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VETM 425 Sys Path > Lecture 37: Special Senses (Eye) > Flashcards

Lecture 37: Special Senses (Eye) Flashcards

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1
Q

Describe the general embryologic origin of the eye? What is a developmental feature of carnivore eyes?

A

it is an outpouching of the brain

in carnivores it continues to develop 5-6 weeks after birth

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2
Q

List the 3 layers of the globe and their respective components

A

outer fibrous layer
- cornea
- sclera

middle vascular layer/uvea
- iris
- clilary body
- choroid
- +/- tapetum lucidum

inner nervous layer
- retina

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3
Q

What are the compartments of the eye and their contents

A

Aqueous humor in the anteroir and posterior chambers

Vitreous humor

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4
Q

What is the function of the eye

A

gathers light and transforms it to electrical signals
- it requires a clear cornea

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5
Q

What are the main adnexa structures of the eye

A

3rd eyelid/nictitating membrane

eyelid (distribute tears)

conjunctiva
- palpebral conjunctiva
- bulbar conjunctiva (covers the globe surface)

orbit (bone)

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6
Q

Describe the capacity for the eye to respond to injury

A

it has a limited number of responses

it has a limited capacity of healing and regeneration
- except the lens and cornea because when they regenerate their function will decrease

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7
Q

What are important considerations when submitting an eye for histo

A

use a 25G needle to inject formalin into vitreous humor
- inject next to the optic nerve

immerse the eye in formalin

need rapid fixation because it will autolyse quickly

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8
Q

Define uveitis

A

inflammation of the uvea

anterior uveitis = iris and ciliary body

panuveitis = all uvea is inflammed

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9
Q

Define the 2 types of opthalmitis

A

endopthalmitis = inflammation of uvea and all 3 chambers of the eye

panopthalmitis = inflammation of the uvea and all 3 chambers of the eye and sclera

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10
Q

Define hypopyon

A

neutrophil and fibrin accumulation ventrally in the anterior chamber

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11
Q

Define hyphema

A

blood in the anterior chamber of the eye

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12
Q

Define phthisis bulbi

A

end stage eye atrophy and collapse and fibrosis

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13
Q

What are the layers of the cornea

A
  1. tear film
  2. anterior epithelium (renewed weekly - no pigment or keratin)
  3. corneal stroma (dehydrated paralled collagen strands, low kieratin)
  4. descemets membrane
  5. endothelium (no regeneration)

no blood vessels or pigment

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14
Q

What are 3 types of damage that can affect the cornea

A

dessication

trauma

chemical injury

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15
Q

What are the defense mechanisms of the cornea

A

blinking and the tear film
- antimicrobial
- removes debris
- there are a few leukocytes

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16
Q

Define keratitis

A

inflammation of the cornea

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17
Q

Define neovascularization

A

development of blood vessels from the limbus

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18
Q

What are 2 responses to injury the cornea undergoes

A

erosion

ulceration (chronic irritation and trauma)

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19
Q

What type of disease can dessication of the cornea cause? What causes it?

A

dry eye

due to…
- breed related (when eyes don’t fully close)
- glaucoma
- defective eyelids

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20
Q

What is the pathogenesis of chronic keratitis

A

abnormal tear production or trauma

chronic corneal irritation

stimulates corneal epithelial metaplasia
- development of rete pegs/pigmentation/fibrosis/vascularization

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21
Q

What is the main consequence of superficial ulcers?

A

corneal edema

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22
Q

How are superficial ulcers repaired

A

epithelial regeneration

rapid process

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23
Q

What are indolent ulcers? What animals are they common in?

A

failure of normal ulcer healing
- the new epithelium doesn’t adhere to the stroma of the eye

dogs

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24
Q

What is another name for a melting ulcer? What is the pathogenesis?

