Theoretically the examination of the double images should render the diagnosis easy and accurate, but in practice the inability of many patients to appreciate and describe the relations of the images, together with secondary contractions and involuntary compensations, makes it oftentimes extremely difficult to attain an accurate chart of the double images. In many recent cases we can tell what muscle is affected without an analysis of the double images. The movement of the eye in the direction of action of the paralyzed muscle is less than normal, and is increased in the opposite direction; its movements are irregular and jerky. The image of the affected eye is projected-i.e., seems to the patient to lie- in the direction of the paralyzed member. The inclination of the head, when present, will be such as to favor the lamed muscle and will be in its line of action.
When, however, there is any uncertainity as to the muscle affected, the examination of the double images should always be made. The double images are best detected by having one eye covered with a red glass, and the patient to describe the position and inclination of the two lights (one red and the other white) seen when looking at the flame of a candle eight to ten feet away. The images are to be noted in the different parts of the field as follows : First on the level with the patient’s eyes directly in front, then to the right and left, and also at about three feet above and below this level at the centre, right and left. The use of the red glass aids the patient in detecting the two images and at the same time informs the physician to which eye each belongs. Paralysis affecting but one single muscle attacks either the external rectus or the superior oblique, because each of these muscles is supplied by an independent nerve. Paralysis of several muscles is usually due to the oculomotor nerve.
Ophthalmoplegia totalis is a paralysis of all the eye- muscles. In this the lids droop, the eye is directed forward and immovable, pupil dilated and no power of accommodation.
Ophthalmoplegia externa, all but the pupil and accommodation affected. Is more frequent than the former and is always of central origin.
Ophthalmoplegia interna, only the pupil and accommodation affected.
Conjugate paralysis affects associated movements, as to the right or left, etc., eyes will only follow to the median line. As for example to the right, and appears as paralysis right externus and left internus. But left internus will converge in median line showing only affected in associated movements. The cause is a lesion in the association centres of the nerves.
Paralysis may result from a lesion anywhere in the course of the nerve tract, intra-cranial, it may affect the centres in the cortex of the brain (cortical paralysis), the association centers, or the nerve nuclei upon the floor of the fourth ventricle (nuclear paralysis), or the nerve trunks along the base of the skull (basal paralysis). Orbital paralyses occur from a lesion of the nerve trunk or its branches after its entrance into the orbit.
Paralysis, External Rectus.-Paralysis of the external rectus muscle causes a limitation in the outward movement of the eye. In complete paralysis the eye can only be turned but little beyond the median line, while in incomplete it may often go to nearly the normal limit, but with an irregular, jerking motion. The head is turned toward the paralyzed side. The deviation of the affected eye is inward; the diplopia is homonymous; the double images are on the same level and parallel, and the distance between the images increases on looking toward the affected side. The line which separates the part of the field in which there is single vision from that in which it is double is not exactly vertical, but is inclined obliquely, the diplopia extending further toward the healthy side below than above.
Paralysis, Superior Oblique.-The restriction in motion is downward and outward, and in complete paralysis of this muscle the motion downward is diminished. The deviation of the affected eye is upward and inward, and the image of the affected eye is inclined inward at the top, owing to the torsion action of this muscle on the eyeball. The obliquity of the false image is increased on looking toward the affected side. The diplopia is homonymous and present only in the lower part of the field. The image of the affected eye is lower than that of the healthy eye, and the difference in height between the two images is increased on looking downward and toward the healthy side. The image of the affected eye generally appears nearer to the patient than that of the healthy eye. The direction of the healthy eye, when the diseased eye fixes, is downward and inward. The line of demarcation between the true and false images is slightly oblique to the horizontal, the end corresponding to the affected side being lower. The face is inclined downward and to the healthy side.
Paralysis, Internal Rectus.-In this, the restricted movement is inward, the affected eye is outward, the diplopia is heteronymous, the double images are parallel and of the same height, the distance between them increases on looking toward the healthy side and on looking upward. The line of demarcation between the true and false images is oblique to the vertical, the diplopia extending further toward the healthy side above than below. The face is turned in the direction of the affected eye.
Paralysis, Superior Rectus.-The restricted motion is upward and slightly inward, the deviation of the affected eye is downward and on looking up is downward and outward; diplopia is slightly crossed and in the upper part of the field the false image is higher than the true, its upper end is inclined to the healthy side; the difference in height between the two images increases on looking upward and the obliquity increases on looking to the healthy side. The line of demarcation is inclined to the horizontal, the diplopia extending lower toward the affected side. The face is directed slightly upward.
Paralysis, Inferior Rectus.-In this we find the restricted movement is downward, the deviation of the affected eye is upward and outward, the diplopia is slightly crossed, especially in the lower part of the field; the false images are lower and inclined toward the affected side; the difference in height increases on looking downward and to the affected side, and the obliquity increases on looking toward the healthy side. The line of demarcation is inclined to the horizontal, the diplopia extending higher toward the affected side. The face is inclined downward and slightly toward the affected side.
Paralysis Inferior Oblique.-The restricted movement is upward and outward, the deviation of the affected eye is downward and inward, the diplopia is slightly homonymous and especially in the upper part of the field, the image of the affected eye is higher and inclined outward, the difference in height increases on looking upward and inward and the obliquity increases on looking to the affected side. The line of demarcation is inclined to the horizontal, the diplopia extending lower toward the affected side. The face is directed upward and slightly toward the sound side.
Complete Paralysis of the Third Nerve.-In this there is ptosis, slight exophthalmos, pupil moderately dilated, accommodation paralyzed; movements are restricted in all direction excepting directly outward; the deviation of the affected eye is outward; there is heteronymous diplopia, the false image is oblique and inclined toward the healthy side; it also appears higher than the true image and nearer to the patient. The distance between the images increases on looking toward the sound side, and the difference in height increases on looking upward. The face is inclined toward the sound side and slightly upward.
COURSE.-Paralysis may occur suddenly or develop insidiously. Relapses may occur, and the course is always chronic. Many cases, especially old ones, are absolutely incurable, and in even the most favorable ones six weeks or more are required for a cure. The prognosis depends mainly upon the cause. Syphilitic and rheumatic cases are the most favorable.
TREATMENT.-The treatment varies according to the nature of the cause, which should always receive due consideration in the selection of a drug. Our chief reliance must be on internal medication.
Prismatic glasses, to which we frequently resort, may be used for two purposes: 1. To relieve the annoying diplopia by giving that prism which neutralizes the double vision. 2. For the purpose of exercising the paralyzed muscle by using a weak prism, which nearly fuses the double images, when by the exercise of the will they may be brought together; by daily using weaker and weaker prisms much improvement can be made in restoring the muscle power.
Electricity is the most valuable agent for the cure of paralysis, and we should employ the constant current, of from two to three milliamperes. The applications should be made daily for from three to five minutes at each sitting, with the negative pole over the insertion of the muscle and the positive at the occiput.
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.