Ophthalmic semiology and diagnosis / by Charles H. Beard.

  • Beard, Charles H., 1855-1916.
Date:
1913]
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Licence: In copyright

Credit: Ophthalmic semiology and diagnosis / by Charles H. Beard. 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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    dicularly to the eye of the observer; and the blood-column is encroached upon in accordance with the density—not the width—of the intervening white substance. The obscura- tion of the blood-stripe is partial or complete owing to the permeability or impermeability of its covering to rays of light. The degree of permeability of its lumen depends upon the seat of the material that imparts the opacity. If it is something which transplants the internal and middle .tunics there will be great narrowing of the lumen, often even to obliteration. If it is a proliferation of connective tissue which concerns only the external tunic and the space immediately surrounding it, while it may be more or less contracted, the calibre is usually patent, and likely to remain so. Unfortunately, one cannot with the ophthalmoscope always make fine distinctions in the phases under discussion. The primary seat of the disease is commonly the intima, and its progress is from within outward, so that one has relatively few opportunities of observing vessels in which the thickening or opacity is superficial and unaccompanied by any deeper affection. The blood-column is most often visible in some part of the vessel, or in one or more of its branches, though not infrequently stem and ramifications are mere white streaks. If the trunks on and near the disc are all whitened, as is often the case in senile arterio-sclerosis, and the medium and smaller branches are free from the streaks, or the latter, if present there, are barely perceptible, and their blood-columns are about normal for the age of the subject, we may conclude that the degeneration of the middle and inner tunics, if present, is not grave. It is supposed that this heavy coating of protective tissue may be provided to re-enforce the walls of the vessel and fortify it against the enormous blood-pressure which often exists, particularly when there is hypertrophy of the heart. It must not be forgotten that, owing to the extreme variability of the lesions in these circulatory diseases, what is true of one vessel of the fundus can by no means be ascribed to the