Eye symptoms in tabes dorsalis / by J. H. Tomlinson.

  • Tomlinson, J. H.
Date:
[1902?]
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Licence: In copyright

Credit: Eye symptoms in tabes dorsalis / by J. H. Tomlinson. Source: Wellcome Collection.

Provider: This material has been provided by UCL Library Services. The original may be consulted at UCL (University College London)

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    the influence of light ? An impulse is sent along certain fibres of the optic nerve, and this is reflected down certain fibres of the third nerve, which terminate in the short ciliary nerves, and the sphincter muscle of the iris is put into a state of contraction. Dilatation is accomplished by the relaxation of this reflex action ■when the source of the stimulus, light, is withdrawn. The action of the third may, however, be inhibited by stimulating the sympathetic in the neck. By cutting the sympathetic, a certain amount of contraction results, showing there is a tonic balance ordinarily in action. Now, what is the condition in the contracted immobile pupil? Some stimulus (equivalent to the stimulus of light) is causing the third nerve to put the sphincter iridis into a state of tonic contraction. Remember the extreme delicacy of the light reflex. May we not suppose that commencing degeneration of the termination of the upper limbs of the spinal ganglion neuraxons is setting up through some intermediate fibres a shght irritation in the region of the middle cells of the nucleus of the third, starting them working in the only way they can work, namely, to contract the sphincter iridis ? This irritation is going on in the dark, so that when the light is removed there is no dila- tation of the pupil as in the normal eye. Later on in the disease we no longer get irritation here, but atrophy. Consequently there is paralysis of the sphincter iridis—mydriasis, not myosis. An interference with the sympathetic, associated with antesthesia of the light-reflex fibres of the optic nerve, probably plays some part in the phenomenon, but this would not explain the pinhole pupils, though it might those cases of moderate contraction, with immo- bility, which are very common. No doubt the process is often complex, but even an incomplete conception of a morbid process may be of use in helping us to form a mental image of what is taking place. The books have much to say about the loss of the light reflex, but I wish to lay stress upon the loss of the darkness dilatation. I have not seen it brought out, but a fixed contracted pupil carries with it a very important subjective symptom, namely, an increased difficulty in seeing in a bad light. Every photo- grapher knows what an enormous diminution in the brightness of the image on the focussing-screen the introduction of a stop pro- duces. So in tabes, the small pupil shuts off a large amount of the light falling into the eye, and sometimes the deficient vision at night-time sends the patient for advice. Take this case: J. B., forty-five, a coachman, applied at the Eoyal Westminster Oph- thalmic Hospital in September, 1898, complaining of failing sight at night. His vision was -} in each eye. Mr. Work Dodd, who.