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As the nerve fibers pass through the lamina cribrosa sclerae they lose their medullary sheaths and are continued onward through the choroid and retina as simple axis-cylinders. When they reach the internal surface of the retina they radiate from their point of entrance over this surface grouped in bundles, and in many places arranged in plexuses .
[1] [2] This reduced axonal transport can then cause swelling or bulging on the surface layer of the retina, increasing the potential for nerve fiber damage. [2] The presence of cotton wool spots may resolve independently over time, typically in 4–12 weeks, or may depend on the underlying disease causing the condition.
The optic nerve contains axons of nerve cells that emerge from the retina, leave the eye at the optic disc, and go to the visual cortex where input from the eye is processed into vision. There are 1.2 million optic nerve fibers that derive from the retinal ganglion cells of the inner retina. [2] Damage to the optic nerve can have different causes:
DOA is characterized as affecting neurons called retinal ganglion cells (RGCs). This condition is due to mitochondrial dysfunction mediating the death of optic nerve fibers. The RGCs axons form the optic nerve. Therefore, the disease can be considered of the central nervous system. [2]
For example, fundus photography can monitor nerve fiber layer swelling. Optical coherence tomography can be used for more detailed study of retinal nerve fiber layer thickness. Red green color vision testing may detect losses. Contrast sensitivity may be diminished. There could be an abnormal electroretinogram or visual evoked potentials.
In a recent study of 26 patients with confirmed FA, all patients had evidence of optic nerve dysfunction, although only five were visually symptomatic. [26] The optic neuropathy differed from that of LHON or DOA, displaying a pattern of retinal nerve fiber layer (RNFL) loss and no preferential involvement of papillomacular bundle. [21]
The term "disc-at-risk" refers to an optic nerve head characterized by a small cup-to-disc ratio and a crowding of optic nerve fibers. This anatomical feature is a significant factor in the development of NAION. [4] [5] Individuals predisposed to this condition typically have smaller optic discs with minimal or no cupping. This anatomical ...
Lesions involving the whole optic nerve cause complete blindness on the affected side, that means damage at the right optic nerve causes complete loss of vision in the right eye. [3] Optic neuritis involving external fibers of the optic nerve causes tunnel vision. [4] Optic neuritis involving internal fibers of the optic nerve causes central ...