The uvea (vascular layer)

• What are the structures included in the uvea?

  Choroid, ciliary body, iris

  
• What can a student explain after the lecture on the uvea?

  Gross anatomy, microstructure, innervation
• What is the anterior extension of the uveal tract?

  The iris
• What is the central aperture of the iris called?

  Pupil
• Where does the iris lie in relation to the lens?

  On the anterior lens surface
• What is the function of the iris in terms of retinal illumination?

  Control of retinal illumination
• How does the iris respond to changes in lighting?

  Maintains constant retinal illumination
• What effect does miosis have during near effort?

  Produces pinhole effect, increasing depth of focus
• What happens to optical aberrations with a large pupil?

  Glare and aberrations commonly occur
• What are the functions of the iris/pupil?

  • Control of retinal illumination
  • Light adaptation
  • Depth of focus
  • Reduction of optical aberration

  
• What are the three areas of the ciliary zone of the iris?

  Inner smooth, middle furrowed, marginal cribriform

  
• What is the width of the pupillary zone?

  1.6 mm wide
• What are Fuchs crypts in the iris?

  Deep radial slits/ridges in the stroma
• How many distinct layers does the iris have?

  Four distinct layers
• What is the composition of the anterior border layer of the iris?

  Collagen fibrils and fibroblasts

  
• What type of connective tissue is the stroma of the iris?

  Loose, pigmented, highly vascular connective tissue
• What types of cells are found in the stroma of the iris?

  Melanocytes and clump cells

  
• What are the two types of iris muscles?

  Sphincter muscle and dilator muscle

  
• What is the function of the sphincter muscle in the iris?

  Causes constriction (miosis)

  
• What nerve supplies the sphincter muscle?

  Parasympathetic nerve
• What is the function of the dilator muscle in the iris?

  Causes dilation of pupil (mydriasis)
• What nerve supplies the dilator muscle?

  Sympathetic nerve
• What are the two types of pupil reactions?

  • Direct light reflex: constriction in the same eye
  • Consensual light reflex: constriction in the opposite eye

  
• What is the composition of the posterior epithelium of the iris?

  Single layer of heavily pigmented columnar cells
• What forms the major arterial circle of the iris?

  Anastomoses from long posterior ciliary arteries
• What is the function of the ciliary processes?

  Increase surface area for secretion
• How many finger-like projections do the ciliary processes have?

  70-80 finger-like projections
• What do zonulas do in relation to the lens?

  They are the suspensory ligament of the lens
• What is the ciliary body part of?

  It is part of the eye.

  
• How many finger-like projections do the ciliary processes have?

  70-80 projections
• What is the diameter of each ciliary process?

  0.5 mm
• What do zonulas do in the eye?

  They are the suspensory ligament of the lens
• What is the role of the ciliary muscle during accommodation?

  It changes the shape of the lens
• What are the components of the ciliary body microstructure?

  • Ciliary epithelium (non-pigmented and pigmented)
  • Stroma (vascular layer)
  • Muscular layer (ciliary muscle)
  • Supraciliaris (outermost layer)

  
• What type of tissue is the supraciliaris made of?

  Loose connective tissue
• What is the function of the supraciliaris?

  Allows ciliary body to slide against sclera

  
• What are the two layers of the ciliary epithelium?

  Pigmented and non-pigmented epithelium

  
• What does the non-pigmented epithelium produce?

  Aqueous humor and glycoprotein of vitreous
• What is the blood-aqueous barrier?

  Diffusion barrier between blood and aqueous
• What is the structure of the choroid?

  • Highly pigmented, vascular loose connective tissue
  • Extends from optic nerve to ciliary body
  • Thickness decreases from posterior to anterior