2 Eye and the Retina

Question 1

Q: What is light in terms of physical properties?

Answer 1

A: Light is a form of electromagnetic energy characterized by wavelength (distance from peak to peak) and intensity/amplitude (distance from peak to trough).

Question 2

Q: What are the psychological aspects of light?

Answer 2

A: The psychological aspects of light are color and brightness.

Question 3

Q: How is light involved in vision?

Answer 3

A: Light is reflected from objects and enters the eye.

Question 4

Q: What is the main function of the eye in the process of vision?

Answer 4

A: The main function of the eye is to focus the image on the retina.

Question 5

Q: What are the roles of the iris and pupil in the eye?

Answer 5

A: The iris and pupil form an adjustable aperture that limits the amount of light passing through, allowing us to handle a wide range of light levels.

Question 6

Q: How does the pupil adjust to different light levels?

Answer 6

A: The pupil can adjust its diameter between 2mm and 9mm to regulate the amount of light entering the eye.

Question 7

Q: What is the role of the cornea in vision?

Answer 7

A: The cornea provides 80% of the eye’s focusing power by focusing light on the retina.

Question 8

Q: How does the lens contribute to focusing light?

Answer 8

A: The lens contributes 20% of the eye’s focusing power and can change shape due to the action of ciliary muscles, becoming fatter to focus on close objects and thinner to focus on distant objects.

Question 9

Q: What is myopia and how is it corrected?

Answer 9

A: Myopia, or nearsightedness, occurs when light is focused in front of the retina. It is corrected with concave lenses.

Question 10

Q: What is hyperopia and how is it corrected?

Answer 10

A: Hyperopia, or farsightedness, occurs when light is focused behind the retina. It is corrected with convex lenses.

Question 11

Q: What is the retina?

Answer 11

A: The retina is the light-sensitive layer at the back of the eye.

Question 12

Q: What are photoreceptors?

Answer 12

A: Photoreceptors are light-sensitive cells in the retina that carry out transduction by reacting to light with visual photopigments, triggering electrical signals.

Question 13

Q: What are the two types of photoreceptors?

Answer 13

A: The two types of photoreceptors are rods and cones.

Question 14

Q: How do rods and cones differ in number?

Answer 14

A: There are more rods than cones in the retina.

Question 15

Q: How do rods and cones differ in sensitivity?

Answer 15

A: Rods are very sensitive and respond well in dim light, making them most useful at night. Cones are less sensitive and work best in daylight.

Question 16

Q: How are rods and cones involved in color perception?

Answer 16

A: Rods do not contribute to color perception, while cones are responsible for detecting color.

Question 17

Q: What is the retinal distribution of rods and cones?

Answer 17

A: Rods are more numerous and are distributed mostly around the periphery of the retina, while cones are concentrated in the fovea, the central part of the retina.

Question 18

Q: How do rods and cones differ in neural convergence and acuity?

Answer 18

A: Rods exhibit high neural convergence, leading to lower acuity, whereas cones have low neural convergence, resulting in higher acuity.

Question 19

Q: What are the three types of vision based on photoreceptor activity?

Answer 19

A: Scotopic (only rods active), photopic (only cones active), and mesopic (both rods and cones active).

Question 20

Q: What happens to photopigments in bright light?

Answer 20

A: Bright light bleaches photopigments, causing photoreceptors to stop responding temporarily.

Question 21

Q: What is dark adaptation?

Answer 21

A: Dark adaptation is the process by which the eyes increase sensitivity in the dark, with sensitivity increasing up to 100,000 times after about 20 minutes.

Question 22

Q: What happens to photoreceptors when moving from bright to dark environments?

Answer 22

A: Photoreceptors must recover and regain their sensitivity when moving from bright to dark environments.

Question 23

Q: Which photoreceptors are responsible for color vision?

Answer 23

A: Cones are responsible for color vision.

Question 24

Q: What types of cones are there and what wavelengths do they respond to?

Answer 24

A: There are red, green, and blue-sensitive cones that respond to different wavelengths of light.

Question 25

Q: What type of vision do rods provide?

Answer 25

A: Rods provide monochromatic (black and white) vision.

Question 26

Q: To which wavelengths are rods most sensitive?

Answer 26

A: Rods are most sensitive to medium wavelengths.

Question 27

Q: What is the Purkinje shift?

Answer 27

A: The Purkinje shift is the phenomenon where, at night, red objects appear darker than green objects.

Question 28

Q: How are cones and rods distributed in the retina?

Answer 28

A: Cones are concentrated in the fovea, the small central area of the retina, while rods are more numerous and distributed around the periphery.

Question 29

Q: What is the fovea?

Answer 29

A: The fovea is a small central area of the retina that contains only cones and is responsible for sharp central vision.

Question 30

Q: What happens to the image of an object when looking directly at it?

Answer 30

A: The image falls on the fovea when looking directly at an object.

Question 31

Q: What is the blind spot in the retina?

Answer 31

A: The blind spot is an area with no photoreceptors where the optic nerve exits the eye.

Question 32

Q: Why don’t we perceive a blind spot in our vision?

Answer 32

A: There is no perceived blind spot because it is located in different places in each eye, and the brain fills in the missing information.

Question 33

Q: What is neural convergence?

Answer 33

A: Neural convergence is when one neuron receives signals from many other neurons.

Question 34

Q: What is the ratio of rods to ganglion cells?

Answer 34

A: There are 120 rods for every 1 ganglion cell.

Question 35

Q: What is the ratio of cones to ganglion cells?

Answer 35

A: There are 6 cones for every 1 ganglion cell.

Question 36

Q: How does neural convergence affect visual acuity?

Answer 36

A: Higher neural convergence (as in rods) leads to lower acuity because the ganglion cell averages information from a larger area. Lower neural convergence (as in cones) results in higher acuity.

Question 37

Q: What is visual acuity?

Answer 37

A: Visual acuity is the ability to detect fine details of a stimulus.

Question 38

Q: Where is visual acuity the highest?

Answer 38

A: Visual acuity is highest at the fovea.

Question 39

Q: How do eye movements contribute to acuity?

Answer 39

A: Eye movements ensure that objects of interest are imaged on the fovea, where acuity is highest.

Question 40

Q: How does lighting affect acuity?

Answer 40

A: Acuity decreases in low lighting conditions.