The Crystalline lens

• What is the main focus of the lecture by Dr. Daniela Oehring?

  Anatomy and physiology of the lens
• What should students be able to do after revising the lecture?

  • Recognize normal anatomical structures
  • Identify physiological variations
  • Locate discussed structures
  • Interpret age-related changes
  • Explain neuronal pathways and associations
• What is one function of the crystalline lens?

  Allows passage of light to retina
• How does the lens enable accommodation?

  It focuses images on the retina
• What percentage of the eye's total dioptric power does the lens constitute?

  1/4 of total dioptric power
• Where is the lens positioned in the eye?

  Between iris and vitreous body

  
• What is the hyaloid canal associated with?

  It is related to the vitreous body
• What is the radius of the anterior surface of the lens?

  10 mm
• What is the refractive index of the lens nucleus?

  1.406
• What is the weight of the lens at birth?

  65 mg
• How does the color of the lens change with age?

  Colorless at birth, yellowish at 30
• What are the main components of the lens structure?

  1. Lens capsule
  2. Lens epithelium
  3. Lens fibers

  
• What type of collagen mainly composes the lens capsule?

  Type-IV collagen
• What is the function of the ciliary zonule?

  Holds the lens in position

  
• What is the diameter range of ciliary zonule fibers?

  0.35 to 1.0 μm

  
• What are the three types of ciliary zonule fibers?

  1. Thick, wavy fibers
  2. Thin and flat fibers
  3. Very fine fibers running circularly
• What is the anterior lens epithelium composed of?

  Single layer of cuboidal cells
• What is the main site for energy production in the lens?

  Lens epithelium
• What is the main source of nutrients for the lens?

  Aqueous humor
• What process is responsible for ATP production in the lens?

  Anaerobic glycolysis
• What are the divisions of the lens?

  • Embryonal nucleus
  • Foetal nucleus
  • Adult nucleus
  • Cortex
  • Anterior epithelium
  • Anterior/posterior capsule

  
• What is the gradient refractive index (GRIN) of the lens?

  Increases from anterior to center
• What is the refractive index at the equator of the lens?

  1.375
• What happens to the lens fibers with age?

  They accumulate more crystallin proteins
• What are the functions of the lens epithelium based on location?

  • Centrally: transport substances
  • Equatorially: mitotic division and differentiation

  
• What is the main composition of lens fibers?

  Crystallin proteins
• What is the role of gap junctions in lens fibers?

  Facilitate communication between fibers
• What is the ionic gradient of Na+ within the lens?

  25 mmol
• What is the role of phospholipids in lens fibers?

  Regulate mitosis and differentiation
• What are the clinical applications related to the lens?

  • Understanding cataract formation
  • Implications for vision correction
• What percentage of light does the lens allow to pass through?

  90%
• What types of light rays does the lens absorb?

  UVA and UVB light rays
• How does the arrangement of proteins in the lens affect light scattering?

  Minimizes scattering of light
• What is the gradient refractive index (GRIN) of the lens?

  Increases from anterior to center
• What is the refractive index at the equator of the lens?

  1.375
• What is the refractive index at the pole of the lens?

  1.385
• What is the refractive index at the nucleus of the lens?

  1.406
• How does the refractive index change towards the posterior surface of the lens?

  It decreases towards the posterior surface
• What factor influences the variation in refractive index within lens fibers?

  Protein concentration within lens fibers
• What does the variation in refractive index provide?

  Differences in refractive power