Ophthalmology · MU Sofia

9. Applied anatomy of the lens and vitreous body

Covers the lens: its refractive role, its accommodation by ciliary muscle control, its roughly 18-dioptre power, and its three parts (capsule, epithelium, fibres) with the note that it lacks nerves and blood vessels. Then describes the three intraocular spaces and fluids, including aqueous humour production, nutrition and circulation through to Schlemm's canal, and how obstruction at the iris-cornea angle raises pressure as in glaucoma. Ends with the stagnant, gel-like vitreous humour and why material trapped in it stays there.

Inside: 1 section · 3 labelled pictures · 14 flashcards · 4 min

Topic 9 of 91 in the MU Sofia syllabus for Ophthalmology (Medicine, Year 4). The free AceMed note covers it in 1 section, about 569 words (4 min of reading), with 14 flashcards.

In this note

  1. Anatomy of the lens and vitreous. Intraocular spaces and fluids.

Anatomy of the lens and vitreous. Intraocular spaces and fluids.

Lens:

  • is a transparent, biconvex structure in the eye that, along with the cornea, helps to refract light to be focused on the retina.
  • by changing shape, it functions to change the focal distance of the eye so that it can focus on objects at various distances, thus allowing a sharp real image of the object of interest to be formed on the retina.
  • lens curvature is controlled by ciliary muscles.
  • the refractive power of the lens in its natural environment is approximately 18 dioptres, roughly one-third of the eye's total power.
  • The lens has three main parts: the lens capsule, the lens epithelium, and the lens fibers.
  • The lens capsule forms the outermost layer of the lens
  • the lens fibers form the bulk of the interior of the lens.
  • The cells of the lens epithelium, located between the lens capsule and the outermost layer of lens fibers, are found only on the anterior side of the lens.
  • The lens itself lacks nerves, blood vessels, or connective tissue
  • Anterior to the lens is located the posterior chamber
  • Posterior to the lens is located the vitreous humour

Intraocular spaces and fluid:

There are 3 intraocular spaces

  1. a) anterior chamber
  2. b) posterior chamber

Are filled with aqueous humour

  1. c) vitreous chamber -> is filled with vitreous humour

a) anterior chamber:

  • is the fluid-filled space inside the eye between the iris and the cornea's innermost surface

b) posterior chamber:

  • is the narrow space behind the peripheral part of the iris and in front of the lens

Anterior and posterior chamber are both filled with aqueous humour:

  • transparent, watery fluid
  • Maintains the intraocular pressure and inflates the globe of the eye -> It is this hydrostatic pressure which keeps the eyeball in a roughly spherical shape and keeps the walls of the eyeball taut.
  • Provides nutrition (e.g. amino acids and glucose) for the avascular ocular tissues; posterior cornea, trabecular meshwork, lens, and anterior vitreous
  • aqueous humour is constantly drained and produced
  • Circulation of aqueous humour:
  • Aqueous humour is secreted into the posterior chamber by the ciliary body
  • then, aqueous humour flow is first through the posterior chamber, then the narrow space between the posterior iris and the anterior lens (contributes to small resistance),
  • then flows through the pupil and enters into the anterior chamber.

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