Diseases of the Ocular muscles


Causticum.-Paralysis of the eye muscles resulting from exposure to cold. It has been especially successful in paralysis of the sphincter pupillae (mydriasis), of the ciliary muscle, levator palpebrae superioris (ptosis), orbicularis, and external rectus….


Anatomy.- The movements of the eyeball are carried on through the action of six voluntary muscles; four of these passing directly from their origin around the optic foramen, to their insertion in the sclerotic, are called the recti muscles. These muscles are inserted at varying distances, from 5.5 to 8 mm. from the corneal margin, and are distinguished by their relations to he eyeball, as internal, external, superior and inferior rectus. The insertion of the internal rectus is the nearest to the corneal margin, and that of the superior rectus is the most posterior.

The remaining muscles, from their taking a curved direction around the eyeball, are known as the superior and inferior oblique muscles. The superior oblique arises at the optic foramen, passes forward along the upper part of the inner orbital wall to a pulley attached at the superior- internal angle at the front of the orbit;from here it is reflected backward and outward between the superior rectus and the eyeball, and is inserted into the sclerotic, 16 to 18 mm. from the corneal margin on the posterior and outer part of the globe, between the superior and external recti.

The inferior oblique arises from the inner and anterior part of the floor of the orbit and passes outward and backward between the inferior and external recti and the globe, and is inserted near the superior oblique, between the superior and external recti and the inferior oblique are supplied by the third nerve (oculomotorius), the superior oblique by the fourth (patheticus) and the external rectus by the sixth (abducens).

The action of all these muscles is to turn the eye around a point, called the centre of rotation, situated on the antero-posterior axis of the globe, about 14 mm. behind the anterior surface of the cornea and about 10 mm. in front of the posterior surface of the sclera. These six muscles form three pairs of antagonistic muscles. The axis of rotation of the internal and external recti is vertical, as these muscles turn the globe directly inward and outward. The axis of rotation of the superior and inferior recti is horizontal, although not exactly straight across; it forms an angle of 67 degree with the visual axis, the nasal end of the line being in front of the temporal and is the axis of elevation and depression. The axis of the superior and inferior oblique is also horizontal, forming an angle of 38 degree with the visual axis, with the temporal extremity in front of the nasal, and the movements about it are those of rotation.(Fig,47.)

Taken singly, the muscles act as follows. The internal rectus draws the cornea directly inward (adduction), the external rectus turns the cornea directly outward (abduction:), the superior rectus turn the cornea upward and slightly inward, the inferior rectus turns the cornea downward and slightly inward, the superior oblique, taking its point of action from the pulley through which it passes, turns the cornea downward and outward and rotates from above downward; the inferior oblique turns the cornea upward and outward and rotates it from below upward.

Each movement of the eye results from the combined action of certain muscles, and there is never a period at which one or the other is entirely inactive, as by its living and elastic tension it aids in guiding a definite movement, though it does not take part in it. In looking directly upward both the superior rectus and inferior oblique are brought into action, the inclination inward of the former being by the outward tendency of the latter, and so in all other movements of the eye the action of all the muscles must be considered. Paralysis of any one muscle will cause all movements of the eye to be less sure.

The function of the ocular muscles is to secure single vision with the two eyes by directing both eyes to the point of fixation in such a manner that the image of the object fixed shall fall simultaneously on the macula lutea of each eye. When this is done, all objects lying in the same horopter will form images upon the respective retinae which will be equidistant from the fovea centralis and will, therefore, be appreciated as single, giving what is called binocular vision.

The horopter, as described by Mueller, is represented by a circle which passes through the centre of rotation of each eye and through the apex of the point of fixation of the visual lines. All objects beyond or inside the horopter will cast images on parts of the retinae not equidistant from the fovea and will create the impression of two objects or double vision; for example, holding two pins in the same line, one eight inches and the other twenty from the eyes, on looking at the nearest pin the other is seen double, and vice versa. This double vision of objects not lying in the horopter causes no annoyance, because the mind ignores the impression of objects with which it does not concern itself. The symmetrical position of the physiological centres of the retina is the anatomical ground for binocular vision. If a distant object be fixed with parallel lines of vision, to fix an object at one side which throws its image in both eyes at an equal distance from the macula lutea, both eyes must move through an equal angle; consequently, equal innervation on both sides is necessary for the symmetrical movements of the eyes. All objects are seen single only when retinal images fall on corresponding points of the two retinae.

