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Contact Lenses > Anatomy and Physiology > Flashcards

Anatomy and Physiology Flashcards

1
Q

How many bones make up the orbit? What is the name of their fusion location?

A

7 bones, fused together at sutures

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2
Q

Why are there thick and thin bones in the orbit?

A

Thick for protection and thin with air spaces to reduce the weight of the skull

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3
Q

How many openings are there in the skull? What is their function and what are they called?

A

8 openings (called foramen), they are for entry and exit of blood vessels and nerves.

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4
Q

What is the eye socket lined with? Why?

A

Fat for protection and to cushion the globe, extrinsic muscles, nerves, blood vessels and tear glands

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5
Q

What are the 6 peripheral nerves that innervate the eye? Which are sensory and which are motor?

A

Nerves 2 to 7

2: Optic nerve (sensory)
3: Occulomotor (motor)
4: Trochlear (motor)
5: Trigeminal (sensory)
6: Abducens (motor)
7: Facial (motor)

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6
Q

What is the Lacrimal Fossa?

A

A smooth deep concave depression on the lacrimal bone where the lacrimal gland sits

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7
Q

What are the two sensory nerves associated with the eyes? What are their numbers, names and function?

A

2 Optic nerve: relays information from the retina to the occipital lobe

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8
Q

What are the 4 motor nerves associated with the eyes? What are their numbers, names and function?

A

3 Occulomotor: controls eye movement, pupil constriction and lifting eye lids

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9
Q

What is the lamina cribosa? Where is it located?

A

A thin sieve-like portion of the sclera at the base of the optic disk. It allows retinal nerve fibres to leave the eye to form the optic nerve

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10
Q

Define Canaliculous

A

A small tube that allows tears to drain from the eye into the lacrimal sac

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11
Q

Define Canthus

A

The junction of the upper and lower eye lids

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12
Q

Define Caruncle

A

Pink mass of modified skin cells at the medial cants - covered in goblet (mucous) cells, fine hairs and sweat and oil glands.

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13
Q

Define Levator Palpeerde Superiosis

A

Muscle that raises the upper lid

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14
Q

Define Meibomian Glands. What is another name for them?

A

OIL GLANDS - secrete sebum which form the lipid layer of the tear film
AKA Sebaceous/Tarsal glands

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15
Q

Define Plica Semilunaris

A

A fold of conjunctiva that allows the eye to move laterally without conjunctival stretch

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16
Q

Define Glands of Moll. What is another name for them?

A

Modified Apocrine glands found on the eyelid margin

AKA Sweat glands

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17
Q

Define Glands of Zeis. What is another name for them?

A

Modified sebaceous glands found on the lid margin

AKA Oil glands

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18
Q

Define Grey Line

A

A landmark on the lid margin - projection of the orbicularis oculi. Denoted the margin between conjunctiva and skin

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19
Q

Define Fundus Oculi

A

Posterior part of the eye.

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20
Q

Define Papilla Lacrimalis

A

Small lump on the lid margin. At the centre you will find a puncture called the punctum

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21
Q

Define Trochlea

A

U-shaped piece of cartilage attached to the rim of the orbit. The tendon of the superior oblique muscle passes through the Trochlea

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22
Q

Define Tenon’s Capsules

A

A thin envelope of conjunctival tissue that surrounds the eye ball and forms the socket.

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23
Q

What is the difference between lacrimal glands and accessory glands?

A

Lacrimal glands are used for reflex tears associated with pain and emotions. Tears are stored in the lacrimal glands and used on command.

Accessory glands produce tears constantly that are sed for lubrications

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24
Q

What are the three layers of the tear film?

A 
Lipid layer (outermost)
Aqueous layer (middle)
Mucous layer (inner most)
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25
Q

What are the 6 layers of the cornea?

A
  1. Epithelium
  2. Bowman’s Layer
  3. Stroma
  4. Dua Layer
  5. Descemet’s membrane
  6. Endothelium
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26
Q

What are hemidesmosomes?

A

A structure that keeps the bowman’s layer and epithelium together

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27
Q

Define Corneal Deturgesence. What is responsible for maintaining this?

