The fundus oculi with an ophthalmoscopic atlas, illustrating its physiological & pathological conditions / By W. Adams Frost.

  • Frost, W. Adams (William Adams), 1853-1935.
Date:
1896
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Licence: Public Domain Mark

Credit: The fundus oculi with an ophthalmoscopic atlas, illustrating its physiological & pathological conditions / By W. Adams Frost. Source: Wellcome Collection.

Provider: This material has been provided by The University of Leeds Library. The original may be consulted at The University of Leeds Library.

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    work which is continuous with the pia mater ; a rather thick process also accompanies the central vessels, forming their connective tissue sheath. The pial sheath ceases at the lamina cribrosa. The space between the dural and pial sheaths, called the intervaginal, or inter-sheath space, is easily visible to the naked eye in the section of the optic nerve seen after enucleation. Posteriorly this space is continuous with the sub-arachnoid space within the cranium; anteriorly it passes up to the sclerotic, extending some- times into the posterior larger end of the scleral opening, or even into the substance of the sclerotic itself It appears to terminate in a cul-de-sac, but injection experiments have shown that there are fine channels passing from it into the substance of the nerve anterior to the lamina cribrosa. A small process of arachnoid is usually described as passing a short distance along the nerve adhering intimately to the dural sheath, but the existence of this is denied by some authorities.^ It is believed that the intervaginal space constitutes a lymph- channel, the direction of the stream being towards the globe, and that a return current exists along the connective tissue sheaths of the central vessels. The optic nerve is supplied with blood by branches from the central vessels. Around the entrance of the nerve into the sclerotic that membrane is perforated by the posterior ciliary arteries, these give off branches in the substance of the sclerotic, which, by anastomosing, form a more or less complete arterial circle—the circle of Haller. From this numerous fine twigs pass into the nerve in front of the lamina cribrosa, anastomosing with those which come from the central vessels. In this way there is formed within the head of the nerve a fine vascular network connected both with the choroidal and retinal systems, which is not without influence on the ophthalmoscopic appearance of the disc. Anterior to this plexus the retinal vessels have no communications with any other blood vessels. ^ See Gowers, Medical Ophthalmoscopy, 3rd edition, 1890.