Optic Nerve Head OPTM4102 PDF

OPTM4102 Optic nerve head Dr. Jason Charng [email protected] Acknowledgement of country The University of Western Australia acknowledges that its campus is situated on Noongar land, and that Noongar people remain the spiritual and cultural...

OPTM4102 Optic nerve head Dr. Jason Charng [email protected] Acknowledgement of country The University of Western Australia acknowledges that its campus is situated on Noongar land, and that Noongar people remain the spiritual and cultural custodians of their land, and continue to practise their values, languages, beliefs and knowledge. Artist: Dr Richard Barry Walley OAM Objectives Anatomy and function of the optic nerve head (ONH) -  Retina - review RNFL feeds into optic nerve Internal limiting membrane Nerve fibre layer Ganglion cell layer Inner plexiform layer Inner nuclear layer Outer plexiform layer Outer nuclear layer External limiting membrane Photoreceptor layer (inner and outer segments) Retinal pigment epithelium G outerlayer Choroid transform light energy into : Standring S, et al. Gray’s Anatomy, 40th Edition. 2008. Elsevier Young B, et al. Wheater’s Functional Histology, 6th Edition. 2014. Elsevier electric energy.  Optic nerve ALL ganglion cell axons converge at - optic nerve Optic disc Four sections anterior to optic chiasm: Q ~ Intraocular (optic nerve head, ONH): within the eye (0.7 – 1.0 mm) O O ~ Intraorbital: edge of globe to end optic canal. of orbit (25 – 30 mm) ③ ~ Intracanalicular: within optic canal - - (4 – 10 mm) ④ ~ Intracranial: (~16 mm) Optic chiasm Yanoff M and Duker JS. Ophthalmology. 2014. Elsevier.  Optic nerve head/optic disc Right Eye - C O optic nerve - - - RNFL Ganglion accons are found in Refraction of RNFL travel to Retinal Herve the optic nerve neuroretinal ring. Fibril layer. * No ganglion ascon cells within www.entokey.com the http://www.drwengsehu.com/media optic sup.  Optic nerve head/optic disc & There is no ganglion itic rup yo. cells are found. C much Optic cup is > - - bigger , less neuroretinal ring... less ganglion cells. www.entokey.com http://www.drwengsehu.com/media O  Optic disc: dimensions Shape: vertical oval of optic thickness disc - Normal neural retinal rim thickest at inferior portion (ISNT rule), I>S>N>T Normal vertical cup to disc ratio 0.3 Area: 2.69 ± 0.70 mm2 ~ Range 0.86 mm2 – 5.54 mm2 Diameter: ~ Horizontal: 1.76 ± 0.31 mm Range 0.91 mm – 2.61 mm ~ Vertical: 1.92 ± 0.29 mm Range 0.96 mm – 2.91 mm https://www.glaucoma.org/glaucoma/optic-nerve-cupping.php https://pubmed.ncbi.nlm.nih.gov/29541648/ http://www.ncbi.nlm.nih.gov/pubmed/3417404  Optic disc Edge slightly raised due to convergence of nerve fibres RE Optic disc excavated by a funnel shaped depression, the optic cup Slightly off-centre temporally - Disc looks pink because of a rich capillary supply to its rim White portion is base of cup Lamina cribrosa not always visible Levin LA, et al. Adler’s Physiology of the Eye, 11th Edition. 2011. Saunders. http://www.ocularbiomechanics.com/predict/index.html https://www.sciencedirect.com/science/article/pii/S0025556414001448  ONH: divisions Optic nerve head extends from inner retina to a plane level with Hayers posterior sclera Q Superficial nerve fibre layer (A) ~ Predominantly nerve fibres O Prelaminar region (B) ~ Nerve fibres and astrocytes ③ Lamina cribrosa (C) ~ Fenestrated connective tissue, nerve fibres, and astrocytes ④ Retrolaminar region (D) ( ~ Nerve fibres, becoming increasingly myelinated from oligodendrocytes, and decreased astrocytes become melonated ganglion cell accons. Allingham RR, et al. Shields’ Textbook of Glaucoma, 5th Edition. 