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Chapter-34 Optic Nerve Disorders

BOOK TITLE: Clinical Ophthalmology: Medical and Surgical Approach

Author
1. Verma Lalit
2. Tandon Radhika
ISBN
9789350250044
DOI
10.5005/jp/books/11246_34
Edition
2/e
Publishing Year
2011
Pages
14
Author Affiliations
1. Centre for Sight; Dr RP Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India, Center for Sight, Dwarka, New Delhi, India, Centre for Sight, New Delhi, India, Center for Sight and Apollo Hospital, New Delhi, India, Apollo Hospital, New Delhi, India, Center for Sight, Group of Hospitals, B-524, Safdarjung Enclave (Opp. Deer Park), New Delhi, India, Center for Sight, New Delhi, India, Centre for Sight, B-5/24, Safdarjung Enclave (Opp. Deer Park), New Delhi-110029, India, Vitreo-retina Services, Dr Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India, AIIMS, India, AIIMS, Delhi, India, Dr RP Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India, Dr Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India, Dr Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, Apollo Hospitals and Center for Sig
2. All India Institute of Medical Sciences (AIIMS), New Delhi, India, Dr Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India, Dr Rajendra Prasad Center for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India, All India Institute of Medical Sciences, Ansari Nagar, New Delhi, India, Dr Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India, Dr Rajendra Prasad Centre, for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India, All India Institute of Medical Sciences, New Delhi, India, AIIMS, New Delhi, India, All India Institute of Medical Sciences New Delhi, India
Chapter keywords

Abstract

Optic nerve transmits visual information from the retina to the lateral geniculate body. Afferent fibers for the pupillary light reflex also leave the eye via the optic nerve. The optic nerve consists of axons arising from the retinal ganglion cells, which are second order neurons of the afferent visual pathway. Therefore, the optic nerve is actually a portion of the central nervous system and is a tract, not a peripheral sensory nerve. Only the anterior portion of this tract is termed the optic nerve, the optic chiasma is the X-shaped partial decussation and the optic tract is the posterior or retrochiasmatic continuation of the same fiber tract to its termination at the lateral geniculate body. The optic nerve is about 5 cm long and is broadly described as consisting of four portions. The intraocular portion or optic disc or optic nerve head is 1 mm long, the intraorbital part is 25 mm long, the intracanalicular portion is about 9 mm long and the intracranial part is approximately 16 mm long. Optic nerve receives its blood supply mainly from 3 major sources: (a) Choroidal vessels, (b) Short posterior ciliary arteries, and (c) Pial arterial network. Optic nerve carries approximately 1.2 million axons from the eye. These axons originate from the retinal ganglion cells. Ninety percent of the retinal ganglion cells are concentrated in the macula and overall 80% of the optic nerve fibers originate from the macular region.

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