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Semester 2 Ocular > Cornea Scott B6 > Flashcards

Cornea Scott B6 Flashcards

1
Q

What gives sensory to the cornea?

A

V1 ophthalmic

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2
Q

The cornea is part of the _______ tunic.

A

fibrous

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3
Q

What is unequal curvature of the cornea?

A

astigmatism

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4
Q

What is flat and steep meridians are 90 degrees apart?

A

Regular astig

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5
Q

What is steeper in vertical meridian?

A

With the rule astig

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6
Q

What is steeper curvature in the horizontal meridian?

A

Against the rule astigmatism

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7
Q

what is steeper curvature in oblique axis?

A

Oblique astigmatism

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8
Q

What is where the steepest and flattest meridians are not 90 degrees apart?

A

Irregular astig

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9
Q

What is unequal curvature of the lens?

A

Lenticular astig

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10
Q

Thicker cornea = ________, false IOP measurement

A

higher

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11
Q

Thinner corneas = ______, false IOP measurement

A

lower

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12
Q

__________ measures central corneal thickness using ultrasound.

A

Pachymeter

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13
Q

When might you want to use a Pachymeter?

A

Glaucoma, refractive surgery

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14
Q

Fascia bulbi that strongly adheres to episclera and conjunctiva.

A

Bulbar limbus

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15
Q

This is the juncture of cornea and sclera, 1-2 mm wide.

A

Corneoscleral junction

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16
Q

conjunctiva extends 1 mm beyond corneoscleral limbus

A

Conjunctival limbus

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17
Q

Central 4 mm of eye

A

Optical zone

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18
Q

Anterior cornea has what liquid?

A

Aqueous humor

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19
Q

Lens has what kind of liquid?

A

Vitreous humor

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20
Q

Name some defining factors of corneal histology.

A

Predominantly extracellular material
Covered on each surface by sheet of cells
Anterior epithelium has 4 layers
Posterior epithelium is monolayer
Attached via basement membranes
Stroma is bulk of cornea (ordered collagen layers)

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21
Q

What are the 5 layers of the cornea?

A 
Tear Film
Anterior Epithelium
Bowman's layer
Stroma
Descemet's membrane
Endothelium
Aqueous Humor (anterior chamber)
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22
Q

Lipid or oily layer is secreted by ______________ glands in the palpebrae and caruncle

A

meibomian

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23
Q

Aqueous layer is secreted by the _______ gland.

A

lacrimal

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24
Q

Mucous layer is secreted by the ________ cells in the conjunctiva.

A

goblet

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25
Q

Oily layer prevents the _______ layer from evaporating , while the mucous layer decreases __________ and provides a smooth, wetable surface for the aqueous layer.

A

aqueous

surface tension

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26
Q

Name the 3 layers of the tear film from anterior to posterior.

A

Lipid layer
Aqueous layer
Mucous layer

27
Q

Corneal epithelium has ______________ cells and rests on a ______________.

A 
Stratified squamous (flat)
Basement membrane
28
Q

Corneal epithelium is composed of 5-7 cell layers what are they?

A

Apical (superficial layer)
-1-2 layers of flat squamous cells near surface
2-3 layers of wing cells
-Attach to each other by desmosomes and gap junctions
A single layer of columnar basal cells

29
Q

______________ are between lateral surfaces of apical cells.

A

Tight junctions

30
Q

Wing cells have ___ layers centrally and ___ layers peripherally.

A

2-3

4-5

31
Q

Wing cells posterior surface is ________ and anterior surface is ________.

A

concave

convex

32
Q

Basal cells are columnar and attached to the basal lamina by _______________.

A

hemidesmosomes

33
Q

Adjacent basal cells communicate via __________and are attached to each other via __________.

A

gap junctions

desmosomes

34
Q

Hemidesmosomes attach to what?

A

Basement membrane

35
Q

Replacement of the corneal epithelium only takes ____ days, but damage to basement membrane can take months to repair.

A

7 days

36
Q

Scratch on the cornea, usually painful but not severe. common in sports from scratch of fingernail

A

Corneal abrasion

37
Q

___________ is used to assess damage to corneal epithelium. Will not stain intact cells

A

Fluorescein dye

38
Q

This structure harbors stem cells around the corneoscleral limbus.

