Week 1 - Overview of the eye

Question 1

The ocular adnexa are the structures that support and protect the eye and include…….. (4)

Answer 1

-The eyelids,
-The conjunctiva,
-The lacrimal gland,
-The lacrimal drainage system

Question 2

What are the 3 main functions of the ocular adnexa?

Answer 2

-Defense against microbial colonization
-Smoothing the tear film for good optical clarity
-tear production

Question 3

What are the 3 types of blinks?

Answer 3

1- Reflex
2 - Conscious
3 - Unconscious

Question 4

Why do we reflex blink?

Answer 4

occurs in response to a tactile, visual, or auditory stimulus

Question 5

What is conscious blinking?

Answer 5

a voluntarily controlled movement

Question 6

What is unconscious blinking? 2

Answer 6

• also called spontaneous
  -most common type occurs 10-15 times per minute

Question 7

What 3 things happen when you blink while wearing contact lenses?

Answer 7

1 - distribution of tear film across the lens
2 - activities with reduced blink rate
3 - movement of the lens during blink

Question 8

What are the 5 layers of the cornea (in order outer to inner)?

Answer 8

• Epithelium
• Bowman’s Membrane
• Stroma
• Descemet’s Membrane
• Endothelium

Question 9

The cornea is a clear transparent structure with a brilliant, shiny surface that is responsible for 2/3 of the refractive power of the eye. T/F

Answer 9

True

Question 10

What are characteristics of the cornea?4

Answer 10

-convex surface
- forms with the sclera
-tough fibrous outer coat that encloses ocular tissues
-protects the eye from injury.

Question 11

The cornea is avascular meaning it does not have a blood supply. T/F

Answer 11

True

Question 12

What does the cornea rely on to get oxygen, glucose, vitamins and amino acids? 3

Answer 12

1 - the atmosphere,
2- the perlimbal vasculature,
3 - the tear film or the
aqueous humour.

Question 13

Can contact lenses cause metabolic stress and why?

Answer 13

Yes as contact lenses reduce the amount of oxygen the cornea gets from the atmosphere

Question 14

What 3 oxygen states can the cornea be in after wearing cls?

Answer 14

• Anoxia - severe lack of oxygen
• Hypoxia - low levels of oxygen
• Hypercapnia - too much carbon dioxide in your blood

Question 15

What is the crystalline lens?

Answer 15

transparent biconvex structure situated between the iris and the vitreous

Question 16

What are the 3 parts of a crystalline lens (inner to outer)?

Answer 16

nucleus
cortex
capsule

Question 17

What is the crystalline lens attached to and where?

Answer 17

Attached to the ciliary processes and to the posterior portion of the ciliary body by fine suspensory ligaments (zonular fibres)

Question 18

If the crystalline lens is thin it is viewing the ………………… (1).
If the crystalline lens is thick it is viewing the …………….. (2) due to …………………..(3).

Answer 18

1 - distance
2 - near
3 - accommodation

Question 19

The iris is the most anterior structure of the uveal tract. T/F

Answer 19

True

Question 20

How does the iris dilate in bright light?

Answer 20

relaxation of the sphincter muscle

Question 21

What are the 3 parts of the conjunctiva and where are they attached?

Answer 21

Bulbar conjunctiva - sclera
Palpebral conjunctiva - eyelid
Conjunctival fornix - where it folds

Question 22

What is the function of the conjunctiva?

Answer 22

acts as a barrier against microbial infection, wounds and scratches

Question 23

What is the function of the epithelium? 3

Answer 23

-regenerates quickly
-blocks foreign bodies
-distributes nutrients

Question 24

What is the function of the Bowman’s Membrane? 3

Answer 24

• composed of collagen
  -function unclear
  -vision loss may occur during healing

Question 25

What is the function of the Stroma? 4

Answer 25

• 90% of the cornea
  -made of water and collagen
  -crystalline proteins maintain clarity in cornea
  -provides structural support/gives curved shape

Question 26

What is the function of the Desment’s Membrane?3

Answer 26

-thin and strong
-regenerates slowly
-protective barrier against injury and infections

Question 27

What is the function of the endothelium? 2

Answer 27

• delicate/does not regenerate
  -endothelium pumps ecess water which help maintains transparency of cornea

Question 28

What is the average dimension of the cornea? (vertically/horizontally)

Answer 28

Vertically - 10.6mm
Horizontally - 11.5mm

Question 29

What is the purpose of keratocytes? 2

Answer 29

-deposition and maintenance of the transparency and clarity of the cornea. -located in the stroma

Question 30

What is meant by corneal innervation?

Answer 30

-most densely innnervated tissue in the body - most amount of nerve endings

Question 31

What are the two eyelid muscles ?

Answer 31

levator palpebrae
orbicularis oculi