L1 - Basic Anatomy

• Eyeball


  Slightly elongated sphere, Length: 24 mm (antero-postero) 22mm(other 2 diameters), Weight: 10 grams, Volume: 6.5 ml (aqeous and vitreous), Suspended on the orbit by LIGAMENT OF LOCKWOOD, Contains the transparent media
• Transparent media in the eyeball

  • Tearfilm
  • Cornea
  • Aqeous humor
  • Crystalline lens
  • Vitreous humor
• Eyeball


  • Composed of 3 coats/tunics: Fibrous coat, Uveal coat, Nervous coat
• Fibrous/Sclero-corneal coat


  Outermost layer
• Sclera


  White of the eyeball (occupy 5/6 of the eyeball), Hard and tough layer (scleros=hard), Functions: Contains part of the eyeball, Protective covering against various forms of injury, Maintains globular shape of eyeball, Firm surface for the attachment of muscles, Being fairly opaque, aids in excluding extraneous light
• Cornea


  Main refractive apparatus of the eye (Corneus= horny), Transparent (occupy 1/6 of the eyeball), Functions: By its rigidity, gives eyeball constant shape, By its transparency, permits light to reach interior of the eye, Refract light rays, By its extreme sensitivity, aids in protecting the eye
• Limbus/Sclero-corneal junction


  Transition zone between sclera and cornea
• Uvea/Vascular coat


  Middle layer
• Choroid


  Thin, dark membrane (due to melanocytes), Covers about 5/6 of the interior of the eyeball, Functions: Nourishing coat of the eye, Nourishes the outer part of the retina (RPE & photoreceptors), Provides dark chamber (many pigmented cells), aids to darken the interior of the eye, Prevent dispersion of light– attain clear image of an object
• Ciliary body


  Prolongation and thickening of the choroid, Blood-rich tissue, whose structures work together to produce aqeous humor, Functions: Nourishes the cornea and lens through aqeous humor, Helps during accommodation, Serves as attachment of zonular fibers
• Iris


  Thin, circular membrane hanging behind the cornea and in front of the lens, Perforated at its center by an aperture (PUPIL), Functions: Reduces chromatic and spherical abberations– increasing VA, Regulate the light entering the eye, Increases the depth of focus
• Nervous/Functional coat


  Innermost and most important layer
• Retina


  Thin, transparent membrane upon which the images are cast and in where nerve impulses are generated, Functions: Rods= for dim illumination/scotopic vision, Cones= for day illumination/photopic vision, color perception, Nerve fibers= for transmission of visual and pupillary impulses