Homonymous Diplopia. If the visual line of the left eye be directed on an object and there is convergence of the right eye, the image, which would in the left eye be formed on the fovea in the right would fall upon the retina to the inner side of the fovea and would be projected outward to the right of the object fixed, or homonymous diplopia.

Heteronymous Diplopia. If there is divergence of the right eye at the time the visual line of the left eye is directed upon on object, the impression from the object fixed would in the right eye fall upon the retina to the outer side of the fovea and when projected outward would appear to the left of the object fixed, causing crossed or heteronymous diplopia. The displacement of the false image is always in the direction which is opposite to that of the deviation of the eye. When the eye deviates inward, the diplopia is homonymous; when outward, heteronymous; when upward, the false image is below, and, when downward, it is above. The false image is of the deviating eye.

Binocular Diplopia is present when the visual axis of one eye deviates from the object of fixation.

Monocular Diplopia is due to the formation of two images of the same object upon one retina and exists when the other eye is closed. As in binocular diplopia there is one image cast upon each one of the two retinae the diplopia disappear on closing either eye, while if the diplopia persists on closing one eye, it is then monocular. The cause of monocular diplopia is either an anomalous refraction or a double pupil.

Paralysis of Ocular Muscles.- We may have one or more muscles paralyzed, and the cause may be either orbital or intra cranial; if the latter, it may be along the course of the nerves or in the brain. Lesions of the spinal cord may cause paralysis through fibres which proceed to the brain.

SYMPTOMS.-The characteristic indications of paralysis are false position of the eye, limitation and irregularly in motion, and double images. As secondary effects, we find dizziness, nausea headache, incorrect projection of the field of vision and inability to guide the hands or feet aright. Indistinct vision may occur in cases of slight paralysis, where actual diplopia is absent due to an overlapping of images. If only one eye is involved, the inclination is to close it. Another peculiar effect is the attitude which the head assumes to obviate the double images. It is turned toward paralyzed muscle to diminish the diplopia.

CAUSES.-The effective causes are localized periostitis, inflammation of the sheath of the nerves, basilar meningitis, haemorrhages, tumors, degeneration of nerve structure or of the cerebral nerve centres, injuries, diphtheria, rheumatism, draught of air, etc. The majority of cases of ocular paralysis occur in syphilitic subjects and are most frequently of orbital origin. Paralysis may also be the first premonition of sclerosis of the spinal cord. Both eyes may be affected, and the cause then intra-cranial and generally basilar. Paralysis may occur at any age and may be temporary or permanent.

DIAGNOSIS.-In paralysis the secondary deviation is always greater than the primary, while in concomitant strabismus the primary and secondary deviations are equal. The primary deviation is the deviation of the affected eye when the healthy eye fixes, while the secondary deviation is the deviation of the good eye when the affected eye fixes. If recovery does not occur, there follows secondary contraction of the opposing or associated muscle. For example, in paralysis of the right external rectus, from diminished resistance, the right internal rectus will turn the eye unduly inward, and the left internal rectus will also undergo contraction, and, if the right eye looks directly forward, the left will consequently squint inward. This fact in old cases often makes the diagnosis as to which muscle was first affected very difficult.

A. B. Norton
Norton, A. B. (Arthur Brigham), 1856-1919
Professor of Ophthalmology in the College of the New York Ophthalmic Hospital; Surgeon to the New York Ophthalmic Hospital. Visiting Oculist to the Laura Franklin Free Hospital for Children; Ex-President American Homoeopathic Ophthalmological, Otological and Laryngological Society. First Vice-President American Institute of Homoeopathy : President Homoeopathic Medical Society of the State of New York ; Editor Homoeopathic Eye. Ear and Throat Journal : Associate Editor. Department of Ophthalmology, North American Journal of Homoeopathy, etc.