A

Palisades of Vogt

39
Q

Bowmans layer characteristics

A

Structural support
Randomly oriented collagen fibers
No keratocytes (acellular)
contains channels for passage of nerve fibers
cant be stripped away from stroma as continuous sheet like descemets can.
Does not regenerate
if damaged is replaced by thickened epithelium (aka epithelial facet)

40
Q

This has 90% of corneal thickness
Collagen, keratocytes, ground substance
GAGs pull aqueous humor into cornea
Keratocytes maintain ground substance and collagen interspersed between lamella

A

Stroma

41
Q

___________ are flat cells, that reside between stromal lamellae, and communicate via gap junctions.

A

Keratocytes

42
Q

Stromal lamella have what kind of spacing?

A

Ordered spacing… 1/2 wavelength of visible light

43
Q

This is a thinning of the stroma leading to bulging of the eye.

A

Keratoconus

44
Q

In advanced keratoconus the corneal protrusion may cause angulation of the lower lid on down gaze.

A

Munson’s sign

45
Q

If you see a asymmetry of arcus senilis you can suspect a blockage of _________.

A

Internal carotid

46
Q

Descemet’s membrane characteristics

A

Basement membrane of endothelium
Thickens throughout life
Regenerates if damaged

47
Q

In descemet’s membrane: anterior banded zone is laid down _______ birth. and posterior banded zone is laid _____ birth.

A

before

after

48
Q

Kayser-fleisher ring (copper deposits in descemet’s membrane)

A

Wilson’s disease

49
Q

Corneal endothelium characteristics:

A

Monolayer of cells composed of about 400,000 to 500,000 cells
Flat and hexagonal in shape
Apex faces anterior chamber
Cells pump aqueous humor out of cornea to maintain hydration
Joined by maccula occludens (leaky barrier)
Form gap junctions with adjacent cells
No pump action causes stromal edema

50
Q

As corneal endothelial cells become stressed they dropout. Remaining cells do what?

A

Remaining cells expand in size and shape to compensate. Less pump available to counterbalance leak of aqueous humor into corneal stroma.

51
Q

True/False: Cornea is avascular.

A

True, nutrients are derived from tear film and aqueous humor

52
Q

How many anterior ciliary arteries are there?

A

7 every rectus muscle has 2 except lateral rectus has 1

53
Q

If cornea is inflammed and you have “redness and ciliary flush”, what are the likely vessels that are involved?

A

Superficial plexus: Anterior conjunctival vessels

54
Q

If cornea is inflammed and you have “pinkness and ciliary flush”, what are the likely vessels that are involved?

A

Deep plexus: Iris and ciliary body

55
Q

The ________ is one of the most highly innervated structures in the body.

A

cornea

therefore it is 300 to 600 times more sensitive than skin

56
Q

Cornea receives sensory innervation via the _____________.

A

Long posterior ciliary nerves

57
Q

Long posterior ciliary nerves course in the ___________ space. They go and make two plexus, what are they?

A

suprachoroidal
Intraepithelial plexus
Subepithelial plexus

58
Q

Know briefly how PRK works.

A

Numbing drops
Smoothens surface of cornea
Laser reshapes corneal surface
Bandage like soft contact lens is put on the cornea until it heals.

59
Q

Lasik surgery is done how.

A

Flap cut around cornea and folded back
Anterior stroma ablated using laser
Flap is replaced

60
Q

What is the surgery called where incisions are cut around the stroma to flatten the cornea?

A

Radial Keratotomy

61
Q

What would be a couple ways of correcting irregular astigmatism?

A

Penetrating keratoplasty or corneal transplant

Scleral contact lenses

62
Q

How do scleral contact lenses work?

A

Liquid reservoir between cornea and contact neutralizes irregular surface of cornea

63
Q

What are a few pros and cons of Scleral contact lenses?

A

Pro: Comfort, Lens life 8-10 years, Short adaptation period, many diseases can be treated
Con: High initial cost, more chair time, poor fit can lead to complications (pinching artery), no overnight wear

Semester 2 Ocular (20 decks)

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