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Ocular Anatomy > Lecture 5: Iris > Flashcards

Lecture 5: Iris Flashcards

1
Q

is the iris the anterior or posterior extension of the uvea?

A

Anterior extension of the uvea

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2
Q

what does the iris separate?

A

Separates the anterior and posterior chambers

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3
Q

what does the iris regulate?

A

Regulates how much light enters the retina

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4
Q

what type of humor does the iris permit to flow in posterior/anterior chambers?

A

Permits flow of aqueous humor between posterior/anterior chambers

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5
Q

T/F: Clinical evaluation of the iris is not very important especially in diabetes and glaucoma patients

A

F

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6
Q

T/F: iris imprint is unique to each person and used as a Biometric ID

A

T

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7
Q

where is the pupil slightly displaced?

A

Slightly displaced inferonasal

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8
Q

what is the pupillary aperture (pupil) range?

A

Ranges from1-9mm

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9
Q

the iris divides the space between where and where?

A

Iris divide the space between cornea and lens into the anterior and posterior chamber

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10
Q

Pupil diameter: normal

A

Normal 3-4 mm (normal room
illumination)

• Can vary 1-9 mm under various lighting

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11
Q

what is the average width of the iris?

A

12 mm

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12
Q

where is the iris the thickest?

A

the “collarette” region

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13
Q

where is the iris the thinnest?

A

thinnest at the base (0.5 mm)

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14
Q

Pupillary zone: encircle the pupil

A

encircles the pupil

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15
Q

Ciliary zone:

A

extends from collarette to iris root

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16
Q

what is Crypts of Fuchs?

A

Large defects in the anterior border layer

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17
Q

Clinical relevance: iridodialysis

A

Blunt trauma to head or eye can cause iris root to tear away

This usually results from fist, sport injury (tennis or squash ball injury).

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18
Q

Iris Root:

A

Thinnest part of the iris
(0.5 mm)

Inserts into the anterior face of the ciliary body

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19
Q

where does the pupillary margin rest?

A

on the lens

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20
Q

Because the pupillary margin rests on the lens, it is displaced where?

A

slightly anterior plane of the iris root

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21
Q

what are the 4 layers of the iris?

A
  1. Anterior border layer
  2. Iris stroma & sphincter (not visible)

]3. Anterior epithelium & dilator

  1. Posterior pigment epithelium
22
Q

the anterior border layer of the iris is composed of what?

A

Composed of fibroblast and pigmented melanocytes

23
Q

The number of melanin granules within melanocytes and area they occupy contributes to what?

A

iris color

24
Q

T/F: Brown –> Grey –> Blue –>Green as pigment density decreases

A

T

25
Q

the second layer of the iris (Iris stroma and sphincter muscle) is composed of what?

A

Pigmented (melanocytes) and non-pigmented cells (fibroblast, lymphocytes, macrophages)

26
Q

The sphincter muscle lies within what?

A

The sphincter muscle lies within the stroma, 1mm wide, encircling the pupil

27
Q

The third layer of the iris (anterior epithelium and dilator muscle) is composed of what type of cells?

A

Composed of myoepitheilial cells

28
Q

how many layers of dilater muscles are within the third layer of the iris? and how are they arranged?

A

3-5 layers of dilator muscle arranged radially

29
Q

where do the dilator muscle layers extend from and to where?

A

extends from iris root to midpoint of iris sphincter muscle

30
Q

how many layers make up the fourth layer (posterior epithelium) of the iris?

A

Single layer of heavily pigmented columnar cells

31
Q

what type of muscle is the iris sphincter?

A

smooth

32
Q

how is the iris sphincter innervated?

A

innervated by postganglionic parasympathetics carried in the short posterior ciliary nerves.

The preganglionic fibers are carried by the oculomotor nerve (CN III)

33
Q

Aniridia:

A

partial or complete absence of iris.

High association with glaucoma (75%)

34
Q

Iris synechia:

A

abnormal attachment of iris surface and another structure (lens or corneal endothelium or trabecular meshwork, TM)

35
Q

Pigment dispersion syndrome:

A

pigment granules shed from posterior iris and dispersed into anterior chamber.

If deposit in TM may affect aqueous outflow (pigmentary glaucoma).

36
Q

Heterochromia:

A

two iris are of different color in the same person, congenital (disruption of sympathetic innervation) or sign of uveal inflammation.

37
Q

how is pseudoexfoliation syndrome characterized?

A

Characterized by ring-like deposits on the anterior lens located at the pupillary margin.

38
Q

T/F: (pseudoexfoliation syndrome) A flaky material sticks to the outer layer of the lens of the eye.

A

A flaky material peels off the outer layer of the lens of the eye.

39
Q

does pseudoexfoliation syndrome usually present unilaterally or bilaterally?

A

often presents unilaterally, but may eventually affect the other eye.

40
Q

when is the onset of pseudoexfoliation syndrome?

A

Onset sixth decade

41
Q

pseudoexfoliation syndrome puts a patient at higher risk for what?

A

Higher risk of secondary glaucoma

42
Q

Debris can accumulate where? Resulting in an increase in IOP for 50 % of affected eyes.

A

Debris can accumulate in the trabecular meshwork resulting in an increase in IOP for 50 % of affected eyes.

43
Q

what causes a Krukenberg’s spindle on the corneal endothelium?

A

Posterior iris rubbing against zonules due to high concavity of peripheral iris

44
Q

A Krukenberg’s spindle puts a patient at higher risk for what?

A

Higher risk of secondary glaucoma

45
Q

if a patient has glaucoma, what has to be removed to facilitate the movement of aqueous from posterior to the anterior chamber?

A

the full thickness tissue of iris is removed

46
Q

Iridectomy:

A

surgically a wedge shape full thickness iris tissue is removed

47
Q

Iridotomy:

A

opening is made using laser without excising the tissue and muscle

48
Q

where does the iris receive blood supply?

A

long posterior ciliary artery

anterior ciliary artery

49
Q

what are three structures that contribute to the iris blood supply? (not aa.)

A

major arterial circle
minor arterial circle
radial blood vessels

50
Q

Rubeosis Iridis:

A

neovascularization of the iris or AC angle

51
Q

how is Rubeosis Iridis seen?

A

Seen with ocular ischemia, proliferative diabetic retinopathy.

52
Q

what can Rubeosis Iridis cause?

A

May cause secondary-angle closure glaucoma due to occlusion of the trabecular meshwork.

Ocular Anatomy (15 decks)

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