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CLIN SCI 4 EX2 > Lens/Vitreous > Flashcards

Lens/Vitreous Flashcards

1
Q

What is the function of the lens capsule

A

barrier function

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2
Q

What is the function of the lens epithelium

A

multiply through life
becomes lens fiber cells

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3
Q

lens fiber cells

A

transparent due to orderly arrangement
protein antigenic

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4
Q

What cells of the lens have antigenic proteins

A

lens fiber cells

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5
Q

Why does the lens fiber cells have antigenic proteins

A

embryonic origin

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6
Q

What are zonule fibers

A

fibers attached to the lens equator
attach to the cilia body
hold the lens in place

if these are not there then we have a lens luxation

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7
Q

What maintains lens transparency

A

-absense of blood vessels
-lack of pigmentation
-orderly arrangement lens fiber cells

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8
Q

Nutrition of the lens comes from the

A

aqueous humor

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9
Q

What is the function of the lens

A

-Refraction of light
-Accommodation

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10
Q

age related changes to the lens

A

nuclear sclerosis

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11
Q

lens opacity

A

cataracts

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12
Q

lens displaced from normal location

A

lens luxation

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13
Q

What are the secondary changes of lens disease

A

-corneal changes
-anterior uveitis
-glaucoma
-retinal detachment

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14
Q

normal aging change
constant lens fiber production
new fibers outside on cortex, old pushed into center onto the nucleus thus pushing fluid out (dehydration)
7+ years old in dogs

A

nuclear sclerosis

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15
Q

What are the signs of nuclear sclerosis

A

-Circle within pupil
-Can see tapetum with transillumination
-Rainbow effect that happens when lights shine through nuclear sclerosis

might need to dilate eye to see better

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16
Q

What causes nuclear sclerosis

A

aging changes (7+)

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17
Q

T/F: nuclear sclerosis happens in all species

A

true

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18
Q

How do you treat nuclear sclerosis

A

not indicated

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19
Q

significant cause of blindness in dogs
opacity of lens
due to disruption of orderly arragement of lens fiber cells

A

Cataracts

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20
Q

Cataract with <15% coverage of lens

A

Incipient

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21
Q

Cataract with 15-99% of coverage

A

Immature (incomplete)

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22
Q

Cataract with complete coverage

A

Mature (complete)

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23
Q

Cataract where the body is trying to reabsorb the cataract

A

Hypermature (reabsorbing)

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24
Q

Characteristics of incipient cataract

A

<15% of lens
small dark spot on retroillumination
minimal impact on vision
no treatment needed

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25
Q

Characteristics of immature cataracts

A

> 15-99% of lens
largest stage where vision is impacts
Still tapetum reflection is present
Ideal stage for cataract sx
refer
Start on topical anti-inflammatory meds

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26
Q

What is the ideal stage for cataract sx

A

Immature

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27
Q

What should you do for immature cataracts

A

Start on topical anti-inflammatory meds (Diclofenac)
Refer- ideal stage for cataract sx

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28
Q

Characteristics of mature cataracts

A

complete lens opacity
complete vision loss
no tapetum reflection
good time for sx (refer)
should always be on topical anti-inflammatory meds (lifelong)

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29
Q

Characteristics of hypermature cataracts

A

complete unless reabsorbing
sparkly
lens capsule wrinking
lens induced uveitis
poorer sx success
should be on topical inflammatory meds

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30
Q

What are the causes of cataracts in dogs

A

1) Inherited: many breeds (Boston Terriers) , non-symmetrical, variable progression

2) Diabetes mellitus: symmetrical, rapid progression, bilateral, refer early

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31
Q

Inherited cataracts or non-symmetrical or symmetrical

A

non-symmetrical - one eye first

but uni or bilateral

and variable progression

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32
Q

Diabetes mellitus caused cataracts

A

-Symmetrical, very rapid progression
-dogs only (increased aldose reductase in their aqueous)
-bilateral
-refer early

33
Q

Why do only dogs develop cataracts with diabetes mellitus

A

(increased aldose reductase in their aqueous)

34
Q

What is the pathogenesis of diabetes mellitus causing glaucoma in dogs

A

1) hyperglycemia- glucose in aqueous humor
2) glucose diffuses across lens capsule
3) Hexokinase pathway to metabolized glucose in lens supersaturated
4) Alternative pathway with aldose reductase produced sorbitol
5) Sorbitol too big to escape lens
6) Osmotic water absorbing occurs in lens leading to cataract

35
Q

What are the signs of lens induced uveitis

A

-Episcleral injection
-Diffuse corneal edema
-Flare (proteins in anterior chamber)
-Miotic pupil
-Dyscoria
-Hypermature cataract

36
Q

you should start all hereditary and diabetic cataract cases on

A

anti-inflammatory medication if fluorescein negative

37
Q

What causes secondary cataract

A

anterior uveitis

38
Q

What is the most common cause of cataracts in horses and cats *

A

secondary cataract from anterior uveitis

39
Q

How might cataracts develop from trauma

A

1) blunt trauma leading to anterior uveitis leading to cataract
2) penetration leading to lens fibers deranged leading to catract

40
Q

You should use topical anti-inflammatory for all cataracts that are ________________________

A

progressive/immature, mature and hypermature

41
Q

What is theo nly option for cataract tx

A

surgery (refer early)

