Lecture 31: Eye

  1. 3 layers of eye
    • 1. Corneoscleral
    • Cornea most refractile part of eye, most imp in focuses image on retina
    • 2. Choroid (uvea)
    • most of eye's vasculature
    • 3. Retina
    • photosensitive (rods & cones), neurons, considered part of brain & CNS
  2. Cornea
    • no blood vessels or pigments
    • Inflammation from limbus: juction of cornea and sclera, appearance of stroma vasculature & disapperance of Bowman's membrane
    • goblet cells in the conjuctiva: statified sq changes to stratified cuboidal
    • Stratified squamous epithelium
    • Bowman's membrane-collagen fibrils formed by stroma below
    • Stroma- thickest, keroatocytes- modified fibroblasts (NOT keratin!), orthagonally arrayed= transparent. continuous in sclera but not the structured arrangement
    • Descemet's membrane- basal lamina, diffusion barrier between stroma and anterior chamber
    • Corneal endothelium- tight junctions
  3. Vision defects
    • problems with cornea
    • Myopia- nearsightedness; cornea too far from retina
    • Hyperopia- farsightedness; cornea too close to retna
    • Astigmatism- light rays can't sharply focus b/c cornea is aspherical
  4. Refractive Surgery
    • on Cornea
    • Radioal Keratotomy & Astigmatic keratotomy- incisions
    • Photorefractive keratotomy (PRK) eximer laser removes corneal epithelium
    • Laser assister in-situ keratomileusis (LASIK)- eximer laser removes stroma
  5. Lens
    • Capsule
    • Cuboidal- only epith on anterior side!!
    • post-mitotic, anuclear flattens lens fibers runs entire width connected by gap junctions
    • zonules- elasic microfibril called fibrillin
  6. Len problems
    • Presbyopia- loss of lens elasticty, NOT corrected by corneal surgery
    • Cataracts- loss of lens transparency
  7. Retina
    • 1. RPE layer- non-neuronal, prevent backscatter
    • 2. PR layer- dendrites of PRs (rods & cons)
    • 3. Outer limiting membrane- tight junctions between PR neurons and Muller glial cells
    • 4. ONL- cell bodies of PRs
    • 5. OPL- axons of PRs and axons/dendrites of bipolar, horizontal, amacrine cells
    • 6. INL- cell bodies of B,H,A cells
    • 7. IPL- dendrites of ganglion cells and axons/dendrites of B,H,A cells
    • 8. GCL- cell bodies and axons of ganglion cell neurons, exit eyr thru optic nerve, signals to optic lobe
    • 9. NFL- axons of ganglion cells, innermost layer
  8. Light path
    • Fovea centralis-highest density of PRs, no rods, lots of cons
    • Macula lutea- yllo zone around fovea
    • Optic disc- where optic nerve joins retina, no retina here =
    • "blind spot"
  9. Iris
    • no anterior layer of epithelium
    • posterior chamber-> between iris and lens
  10. Ciliary Process/Body
    • makes aqueous humorpumped into post chamber by inner non-pigmented layer
    • outer layer- pigmented, continuous with pigmented iris epith layer
    • inner layer- non-pigmented, produce zonules (onto lens), pumps aqueous humor into post chamber
  11. Accomodation
    ciliary m contract, loosens zonules, thicken/curve lens-> increase index of refraction can see nearby objects
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Lecture 31: Eye