 15)

; in the decided forms the image is either disregarded or remains double. The deviation may be in any direction. How may double images be united ? If double images are present, are of the same color, and are near each other, an effort is made on the part of the eye-muscles, entirely without conscious volition, to place the visual lines in the direction necessaiy for the fusion of the images, and diplopia will be overcome. How can the effort be detected? If a prism with the base up or down of sufficient strength is placed before one eye, and a red glass is placed before the other eye, double images are produced, and because of the change in the color of the images and the forced perpendicular displacement the effort at fusion is reduced to a minimum. If there exists a tendency to deviation in the internal or external recti muscles, the images will be displaced laterally. THE MUSCULAR APPARATUS. 115 If toward the interni, the image seen through the red glass will cor- respond to the side of the eye over which it is placed. If toward the externi, the images will be crossed. Where the images are found on the side corresponding to the position of the eyes they are said to be homon- ymous ; if crossed, heteronymous. What are the varieties of strabismus or squint ? Apparent or false, concomitant, and paralytic. What is apparent strabismus? It is a form in which the visual lines and the optic axes do not cor- respond. The visual line usually cuts the cornea to the inner side and a little below the centre of the cornea, forming an angle with the optic axis which is known as the angle a. When, as in some cases of hyper- metropia, the visual line passes to the inner side of the optic axis, the angle a is large and the eyes appear as though they diverged. If, as in some cases of high degrees of myopia, the visual line passes to the outer side of the optic axis, the eyes appear to converge. In the first case the angle a is said to be positive ; in the second case the angle a is said to be negative. How do you differentiate between apparent or false and true strabismus ? If the eyes are caused to fix on an object, and are then alternately cov- ered and uncovered, the uncovered eye describes a movement when it first sees the object if squint be present. If the squint is only apparent, the eyes remain stationary. What is concomitant strabismus ? A condition in which the tendency to deviation is real, but in which the normal degree of rotation of the globe is present and the conjugate movements of the eye unimpaired. There is no loss of muscle-power. Double images are seldom observed, as the mind has become accustomed to disregard the image formed on the squinting eye. What are the forms of concomitant strabismus ? In regard to constancy they are divided into periodic, alternating, and absolute ; in regard to direction, into convergent, divergent, upward, and downward squint. Periodic strabismus is a condition in which the squint obtains only at intervals. Alternating strabismus is a condition of con- stant squint, sometimes with one eye, sometimes with the other. Abso- lute strabismus is a form where one eye always squints. The terms convergent, divergent, upward, and downward squint explain themselves. What are the causes of concomitant strabismus ? In the hypermetropic eye the near-point is carried to such a distance from the eye that the effort at accommodation is reinforced by the effort at convergence, and the tendency to convergence becomes confirmed in 116 THE EYE. many cases ; thus, at first periodic strabismus of the convergent variety becomes manifest. As the case goes on without the correction of the hypermetropia the squint becomes alternating, and finally is confined to one eye. Hypermetropia is instrumental in producing probably 90 per cent, of the cases of convergent strabismus. Divergent strabismus is probably also produced by an unconscious effort on the part of the indi- vidual to avoid using convergence, as the near-point is already too near to the eye in the myope, the individual whose class presents the greater number of cases of concomitant divergent strabismus. Inequality in the vision of the eyes, irregularities in the surface of the cornea, or opacities of the cornea, cataractous conditions of the lens, and other conditions in which imperfect vision obtains, serve to produce a certain number of cases of strabismus of all varieties. What is meant by the term " heterophoria " ? A tendency to the deviation of visual lines which does not result in decided strabismus, but which, from the effort on the part of the eye- muscles to properly adjust the eyes for the visual acts, often produces headache and other disturbances of a very annoying character. How is this detected? The test for the detection of fused double images reveals the presence of this condition, and its amount may be measured by the employment of prisms which serve to superimpose or to bring the images on the proper level, as the case may be. What is the treatment of concomitant strabismus and of hetero- phoria ? When symptoms of the production of strabismus first become mani- fest a correction of the error of refaction may often prevent its develop- ment. Appropriate glasses should be fitted to the eyes and the patient made to wear them constantly. Strabismus which has already become alternating may sometimes be corrected by this simple procedure. Where this will not suince operative procedure is usually necessary. At what age does strabismus make itself manifest? and what are its effects on vision ? It usually develops in children between the ages of two and eight years, or during the time in which near vision is beginning to be em- ployed very constantly by the individual. If the eyes are tested shortly after the first evidence of strabismus is manifest, the vision seems to be about the same in each eye. When the strabismus is confirmed it is found that the squinting eye has less acute vision, as a rule, than its fel- low, and if squint has been present for a number of years the vision in the squinting eye becomes greatly reduced. A strabismus established at the age of five often shows vision reduced to counting fingers at a few feet when the individual reaches adult life. This loss of vision is termed " amblyopia from non-use," as it is thought that by disregarding the im- THE MUSCULAR APPARATUS. 