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Vitreous anatomy
Anatomy & Optics
Key Points
- •Vitreous is ~99% water + ~1% structural components (type II collagen - primary scaffold, type IX collagen - prevents fibril aggregation/maintains transparency, hyaluronic acid - binds water, maintains gel hydration and interfibrillar spacing); volume ~4 mL; refractive index 1.336
- •Key vitreous spaces: Berger's space (retrolental, between posterior lens capsule and anterior hyaloid face - bounded by Wieger's ligament), Cloquet's canal (hyaloid artery remnant connecting disc to retrolental space, ~1-2 mm diameter), area of Martegiani (funnel-shaped depression around the optic disc - posterior opening of Cloquet's canal)
- •Vitreous attachments (strongest to weakest): (1) vitreous base (strongest, 2mm anterior + 2mm posterior to ora serrata, cannot be cleanly separated - horseshoe tears form here), (2) optic disc margin (Weiss ring forms when this releases), (3) fovea/macula (VMT and macular hole when adhesion persists), (4) retinal blood vessels (VH when these avulse during PVD)
- •Vitreous ageing: synchysis (HA degradation → liquefaction) + syneresis (collagen aggregation → gel collapse) → PVD (posterior cortex separates from ILM); ~8-15% of acute PVDs cause retinal tears; vitreous haemorrhage at PVD presentation → ~70% have a retinal tear → urgent scleral depression examination mandatory
- •Embryology: primary vitreous (vascular, hyaloid artery - failure to regress = PFV/PHPV, unilateral), secondary vitreous (avascular gel, definitive - type II collagen + HA), tertiary vitreous (zonules); hyaloid remnants: Mittendorf's dot (anterior, on lens) and Bergmeister's papilla (posterior, on disc)
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13 more sections are included with the Clinical plan.
- Definition
- Epidemiology
- Aetiology and causes
- Pathogenesis
- Classification
- Clinical features