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CVSOH BVSc4 > Ophth - posterior segment conditions > Flashcards

Ophth - posterior segment conditions Flashcards

1
Q

What are some normal fundus variations?

A

Presence or absence of tapetum
Colour of tapetum
Amount of pigment of retinal pigment epithelium of non tapetal fundus

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2
Q

When does the tapetum tend to be blue?

A

When it is not fully developed - in puppies and kittens

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3
Q

Where is retinal pigmented epithelium found?

A

In the non tapetal fundus

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4
Q

Where is the optic disc found?

A

Can be in the tapetal or non tapetal fundus - varies between individuals

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5
Q

What is the difference between cats and dogs optic discs?

A

Cats - non myelinated, usually looks grey
Dogs - more white, can see blood vessels on it

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6
Q

What can cause blindness?

A

A lesion anywhere along the visual pathway can cause blindness
eg. Ocular media opacity - eye itself
Retinal dysfunction
Optic nerve dysfunction
Optic tract lesion
Chiasm lesion
Visual cortex lesion - in brain

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7
Q

Hoe can you test an animals retina?

A

Electroretinography
Pupillary light reflex
Dazzle reflex
Menace response

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8
Q

How does electroretinography work?

A

Electrode in gold contact lens is placed on eye, and needles are placed on head to ground and act as reference electrode
Shine measured intensity flash into eye
Electrode in contact lens collects retinal response
Measures electrical activity/action potential of stimulus

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9
Q

How does the pupillary light reflex work?

A

Light shone in one eye will cause both irises to constrict
Photoreceptors send impulse to chiasm - some run down other side down oculomotor nerve

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10
Q

What is the dazzle reflex?

A

Similar to pupillary light reflex but facial nerve causes eye to blink/squint

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11
Q

What is the menace response?

A

Advancing hand causes blink

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12
Q

When is the menace response developed in puppies and kittens?

A

Not until 8-14 weeks

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13
Q

What does cateracts look like on ocular ultrasound?

A

Opacity in the lens - hyperechoic (white) lens

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14
Q

What does detached retina look like on ocular ultrasound?

A

Like a seagull

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15
Q

What is a persistent hyaloid system?

A

Where the neonatal system hasnt regressed which can cause lens abnormalities, cateract or bleeding in the vitreous humour

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16
Q

What are two causes of vitreal opacity/haze?

A

Asteroid hyalosis
Synchisis scintillans

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17
Q

What is asteroid hyalosis? What does it look like?

A

When calcium phospholipids are suspended in the gel at back of the eye
Look like a starry sky - dont move

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18
Q

What is synchisis scintillans? What does it look like?

A

When mobile cholesterol particles in liquefied vitreous
Looks like a snow globe

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19
Q

What is vitreal syneresis? What can it lead to?

A

When the vitreous liquefies - can lead to retinal detachment

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20
Q

What is retinal dysplasia?

A

Abnormal retinal development during embryonic growth - dark lines/folds in the retinal sheet where layers have been incorrectly laid down

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21
Q

What are the two types of retinal dysplasia?

A

Multifocal
Total

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22
Q

What does retinal inflammation look like?

A

Hyporeflective tapetal lesions - dark patches
White/cream lesions in non-tapetum

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23
Q

What is active chorioretinitis?

A

Inflammation of the retina and choroid (closely associated structures)

24
Q

What does active chorioretinitis look like?

A

Infiltrates of protein/cells across damaged blood retinal barrier
Multifocal bullous retinal detachments - look like blisters

25
Q

What causes the bullous retinal detachments in active chorioretinitis?

A

Inflammatory fluid accumulating under the retina and pushing it off the choroid

26
Q

What does inactive chorioretinitis look like?

A

Hyperreflective tapetal lesions
Pigmentation of the tapetum
Depigmentation in a non tapetal lesion

27
Q

Why do you get hyperreflexctive tapetal lesions in inactive chorioretinitis?

A

The retina gets thinner
Can partially reattach - tapetum appears shinier in these areas as there is less tissue between you and the tapetum

28
Q

What most commonly causes retinal haemorrhage?

A

Systemic hypertension - hypertensive retinopathy

29
Q

What does hypertensive retinopathy cause?

