Topic 8 Vitreous humour

Question 1

what is the composition of vit?

7 components

Answer 1

• 98-99% water
• hyaluronic acid + collagen fibres (interaction of these 2 gives vitreous the gel-like property)
• fibres are coated with glycosaminoglycans
• amino acids, proteins, ascorbic acid

Question 2

what are the 4 vit attachments, their strengths and their locations?

Answer 2

1. vitreous base (strongest, will not detach)
   at the ora serrata

** hyalocytes are seen here (they produce the hyaluronic acid)

2.Weiger’s adhesion (strong, weakens with age)
at the posterior lens surface

3. area of martegiani (moderate)
   at the optic disc margins
4. posterior hyaloid (weakest vit easily detach from ret)
   at macular area (posterior pole)

Question 3

what is berger’s space?

Answer 3

space between the posterior lens surface and the anterior vitreous

Question 4

what is mittendorf’s dot and cloquet’s canal?

Answer 4

remnant of the hyaloid artery attached to the posterior lens surface

-the cloquet’s canal contains the hyaloid artery during foetal development

Question 5

what is the function of hyaloid artery and what happens to it with age?

Answer 5

• the hyaloid artery provides nutrition to the lens during development
• the artery and the canal usually disintegrate at birth

(this is NOT a vitreous attachment!)

Question 6

what are the 4 ageing changes of the vitreous?

Answer 6

1.Breakdown of the hyaluronic acid-collagen fibre interaction, collapse of vitreous gel structure

2 Vitreous liquefaction,

3. accumulation of the free collagen fibres (shadow of fibres cause floaters to be seen)
4. Posterior vitreous detachment (separation of vitreous from its weak attachment sites, mainly the posterior hyaloid, at the macula)

Question 7

why is it important to further evaluate vitreous detachment?

Answer 7

Vitreous detachment can predispose to retinal detachment (separated vitreous can pull on the retina, and lead to retinal detachment where px will complain about flashes)

Question 8

what are the 3 mechanical functions of the vit?

Answer 8

1. Prevents the globe from collapsing
2. Protect the internal structures of the eye during eye movement and physical activity i.e. protection against friction & vibration.
3. Support for the retina

Question 9

what are the 3 optical functions of the vit? how does it maintain transparency for light transmission?

Answer 9

1. Low concentration of macromolecular (large size) solutes
2. Collagen of small diameter
3. Hyaluronic acid acts as a physicochemical barrier to prevent influx (entry) of cells and macromolecules into vitreous.

Question 10

what are the 2 nutritional functions of the vit? Hint includes an acid as well

Answer 10

1. provides nutrition to crystalline lens and retina & removes the waste products
2. contains ascorbic acid which is an anti-oxidant (helps remove free radicals which can cause oxidative damage to the cells)

Question 11

what are hyalocytes? where are they present and what is their function?

Answer 11

• Hyaloctes are vitreous cells
• They are present in the vitreous cortex (periphery)
• Maximum hyalocytes are seen at the vitreous base

Functions: have phagocytic properties, synthesis of hyaluronic acid