The Eye

IRIS

SCLERA

RETINA

PUPIL

CORNEA

LENS

OPTIC NERVE

AQUEOUS

HUMOUR

VITREOUS HUMOUR

STRUCTURE FUNCTIONCornea Outermost structure in front of the eye; protects eye; refracts

light first.Aqueous Humour

Clear liquid; helps maintain pressure within eye.

Iris The coloured part of the eye. A ring of muscle whichcontrols the amount of light entering the lens.

Pupil In the centre of the iris; a hole that lets light into the eye.Lens Located behind opening of pupil; elastic and can change its

shape; a converging lens!Vitreous Humour

jelly-like; mixture of protein and water; maintains eye shape; transparent so light can pass through.

Retina Located at back of eye; the “screen” where image is formed; image is inverted by convex lens of eye. Lined with sight receptors (rods & cones).

Optic Nerve Bundle of nerves on back (outside) of eye; carries message from eye to brain.

Sclera Tough, white fibrous connective tissue that covers the eyeball, giving it a great deal of protection.

BLIND SPOT - Activity

• Cover your RIGHT eye and with your LEFT eye, look at the +.• At a certain distance, the dot will disappear from sight.• This is when the dot falls on the BLIND SPOT of your RETINA.

• Now, reverse this process by closing your LEFT eye and looking at the dot with your RIGHT eye.

• Move the image slowly closer to you and the + should disappear.

Interactive Eye

http://www.biologymad.com/resources/eye.swf

http://www.freezeray.com/flashFiles/eye.htm

http://www.nei.nih.gov/health/eyediagram/index.asp

VIRTUALEye DISSECTION

www.eschoolonline.com/company/examples/eye/eyedissect.html

Vision Problems

LENSES vs VISION PROBLEMS VISION

PROBLEMDEFINITION CORRECTIVE LENS

MYOPIA • SHORT-Sightedness• Images are focuses IN FRONT of the retina.• ABILITY to focus clearly on NEARBYobjects but INABILITY to obtain a sharp image of DISTANT objects.

• Concave (Diverging)

HYPEROPIA • LONG-Sightedness• Images are focused BEHIND the retina.• ABILITY to focus clearly on DISTANTobjects but INABILITY to obtain a sharp image of NEARBY objects.

• Convex (Converging)

ASTIGMATISM • IRREGULAR shaped CORNEA and/or LENS.• Produces TWO FOCUSING POINTS in front of or behind the retina. • INABILITY to obtain a sharp image of ANY OBJECT.

• Special shaped lenses. • Hard contact lenses

MYOPIA

Corrected with a CONCAVE LENS

SHORT-SIGHTEDNESS

HYPEROPIA

Corrected with a CONVEX LENS

LONG-SIGHTEDNESS

ASTIGMATISM

Irregular Shaped Cornea and/or Lens.

ASTIGMATISMProduces TWO FOCUSING POINTS in front of or behind the retina.

HARD Contact Lenses