42
Q

What is the surgery for cataracts

A

Phacoemulsification - used phaco-machine, ultrasound that will breakdown the cataract and aspirate it out of the lens capsule
removes the cortex of the lens

then places an intraocular lens (artificial) if possible
can only be done if lens capsule is intact

43
Q

you can only place an intraocular lens if

A

the cortex is intact

44
Q

pseudophakic

A

a patient that has intraocular lens (IOL) after phacoemulsification sx

45
Q

aphakia

A

patient that is missing their lens after phacoemulsifcation sx for cataracts
artifical lens was unable to be placd because cortex was not intact

46
Q

What holds the lens in place and is broken down in lens luxation

A

zonule fibers

47
Q

partial breakdown of the zonule fibers

A

lens subluxation

48
Q

complete breakdown of the zonule fibers

A

lens luxation

49
Q

What breed commonly gets lens luxations ***

A

Terriers - be careful when terriers shake toys

50
Q

causes of lens luxation

A

1) Primary- inherited: terriers, chihuahuas, chinese crested, border colies

2) Secondary - uveitis, glaucoma, trauma

51
Q

Clinical signs of lens subluxation

A

-Shallow, deep or unequal anterior chambers (AC)
-Anisocoria
-Aphakic crescent * see equator of lens
-Vitreous presentation in AC
-Iridodenesis (iris is moving)
-Phacodensis (lens is moving)
-Ocular hypertension (glaucoma)
-Anterior or posterior= lens in front of iris or behind it

52
Q

iris that is moving, seen in lens luxation

A

iridodenesis

53
Q

lens is moving
seen in lens luxation

A

phacodenesis

54
Q

lens that is infront of the iris

A

anterior lens luxation

55
Q

lens is behind the iris

A

posterior lens luxation

56
Q

What are the clinical signs of anterior lens luxation

A

blepharospasm (painful)
Epiphora
lens in anterior chamber
indistinct pupillary border
central corneal edema
anterior uveitis
glaucoma

57
Q

How do you diagnose anterior lens luxation

A

1) narrow to absent anterior chamber - slit lamp exam
2) Increased intraocular pressure (stopping angle)
3) Direct PLR often absent
4) Indirect PLR is very important *if intact then you still have vision in the other affected eye

58
Q

With anterior lens luxation, what you tell you you have intact vision

A

indirect PLR

59
Q

How do you treat anterior lens luxation

A

Surgery is required to save vision
-170 degree perilimbal clear corneal incision
-Lens and lens capsule is removed resulting in aphakia (no lens) hyperopia after surgery (farsighted)

Otherwise we need to remove the lens

60
Q

What happens after lens and lens capsule is removed

A

hyperopia after surgery (farsighted)

61
Q

How do you fix the hyperopia after lens removal surgery

A

Doggles- fixes post surgery vision deficits

62
Q

What are the clinical signs of posterior lens luxation

A

-apparent aphakic crescent *
-DEEP anterior chamber
-Vitreous strands through pupil
-Lens on floor of vitreous
-Eye usually comfortbale

63
Q

How do you treat posterior lens luxation

A

Monitor IOP
Control uveitis
Use miotics (Demecarium Bromide, Latanoprost)
-monitor for uveitis +/- steroid

64
Q

What Miotic medications are used for posterior luxation cases

A

1) Latanoprost- prostaglandin analogue *
2) Demecarium Bromide - cholinesterase inhibitor

65
Q

prostaglandin analgoue that is a miotic, used for posterior lens luxation

A

Latanoprost

66
Q

Cholesterase inhibitor that is a mitiotic, used for posterior lens luxation

A

Demecarium Bromide

67
Q

How can trauma to lens occur

A

secondary to fights or foreigh body penetration

68
Q

What are signs of trauma to lens

A

-Blepharospasm
-Epiphora
Episceral injection
Fibrin in AC ***
Corneal opacity
Lens opacity
Miotic pupil

69
Q

How do you treat trauma to lens in dog

A

Topical steroids if no ulcer
Topical NSAID if no ulcer, IOP normal
Oral pred or NSAID
Ecollar
cage rest

referral if possible

70
Q

highly malignant neoplasia that is unique to domestic cats
secondary to lens trauma

A

Feline traumatic sarcoma

71
Q

What are signs of feline traumatic sarcoma

A

middle age-older
history of penetrating trauma year prior
Phthisis bulba (small eye due to chronic intraocular inflammation) or glaucoma

72
Q

What causes feline traumatic sarcoma

A

historically lens trauma leading to malignant metaplasia

73
Q

How do you treat feline traumatic sarcoma

A

remove the eye immediately

74
Q

What are the 3 stages of development of the vitreous

A

1) Primary: hyaloid system
2) Secondary: definitive vitreous
3) Tertiary: lens zonules

75% volume of eye

75
Q

aging change in some animals where small white deposits of calcium and/or phosphorus
looks like eye is a snow globe

A

Asteroid hyalosis

76
Q

persistence of hyaloid artery leading to vascularization of the lens +/- fibrosis
embryonic remnant
can rupture with trauma

A

Persistent hyperplastic primary vitreous (PHPV)

77
Q

Two diseases seen with the vitreous

A

1) Asteroid hyalosis
2) Persistent hyperplastic primary vitreous (PHPV)

78
Q
A

CLIN SCI 4 EX2 (5 decks)

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