Vision - Part 1

Front 1

What is the sclera?

Where does it specialise?

Back 1

1. The sclera is a white capsule around the eye.

2. At the anterior surface of the eye the sclera specialises into the cornea.

Front 2

What is the function of the sclera?

Back 2

A tough area which serves as an insertion point for external muscles that move the eyeball.

Front 3

What is the choroid layer?

Back 3

Darkly pigmented layer which is found at the back and at the front of the eyeball.

Front 4

What is the function of the choroid layer?

Back 4

At the back of the eyeball it absorbs light rays. At the front of the eyeball it is specialised into the iris, ciliary muscle and zonular fibres.

Front 5

How is the diameter of the pupil determined?

Back 5

Smooth muscle of the iris determine the diameter of the pupil.

Front 6

What is the function of the ciliary and zonular fibres?

Back 6

Ciliary muscles causes tension on the zonular fibres when contracted. The tension in the zonular fibers changes the shape of the lens - thus determining its focusing power.

Front 7

What does the retina form?

Back 7

Forms the inner posterior surface of the eye

Front 8

What is the sensory receptor of the eye called?

Back 8

The photoreceptor.

Front 9

What is the macula lutea?

Back 9

The macula lutea is an oval-shaped pigmented area near the center of the retina of the human eye.

Front 10

What is the Fovea Centralis?

Back 10

Central shallow pit containing a very high number of cone cells.

Front 11

What is the function of the fovea centralis?

Back 11

Specialised in delivering high visual acuity.

Front 12

What is the optic disc?

Back 12

Where neurons exit the eye to the brain in the form of the optic nerve.

Front 13

What are the two major subdivisions of the eye?

What is the main composition of each?

Back 13

1. Anterior chamber - filled with aqueous humor

2. Posterior chamber - filled with vitreous humor

Front 14

What is refraction?

Back 14

The phenomenon that when light moves from air to a denser medium it will bend.

Front 15

How does 'refraction' help us to see?

Back 15

Refraction allows us to focus an accurate image of an object onto the retina.

Front 16

When an object is:

1. Close

2. Far away

how must refraction be manipulated to focus the image on the retina?

Back 16

1. When an object is close to the eye it must be refracted at greater angles to converge on the retina.

2. When an object is far away from the eye it must be refracted at very low angles to converge on the retina.

Front 17

What dictates the level of refraction of light entering the eye?

Back 17

The shape of the lens.

Front 18

How is the shape of the lens controlled?

Back 18

The shape of the lens is controlled by the ciliary muscles which contract/relax the zonular fibres.

Ciliary contraction = zonular relaxation

Ciliary relaxation = zonular contraction

Front 19

What happens to the lens during the ageing process?

Back 19

As people age the lens tends to lose elasticity, reducing its ability to assume a spherical shape.

Front 20

What does the lessening elasticity of the lens with age cause?

Back 20

Progressive decline in the ability to accomodate for near vision

Front 21

What is the scientific term for losing the ability to focus on close objects?

Back 21

Presbyopia

Front 22

Why over time does the lens lose its elastic properties?

Back 22

The central cells in the lens cannot divide and over time yellow and then black. Acquiring a dense, stiff complexion

Front 23

What are cataracts?

What is a major causative agent?

How are cataracts treated?

Back 23

1. Clouding of the lens over time

2. UV light partially to blame

3. Can be surgically removed but ability to accommodate is lost

Front 24

What is:

1. The scientific term for nearsightedness?

2. Why does nearsightedness occur?

3. How is it corrected?

Back 24

1. Myopia

2. Eyeball too long in relation to the lens - images focus in front of the retina

3. Convex lens

Front 25

What is:

1. The scientific term for farsightedness?

2. Why does farsightedness occur?

3. How is it corrected?

Back 25

1. Hyperopia

2. Eyeball too short in relation to the lens - images focus behind the retina.

3. Concave lens

Front 26

What is astigmatism?

Back 26

When the lens or cornea is not smoothly spherical.

Front 27

What condition relates to the maintenance of the aqueous humor in the eye?

Back 27

Aqueous humor is constantly formed and drained at the edge of the cornea. If formation is greater than drainage this can lead to increasing intraocular pressure = glaucoma.

Front 28

What is the result of glaucoma?

Back 28

Permanent damage of retinal cells through increased intraocular pressure.

Front 29

What does the iris regulate?

Back 29

The diameter of the pupil.

Front 30

What does the diameter of the pupil dictate?

Back 30

As the iris blocks the passage of light and the pupil does not. The diameter increases the amount of light which enters the eye.

Front 31

How is the iris composed?

Back 31

The iris is composed of two layer of smooth muscle that are innervated by autonomic nerves.

Front 32

How does the nervous system influence the diameter of the pupil?

Back 32

1. Sympathetic stimulation of the iris = enlarged pupil.

2. Parasympathetic stimulation of the iris = smaller pupil.

Front 33

How and why does the pupil diameter change in bright light?

Back 33

When bright light is detected the pupil diameter is decreased. This prevents the light from flooding the vision allowing for very focused vision.

The decrease in size of the pupil also protects the retina from damaging, very bright light.

Front 34

How and why does the pupil diameter change in low light level environments?

Back 34

Dilation of the pupil allows limited light to fill the eye allowing for vision in dim light conditions.