OPTM4102 Vitreous Humour PDF

OPTM4102 Vitreous humour 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 cu...

OPTM4102 Vitreous humour 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 Vitreous anatomy Vitreous composition Vitreous functions  volume the bulk of eye. up = make Vitreous – gross structure Flattened sphere, takes up Transparent most of the volume (~80%) of the globe Patellar Gel surrounded by a thin fossa collagenous membrane Anterior indentation (aka hyaloid/patellar fossa) m surrounds lens Firm attachment to retina Majority of volume: water Viscosity 2-4 times of water (i.e. firmer than egg white)  Anatomical zones 3 zones. Central/Medullary ~ Cell-free ~ Collagen fibrils+ hyaluronic acid ~ Gel state fron the vitreous. > Separate retina Anterior hyaloid. - - Cortex - posterior hyaloid ~ Appro 100 µm thick ~ Higher collagen concentration ~ 2% of vitreous volume ~ Metabolic centre of the vitreous ~ Contains hyalocytes Basal Liliane & between retina ~ At ora serrata= junction - ~ Dense, thickened collagen fibres https://pubmed.ncbi.nlm.nih.gov/28028001/ ~ Highest hyalocyte density ~ Strongest adherent site to retina Most common site for retinal detachment  Anatomical zones Anterior hyaloid membrane ~Anterior border of vitreous ~High collagen density ~Attached to posterior lens capsule at egger's line. Posterior hyaloid membrane ~Separates vitreous from retina ~NOT a typical membrane ~Densely packed type II collagen arranged tangentially to retina https://pubmed.ncbi.nlm.nih.gov/28125844/ https://www.naturaleyecare.com/eye-conditions/vitreous-detachment/  Site of attachments Attachment points Q ~ Inner limiting membrane of the retina ③ ~ Ora serrata ③ ~ ONH ④ ~ Posterior lens capsule ⑤ ~ Ciliary epithelium Strong attachment ~ Vitreous base ~ ONH ~ Blood vessels ~ Around foveola ↑ of the gap in between vitreous & the retina. https://pubmed.ncbi.nlm.nih.gov/23989078/ Attachments weaken with age https://pubmed.ncbi.nlm.nih.gov/31864940/ Attachment Dissection of Human Vitreous Body Elements for Proteomic Analysis https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3182653/ Vitreous components involved modulating immune response Y vitreous in - 99% water, 1% structural proteins, few hyalocytes in periphery - - - 15-20% water bound to structural proteins Structural proteins: ~ 75% type II collagen ~ 15% type IX collagen ~ Rest V, VI, XI collagen, hyaluronic acid (aka hyaluronan, major GAG) https://pubmed.ncbi.nlm.nih.gov/18309340/ Vitreous biochemistry – collagen collagen fibrils provide mechanical Type II – forms fibrils strength to the vitreous. Type IX – provide structural support to fibrils Type V/XI – co-assemble fibrils with Type II Type VI – linking fibril and hyaluronan Highest concentration at vitreous base Provides mechanical strength https://pubmed.ncbi.nlm.nih.gov/18309340/ Vitreous biochemistry – hyaluronic acid H Large glycosaminoglycan maintaining Vitreous hydration Arranged in network of long chains Interconnected to collagen fibrils Highest concentration in posterior vitreous cortex Ensure proper vitreous hydration and collagen spacing, also provide vitreal viscoelastic property https://pubmed.ncbi.nlm.nih.gov/18309340/  Vitreous biochemistry – hyalocytes Mononuclear cells Low numbers Stellate cells with oval nucleus Produce: ~Hyaluronic acid ~Collagen Collagen fibril network https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1772586/ Collagen fibril topography to the travels fromthe lens light Varies within the vitreous f the central retina mainly through Central Cortex Vision Structure Vitreous base Attachment https://pubmed.ncbi.nlm.nih.gov/11006509/ Vitreous function – optical clarity Transparent due to biochemical structure ~ Type II Collagen (Also V, IX, XI) ~ Hyaluronan ~ Glycoproteins Low concentration of structural macromolecules and soluble proteins Refractive Index = 1.337 just above waters. Vitreous function – globe shape Vitreous body makes up about ~80% globe volume Damage to vitreous volume or structure can affect the overall shape of eye Supports the lens anteriorly - & retina posteriorly Ts Keep retinal adherence to choroid/sclera Absorbs external forces and reduces mechanical deformation of the globe Vitreous function – molecule repository Receives metabolite from ciliary body and retina Contains ions and organic molecules (i.e. glucose) Promotes intraocular wound healing via vitamin C > - - reservoir Vitamin C also antioxidant Vitreous function – blood-ocular barrier Barrier preventing movement of macromolecules and cells between anterior and posterior segments High viscosity slows diffusion TFF *T Aging changes Liquefaction ~ Originate in the central region Due to change in hyaluronic acid Balazs EA, Denlinger JL. Aging changes in the vitreous. In Sekular R, Kline D, Dismukes N, eds. Aging and Human Visual Function. New York: Alan R. Liss, 1982:45 conformation Floaters ~ collagen fibril network becomes free-floating bundles https://retinavitreous.com/diseases/pvdstart.php Summary Vitreous maintains optical clarity while provides structural support to the globe Collagen fibrils provide mechanical strength Hyaluronic acid maintains vitreous hydration, gel consistency and collagen fibril spacing Aging changes to the vitreous