Vision

Question 1

What are the these parts of the eye?
- sclera
- cornea
- conjunctiva
- choroid
- lens
- iris
- uvea

Answer 1

Sclera = “white of the eye”
- No light passes through
- Continues with cornea in the front
Cornea = clear/ transparent
- Light passes through
- Lateral margin = conjunctiva
Conjunctiva = clear mucus membrane
- Covers the sclera
Choroid = inside of sclera
- Where the vascular supplies are located
Lens
- Held in suspension by lens suspensory ligament (zonule)
- Zolnule is controlled by ciliary body
Iris = colored par of the eye
- Has muscles that will change pupil
size
Uvea = iris + ciliary body + choroid

Question 2

what are the layers of the retina?

Answer 2

• Outer nuclear layer = photoreceptors –> rods and cones
• Inner nuclear layer = cell bodies of interneurons –> horizontal cells, amacrine cells, bipolar cells
• Ganglion layer = various types of ganglion cells –> only output neuron –> the axons form the optic nerve
• Neural elements are bound by Muller cells
  
  • Forms the inner limiting membrane
    (between retina & vitreous
    chamber)
    
    • Out limiting membrane (between
      the inner segment portion of the
      rods/cones from their cell body

Question 3

Where do the optic nerves enter?

Answer 3

optic disc

Question 4

What are the following terms?
- macula
- fovea
- fundus

Answer 4

Macula
- Close to the pole of the eye
Fovea = centre of macula
- No rods in humans/ primates ; lots
of cones
- Greatest visual acuity
Fundus = retina + optic disk + macula & fovea + posterior pole
- Can also see the blood vessels

Question 5

Describe the visual neural pathway. ***

Answer 5

• Axon of ganglion cells pass caudally from the optic nerve and optic tract to the lateral geniculate body
• The fibers from the nasal side of each eye crosses at the optic chiasm
• So in the geniculate body, you will have the temporal field of the ipsilateral side with the nasal field of the contralateral side –> forms the geniculocalcarine tract
• The tract then goes through the occipital lobe or the cerebral cortex to the occipital cortex

Question 6

What are the sequence of events of electrical response in the eye?

Answer 6

Question 7

Which are the cortical areas concerned with vision?

Answer 7

Dorsal or parietal pathway
- Motion
Ventral or temporal pathway
- Shape and recognition of form and
faces

Question 8

What happens in dark adaptation?

Answer 8

Dark Adaptation = retina slowly becomes more sensitive to light in the dark
2 components:
1. Drop in visual threshold (small magnitude) from the cones
2. More drop occurs from the rods

Fovea (centre of macula) = greatest visual acuity

Question 9

Which nerves innervate eye movement?

Answer 9

Eye movement is innervated by oculomotor (CN III), trochlear (CN IV), and abducent (CN VI)
- Trochlear = Oblique muscles pull medially
- Abducent = lateral movement of the eyeball