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Ophthalmology > Unit 2 - The Lens and Vitreus > Flashcards

Unit 2 - The Lens and Vitreus Flashcards

1
Q

In utero, what does the pupillary membrane develop from?

A

The iris

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2
Q

In utero, what does the tunica vasculosa lentis develop from?

A

The hyaloid artery

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3
Q

T/F: Vasculature from in utero development of the eye atrophies by the time of the eyelid opening.

A

True

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4
Q

T/F: Lens growth stops at the end of puberty.

A

False - it continues throughout life

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5
Q

Explain how the lens grows throughout life.

A

The lens epithelial cells form the cortex and new fibers force the older ones to the center

The nucleus hardens with age resulting in nuclear sclerosis

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6
Q

What are the components of the lens?

A

Lens capsule

Anterior epithelium

Lens fibers

Equator

Nucleus

Cortex

Y sutures

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7
Q

How big is the lens capsule of the anterior lens in the dog?

A

50-70 microns

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8
Q

How big is the lens capsule of the posterior lens in the dog?

A

2-4 microns

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9
Q

What are the Y sutures?

A

The location where the lens fibers come together - as long as there is no cataract associated with them, they are not a problem

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10
Q

How are the Y sutures oriented on the anterior lens? Posterior lens?

A

Anterior - upright Y

Posterior - upside down Y

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11
Q

What is the lens suspended by?

A

Zonules from the ciliary body

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12
Q

The lens is _________ and (avascular/vascular). It recieves its nutrition from ________ ______. Its primary function is _______ of light to focus on the retina.

A

Transparent

Avascular

aqueous humor

refraction

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13
Q

What are the categories of abnormalities that the lens can have>

A

Congenital defects

Nuclear sclerosis

Cataract

Lens luxation/subluxation

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14
Q

What congenital defects are associated with lens abnormalities?

A

Lens coloboma

Microphakia

Spherophakia

Aphakia

Cataract

Persistent fetal vasculature

Persistent pupillary membrane

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15
Q

What is lens coloboma?

A

Defect/notching of the lens equator

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16
Q

What is microphakia?

A

small lens

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17
Q

What is spherophakia?

A

Spherical lens

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18
Q

What is aphakia?

A

Absence of a lens

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19
Q

What persistent fetal vasculature can there be in the lens?

A

Persistent hyaloid artery

Persistent tunica vasculosa lentis

Persistent hyperplastic primary vitreous

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20
Q

T/F: Nuclear sclerosis is a normal aging process.

A

True

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21
Q

What does nuclear sclerosis look like?

A

Grayish blue haze of the lens - can be seen in dogs that are greate than 6 years of age

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22
Q

T/F: Nuclear sclerosis has minimal effect on vision.

A

True

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23
Q

What is it important to differentiate nuclear sclerosis from?

A

Cataracts

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24
Q

What is a cataract?

A

An opacity in the lens or lens capsule

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25
Q

What are cataracts classified based on?

A

Etiology

Age of onset

Location in the lens

Stage of development

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26
Q

A patient with only a cataract should have a normal ____.

A

PLR

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27
Q

Nuclear sclerosis or cataract?

A

Cataract

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28
Q

Nuclear sclerosis or cataract OU?

A

Nuclear sclerosis

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29
Q

Nuclear sclerosis or cataract OU?

A

Nuclear sclerosis

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30
Q

Nuclear sclerosis or cataract?

A

Nuclear sclerosis

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31
Q

Nuclear sclerosis or cataract?

A

Cataract

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32
Q

Nuclear sclerosis or cataract?

A

Cataract

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33
Q

Nuclear sclerosis or cataract?

A

Nuclear sclerosis

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34
Q

Nuclear sclerosis or cataract?

A

Cataract

35
Q

Nuclear sclerosis or cataract OU?

A

Cataract

36
Q

Nuclear sclerosis or cataract OS?

A

Cataract

37
Q

Nuclear sclerosis or cataract OD?

A

Cataract

38
Q

What are the causes of cataracts?

A

Hereditary

Metabolic

Secondary to uveitis

Traumatic

Radiation

Toxic

39
Q

What is the most common cataract cause in dogs?

A

Hereditary

40
Q

What are the metabolic causes of cataracts?

A

Diabetees mellitus (dogs)

Galactosemia

Milk replacer

Hypocalcemia

41
Q

What species commonly get cataracts secondary to uveitis?

A

Cats and horses

42
Q

What traumatic situations can result in cataract formation?

A

Blunt or penetrating trauma

Electric cord shock or lightening strike

43
Q

What toxins can result in cataract formation?

A

Ketoconazole

Retinal degeneration (due to toxin)

44
Q

Where can a cataract be located?

A

Capsular

Subcapsular

Nuclear

Perinuclear/lamellar

Cortical

Equatorial

Axial

Anterior/posterior

45
Q

How do you differentiate the location of a cataract?

A

Dilate the pupil and differentiate by direct exam and retroillumination

46
Q

What are the four stages of a cataract?

A

Incipient. iimmature, mature, hypermature

47
Q

What is an incipient cataract?

A

Punctate opacity, <15% of the lens

48
Q

What is an immature cataract?

A

15% to 99% opacification

Some tapetal reflection remains +/- vision

49
Q

What is a mature cataract?