A

keratomalacia

ulceration causes an increase in lytic enzymes resulting in stromal malacia/necrosis

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25
What are the common causative agents of keratomalacia
gram - bacteria fungi like aspergillus
26
Give 1 example of keratomalacia in horses
keratomycosis/fungal keratitis due to aspergillus secondary to immunosuppression or antibiotic use
27
What is a descmetocele? What are the sequelae?
A deep ulcer that reaches the descemets membrane causing - edema - neovascularization - perforation - iris prolapse
28
Can you use fluoroscein to detect a descmetocele?
No
29
What is a corneal sequestrum? What animals is it more common in?
A fragment of necrotic cornea - forms secondary to chronic ulcers more common in cats (himalayan and siamese prone) - can also occur in horses and dogs
30
What is the gross appearance of a corneal sequestrum
brown pigment in the superficial stroma
31
List 7 possible outcomes/consequences of corneal ulcers
it resolves! (if superficial and the inciting cause is removed) indolent ulcer melting ulcer descmetocele corneal sequestrum perforation/iris prolapse phthisi bulbi
32
What is the pathogenesis of keratoconjunctivitis sicca?
immune mediated lacrimal adenitis results in less of a tear film and dessication
33
What animals are primarily affected by keratoconjunctivitis sicca?
dogs
34
What are the common sequelae of keratoconjunctivitis sicca
ulcerative keratitis cutaneous metaplasia of the cornea
35
What is a dermoid
ectopic hair growth on the cornea or bulbar conjunctiva
36
What is another name for infectious bovine keratoconjunctivitis? What are the common causative agents?
pink eye morexella boxis mainly - also (morexella bovoculi, mycoplasma, and infectious bovine rhinotracheitis)
37
What animals does bovine keratoconjuctivitis affect? What are 3 main risk factors
small ruminants - calves > adults summer dusty flies
38
What are the associated lesions for bovine keratoconjunctivitis
red conjunctiva edema central corneal ulceration +/- corneal rupture, iris prolapse, phthisis bulbi
39
What animals are most affected by herpesvirus keratitis? What is the causative agent?
cats - especially kittens in shelters feline herpesvirus 1
40
What structures does herpesvirus keratits affect? What are the lesions
feline herpes virus 1 - upper resp - cornea - conjunctiva increase risk of secondary bacterial infection rhinotracheitis conjunctivitis serous/mucopurulent nasal discharge keratitis only occurs in adults - corneal ulceration (dendritic branching ulcer) is pathogneumonic
41
What is another name for chronic superficial keratitis? What animals are most affected?
pannus dogs - GSD - sighthounds
42
What is the pathogenesis of chronic superficial keratitis? List 2 risk factors
immune mediated destruction due to altered antigens on the cornea - bilateral risk = - high altitude - solar radiation
43
What are the gross lesions of chronic superficial keratitis
thick lateral conjunctiva pigmented corneal plaques neovascularization
44
List 3 types of corneal neoplasias
limbal melanocyte neoplasia squamous cell carcinoma hemangiosarcoma
45
What animals are primarily affected by limbal melanocyte neoplasias? What is the cell of origin? What are the gross features?
dogs mainly (also cats) melanocytes dark pigment
46
What are persistent papillary membranes? Why do they occur? What is their significance?
They are congenital and incidental (unless they contact the cornea) fibrovascular structures that persist in the lens
47
What animals are uveal cysts most common in? What are uveal cysts?
old dogs - also cats (burmese) cysts in the iris or free floating in the anterior chamber that can cause fluid accumulation in the anterior chamber - benign - a degenerative change
48
What is the significance of uveal cysts?
usually no significance - degenerative change and benign in golden retrievers and wolfhounds it can predispose to glaucoma and pigmentary uveitis
49
What is another name for phacoclastic uveitis? What causes it (2 examples)?
lens induced uveitis ex. rabbits with Encephalitozoon cunniculi dogs with diabetes
50
What is the pathogenesis of phacoclastic uveitis?
due to trauma and rupture of the lens capsule - it will develop 2 weeks after trauma lens protein is seen as foreign - result in immune mediated inflammation and granulomatous endopthalmitis
51
What is another name for equine recurrant uveitis? What is it associated with?
moon blindness it is the #1 cause of glaucoma, cataracts, and blindness in horses
52
What are the lesions associated with recurrent uveitis
lymphoplasmocytic uveitis amyloid accumulation in the posterior surface of the ciliary body
53
What is the pathogenesis of recurrent uveitis
