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Ocular 6 > Sclera And Epi > Flashcards

Sclera And Epi Flashcards

1
Q

What kind of connective tissue is the sclera? What is is continuous with?

A
  • thick, dense connective tissue

- continuous with the corneal stroma at the limbus

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2
Q

Describe the collagen fibrils in the sclera and how they are arranged

A
  • diameter carries from 25-230nm (not uniform)

- arranged in irregular bundles that branch and interlace

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3
Q

Name some differences in the cornea and the sclera collagen ****

A
  • not uniform diameter in sclera (thin and narrow fibrils on the outside and thicker ones on the inside)
  • not uniform lamellae orientation in sclera
  • cornea is clear for healthy eyes and sclera is opaque in healthy eyes
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4
Q

Describe the lamella orientation in the sclera

A
  • lamella in outer regions run parallel to the surface with interweaving between them
  • lamella in inner regions run in all directions
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5
Q

What contributes to the strength and flexibility of the sclera?

A
  • random arrangement and amount of interweaving between lamella
  • interweaving gives flexibility despite absence of elastic fibers
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6
Q

Are there elastic fibers in the sclera?

A
  • very very low incidence

- sometimes within bundles

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7
Q

Are fibroblasts in sclera?

A

-yea, but there are a lot less than cornea

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8
Q

What is the difference between the stromal ground substance of the cornea and the sclera?

A

Sclera has fewer GAGs than cornea

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9
Q

Does the sclera or the cornea have more moisture?

A

Cornea

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10
Q

What is the scleral spur?

A
  • region or CIRCULARLY oriented collagen bundles that extend from the inner aspect of the sclera
  • ring of collagen
  • forms angle with Iris and cornea
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11
Q

What is the scleral spurs posterior edge in contact with? Anterior?

A
  • posterior edge blends with oblique scleral fibers

- anterior edge collagen of the spur becomes continuous with trabecular mesh work

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12
Q

What are the factors that determine the opacity? Why is the sclera opaque?

A
  1. Number of GAGs-sclera has few
  2. Amount of water-sclera is dehydrated more than cornea (68%)
  3. Size and distribution of fibers-more variety means more scatter means more opaque
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13
Q

What could cause a blue sclera?

A
  • babies: uveal layer shows through

- connective tissue disease- scleral thinning

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14
Q

What would cause a yellow sclera?

A
  • fat deposits with age

- liver disease from build up of metabolic waste

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15
Q

What are the two MAJOR foramina/canals?

A
  1. Anterior scleral foramen-area occupied by the cornea

2. Posterior scleral foramen-optic nerve passes through

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16
Q

What is the weakest spot of the sclera?

A
  • where the optic nerve leaves the eye

- Lamina cribrosa (mesh work of connective tissue)

17
Q

What is the weakest area of the outer connective tissue tunic?

A

Lamina cribrosa

18
Q

What is the area that is most affected by increased pressure?

A

Lamina cribrosa

19
Q

What is cupping out/ectasia of the center area of the optic nerve causes by? What is it a sign of?

A
  • elevated IOP
  • glaucoma
  • can also be attributed to loss of nerve fiber tissue of the optic nerve head
20
Q

How many posterior scleral canals are there? What are they for?

A
  • 2 for long ciliary nerves
  • 2 for long ciliary arteries
  • 8-12 for short ciliary arteries
  • 8-12 for short ciliary nerves
21
Q

How many middle scleral canals are there? What are they for?

A

-4 or more for vortex veins

22
Q

How many anterior scleral canals are there? What are they for?

A

-7 for the anterior ciliary arteries

23
Q

Why is the sclera considered avascular?

A

-it contains a small number of vessels that pass through to ge to other tissues, but it does not contain any capillary beds

24
Q

How does the sclera get its nourishment>

A

-small branches from the episclera and choroidal vessels and branches of the long ciliary arteries

25
Q

What innervates the sclera?

A

-posterior by short ciliary nerves, the rest by long ciliary nerves

26
Q

What causes scleral thinning? What does it lead to?

A
  • progression of myopia and axial elongation causes thinning ar posterior pole especially due to the reduced collagen diameter and size
  • can lead to scleral ectasia where tissue can budge outward
27
Q

Does the choroid thin and spread with scleral thinning?

A

Nah

28
Q

What is the episclera?

A
  • loose, vascularized connective tissue layer outside of the sclera
  • large episclera vessels are visible through conj
29
Q

Where is the capillary network in the episclera? What forms it?

A
  • it is anterior to the rectus muscle insertions and it surrounds the peripheral cornea
  • branches of anterior ciliary arteries
30
Q

What happens to the thickness of the episclera as you move towards the back of the eye?

A

It thins

31
Q

What is episclera joined to tenon’s capsule by?

A

Strands of connective tissue

32
Q

How would you identify episcleritis?

A
  • usually one sided (not entire eye)

- nodal or diffuse

Ocular 6 (6 decks)

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