A

Vascular tortuosity - wiggly
Vessel bleeding
Haemorrhages
Multifocal bullous detachments

30
Q

What are the different types of retinal detachment?

A

Serous
Epulsive haemorrhage
Subretinal cellular infiltrate
Granuloma
Solid tissue/tumour
Tears/holes

31
Q

What disease can cause retinal degeneration?

A

Inherited progressive retinal atrophy

32
Q

What changes to the retina does inherited progressive retinal atrophy cause?

A

Hyperreflectivity - thin retina
Vascular attenuation - blood vessel atrophy as cells dying so dont need blood
Night blindness

33
Q

What happens in inherited progressive retinal atrophy?

A

Rods and cones die - rods first

34
Q

What is sudden acquired retinal degeneration (SARDs)?

A

Acute degeneration of the retina for unknown cause
There is no electrical activity in neurosensory retina

35
Q

What does total retinal atrophy look like?

A

No blood vessels remaining
Very hyperreflective tapetum

36
Q

What drug can cause total retinal atrophy?

A

Enrofloxacin

37
Q

What is optic coloboma?

A

Missing tissue - the optic nerve did not develop
Blood vessels dont go all the way onto the optic nerve because its not there - disappear down it like a waterfall

38
Q

What species are prone to optic nerve disease?

A

Collies - collie eye anomaly

39
Q

What is collie eye anomaly?

A

Chorioretinal dysplasia
Bizarre branching vessels
Can cause haemorrhage and vision loss

40
Q

What is optic neuritis? What does it look like?

A

Inflammation of the optic nerve head - looks fuzzy

41
Q

What is papilloedema?

A

When the optic nerve head is pushed forward secondary to increased intracranial pressure
No exudate, cells, blood, blood vessels look straight as if they are climbing a hill

42
Q

What is glaucoma?

A

Increase intraocular pressure - due to reduced draining of aqueous humour through the iridocorneal drainage angle

43
Q

What is the normal intraocular pressure in the eye?

A

10-25mmHg

44
Q

What intraocular pressure suggests glaucoma?

A

More than 30mmHg

45
Q

What intraocular pressure suggests uveitis?

A

Less than 10mmHg

46
Q

What are two inherited causes of primary canine glaucoma?

A

Goniodysgenesis - pectinate ligament dysplasia
Primary open angle glaucoma (POAG)

47
Q

What are the clinical signs of glaucoma (non-chronic)?

A

Pain
Blindness
Conjunctival congestion
Episcleral hyperaemia - red eye
Corneal oedema - blue tint to eye
Mydriasis - dilated pupil

48
Q

What are the clinical signs of chronic glaucoma?

A

Globe enlargement
Secondary lens luxation
Cataracts
Phthisis bulbi - shrunken globe due to degenerate ciliary body not producing aqueous

49
Q

How do you diagnose glaucoma?

A

Tonometry - measure intraocular pressure
More than 30mmHg - suggests glaucoma

50
Q

What are the different types of tonometers?

A

Indentation tonometry - cheap but tricky to use
Applanation tonometry - expensive, accurate but need local
Rebound tonometry - expensive, accurate, no local needed

51
Q

What can you use to treat glaucoma medically?

A

Carbonic anhydrase inhibitors
Beta blockers
Prostaglandin analogues

52
Q

How do carbonic anhydrase inhibitors treat glaucoma?

A

Inhibit the ciliary body from creating bicarbonate ions so cant draw water into aqueous
So reduce aqueous production

53
Q

How do beta blockers treat glaucoma?

A

Reduce aqueous production

54
Q

How do prostaglandin analogues treat glaucoma?

A

Increase aqueous outflow - open an outflow route for the aqueous through the uveoscleral outflow & out into more superficial blood vessels

55
Q

When should you not use prostaglandin analogues to treat glaucoma?

A

In uveitis - pgs are pro-inflammatory
In cats - dont work

56
Q

What surgical treatment is there for glaucoma patients that can still see?

A

Gonioimplant - increase outflow
Transcleral cyclophotocoagulation - decrease output of aqueous

57
Q

What surgical treatment is there for glaucoma patients that are blind?

A

Enucleation
Evisceration and intrascleral prosthesis - prosthetic eye

CVSOH BVSc4 (86 decks)

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