Visual system

Question 1

Define light

Answer 1

Patterns of illumination
(luminance) of various objects

Question 2

Function of the Eye

Answer 2

focuses light onto the retina
which contains the light-sensitive
photoreceptors

Question 3

Function of the Retina

Answer 3

After detection, it also
performs some basic processing

Question 4

Where is the light picked up by the retina processed?

Answer 4

Further processing takes place in
the thalamus, followed by cortical
processing (in visual and associative
cortices)

Question 5

What are the protective mechanisms of the eye? (4)

Answer 5

➢Bony socket: protects the eye
except its anterior part
➢Eye lids: Protect anterior part of the
eye by closing (corneal/blink reflex)
➢Tears: lubricating, cleansing and
bactericidal fluid (produced by
lacrimal gland)
➢Eye lashes: capture/trap fine debris

Question 6

Name the third eyelid

Answer 6

Nictitating membrane

Question 7

How does the nictitating membrane (third eyelid) work?

Answer 7

Retractor muscles retract the eyeball allowing the nictitating membrane to slide over the eye

Question 8

Name the basic anatomy of the eye (9)

Answer 8

1. Sclera
2. Anterior and posterior chambers of the anterior cavity
3. Vitreous or posterior cavity
4. Choroid
5. Iris and ciliary body
6. Lens
7. Retina
8. Pupil

Question 9

Describe Sclera

Answer 9

• outer protective fibrous layer
  
  • Anteriorly it is transparent and called cornea
    
    • Cornea refracts light helping to focus it

Question 10

Describe the anterior and posterior chambers of the anterior cavity

Answer 10

• Filled with aqueous humor under pressure – maintains eyes spherical shape
• Provide nutrients to cornea and lens (no blood supply)

Question 11

Vitreous or posterior cavity

Answer 11

• Contains vitreous humor (and phagocytes that clear debris)
• Maintains spherical shape of the eyeball

Question 12

Describe the functions of Choroid (2)

Answer 12

1. Posteriorly →nourishment of retina
2. Anteriorly → production of aqueous humor and accommodation
   of the iris (control of pupil diameter)

Question 13

Describe the function of Iris and ciliary body

Answer 13

• Separates anterior and posterior chambers
• Movable

Question 14

Describe the function of Lens

Answer 14

transparent – refracts and focuses light

Question 15

Describe the function of Retina

Answer 15

• Sensing (and processing) of light
• Has a blind spot (the optic disk)

Question 16

Describe the function of Pupil

Answer 16

The adaptive opening that controls amount
of light that passes through the lens

Question 17

What is reflection?

Answer 17

Light bounces off at the boundary
between two media (e.g. air and
glass)

Question 18

What is refraction?

Answer 18

Light rays change direction at the
boundary between two media

Question 19

Describe the Optics of refraction in the eye

Answer 19

• At material interfaces (e.g. air/light) refraction
  occurs
• Cornea & lens refract light
• Convex surfaces converge light
• Cornea contributes most of the refractive ability