Vision

Question 1

Illuminance

Answer 1

The amount of light received by an object per unit area (lux).

Question 2

Lux

Answer 2

The degree of illumination of a surface 1m from a source of 1 candela radiating uniformly in all directions.

Question 3

What is the illuminance of full sunlight?

Answer 3

100 000 lux

Question 4

Luminance

Answer 4

The amount of light emitted by an object per unit area (candelas per m^2)

Question 5

Light adaptation

Answer 5

Retinal ability to decrease sensitivity to bright light. Results in eye having weaker responses to increasing increments of light intensity when light is v. bright

Question 6

Chromatic abberation

Answer 6

Lens aberration where different colours of light are each refracted at different angles due to different wavelengths. Result = defected images with coloured fringes.

Question 7

Spherical abberation

Answer 7

Defect in lens shape - becomes spherical rather than ellipsoid. Results in blurred image thus reduced visual acuity.

Question 8

Glare

Answer 8

When small particles in optical media scatter light in all directions. Reduces contrast.

Question 9

Tritanopia

Answer 9

• Lack of blue cones
• Blue-yellow colour blindness
• Blue appears green
• Yellow appears violet

Question 10

Presbyopia

Answer 10

Reduction in accomodation power due to decrease in lens elasticity.

Question 11

Visual acuity

Answer 11

.

Question 12

Diffraction

Answer 12

When light waves spread out when they pass through a small aperture.

Question 13

Effect of diffraction on image quality.

Answer 13

Causes the image of a point source to be a blurred circle known as the pointspread function.

Question 14

How does pupil size affect lens aberrations?

Answer 14

As the pupil dilates, lens aberrations become more significant and the pointspread function broadens.

Question 15

What is the difference btw refractive errors and aberrations?

Answer 15

Aberrations involve the lens and refractive errors involve the shape of the eye.

Question 16

Emmetropic

Answer 16

When an object at infinity is sharply focused. If not, eye is ametropic

Question 17

Hypermetropia

Answer 17

Long-sightedness - image forms behind the retina (eye squashed inwards)

Question 18

Myopia

Answer 18

Short-sightedness - image forms in front of retina.

Question 19

Accommodation

Answer 19

When the focal length of the lens changes to focus on objects at different distances.

Question 20

Describe the near reflex.

Answer 20

Simultaneous constriction of the pupli to improve depth of focus and convergence of two eyes to fixate on new target.

Question 21

What overall system controls pupil diameter?

Answer 21

The ANS

Question 22

What muscles does the parasympathetic system control?

Answer 22

Sphincter

Question 23

What muscles does the sympathetic system control?

Answer 23

Diator

Question 24

Which muscle primarily controls pupil diameter?

Answer 24

The sphincter

Question 25

Describe a test used to test intact brainstem function in unconscious patients.

Answer 25

.

Question 26

Dark adaptation

Answer 26

The adjustment of the eye to low light intensities. Involves dilation of the pupils and activation of rod cells.