117 age formed on the retina of the squinting eye the acuity of vision does not develop. When should the operation for strabismus be performed ? Many operators are of the opinion that the patient should not be operated upon before he has reached the age of six or seven years ; others are of opinion that it should be corrected by operative measures, if necessa^, as soon as the strabismus has become confirmed. Since it has been observed that strabismus sometimes corrects itself before the individual reaches the age of ten or twelve years, and since there is greater danger of over-correction by operation in young children, it is probably wiser to wait until there can be no doubt of the permanent nature of the condition before operating. What are the operations for the correction of strabismus ? Tenotomy of the muscle acting in the direction of the squint, and in some cases advancement of the tendon of its opponent, are necessary. What instruments are necessary in the operation for strabismus ? A stop speculum, fixation forceps, strabismus scissors, two strabismus hooks, thread, needles, and needle-holder. Describe the operation of tenotomy for correction of strabismus. The operation may be subconjunctival or open. The subconjunctival operation is done as follows : Cocaine or ether may be employed. The stop speculum is introduced to separate the lids, and the conjunctiva and subconjunctival tissues are grasped by the fixation forceps at the lower margin of the tendon at its insertion. This will be found for the inter- nal rectus at a distance of 6 mm. from the sclero-corneal junction, at the inner lower part of the eye, at an angle of 45° from the horizontal me- ridian of the cornea, and at 8 mm. for the externus on the same angle to the outer side. With the scissors the conjunctiva and subconjunc- tival tissues are divided with one snip, and the opening continued along the sclerotic far enough to divide the thin aponeurosis of connective tissue which is attached to the borders of the tendons. A strabismus hook is then passed through the small opening, the point always being pressed against the sclerotic, and brought up beneath the tendon of the muscle. The fixation forceps are removed, and the tendon divided between the sclerotic and the strabismus hook close to the sclerotic. The hook should be passed again, to be sure that all fibres of the tendon are divided. When this has been accomplished, the strabismus hook may be drawn to within 1 mm. of the margin of the cornea beneath the conjunctiva. How is the open operation performed ? The conjunctiva is seized with the fixation forceps over the centre of the insertion of the muscle, and a vertical incision made through the conjunctiva at this point, running parallel with the perpendicular meridian of the cornea when a tendon of the lateral muscles is to be 118 THE EYE. Fig. 38. Fig. 39. Strabismus Scissors. Fixation Forceps. divided. The tendon at the middle of its insertion is then seized and a small opening made through it. The strabismus hook is then passed so as to catch up either the upper or lower half of the tendon, and each is divided successively. The conjunctival opening in the subconjunctival THE MUSCULAR APPARATUS. 119 Fig. 40. Strabismus Hook. and in the open operations is usually closed with sutures to prevent in- fection. What effect may be produced by the operation of simple te- notomy ? A deviation of from 13° to 20° may often be corrected by simple tenotomy. It often occurs that the operation must be divided between the two eyes, as excessive motility inward often exists in each eye. The extent of the operation may be somewhat limited, a small effect being- produced by simple division of the tendon ; a greater effect by division of the thin aponeurosis of Tenon's capsule attached to the borders of the tendon. What is the operation for advancement of the tendon of a muscle in strabismus? This operation is performed for the purpose of exaggerating the effect of a simple tenotomy. The open operation of the opponent of the tenotomized muscle is performed. The conjunctiva next to the cornea is dissected up and sutures are passed. These are three in number— a central, one above, and one below, each passing through the margins of the muscle, the conjunctiva, and Tenon's capsule, beginning at a distance usually of i inch from the insertion of the tendon. The sutures are then tied, after first having removed a small piece of the tendon. The mid- dle is first tied and tightened, and then the lateral sutures, until the de- sired effect is reached. What are the varieties of heterophoria ? Esophoria, or deviation inward ; exophoria, or deviation outward ; hyperphoria, or deviation upward. What is the treatment of heterophoria ? Not infrequently the condition may be remedied by a simple correction of the error of refraction. When this does not suffice, an attempt may be made to relieve the patient by combining a prism with the lens of proper strength to correct the deviation, with the base placed outward in esophoria, inward in exophoria, and downward in hyperphoria. If the heterophoria is excessive, it becomes necessary to perform a partial or complete tenotomy of the stronger muscles, and in some cases to advance the opponent. 