A

A semi-dehydration (about 78%) state of the entire cornea. Maintained by the endothelium.

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28
Q

What are the three layers within the epithelium?

A 
Squamous cells (outer most)
Wing cells (middle)
Basal Cells (inner most)
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29
Q

Name 8-10 structures of the outer adnexa.

A
  1. Accessory Lacrimal Glands
  2. Canaliculus
  3. Canthus
  4. Caruncle
  5. Conjunctiva (Bulbar or Palpebrae)
  6. Cornea
  7. Eye Brows
  8. Eyelid Margin
  9. Eyelids (palpebral)
  10. Glands or Moll
  11. Glands of Zeis
  12. Gray Line
  13. Interpalpebral fissure
  14. Iris
  15. Lacrimal Glands
  16. Lashes
  17. Levator Palpeerde Superiosis
  18. Limbus
  19. Meibomian Glands
  20. Orbicularis Oculi
  21. Plica Semilunaris
  22. Puncta
  23. Pupil
  24. Sclera
  25. Tarsal Plate
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30
Q

What is the function of the epithelium?

A

Acts as a primary barrier and allows O2 and CO2 exchange.

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31
Q

How long does it take to heal the epithelium? What is the method of healing?

A

1-7 days (superficial scratch). The cells surrounding the wound migrated to the opening and fill in the traumatized area. There is NO SCAR

32
Q

What are the 5 layers of epithelium? (outermost to innermost)

A
  1. Microvilli
  2. Squamous cells
  3. Wing Cells
  4. Basal Cells
  5. Basement membrane (square cells)
33
Q

How is the epithelium anchored to the Bowman’s layer?

A

Hemidesmosomes

34
Q

What is the function of Bowman’s Membrane?

A

Keeps the cornea from swelling forward to maintain the refractive power. Also acts as a barrier to prevent bacteria from entering the eye (if intact)

35
Q

Describe the structure of Bowman’s Membrane.

A

Very thin layer made up of irregularly placed collagen fibres. It is very tough.

36
Q

How do injuries to Bowman’s layer heal?

A

With a scar. If it is punctured it is a prime culture for bacteria (moist and warm)

37
Q

Describe the structure of the Stroma? What is the benefit of the pattern?

A

Collagen fibres arranged in a uniform lamellar pattern (90 degrees apart). It is made of 80% water, 16% collagen, 3% matrix and 1% keratocytes (fight infection.)

Provides clarity.

38
Q

How much of the cornea is made up of stroma?

A

90%.

39
Q

What is the main function of the stroma?

A

Clarity to the cornea.

40
Q

What is the function of Descemet’s Layer? What happens to it over time?

A

To provide protection to the endothelium. It is very strong and flexible. Over time it becomes thicker and less flexible.

41
Q

What is unique about the Descemet’s Layer?

A

It only covers the central 60-65% of the cornea and is produced by the endothelium.

42
Q

What is another name for the endothelium? Why?

How is this energized?

A

The endothelial pump. It is responsible for maintaining a corneal deturgesence. (a state of 78% semi-dehydration).

Energized by the glycogen found in the aqueous humour

43
Q

Describe the appearance of the endothelium.

A

A single layer of hexagonally shaped cells in a mosaic pattern.

44
Q

What happens if the endothelium becomes damaged?

A

It can heal, but function cannot regenerate. If too many cells are damaged/destroyed corneal edema or blindness may occur.

45
Q

What is the main function of the endothelium?

A

To provide transparency by pumping water out of the cornea and back into the aqueous humour.

46
Q

What causes morphology changes in the endothelium? What are they called? Do they impact the function of the pump?

A

Occur due to prolonged hypoxia, age or disease.

They are called Pleomorphism and Polymegathism. These do not affect the endothelial pump.

47
Q

Describe the Dua Layer

A

It is a “layer” of the cornea that is found between the stroma and Descemet’s layer. It is 15 microns thick. It is very strong and flexible. It is a hydrophobic layer and functions to prevent water from moving anteriorly in the cornea.

48
Q

What are the 3 layers of the pre-corneal tear film?