2005. Lippincott Williams and Wilkins  ONH: superficial RNFL Fibres organised into bundles RE ~ Converge towards the disc No overlap between upper and lower halves of the retinal fibresdivide superior & inferior retina to ensure that there is no ~ Horizontal raphe of nerve fibres overlaping. ~ Arcuate pattern ↳ ~ Papillomacular bundle ! For the Nerve fibres at edge of the nerve serve retina furthest from the nerve If fibers horizontal nerve fibres nasal to the nerve raphe need , to they travel to must optic do that leves without in an arc crossthe pattern. forea a bundle ,they traveltotheopti. https://eyerounds.org/tutorials/VF-testing/ Allingham RR, et al. Shields’ Textbook of Glaucoma, 5th Edition. 2005. Lippincott Williams and Wilkins ONH: superficial RNFL Approximately 1.2 million Segregation of RE nerve fibre bundles at optic nerve retinal ganglion cells per nerve Larger optic discs have Fovea more nerve fibres S- superior I- inferior M N- nasal T- temporal M- macula Allingham RR, et al. Shields’ Textbook of Glaucoma, 5th Edition. 2005. Lippincott Williams and Wilkins  ONH: superficial RNFL membrane of = Separate Vitreous Elschnig from layer nerve fiber Inner surface of ONH separated from vitreous by membrane of Elschnig (a) ~Astroglial membrane lunderneath membrane of Elschnig). continuous with ILM (b) of - retina ~Thickens centrally to become Elongated astrocytes in Elschnig’s membrane the central meniscus of Kuhnt (c) Elongated astrocytes in enter ONH from the retina superficial nerve fibre layer Astrocytes also enter ONH - becoming stellate towards the prelaminar region with retinal ganglion cells - http://www.ncbi.nlm.nih.gov/pubmed/8776468 Allingham RR, et al. Shields’ Textbook of Glaucoma, 5th Edition. 2005. Lippincott Williams and Wilkins  Cell bodies are located - - - in nerve fibre layer Astrocytes Thin Thick of Retina Bodied Bodied support cells Glial cells (supporting cells) - - - ~ Fibrous with a large cell body and Limiting membrane many long, coarse processes ~ Co Type 1 astrocytes line the periphery of the optic nerve ~OType 2 astrocytes primarily located Anterior prelaminar in the interior of the optic nerve Functions: Posterior prelaminar and laminar region Superficial nerve fibre layer ~ Physical support for neurons (structural support) · Do not bind individual axons together Hence ON can swell easily but surrounding retina does not ~ Repair ~ Blood-retina barrier At termination of retina/choroid - - at ONH > - Parallel to axons in prelaminar Retrolaminar region and laminar regions ~ Protection (potassium buffering) I maintain homeostasis of extra cellular substances. e. potassium) http://www.ncbi.nlm.nih.gov/pubmed/8776468 f ONH: Prelaminar Region Thick bodied Ganglion facilitated by Astrocytes astrocytes cell bundle Ganglion cell axons arranged in bundles ~ Surrounded by tube-like glial channels formed by astrocytes (2; anterior prelaminar region) ~ Capillaries located within the glial septa Astrocytes increase in number posteriorly forming a sieve-like structure, the glial lamina cribrosa (3; Capillaries posterior prelaminar Levin LA, et al. Adler’s Physiology of the Eye, 11th Edition. 2011. Saunders. region) http://www.ncbi.nlm.nih.gov/pubmed/8776468 Levin LA, et al. Adler’s Physiology of the Eye, 11th Edition. 2011. Saunders. ONH: Prelaminar Region A layer of astrocytes several cells thick, the intermediary tissue of Kuhnt (d), intermediary Tissue of Kuhnt. border tissue of separates the ON Jacoby. from the outer retinal layers Continues posteriorly as the border tissue of Jacoby (e), separating the ON from the choroid Allingham RR, et al. Shields’ Textbook of Glaucoma, 5th Edition. 