Volume 1

The American encyclopedia and dictionary of ophthalmology / edited by Casey A. Wood, assisted by a large staff of collaborators.

Date:: 1913-1921

Credit: The American encyclopedia and dictionary of ophthalmology / edited by Casey A. Wood, assisted by a large staff of collaborators. Source: Wellcome Collection.

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$720 AXIS, VISUAL ably placed at 95° and 85° respectively; and in these latter posi- tions, the shadow of each eye, both being uncovered, may seem a perfect spherical shadow, while with the cylinders at 90° and 75°, it is not so. Not only is the foregoing contention cons])icuonsly true of an un- certain number of cases—uncertain, because no observer has as yet carried to completion the examination of a sufficiently large number of instances to give us the true percentage—but it cannot be too much insisted upon that in looking from the distance to the near point a rotation of the globe may occur in one or both eyes, that will invariably cause asthenopic symptoms if the i^atient attempts to read with his high-grade cylinders, and not uncommonly some discomfort in lower degrees of astigmatism. In doing perfect re- fraction the eyes should be carefully tested sej^arately and together not only at six meters but also at the near working distance, what- ever the age or refraction of the patient. Failure to give the patient refractive eomfoi’t not infrequently hinges upon care in these par- ticulars. See Refraction and accommodation. Axis, Visual. The line drawn from the point of fixation (object) through the nodal point to the fovea centralis. Axite. The end filaments of the axis-cylinder. Axometer. An instrument used in adjusting the height of the bridge of a pair of spectacles, to bring the centers of the lenses in line hori- zontally with the centers of the pupils of the eyes. Axonometer. An annular disk used in the ordinary trial frame to locate the position of One of the chief meridians of astigmatism. Axoneuron. The intracranial nerve-cell of the neuron. Axoneurons are divided into endaxoneurons and rhizoneurons. Axons of the retina. Long processes of the ganglion cells which pass into the nerve-fibre layer of the retina to the papilla and optic nerve. Axoplasm of Schiefferdecker. This is a term applied to the inter- fibrillar matrix found, in small amounts, however, so far as the retina is concerned, along the axis-cylinder. See Histology of the eye. Axungia ardeae. (L.) Heron’s fat; an ancient remedy once used for removing specks from the eyes. Axungia halsamica. See Benzoated lard.$