The American encyclopedia and dictionary of ophthalmology Edited by Casey AWood, assisted by a large staff of collaborators . ressions are most acute; it is this point thatis directed toward the object which one wishes to see distinctly. The layer of rods and cones attains its greatest thickness in themacular region. The rod element, however, disappears at the marginof the fovea centralis, the floor of which is occupied mainly byelongated cones, and by the thickened outer nuclear layer. Themembrana limitans externa continues to separate these two layersas in the extra-foveal region. As the fov
The American encyclopedia and dictionary of ophthalmology Edited by Casey AWood, assisted by a large staff of collaborators . ressions are most acute; it is this point thatis directed toward the object which one wishes to see distinctly. The layer of rods and cones attains its greatest thickness in themacular region. The rod element, however, disappears at the marginof the fovea centralis, the floor of which is occupied mainly byelongated cones, and by the thickened outer nuclear layer. Themembrana limitans externa continues to separate these two layersas in the extra-foveal region. As the foveal region is approached, ANATOMY (GROSS) OF THE HUMAN EYE 395 the rods and cones assume an obli(iue direction. The supportingfibres of Mueller also become oblique as the fovea is approached, anddisappear at its margin. The outer plexiform layer becomes modified into an outer fibrelayer of Henle; it becomes very thin as it passes over the floor of thefovea. The inner nuclear layer and the layer of ganglion cells increasemarkedly in thickness at the margin of the fovea, but almost dis-appear in the center of this Transverse Section of Optic Nerve in Front of the Entrance of the Centralartery showing dural, subarachnoid and pial sheaths, enclosing correspondinglymph spaces. The shaded portion shows the nerve fibres supplied to the macularregion. (Merkel, Ball.) The inner plexiform layer and the nerve fibre layer apparentlycease at the margin of the fovea, although, according to Dogiel, awide-meshed plexus of fibres extends over the floor. The membrana limitans interna continues unchanged over the floorof the fovea. The optic nerve proper is divided into an orbital and an intra-cranial portion. The nerve pierces the eyeball at the posterior endof the optic axis, about 3 mm. to the inner or nasal side, and about1 mm. below the horizontal meridian. Here it forms the ner\-e-head,optic papilla, or optic entrance. It is made up of nerve bundlesseparated by connective tissue an
Size: 1612px × 1550px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, booksubjectophthalmology, bookye
