Topic 8: Vitreous Humour

Question 1

State the physical properties/composition of VH

Answer 1

(1) 99% water
(2) gel-like property: Hyaluronic acid (HA) & collagen fibres interaction
(3) fibres coated with glycosaminoglycans
(4) amino acids, proteins, ascorbic acid

(+) RI: 1.33

Question 2

State the site of attachments of VH

Answer 2

Weiger’s ligament, vitreous base, area of martegiani, posterior hyaloid

Question 3

Explain the site of attachments of VH

Answer 3

(1) : circles around the posterior of the lens, Berger’s space/retrolental between attachments and lens posterior, STRONG attachment during childhood but weakens with age
(2) : @ora serrata (2mm anterior, 2-4mm behind), STRONGEST attachment hence cannot separate from retina, hyalocytes & vitreous cells seen here (produce hyaluronic acid)
(3) : @optic disc margins, MODERATE
(4) : @macular area (posterior pole of eye), WEAKEST attachment hence can easily detach from retina

Question 4

Explain mittendorf’s dot

Answer 4

• REMNANT of hyaloid artery/cloquet’s canal that was attached to posterior lens surface
• cloquet canal contains hyaloid artery during foetal development, provided nutrients to lens
• artery & canal usually disintegrate at birth BUT MAY leave remnant aka mittendorf’s dot

Question 5

Explain vitreous cells

Answer 5

Hyalocytes found in cortical vitreous (vitreous base, optic disc & retinal vessels)

• has phagocytic properties (removes waste products from VH)
• helps in the synthesis of hyaluronic acid

Question 6

State ageing changes in VH

Answer 6

Breakdown of the HA&CF interaction, Collapse of vitreous gel structure, Liquefaction of VH, Accumulation of the free collagen fibres, posterior vitreous detachment

Question 7

Explain the ageing changes of VH

Answer 7

(1) breakdown of HA&CF interaction
(2) causing Liquefaction of VH aand separation of CF & hence the collapse of gel structure
(3) the free CF accumulates in liquid (aka floaters)
(4) due to fallen gel structure, posterior vitreous detaches at WEAK sites (mainly posterior hyaloid & macula region)

Vitreous detachment can predispose to retinal detachment since the vitreous can pull on the retina (Symptoms: sudden increase in size/number of floaters or flashes)

Question 8

Explain the mechanical functions of VH

Answer 8

(1) prevents the globe from collapsing
(2) protects the internal structures of The Eye during eye movement (protection against friction & vibration)
(3) support for the retina

Question 9

Explain the optical function of the VH

Answer 9

Aka maintaining transparency of VH for max transmission of light to focus on retina

(1) Low concentration of macro(large)molecular solutes
(2) collagen of small diameter
(3) HA acts as physicochemical barrier (phagocytosis removing unwanted substances) preventing influx/entry of macromolecules &cells into VH

Question 10

Explain nutritional function of VH

Answer 10

(1) provides nutrients to crystalline lens & retina (courtesy of highly active water movement) and removes waste products
(2) contains ascorbic acid (anti-oxidant) for free radicals that reach the retina so as to prevent oxidation damage to cells