120 THE EYE. What is paralytic strabismus ? A deviation of the eyes caused by paralysis of one or more muscles. How may we differentiate between concomitant and paralytic strabismus ? If the eyes are made to follow the movements of an object in various directions, in concomitant strabismus both eyes will move to the same extent and their movements will not be restricted in any direction. In paralytic strabismus the movement of the affected eye will be restricted in the direction of the action of the paralyzed muscle. If in concom- itant strabismus the fixing eye is covered and the squinting eye is caused to fix the object, it will be found that the deviation of the first eye is the same as that of the squinting eye. In paralytic strabismus the deviation of the non-squinting eye, when it is covered and the squinting eye made to fix the object, is greater than that of the squinting eye. In other words, the secondary deviation in concomitant strabismus equals the primary deviation ; in paralytic strabismus the secondary is greater than the primary. What is the cause of paralytic strabismus ? Traumatism, syphilis, tabes dorsalis, tumors and hemorrhages in cer- tain parts of the brain, diphtheria, inflammatory processes at the apex of the orbit, and peripheral neuritis resulting from poisoning with alco- hol, tobacco, etc. How is paralytic strabismus classified? Usually according to the nerve affected ; sometimes according to the muscles or muscle affected. What are the symptoms in paralysis of the third or motor oculi ? This nerve supplies the levator palpebrse superioris, the internal, infe- rior, and superior recti, and the inferior oblique. When these are para- lyzed the lid droops and the eye turns outward and a little downward. The sphincter of the iris is supplied by the third, and in paralysis of this nerve the pupil becomes dilated. The dropping of the lid often causes such pronounced closure of the eye that the eyeball itself can be seen with difficulty. Diplopia exists, the images being crossed. _ The image of the squinting eye is on the opposite side and slightly higher, its apex turning a little inward above. The outward and downward movements are preserved. What are the symptoms in paralysis of the sixth or abducens nerve ? As only the external rectus is affected, the eye turns inward, pro- ducing a convergent strabismus. Double images result, the image of the affected eye being on the same side or homonymous. Diplopia is DISEASES OF THE ORBIT. 121 most marked when the object is passed in the direction of the action of the paralyzed muscle. The image is upright. What are the symptoms in paralysis of the superior oblique ? Since this muscle helps to rotate the cornea downward and outward, the cornea passes upward and a little inward. The diplopia is most marked in the direction of the action of the muscle, as is the rule in all cases of paralysis. The images are homonymous, the apex of the image inclining a little inward above. What is the treatment of paralytic strabismus ? Treatment must be directed to a correction of the cause. Since syph- ilis is the most frequent cause, its possible influence must be carefully inquired into and antisyphilitic remedies given if it exists. Paralysis from diphtheria usually follows some two or three weeks after the pseudo-membrane in the pharynx has disappeared, and generally disap- pears spontaneously in from three to six weeks. Operative procedure is only permissible when the paralysis has lasted for a long time and is not complete. What is ophthalmoplegia externa? A condition where all the extrinsic muscles of the eye are paralyzed. What is ophthalmoplegia interna? A condition in which the internal muscles of the eye — i. e. the muscle of accommodation — and the sphincter of the iris are paralyzed. These are supplied from the motor oculi, but may become paralyzed independently of the extrinsic muscle. What is the treatment of ophthalmoplegia externa and interna ? Treatment must be directed to the cause. It is often unsatisfactory regarding the external muscles, but recovery of function of the internal muscles is the rule. DISEASES OP THE ORBIT. What are the contents of the orbit ? The eyeball, Tenon's capsule, the ocular muscles, the optic nerve, nerves, blood-vessels, and the orbital fat. The orbital fat is a cushion of adipose tissue which assists to support the globe in its position. What inflammatory diseases is the orbital tissue subject to ? Orbital cellulitis is the principal form. It is produced by traumatism, erysipelatous infection, and also at times accompanies la grippe. What are the symptoms of orbital cellulitis ? The patient usually experiences considerable pain, which he refers to the side of the head and orbit. The eye becomes prominent, and sooner 122 THE EYE. or later, as the inflammation proceeds, the pus which usually forms finds an opening into the conjunctival sac or on the surface of the lids. What is orbital periostitis? An inflammatory condition affecting the periosteum, usually at the margin of the orbit, Caries of the bone in the vicinity involved some- times occurs, and a suppurating sinus opening on to the face may result, and continue to discharge pus and debris for a long time. What is the treatment of these two affections ? In orbital cellulitis free drainage by incision must be established at the earliest possible moment, escape being given to all pus that may form. Orbital periostitis is treated as periostitis is in other parts of the body. What tumors are found in the orbit? Solid and cystic tumors are met with. Sarcoma, carcinoma, neuroma, exostoses, and polypoid growths from the ethmoid cells are the principal forms. What is the treatment of tumors of the orbit ? Eemoval at the earliest possible date. What are the cystic tumors met with in the orbit ? Echinococcus, dermoid and cystic tumors. The treatment