A

Complete (100%) opacification

No tapetal reflection visible and blind

50
Q

What is a hypermature cataract?

A

Resorption of cataractous lens

Highly variable appearance: sparkling, wrinkled capsule

51
Q

What is the pathogenesis of Diabetic cataracts?

A

Normally, glucose is metabolized by anaerobic glycolysis.

High blood glucose increases lens glucose and overwhelms hexokinase enzyme.

The excess glucose is metabolized by aldose reductase system to sorbitol.

Sorbitol accumulates within the lens and causes an osmotic effect.

Fluid is drawn into the lens and causes architectural changes in the lens fibers

52
Q

What species are especially susceptible to diabetic cataracts?

A

Mice, dogs, and rats

53
Q

What is phacolytic uveitis?

A

The leakage of some lens proteins through an intact lens capsule resulting in mild/moderate lens-induced uveitis

54
Q

Phacolytic uveitis is common in what cataract scenarios?

A

Diabetic, hypermature, and some juvenile cataracts

55
Q

What is phacoclastic uveitis?

A

The rupture of the lens capsule due to trama or rapidly progressing cataracts. It is associated with severe inflammation and requirse medications and maybe surgery ASAP.

56
Q

What should you monitor for in patients with phacoclastic uveitis?

A

Secondary glaucoma

57
Q

What is the general medical therapy recommended for cataracts?

A

Treat/prevent lens-induced uveitis

Monitor eye status and intraocular pressure

Prevent diabetic cataracts

58
Q

What can be given to treat/prevent lens-induced uveitis (general)?

A

Topical NSAID BID

Topical steroid SID-QID

Systemic anti-inflammatories

59
Q

What is the preferred topical NSAID for the treatment/prevention of lens-induced uveitis? Other options?

A

Preferred: Diclofenac

Other options: Flurbiprofen, ketorolac

60
Q

What is the preferred topical steroid for the treatment/prevention of lens-induced uveitis? Other options?

A

Preferred: Prednisolone acetate 1%

Other options: Dexamethasone 0.1% (Neo-Poly-Dex)

61
Q

When should you refer for cataract surgery?

A

Refer early - when cataracts are first noted

The ideal time for surgery is when cataracts are immature and there is no lens-induced uveitis

62
Q

What are the components to a cataract surgery work-up?

A

Complete ophthalmic examination

Physical examination

Gonioscopy

Electroretinogram

Ocular ultrasound

63
Q

What does a gonioscopy evaluate?

A

Iridocorneal angle

64
Q

What does an electroretinogram evaluate?

A

Electrical activity of the retina

65
Q

What does the ocular ultrasound evaluate?

A

The posterior segment

66
Q

What are the post operative complications of cataract surgery?

A

Uveitis, glaucoma, retinal detachment, and endophthalmitis

67
Q
A

C

68
Q

What is the cause of primary lens luxation?

A

Hereditary - Terrier breeds are predisposed

69
Q

What are the secondary causes of lens luxation?

A

Glaucoma, uveitis, trauma, introcular tumors, cataracts`

70
Q

What is lens subluxation?

A

Partial detachment of lens zonules

71
Q

What possible clinical findings are associated with lens instability?

A

Aphakic crescent

Iridodensis

Phacodensis

Vitreous coming into the anterior chamber

72
Q

What is lens luxation?

A

Complete detachment of the lens zonlues

73
Q

What is anterior lens luxation? Posterior?

A

Anterior - lens luxation anterior to the iris (behind the cornea)

Posterior - lens is posterior to the iris (deep anterior chamber)

74
Q

When is an anterior lens luxation emergent?

A

If the lens luxation is recent and the dog/cat is visual

75
Q

How do you treat emergent anterior lens luxations?

A

Intracapsular lens extraction +/- sulcus IOL fixation

Trans-corneal reduction

76
Q

What condition do you need to make sure to treat if there has been an anterior lens luxation? How is it treated?

A

Secondary glaucoma - mannitol IV, topical/oral carbonic anhydrase inhibitors, DO NOT GIVE MIOTICS

77
Q

T/F: Secondary lens luxation is emergent.

A

False - it is not

78
Q

What is the treatment for primary lens subluxation?

A

Proactive surgical lens removal OR

Medical therapy BID to keep pupil miotic and lens back (prostaglandin analogs and parasympathomimmetics)

79
Q

How is posterior lens luxation managed?

A

No management is necessary if the lens is in a fixed position

Miotic therapy is warranted if possible to lens shift

80
Q

Vitreous is ____ of the globe volume. Its appearance is _____ and ____-like. It is made up of 99% ____ and 1% ________/______.

A

>2/3

Transparent

Jelly-like

Water

Collagen/hyaluronic acid

81
Q

What is the funciton of the vitreous?

A

Supports lens anteriorly

Maintains globe shape

Transmits light to the retina

Supports retina posteriorly

82
Q

What vitreous abnormalities can occur?

A

Vitreal cells

Vitreal hemorrhage

Vitreal degeneration

Asteroid hyalosis

83
Q

What is asteroid hyalosis?

A

Small white particles that are calcium or phospholibids that create a snow globe effect in the eye

Ophthalmology (13 decks)

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