2005. Lippincott Williams and Wilkins  intraocularpressuremaycrashthenervebundleit's ↑ in thinner wall ONH: Laminar Region has pressure gradient. A band of dense, specialised extracellular matrix, the lamina cribrosa (4) lunderneath the optic mup / ~ Sieve-like fenestrated sheets of connective tissue and occasional elastic fibres ~ CT extension of the sclera ~ 3-10 sheets of connective tissue, ~400 fenestrations must be porins enough O to allow the passage of ~ Bridges the scleral canal - nerve bundles allow the passage of nerve - O * zroles ② dies I Lamina cribrosa. - must stabilize the O the esque is btw~ Allow passage of RGC axons and blood pressure by batrier vessels forming a barrier space ↓ the the ~ Provide mechanical protection to ONH intraocular inside against IOP & extraocular large holes allow e pass eye The ~ Fenestrations larger in superior and Space - age of central veine - retinal behind higherinferior regions - arteries central retinal - pressureinside ~ Anchored to surrounding sclera by -. inspace ele thick columns of connective tissue The Salobrar-Garcia E et al. Glial and blood retinal barrier: effects of ocular hypertension 2014. iConcept Press Ltd  ONH: Retrolaminar Region Transition zone from the optic nerve head to the orbital optic nerve Nerve axons become myelinated myelination allows : ~ Doubles nerve diameter allows faster signal ~ Insulates axons, greatly transimition by allowingacross electrical signal to JUMp increasing speed and each myelin shed - efficiency of signal conduction ~ Secreted by oligodendrocytes (B) http://www.eyecalcs.com/DWAN/pages/v7/v7c025.html http://www.eyecalcs.com/DWAN/pages/v7/ch025/002f.html  ONH: Retrolaminar Region Optic nerve surrounded by the meningeal sheath Outer ~ Dura mater (Du) Continuous with - reflected sclera - ~ Arachnoid mater (Ar) Cerebrospinal fluid in the subarachnoid - - space - Inner ~ Pia mater (Pia) Standring S, et al. Gray’s Anatomy, 40th Edition. 2008. Elsevier ONH: Retrolaminar Region Fine fibrous septa (Sep) penetrate the nerve ~ Divide the nerve into optic nerves are subdivided into 300-400 fascicles fascicles (bundled (bundles) ~ Provide pial blood vessels access to the nerve ~ Anteriorly, pial septa merge to lamina cribrosa Standring S, et al. Gray’s Anatomy, 40th Edition. 2008. Elsevier  ON: Blood Supply Optic disc surface: * Inner retina supplied by ~ CRA & choroid central retina artem * outer retina Choroid supplied by. Prelaminar and laminar: ~ Short posterior ciliary arteries main form a circular arterial supply anastomosis at the scleral level, the circle of Zinn-Haller mino ~ Some small branches from CRA supply Retrolaminar ~ Pia Independent. Shaarawy TM, et al. Glaucoma, 2nd Edition. 2015. Elsevier http://www.retinareference.com/anatomy/arterial.jpg Blood-retina barrier Plasma proteins readily leak from choroid into ONH directly, and also through the sclera Entry of proteins from the ONH into the retina is blocked by a series of tight junctions between the lining glial cells and the adjacent RPE http://www.eyecalcs.com/DWAN/pages/v7/ch001/020f.html Summary Optic nerve is the exit point for ganglion cell axons from the globe, carrying visual information to the brain Consists of four layers: ~ Surface nerve fibre layer ~ Prelaminar region ~ Lamina cribrosa ~ Retrolaminar region Astrocytes are supporting cells of the optic nerve Nerve bundle increase thickness posteriorly from myelination Different blood supply at each subregion