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Optic nerve Clinical significance
This document provides an overview of the anatomy and clinical assessment of the optic nerve in 3 paragraphs: 1) It describes the anatomy of the optic nerve, including its origin from the ganglion cells and path from the optic disc to the optic chiasm. It is composed of over 1 million axons and is divided into intraocular, intraorbital, intracanalicular, and intracranial portions. 2) Clinical assessment of the optic nerve involves testing visual acuity, color vision, visual fields, and the pupillary light reflex. Signs of optic nerve pathology include an afferent pupillary defect. 3) Different pathologies like papilledema, optic neuritis, and optic
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Optic nerve Clinical significance
- 1. E-mail: Shaf3y_h@hotmail.com facebook/shafie eyeclinic Symptoms & Signs in Clinical Medicine By/Mohamed Ahmed El –Shafie Assistant Lecturer in ophthalmology department KafrELShiekh University
- 2. Anatomy of opticnerve • Optic nerve- more than 1 million axons. • Consisting of axons originating from ganglion cells. • Starts from optic disc upto optic chiasma. • Contains the afferent fibers of light reflex. • Elongated tract of white matter • Not covered by neurilemma. 2
- 3. • Optic nervedivided in topographic areas: Intraocular portion. Intraorbital portion. Intracanalicular portion. Intracranial portion. 3
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- 5. Intraocular optic nerve •1 mm in length. • 1.5 mm diameter. • Which expands approximately 3-4 mm behind the sclera. 5
- 6. Intraorbital optic nerve Relationof ophthalmic artery At the optic foramen: inferior and lateral Lateral to optic nerve (in posterior orbit) Inferior division of 3rd nerve-Sixth Nerve Ciliary ganglion Nasociliary artery 6
- 7. At the orbitalapex – optic nerve surrounded by annulus of Zinn. Blood supply: Ophthalmic artery with meningeal branches 7
- 8. Intracanalicular optic nerve •9 mm • Tightly fixed within the canal (compressive optic neuropathy Optic nerve edema) • Blunt trauma Blood supply: Pial branches from ophthalmic artery. 8
- 9. Intracranial optic nerve •Length-10mm • Diameter-4.5mm Extends post & medially ascending at an angle of 45º to join the chiasma Blood supply: pial vessels arising from ICA branches from ant cerebral and anterior communicating artery 9
- 11. Normal optic disc -Color: Orange or pink - Margin - Counter - Crescent - Distribution of veins.
- 12. Why the normaldisc is pink? • Thickness and the cytoarchitecture of fiber bundles passing between glial columns containing capillaries 12
- 13. • Pathologies ofthe optic nerve, even though not always detected on ophthalmoscopic exam, may compromise its function and cause the following sign;
- 14. Visual Acuity Nearvision - Reading from a book Far vision - Snellen chart. - Ishihara charts
- 15. Dyschromatopsia • Impaired colorvision = 94% • Desaturation • – eg: red = dark/ beached • Distinguishes b/w macular lesion
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- 17. Kinetic perimetry StaticperimetryKinetic perimetry Static perimetry
- 18. • all patientsshow V.F abnormalities in acute phase Central ⁺⁺⁺, peripheral⁺, particular region⁺ • If Vn severely impaired – confrontation test • Vision improved – • kinetic Goldman Perimetry ( only central scotoma) • Automated static Perimetry • Focal defect – • Altitudinal • Arcaute • Nasal step defect
- 19. • Stimulus • Receptors •Afferent • Center • Efferent • Effector organ • Effect Pup. light reflex
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- 21. Afferent pupillary defect •In the absence of an optic nerve lesion in the fellow eye, RAPD can be demonstrated by swinging flash light • -ve RAPD in recurrent attacks Causes:Causes: • Optic neuropathyOptic neuropathy • Total retinal detachmentTotal retinal detachment • Dense vitreous haemorrhageDense vitreous haemorrhage • Dense amblyopiaDense amblyopia
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- 23. Contrast sensitivity • -good for subclinical ON
- 24. Optic Disc SwellingOpticDisc Swelling How do you approach?How do you approach?
- 25. PapilloedemaPapilloedema vsvs OpticNeuritisOptic Neuritis
- 26. Papilloeodema Definition , Non-inflammatoryswelling of Optic disc Causes 1. Raised Intracranial Pressure: - Space-occupying lesions -Occlusion of :retinal veins cavernous sinus -Other cause.
- 27. Optic Neuritis (ON)• Inflammationof optic nerve - ON • Associated with swollen disc – papillitis • Normal disc – retro bulbar ON
- 28. Papilledema Optic neuritisAION increased ICP Inflammatory swelling Vascular accident (occlusion of short posterior ciliary artery causing infarction Brain tumors , hematomas, meningitis Multiple Sclerosis is highly associated Hypertension, giant cell arteritis, hypercoagulable state Bilateral , may be asymmetric Unilateral Unilateral 28 Headache, nausea, vomittingHeadache, nausea, vomitting No visual loss usually,No visual loss usually, only enlarged blind spotonly enlarged blind spot Retrobulbar pain on ocularRetrobulbar pain on ocular movement, early centralmovement, early central scotoma, decreased acuity,scotoma, decreased acuity, impaired color vision,impaired color vision, presence of APDpresence of APD Acute painless visual loss, usuallyAcute painless visual loss, usually hemialtitudinal defect involvinghemialtitudinal defect involving the lower visual fieldthe lower visual field Variable degree of disc swelling, hemorrhages Fewer hemorrhages and cotton wool spots Pale segmental swelling and splinter hemorrhages at its margins Prognosis usually good if primary cause of increased ICP is treated Vision usually returns to normal Poorer prognosis, permanent loss. Second eye is involved in one third of cases.
- 29. OPTIC ATROPHY Degeneration ofthe optic nerve occurs as an end result of any pathologic process that damages axons Ophthalmoscopic classification Primary optic atrophy Secondary optic atrophy Consecutive optic atrophy Glaucomatous optic atrophy
- 30. Primary optic atrophy Consecutive optic atrophy Secondaryoptic atrophy Glaucomatous optic atrophy chalky white or white Disc appears yellow waxy dirty white in colour Pale disc Margins are sharply outlined edges are not so sharply defined Edges are blurred,. Edges well defined Lamina cribrosa is clearly seen at the bottom of the physiological cup physiological cup is obliterated deep and wide cupping of the optic disc and nasal shift of the blood vessels Major retinal vessels and surrounding retina are normal Retinal vessels are attenuated vessels are attenuated and perivascular sheathing Normal
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