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Lecture 2

HTHSCI 1H06 Lecture Notes - Lecture 2: Far-Sightedness, Bitemporal Hemianopsia, Presbyopia

Health Sciences
Course Code
Peter Helli

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CNS – Vision
Elements in Vision
1) Refractive Media
bends the light and shines on to the retina
consists of cornea, aqueous humor, lens and vitreous humor
2) Neural Detection and Transmission to Brain
- occurs through the detection of the light by the retina and sending that information out
to the lateral geniculant of the thalamus for conscious perceptual vision and to the
superior colliculus for unconscious use of vision
3 Coats of the Eye
1) Schlera/Cornea – fibrous coat
2) Choroid/Cillary Body/ Iris – vascular coat
3) Retina – neural coat
Sensory Aspects of Vision
- Sclera
- Cornea
- Lens
- Retina & visual pathway
- Glaucoma
Normal vision depends on the shape of the cornea and sclera
- Refractive power: air/water interface (80%)
oMost of light is bent by the cornea
- Accommodation: lens (20% refraction)
oCapable of adjusting the focus of the eye
- Hyperopia (farsightedness)
oImage is elongated
oEyeball is flattened
oNeed a lens with positive diopters (convex)
o60% of population
- Myopia (nearsightedness)
oEye is elongated, visual pathway is short
oNeed lens with negative diopters (concave)
o20-30% of population
- responsible for bending the light
- made up of collagen bundles
- cornea is clear
- epithelial layers get rid of water
- cant have water in the stroma
To keep cornea clear:
- make sure all bundles of collagen fibers are running in the same direction
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