The Vitreous

• The vitreous chamber is filled with the gel-like vitreous body and occupies the largest portion of the globe. Its avascularity makes it transparent.
• It is bounded on the front by the posterior surface of the lens and the retrozonular portion of the posterior chamber.
• The vitreous outer surface called the hyaloid membrane is peripherally and posteriorly bounded by the pars plana of the ciliary body, the retina, and the optic disc. Anteriorly it is the posterior lens capsule and zonular fibers.
• All surfaces that interface with the vitreous are basement membranes.
• The vitreous cavity occupies 2/3 volume of the globe. The volume of the globe is 6ml.
• It is about 99% water in weak solution of salts and proteins, 1% with collagen and hyaluronic acid which gives it a gel-like substance. Its volume is 4ml and it weighs 4g.
• The cloquets canal is present in children but disappears as they age.

NOTE:

• When the vitreous is lost the eye shrinks. Vitreous is made once and so if lost, it cannot be reformed.
• Senile changes into the vitreous:-
  • In the aged, the vitreous tends to undergo degeneration and liquefaction. This process can lead to detachment and predispose to retinal detachment.

Functions of Vitreous

• Maintains the shape of the globe.
• The vitreous body is a storage area for metabolites (nutrients and excretes) for the retina and lens and provides an avenue for the movement of these substances within the eye.
• The vitreous, because of its viscoelastic properties, acts as a “shock absorber,” protecting the fragile retinal tissue.
• The vitreous maintains clarity of ocular media and hence transmits light, aiding in focusing the rays on the retina.