Uvea

• Uvea is th middle vascular pigmented layer. It has an opening of the pupil and the optic nerve canal, and has continuous layers into the iris, ciliary body and the choroid
• the iris controls the amount of light entering the eye, and increases the depth of focus during accommodation. it also has a low permeability of iris blood vessels which contributes to the blood aqueous barrier.
• ciliary margin is attached to the ciliary body and is the thinnest part which is prone to tearing.
• collarette contains minor arterial circle and separates the ciliary zone and pupillary zone
• iris has

  • ciliary margin
  • collarette
  • crypts of Fuchs
  • pupillary margin
• colour of the iris is governed by melanin which is also known as pigment.

  • little melanin = blue
  • large amount = brown
• iris heterochromia is when the two iris‘ are different colour, can be partial or complete
• iridodialysis is the separation of the iris from the ciliary body.

  it causes

  • blunt trauma
  • penetrating injury
  • surgical complication
• pupil diameter is controlled by the ciliary muscles and the iris (2-8mm)
• miosis is when the pupils are smaller than normal and the iris is constricted. due to ageing. slower light reactions
• iris border layer is condensed connective tissue and includes

  • melanocytes
  • blood vessles
  • nerves
• iris stroma is loose connective tissue so its flexible when pupil size moves.

  it includes

  • melanocytes
  • pigmented cells
  • blood cells
  • nerves
  • sphincter pupillae
• iris epithelium has two layers

  • anterior: smooth muscles, pupil dilation, sympathetic nerves
  • posterioir: melanin so pigmented
• ciliary body functions:

  • accommodation
  • aqueous production
  • formation of the lens zonules and vitreous component
  • tight junctions in ciliary epithelium contribute to blood aqueous barrier
• ciliary body structure:

  • ring of tissue comes from the sclera spur and goes to the ora serrata
  • the base faces the anterior chamber and connects to the iris
  • the apex blends into the choroid and retina
• pars plicata contains ciliary processes

  • high vascular
  • aqueous production
  • lens zonules attachment site
• pars plana (orbicularis ciliaris)

  • flat surface
  • may come from some vitreous components
  • scalloped boarder - ora serrata is the junction between the ciliary body and retina
• ciliary body epithelium has two layers: inner (non pigmented) and outer (pigmented)

  contains tight and gap junctions
• ciliary body stroma is loose connective tissue and contains

  • melanocytes
  • blood vessels (closed fenestrations and aqueous production)
  • nerves
  • contains major arterial circle
  • ciliary muscle
• choroid

  • nourishes the outer retina removes waste from retinal disc replacement
  • removes waste from retinal disc replacement
  • passage for nerves and blood vessels
  • absorbs stray light
• chorioid structure:

  • posterior portion of the uvea
  • choroid is between the sclera and the retina
  • pigmented
  • vascular
  • thicker at the back
• choroid layers:

  • brunch’s membrane - attached to the retina and passes material to and from the retina
  • vascular layer - choriocapilaries (has capillaries and closed fenestrations), sattlers layer (small blood vessels), hallers layer (large blood vessels)
  • suprachoroid - attached to the sclera, contains melanocytes
• mydriasis is when the pupil gets larger via the trigeminal nerve carried out by the sympathetic supply
• miosis is when the pupil gets smaller and the ciliary body muscles accommodate in the inferior division of the oculomotor nerve carried out by the parasympathetic system
• • sympathomimetic stimulates receptors on the iris dilator pupillae
  • sympatholyic blocks action of sympathetic nerves
  • parasympathomimetic stimulates receptors on sphincter pupillae and ciliary muscle
  • anti-muscarinic blocks action of parasympathetic nerves
• pigment dispersion syndrome:

  • posterior layer pf iris epithelium is pigmented
  • pigment can block trabecular meshwork
  • iris pigment carried in thermal currents
• aqueous flare:

  • scattering of beam of light by particles in suspension is known as the Tyndall effect
  • the iris blood aqueous barrier is disrupted and leaks blood plasma proteins
  • can form keratin precipitates on the corneal endothelial
• choroiditis can cause infections, autoimmune diseases and parasites

  pale areas are active

  scars are often pigmented or have pigmented borders when inactive
• naevi is often benign in iris and choroid.
• drusen is yellow ish spots and commonly seen in ageing eye. it is deposits of bucos membrane

  2 types:

  • small (hard)
  • large (soft)