On throat deafness and the pathological connexions of the throat, nose, and ear / by James Yearsley.

  • James Yearsley
Date:
1853
Catalogue details

Licence: Public Domain Mark

Credit: On throat deafness and the pathological connexions of the throat, nose, and ear / by James Yearsley. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    Czermatt s Phosphene. s7 to a near object, it springs rapidly back to its original seat when the eye is directed to a distant object. The cause of this is obvious, for in near accommoda- tion the force of the ciliary muscle is exerted in over- coming the resistance of elastic structures in order to rotate the lens on its axis, whereas when the change takes place to distant accommodation the elastic forces and the internal portion of the muscle acting together cause the lens to resume its normal position with great velocity. 84. If the transition from near to distant accommo- dation takes place in the dark, there occurs, as Czermak* has remarked, a sudden flash of light in the eye, which he calls a phosphine. This phenomenon is, I believe, caused by the sudden springing back of the lens to its normal unaccommodated position, communicating a shock to the retina whereby the sensation of light is evoked, just as a slight blow on the eye will pro- duce the sensation of a flash of light. At the same time the sudden relaxation of the ciliary muscle or tensor chorioideae, permitting the strained choroid membrane to resume its position, will intensify the shock that produces the flash. 85. Another proof of the correctness of my view respecting the rotation movement of the lens in ac- * ‘ Arch. f. Ophthalmologie,’ Bd. vii.