A
  1. Lipid layer
  2. Aqueous layer
  3. Mucous Layer
49
Q

What is the main function of the Lipid layer of the tear film?

A

To prevent quick evaporation of tears and to help lubricate the eye with each blink.

  • It also stabilizes the tear film
  • It also acts as a barrier against microbial contamination
50
Q

How is the Lipid layer produced?

A

Produced by the meibomian glands at the lid margin

51
Q

What would happen if your tear film did not have a lipid layer?

A

Your tears would evaporate 20x faster

52
Q

What is the average blink rate?

A

12,000/day

53
Q

Describe the Aqueous layer of the tear film

A

The middle layer of the tear film that consists of salt, protein and 98% water. It makes up 98% of the tear film.

54
Q

What is the function of the aqueous layer of the tear film?

A

Provides protein, nutrients and oxygen to the cornea. It also washes away debris and helps hydrate the eye.

55
Q

What is the mechanisms that the aqueous layer uses to fight bacteria?

A

Lysozyme

56
Q

How is the aqueous layer produced?

A

Lacrimal accessory glands (located near the fornix OU)`

57
Q

What would happen if your tear film did not have an aqueous layer?

A

You would not have enough tears and your eye would not be properly nourished/oxygenated

58
Q

What is the main function of the mucous layer of the tear film?

A

To convert the hydrophobic surface of the cornea to become hydrophillic. It fills the space betweenn the microvilli and sticks to them to help create a layer of mucous on top.
- Also help the tears defy gravity, helps the tears fall down the eye more slowly

59
Q

Where is the mucous layer of the tear film produced?

A

By the goblet cells found in the conjunctiva

60
Q

What would happen if your tear film did not have a mucous layer?

A

Extreme dry eye because the cornea would be hydrophobic

61
Q

What are the main causes of dry eye?

A

Environmental, medications, systemic disease (Diabetes and Sjogrens)
DIET - alcohol, salt, preservatives, caffeine

62
Q

What are the two classifications of dry eye? What are their causes?

A
  1. Aqueous deficiente - typically disease or lacrimal deficiency
  2. Evaporative loss - intrinsic or extrinsic (Meibomian Gland Deficiency MDG)
63
Q

What are some “treatments” for dry eye?

A

Add Omega 3, vitamin A and water to your diet

64
Q

Define Total Astigmatism

A

The combined astigmatism of all the refractive surfaces in the optical system: tear film, cornea, lens, aqueous and vitreous humour (The amount of cylinder power prescribed by the Doctor)

65
Q

Define corneal Astigmatism

A

Astigmatism from the corneal surface

66
Q

DefineResidual Astigmatisms

A

The uncorrected astigmatism after the glasses or CLs have been dispensed. Can be detected by using an astigmatic clock

67
Q

Define With the Rule Astigmatism. Give an example of how it is written

A

A cornea that has its steepest curves at 90 degrees +/- 30 degrees

(The higher the K reading, the steeper the lens)
43.00/46.00 x 090 therefore corneal cyl = -3.00 x180

68
Q

Define Against the Rule Astigmatism. Give an example of how it is written

A

A cornea that has its steepest curves at 180 +/- 30 degrees

45.00/43.50 x 090 therefore corneal cyl = -1.50 x 090

69
Q

Define Oblique Astigmatism. Give an example of how it is written

A

Steepest curve at 45 or 135 +/- 15 degrees

39.00/40.00 x 045 therefore corneal cyl is -1.00 x 135

70
Q

What is HVID?

A

Horizontal Visible Iris Diameter

71
Q

What is the significance of HVID?

A

It helps determine the recommended diameter of an RGP

72
Q

What is the average HVID?

A

11 mm

73
Q

What is the Average pupil size? Under what conditions do you need to measure this?

A

4-5 mm under normal lighting conditions

74
Q

What is the significance of measuring pupils size?

A

Helps determine the optic zone diameter of an RGP

75
Q

What is the Interpalpebral aperture?

A

The Distance between lid margin to lid margin at the deepest depth when the patient is looking naturally straight ahead.

76
Q

What is the significance of Interpalpebral Aperature?

A

Helps determine what size of lens would work for the patient

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