immune mediated may be associated with leptospira infection associated to spotted appoloosa breed
54
List 7 potential consequences of uveitis
synechiae (adhesion betweeen the iris and the lens/cornea) retinal detachment cataracts corneal neovascularization pre-iridial fibrovascular membrane (granulation tissue forming in front of the iris - it can cause synechiae) glaucoma phthisis bulbi
55
List an example of an infectious agent that can cause uveitis in cattle, cats, and rabbits respectively
cattle - malignant catarhhal fever cats - FIP rabbits - E cunniculi systemic fungi
56
Compare the most common type of uveal neoplasia in cats and dogs
melanocyte tumors dog = iris/ciliary body - benign cat = diffuse iris melanoma - malignant - multifocal hyperpigmentation of iris - can cause glaucoma - tx = enucleation
57
What is the lens's primary response to injury?
cataract - increased opacification can be congenital or acquired
58
What is the pathogenesis of diabetic cataracts
hyperglycemia causes increased glucose in the aqueous humor the lens absorbs glucose and converts it to sorbitol there is a hyperosmotic effect in the lens causing osmotic stress and swelling lens damage occurs resulting in fibrin and epithelium deposition = cataracts (bilateral and progressive)
59
What is the primary sequelae of diabetic cataracts
can cause lens rupture = phacoclastic uveitis
60
What is another name for nuclear sclerosis? What causes it?
lenticular sclerosis due to old age and degeneration
61
What are the gross lesions of nuclear sclerosis?
cloudy blue discoloured lens - not opaque bilateral and symmetrical
62
Compare nuclear sclerosis with cataracts
nuclear sclerosis low/no impact on vision - can still see the tapetum lucidum reflection cataracts - vision impairment - wont see the tapetum lucidum reflection
63
Compare the 2 types of lens luxation
anterior luxation is very painful and can increase the risk of glaucoma posterior luxation has little consequence they can cause the development of cataracts
64
What causes lens luxation
either congential or acquired (due to trauma or glaucoma)
65
What is the main type of lens neoplasia
feline post traumatic ocular syndrome
66
What causes feline post traumatic ocular syndrome? What is the cell of origin?
secondary to a primary eye trauma from the lens epithelium - infiltrative and recognized late in the disease process
67
How is a normal retina held in place? What layers are most likely to detach?
normally it is held on by the retinal pigmented epithelium by the pressure of the vitreous fluid detachment usually occurs between the retinal pigmented epithelium and the outer nuclear membrane
68
What are 2 main causes of retinal detachment?
uveitis endopthalmitis
69
What are 2 mechanisms of retinal detachment? What is the consequence?
exudative detachment - increased vascular permeability resulting in edema pushing the retina off traction detachment - fibrin and exudate in the vitreous humor that pulls the retina off = ischemic degeneration (no nutrients from the choroid - can also be an artifact of being dead
70
Define trichiasis
normal har but other anatomy pushes it into the eye causing corneal irritation ex. brachycephalics
71
Define distichiasis
abnormally poisitioned eyelash extending from the mebomian gland there is no corneal damage
72
Define ectopic cilia
abnormally positioned eyelash from the palpebral conjunctiva causes lots of corneal irritation
73
Define entropion
Eyelid rolling in causing trichiasis causes corneal irritation
74
Define ectropion
Eyelid rolling out causing chronic keratitis and conjunctivitis due to dry eye
75
What is another name for prolapse of the 3rd eyelid? Can you cut it out?
cherry eye no - because the gland is needed to prevent dry eye
76
What is the most common eyelid tumor in dogs and horses respectively?
dog = mebomian gland tumor horse = SCC
77
What are the features of a mebomian gland tumor? What does it look like?
benign - similar to sebaceous adenoma grey/pink/exophytic and alopecia
78
What are the features of eyelid melanocytoma
benign it is the second most common eyelid tumor in dogs
79
What are the features of conjunctival melanoma
malignant and aggressive from the bulbar conjunctiva can be amelanotic
80
What animals are most affected by eyelid SCC? What are 2 risk factors?
horses and cows > cats UV light white face
81
What is orbital meningioma?
optic nerve has a myelin sheath formed from oligodendrocytes oligodendrocyte tumor conpress and degeneration of optic nerve
82
What is orbital cellulitis? What is another name?
retrobulbar abscess infection - either a direct wound or extension of inflammation

VETM 425 Sys Path (38 decks)

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