BOVINE EYE DISSECTION INTRO – Spring 2012
Can humans or non-human animals
see in the dark?
Light?
Waves of electromagnetic energy
Photons = discrete particles of energy
Travel in space at high speeds (186,000/mi/second!)
Measure in length nanometers (billionth of a meter)
So, we call these wavelenths
Visable to humans  380 – 760 nm
Visible Spectrum of Wavelength - Humans
*snakes see infrared
1. Sclera: covering of eye
Anatomy of the Eye
5.
2. Cornea: covers iris &
pupil focusing begins (80%)
2.
4.
6.
3. Anterior Chamber (aqueous):
clear fluid nutrients/shape
3.
4. Iris: muscle, control of
light intake, color (melanin)
5. Pupil: hole in iris -dilates/contract based
on available light
1.
7.
8.
11.
7. Vitreous Humor: gives
eyeball shape
9.
10.
6. Lens: adjusts the eye’s
focus (20%) accomodation
10. Optic Nerve
8. retina: transduction
rods & cones
11. choroid
9. Fovea: acuity, cones
Anatomy of the Eye
Light entering the eye
Normal Vision
Problem in lens  Cataracts
protein clumping together
Problem in the macula (fovea)
Macular Degeneration: loss of
acuity and center vision
Anatomy of the Eye - Retina
Retina: Photoreceptors
Transduction of light
Into electrical chemical
Message
Instead of NT
Binding to receptor…
Light cause cascade of
Intercellular messages
Ganglion
Cell Axons
form optic
nerve
Cell Layers in the Retina
…notice anything funky about the set up?
Rods (scotopic)
Duplexity Theory
-responsible for night vision
-very sensitive to light (low levels)
-found in the periphery of retina
- more than cones
- Provide monochromatic info
(Achromatic)
- Provides poor acuity
- Night blindness
Cones (photopic):
-responsible for day vision (sensitive to
mod-hi light)
- found in fovea
- provides greater acuity
- trichromatic – color vision
- legally blind (day blindness)
Anatomy of the Eye – Blind Spot
blind spot
The blind Spot
1 million nerve fibers
IPSI & CONTRALATERAL PATHWAYS
Optic Tract
1/2 axons go to right side of the brain
1/2 go to left side of brain
Not the same in all animals – depending on location of eyes
Ex: Rabbits & Guinea Pigs
How does the signal get to the
Visual Cortex?
VIA the Retinal Ganglion Cell Axons
OPTIC TRACT
OPTIC TRACT
Damage to the optic nerve = Glaucoma
Glaucoma: problem in the Anterior Chamber  fluid
there doesn’t drain correctly which puts pressure on
the back of the eye especially the optic nerve