The eyeThe eye

WALTTo identify the main parts of the eye and

their functionsTo explain how light is focussed onto the

retina

Eye, eyeEye, eye

EYEEYE

The eye is an extension of the brain

Eye brain Eye brain proxomityproxomity

Can you see :

the optic nerve bundle?

Spinal cord?

The eyeThe eye

Cross Cross sectionsection

You must know the position of:

Retina

Lens

Cornea

Sclerotic

Optic nerve

Cilary muscles

Suspensory ligaments

Retina – receives the imageRetina – receives the image

Full of light receptors which are sensitive to:

Colour Light levels

Massive blood supply is also needed

Fovea is the main focal point and has greatest density of light receptors

The LensThe Lens

The crystalline lens is located just behind the iris. 

Its purpose is to focus light onto the retina. 

The lens is encased in a capsular-like bag and suspended within the eye by tiny "guy wires" called zonules or suspensory ligaments.  

The CorneaThe CorneaThe cornea is the

transparent, dome-shaped window covering the front of the eye. 

It is a powerful refracting surface, providing 2/3 of the eye's focusing power. 

The ScleraThe Sclera

The sclera is commonly known as "the white of the eye."  It is the tough, opaque tissue that serves as the eye's protective outer coat.  Six tiny muscles connect to it around the eye and control the eye's movements. 

The optic nerve is attached to the sclera at the very back of the eye.

Ciliary MusclesCiliary MusclesOne function of the

ciliary body is the production of aqueous humor the clear fluid that fills the front of the eye. 

It also controls accommodation by changing the shape of the crystalline lens. 

The Optic NerveThe Optic Nerve

The optic nerve transmits electrical impulses from the retina to the brain.   

When examining the back of the eye, a portion of the optic nerve called the optic disc can be seen.  

The retina's sensory receptor cells of retina are absent from the optic nerve. 

The IrisThe IrisThe colored part of the eye is called

the iris.  It controls light levels inside the eye similar to the aperture on a camera. 

The round opening in the center of the iris is called the pupil. 

The iris is embedded with tiny muscles that dilate (widen) and constrict (narrow) the pupil size.  

Aqueous HumorAqueous HumorThe aqueous is the thin,

watery fluid that fills the space between the cornea and the iris (anterior chamber). 

It is continually produced by the ciliary body, the part of the eye that lies just behind the iris. 

This fluid nourishes the cornea and the lens and gives the front of the eye its form and shape.

Vitreous HumorVitreous HumorThe vitreous is a thick,

transparent substance that fills the center of the eye.

It is composed mainly of water and comprises about 2/3 of the eye's volume, giving it form and shape.

The viscous properties of the vitreous allow the eye to return to its normal shape if compressed. 

The ChoroidThe Choroid

The choroid contains many blood vessels

The choroid is dark in colour as it contains pigment

This means that it absorbs light and prevents internal reflection of the light rays