Copy of the eye structure

Vision & The Eye

Anatomy, Physiology and How we see

Learning Objectives

• Explain how the eye works to see the world around us
• Describe the anatomy of the eye & Label Diagrams

Vision is your ability to see.

Vision involves the eye and the brain.

The Eye

The eye is one of your sense organs.

The eye is made of the iris and the pupil.

The eye gathers pictures and sends them to the brain.

The Parts of the Eye

The colored part of the eye is the iris.

The black part of the eye is the pupil.

The pupil becomes larger and smaller as it controls the light coming into the eye.

Iris

Pupil

Iris and Pupil

• Smooth radial muscles

• Circular muscles

• These surround a hole – the pupil

Changing the size of the pupils

• muscle in the iris contracts making the pupil smaller in bright light

• different muscle in the iris contract to make the pupil larger in dim light

Key terms

• Sclera
• Retina
• Cornea
• Iris
• Pupil
• lens
• Suspensory ligaments
• Ciliary muscle
• Refract
• Focus

• Sclera
• Retina
• Cornea
• Iris
• Pupil

• Suspensory ligaments
• Ciliary muscle
• Refract
• Focus
• Lens

Structure of the eye

Surrounds the cornea, lubricated by watery tear fluid

Light sensitive rod and cone cells

Conjunctivia

Blood vessels

Sensory neurone Blind spot (no rods and cones)

Transparent part of the sclera, Allows light to enter the eye.

Tough and fibrous

Structure of the Eye: Cornea and Lens

Retina

Cornea

Eyelens

• There are two lenses in your eye, the cornea and the eyelens.
• The cornea, the front surface of the eye, does most of the focusing in your eye
• The eyelens provides adjustable fine-tuning of the focus

Refract (bend)

• Light is refracted when it enters the eye

• Cornea

• Front of Lens

• Rear of Lens

• Image forms on retina

Blind Spot

Lens held in place by suspensory ligamentsSuspensory ligaments are attached to ciliary ,muscle

Looking at a distant object

• Ciliary Muscles relax
• Suspensory ligaments pulled taught
• Lens pulled thin
• Light rays enter at a less acute angle
• less bending power, longer focal length

Looking at a close object

• Ciliary muscles contract
• Suspensory ligaments loosen
• Lens bulges
• Light rays enter at a more acute angle
• bending power Is more
• Shorter focal length

Accomodation

Short and long sighted

Short sighted (myopia)- the focal point falls short. Near image will be clear

long sighted (hyperopia)- the focal point is too long Distant image will be clear

Correction

Optics of the Human Eye