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Optic neuropathy is damage to the optic nerve from any cause. The optic nerve is a bundle of millions of fibers in the retina that sends visual signals to the brain. Damage and death of these nerve cells, or neurons, leads to characteristic features of optic neuropathy.
An optical attenuator, or fiber optic attenuator, is a device used to reduce the power level of an optical signal, either in free space or in an optical fiber. The basic types of optical attenuators are fixed, step-wise variable, and continuously variable.
Chronic relapsing inflammatory optic neuropathy (CRION) is a form of recurrent optic neuritis that is steroid responsive and dependent. [1] Patients typically present with pain associated with visual loss. [1] CRION is a clinical diagnosis of exclusion, and other demyelinating, autoimmune, and systemic causes should be ruled out. [3]
There are several causes of toxic optic neuropathy. [1] Among these are: ingestion of methanol (wood alcohol), ethylene glycol (automotive antifreeze), disulfiram (used to treat chronic alcoholism), halogenated hydroquinolones (amebicidal medications), ethambutol and isoniazid (tuberculosis treatment), and antibiotics such as linezolid and chloramphenicol as well as chloroquine and the related ...
Autoimmune optic neuropathy (AON), sometimes called autoimmune optic neuritis, may be a forme fruste of systemic lupus erythematosus (SLE) associated optic neuropathy. AON is more than the presence of any optic neuritis in a patient with an autoimmune process, as it describes a relatively specific clinical syndrome.
Neuromyelitis optica (NMO) is a particular disease within the NMOSD spectrum. It is characterised by optic neuritis and longitudinally extensive myelitis. In more than 80% of NMO cases, the cause is immunoglobulin G autoantibodies to aquaporin 4 , the most abundant water channel protein in the central nervous system. [5] [1] [4]
The optic disc is where the axons from the retinal ganglion cells collect into the optic nerve. The optic nerve is the bundle of axons that carry the visual signals from the eye to the brain. This optic nerve must penetrate through the wall of the eye, and the hole to accommodate this is usually 20-30% larger than the nerve diameter.
Attenuation is an important factor limiting the transmission of a digital signal across large distances. Thus, much research has gone into both limiting the attenuation and maximizing the amplification of the optical signal. Empirical research has shown that attenuation in optical fiber is caused primarily by both scattering and absorption.