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Information on pupil dilation, constriction and testing the eye.
Pupil Changes - Testing of the Eye
The iris being under the control of two mechanisms, the one reflex (contracting) the afferent fibres lying in the optic nerve, the efferent in the 3d nerve, and the centre in the corpora quadrigemina; and the other a dilating me chanism the efferent fibres being in the sympathetic and the centre in the cilio-spinal region of the cord (lower cer vical and upper dorsal); so spasm or paralysis of any of these structures will give rise to changes in the size of the pupils. There is probably, however, a third mechanism viz., a local centre for the movements of the iris, lying either in the iris itself or in the neighboring choroid, and on this mechanism act various drugs when dropped on the con junctiva, such as atropin (dilating) and physostigmin (con tracting).
The most common causes of change in the pupils are as follows: Contraction (myosis) occurs normally when the eye is ac commodated for near objects, when the optic nerve or retina is stimulated, when the eyeball is turned inwards, when the aqueous humor is defective, and under the influ ence of various drugs morphia, physostigmin, etc. It may, further, be due to disease of the retina, or to irritation of the 3d nerve in its course, or of the higher nerve centres, to paralysis of the sympathetic, or to disease of the cilio spinal region of the cord.
Dilatation. Paralysis of the 3d nerve gives rise to dilata tion of the pupil, and no movements of the iris are caused by exposure to light or by efforts at accommodation. Irritation of the sympathetic or of the cilio-spinal region may also cause dilatation of the pupil. Total paralysis of the iris may probably arise from disease of the lenticular gan glion (Hutchinson).
Hippus, or clonic spasm of the iris, shows itself in quickly alternating contraction and dilation of the pupil. It is sometimes seen in cases of paralysis of the 3d nerve, and probably in disease of the sympathetic.
Argyle-Robertson Symptom consists in the absence in the pupil of any response when the retina is stimulated by light, while at the same time it moves normally when ac commodation is made. This condition is frequently met with in locomotor ataxia.
Ophthalmoscopic Examination should be practised by every student as frequently as possible, and should be a matter of routine in the examination of all nervous cases. Both the direct and the indirect methods should be used. When the fundus has been brought into view, we have to consider the condition of (a) the retinal vessels, (b) the optic nerve,
(c) the retina, and (d) the choroid.
(a.) Retinal Vessels* Note the size and arrangement of veins and arteries, and observe whether there be visible ar terial pulsation (in cupping of the disc and in aortic in competence), anasmia, hyperaemia, or hemorrhages.
(b.) The Optic Nerve. Of abnormalities there may be:
(1. ) Simple Congestion of the Disc Vascularity; edges ill defined.
(2. ) (Edematous Congestion of the Disc Disc red; swol len; edges obscured.
(3. ) Neuritis Increased redness and swelling; the edges of the disc totally obscured.
* The arrangement of the morbid appearance of the fundus oculi here given corresponds pretty closely to that adopted by Dr. Gowers in his work on " Medical Ophthalmoscopy."
(4. ) Atrophy Disc white or gray; may be simple or secondary to congestion or to neuritis.
(5.) The Retina. The chief abnormalities to be detected by the ophthalmoscope are hemorrhages, white spots, and patches.
(6. } The Choroid. White spots occur, either new formations or the results of atrophy, with destruction of the pig ment normally found there.
It may be convenient here to indicate shortly the ophthal moscopic appearances in one or two diseases in which reti nal changes are most frequent and important.
Cerebral Tumors.In most cases optic neuritis is present.
At first there is congestion, increased redness, swelling, and cloudiness in the disc; then neuritis sets in, with ob scuration of the edges, followed by great swelling and strangulation of the papilla (choked disc).
Locomotor Ataxia. Atrophy of the optic nerves is a fre quent symptom in locomotor ataxia, and it is also some times seen in general paralysis, and occasionally in insular sclerosis. The disc is pale, small in size, and excavated, and the retinal vessels are usually diminished in calibre.
Bright 's Disease. Particularly in the cirrhotic form of this disease, special retinal changes (retinitis albuminurica) take place. These consist in (a) cedematous swelling of the retina; (b) white degenerative spots and patches; (c small extravasations; (d) inflammation of the papilla; (e) consecutive atrophy of the nerve and retina.
Leucocythcemia. In this disease the retina is pale, the veins dilated. Small extravasations of blood are frequent, and sometimes small white, lymphoid deposits are seen scattered over the retina.
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