1. Vision

2. Parts of the Eye The Sclera The Cornea Conjunctiva The Choroid Coat
The Ciliary Body
The Iris
The Pupil
The Retina
The Macula lutea
Fovea
The Optic Nerve
The Optic Disk
The Vitreous Humor
The Aqueous Humor

4. The Conjunctiva
lines the inside of the eyelids and covers the sclera (white part of the eye). It is composed of rare stratified columnar epithelium.

5. The Sclera The Cornea Window of the eye
Helps focus entering light rays
Composed of connective tissue w/ thin layer of epithelium
Has many nerve fibers that enter the margin and radiate toward the center – associate with many pain receptors w/ low threshold
Cold receptors abundant
White portion of the eye
Makes up 5/6 of posterior outer tunic
Opaque b/c of how the collagen and elastic fibers are arranged.
Protects the eye
Attachment for extrinsic muscles

6. The Optic Nerve The Choroid Coat
Located in the back of the eye
Attached to the retina
Transmits images from the retina to the brain
Flips the pictures
Part of the middle tunic
Posterior 5/6 of the globe of the eye
Has blood vessels that nourish surrounding parts
Contains melanocytes
Melanin from melanocytes absorb excess light and keep the inside part of the eye dark

7. The Ciliary Body The Iris
Thickest part of the middle tunic
Extends to the front from the choroid coat
Forms internal ring around the eye
Contain folds called ciliary processes
2 groups of muscle fibers – ciliary muscles
Controls how much light enters the eye
Thin diaphragm composed of connective tissue & thin connective tissue
It is the colored portion of the eye
Extends from the front of the periphery in the ciliary body to the middle of the cornea and the lens
Divides the anterior cavity (cornea & iris) into anterior chamber (iris and vitreous humor)

8. The Pupil The Lens The circular opening in the center of the iris
Black spot in the center of the iris
Controls how much light enters the retina
Its diameters is usually 3-7 mm
Transparent
Held in position by fibers called suspensory ligaments (zonular fibers) from the ciliary processes
Lacks blood vessels
Located behind the iris and the pupil
Composed of special epithelial cells

9. Vitreous Humor Aqueous Humor
Jelly- like fluid
Fills the central core of the eye
Helps maintain spherical shape to the eye
this with collagenous fibers form the vitreous body
Front of iris and pupil
Watery fluid created by epithelium on inner surface of ciliary body
Separated into anterior and posterior chambers
Maintains eye pressure
Nourishes front part of the eye

10. The Macula Lutea The Fovea Centralis
Yellowish spot in the retina
The central focusing spot
Responsible for seeing details (reading) and color vision
A depression in the macula lutea
In the region of the retina that produces the sharpest vision
Has no rods – only cones

11. The Optic Disk Lacks receptors, often called the blind spot
The nerve fibers from the retina and became part of the optic nerve.
A central artery and vein pass through here
These vessels with vessels in the choroid coat supply blood to the cells of the inner tunic
Jelly- like fluid
Fills the central core of the eye
Helps maintain spherical shape to the eye
this with collagenous fibers form the vitreous body

12. The Retina Complex structure
Layers of (epithelium, nerve fibers, & membranes)
Contains photoreceptors called rods and cones
Continuous with the optic nerve and extends to the front as the inner lining of the eyeball
6 retinal cell groups: rods, cones, bipolar neurons, ganglion cells, horizontal cells and amacrine cells.
provide direct path for impulses to the receptors to the optic nerve & brain
The retina contains two types of photoreceptors, rods and cones.
The rods are more numerous, some 120 million, and are more sensitive than the cones.
However, they are not sensitive to color. The 6 to 7 million cones provide the eye's color sensitivity and they are much more concentrated in the central yellow spot known as the macula.
In the center of that region is the " fovea centralis ", a 0.3 mm diameter rod-free area with very thin, densely packed cones.

13. The receptors in the retina

14. Pigment epithelium
the pigmented cell layer just outside the neurosensory retina
nourishes retinal visual cells
firmly attached to the underlying choroid and overlying retinal visual cells.

15. Rods Cones Responsible for color vision
Responsible for black and white vision
The rods are more numerous and more sensitive than the cones
they are absent in the fovea centralis
Responsible for color vision
Densely packed in the fovea centralis

16. Horizontal cells Bipolar cells
Bipolar cells exist between rods and cones and ganglion cells.
They transmit signals from the rods and cones to the ganglion cells.
Horizontal cells integrate and regulate the input from rods and cones.
They are also responsible for allowing eyes to adjust to see well under both bright and dim light conditions.

17. Amacrine cell Ganglion cell
A Ganglion cell is a type of neuron located near the inner surface of the retina
It receives visual information from rods and cones via two intermediate neuron types: bipolar cells and amacrine cells.
It transmits visual info to thalamus, hypothalamus and midbrain.
Amacrine cells are interneurons in the retina.
They are responsible for 70% of input to retinal ganglion cells.
They lack axons – but have many dendrites

18. Direction of Impulse
Photons move through the 6 layers of cells and strike the rods and cones
They process the light information
This info is integrated by the horizontal cells
The info travels to the bipolar cells
This info then travels to the amacrine cells
The impulses (info) finally converge at the ganglion cells
The axons of the ganglion cells carry the info to the brain

20. Optic Nerve (Cranial nerve 2)
The optic nerve, also known as cranial nerve 2, transmits visual information from the retina to the brain
It is composed of the axons of the retinal ganglion cells
The ganglion cell axons are myelinated by oligodendrocytes – since it is part of the CNS

24. THE END