Vision

Question 1

List the accessory structures of the eye

Answer 1

• eyebrow
• eyelids
• eyelashes
lacrimal curuncle
• lacrimal apparatus
• extrinsic eyeball muscles

Question 2

Describe the eyelids

Answer 2

palpabrae
• epidermis, dermis, fibres of orbiculares oculi muscles (CNVII), tarsal plate (connective tissue), tarsal glands, conjunctiva
• upper lid contains levator palpabrae superioris and tarsal muscles (sympathetic)

Question 3

What is the conjunctiva?

Answer 3

Mucous membrane of non-keratinized stratified columnar epithelium and goblet cells
• palpabral conjunctiva -inner lining of eyelid
• bulbar conjunctiva -surface of eyeball
-over sclera is vascular
-joins cornea at the limbus

Question 4

What are the contents of the lacrimal fluid?

Answer 4

• water
• salts
• mucus
• lysozyme (bacteriocydal enzyme)
• immunoglobulins
• enzymes (eg. peroxidase)
• lactoferrin

Question 5

Describe the path of the flow of tears

Answer 5

Lacrimal gland -> excretory lacrimal ducts

• > superior or inferior lacrimal canal
• > lacrimal sac
• > nasolacrimal duct
• > nasal cavity

Question 6

List the layers of the eyeball

Answer 6

1- Fibrous tunic -outer layer
2- Vascular tunic or uvea -middle layer
3- Retina -inner layer

Question 7

Describe the fibrous tunic layer of the eye

Answer 7

Sclera
• whites of the eye
• collagen fibres

Cornea
• transparent
• 3 parts: stratified squamous epithelium, connective tissue + collagen, simple squamous epithelium
• 2/3 of refractive power of eye

Question 8

Describe the vascular tunic layer of the eye

Answer 8

• Choroid: vascular, give nutrients to retina, melanocytes
• Ciliary body: ciliary processes and ciliary muscle
• Iris: control pupil size

Question 9

Describe the retina layer of the eye

Answer 9

• lines posterior 3/4 of eyeball
• 2 layers:
-pigmented (melanin)
-neural (photoreceptors, bipolar cells, ganglion cells)

Question 10

Compare the innervation for pupil dilation vs pupil construction?

Answer 10

Dilation: superior cervical ganglion of sympathetic chain

Constriction: CNIII parasympathetic

Question 11

What is the position of the iris muscles during: pupil constriction, normal, pupil dilation?

Answer 11

Constrict:
• circular iris muscles constrict
• radial muscles of iris relaxed

Normal: both muscles relaxed

Dilate:
• circular iris muscles relax
• radial muscles of iris constrict

Question 12

What is the role of the ciliary muscle in accommodation?

Answer 12

• ciliary muscle attached to lens by ligaments
• ciliary muscle relaxed -> ligaments pull lens flat -> goof for distant vision
• ciliary muscle contract -> ligaments loose -> lens rounded -> good for near vision
• muscle innervated by CNIII-parasympathetic

Question 13

Fovea

Answer 13

• center of the eye back

* mostly cones there

Question 14

Rods vs cones

Answer 14

Rods:
• dim light
• no colours

Cones:
• bright light
• colour vision
• 3 types: red, green, blue

Question 15

Describe the parts of rods and cones

Answer 15

1- Outer segment -rhodopsin (photopigment) transact light into receptor potential
2- Inner segment -golgi complex and mitochondria
3- nucleus
4- synaptic terminal

Question 16

red

Answer 16

L

long wavelength

Question 17

green

Answer 17

M

medium wavelength

Question 18

blue

Answer 18

S

short wavelength

Question 19

What is the pathway of vision?

Answer 19

Light -> eye

• > optic nerve -> chiasm
• > optic tract
• > Lateral geniculate body (thalamus)
• > visual cortex (occipital lobe)

Question 20

Binocular zone vs mononucula zone

Answer 20

• where left and right visual fields overlap

* portion of visual field of only one eye

Question 21

What is the consequence of a lesion of the optic nerve?

Answer 21

complete loss of vision in homolateral eye

Question 22

What is the consequence of a lesion of the optic chiasm?

Answer 22

• loss peripheral vision

* bitemporal hemianopia

Question 23

what is the consequence of a lesion of the optic tract?

Answer 23

lost contralateral visual field in both eyes