Lecture 53 - Ocular Structure 2

Question 1

what maintains a clear visual axis

Answer 1

eyelids
tears
cornea
uvea

Question 2

what are the 4 functions of eyelids

Answer 2

1. protection of the globe
2. contributes to precorneal tear film
3. spreads and minimizes evaporation of tear film
4. “pumping” of tears down the nasolacrimal duct

Question 3

what is eyelid agenesis

Answer 3

absent eyelid margin

Question 4

what are the dorsal and ventral lacrimal puncta

Answer 4

located near the medial canthus and drains the lacrimal system

Question 5

in equine, what nerve is commonly blocked to examine the eye

Answer 5

palpebral branch of the facial nerve

Question 6

what are two “blinding” diseases

Answer 6

1. KCS (dry eye disease)
2. glaucoma

Question 7

what are the functions of the lipid layer of the tear film

Answer 7

• limit evaporation of the aqueous layer
• binds precorneal tear film to prevent overflow

Question 8

what are the functions of the aqueous layer of the tear film

Answer 8

• flush foreign material
• supply cornea with nutrients and remove metabolic waste products
• source of antibacterial substance

Question 9

what are the functions of the mucoid layer of the tear film

Answer 9

• binds aqueous layer to corneal surface
• prevent tear film from “beading up”

Question 10

what makes the cornea transparent

Answer 10

• avascular
• no melanin
• no keratinization
• low cell density
• maintain dehydrated state
• highly regular arrangement of stromal collagen fibers

Question 11

T/F: the endothelium maintains stromal deturgescence via active transport by Na+/K+- ATPase pumps

Answer 11

TRUE

Question 12

what plays a key role in maintaining the blood-ocular barrier

Answer 12

the uvea

Question 13

function of the blood-ocular barrier

Answer 13

prevents excessive amounts of protein/cells from entering into the aqueous, vitreous, or subretinal space

Question 14

what is the function of aqueous humor

Answer 14

source of nutrients for cornea and lens
maintain shape of the eye

Question 15

glaucoma is

Answer 15

increased intraocular pressure

Question 16

what are the visual pathway components of the retina (inner to outer)

Answer 16

photoreceptors
retinal ganglion cells
nerve fiber layer

Question 17

rod cell

Answer 17

• nighttime
• detection of shapes
• detection of motion

Question 18

cone cell

Answer 18

• daytime
• visual acuity (details)
• color

Question 19

describe the visual pathway in 3 steps

Answer 19

1. photoreceptors absorb photons and initiate a phototransduction cascade
2. retinal ganglion cells receive input
3. axons coalesce to form fiber layer and optic nerve

Question 20

phototransduction

Answer 20

visual signals converted to neural signal