Equine retina, optic nerve, vitreous Flashcards Preview

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Flashcards in Equine retina, optic nerve, vitreous Deck (57)
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1
Q

Depigmented areas at 6 o’clock below optic nerve in a HORSE. Before you diagnose ERU, what else must also be present?

A

Must have evidence of degeneration ELSEWHERE in the eye, not this single lesion

2
Q

“Sunburst”/band appearance of depigmentation/white radiating out from the optic nerve in the non-tapetal region in a HORSE is pathognomonic for…

A

Had previous chorioditis (from ERU) –> this lesion is from retinal folds from a detached retina that re-attached

3
Q

How do you treat chorioretinitis in the horse?

A

Systemic meds – Banamine or steroids (dex, pred)

4
Q

What are 3 signs of choroiditis in the horse?

A
  1. Bullet hole lesions in retina
  2. Vitreal degeneration
  3. Vitreal discoloration
5
Q

Are bullet hole lesions pathognomonic for ERU in horses?

A

NO

6
Q

In a horse with choroiditis, what color is the vitreous and why?

A

Green, because serum leaks into the vitreous

7
Q

What are the “butterfly” like lesions seen around the optic nerve?

A

Peripapillary chorioretinal scars

8
Q

If there is peripapillary scarring AND vitreal changes, what does that mean?

A

That when it was active, some plasma leaked into the vitreous

9
Q

White or myelin appearing bleb on the edge of the optic nerve in a HORSE. What are the 5 DDx?

A
  1. Optic neuritis
  2. Proliferative optic neuropathy (PON, discrete)
  3. Optic nerve tumor
  4. Ectopic myelination or peripapillary ganglion cells (more diffuse)
  5. Coloboma of RPE (diffuse, white)
10
Q

In a visual horse eye with something on the nerve, what is NOT your DDx?

A

Optic neuritis (horse will be blind)

11
Q

What is more common: PON or an optic nerve tumor?

A

PON by FAR (optic nerve tumors are RARE)

12
Q

What is PON in a horse?

A

Benign glial tumor [oligodendrocytoma]

13
Q

What is the signalment for PON in a horse? What will its PLR be like?

A

> 15 yr old with normal PLR

14
Q

What is the treatment for PON? Optic nerve tumors?

A

None for either, but PON isn’t a big deal usually

15
Q

What is the normal color of an equine optic disc and why?

A

Orange/beige d/t capillaries

16
Q

How does the color of the equine optic disc change with optic nerve atrophy?

A

Becomes lighter with atrophy

17
Q

What is the normal location for vessels around an equine optic nerve?

A

Everywhere but 6 o’clock

18
Q

What is the reticular pattern on the equine optic nerve?

A

The lamina cribosa

19
Q

The lamina cribosa is normally hard to see on a horse. What is happening if it is easy to see?

A

Optic nerve atrophy (there has been DEMYELINATION, exposing it)

20
Q

What are Stars of Winslow? Are they normal? Species? Appearance?

A

“Dots” on the TAPETAL fundus of a HORSE
They are NORMAL

These are end-on choriocapillaries in the retina

21
Q

What is breed is Congenital Stationary Night Blindness seen in (CSNB) most commonly seen in? Specifically which horses?

A

Appaloosa (up to 1/3 of all apps!), most commonly leopard complex gene (which can also occur in POAs, Knabstruppers, Miniatures)

22
Q

What are the clinical signs of CSNB? Appearance of the retina? Histologic appearance? ERG appearance?

A

Vision impaired in dim light, normal in bright light
Normal retina
Normal histology
ERG: all a wave (aka a “negative ERG” since no positive B wave present)

23
Q

What is the cause of CSNB?

A

Defect in the TRPM1 gene

Transient receptor potential melatansin 1

24
Q

What is the treatment for CSNB? Recommendation to breed?

A

No treatment; do NOT breed

25
Q

Retinal hemorrhage in foal. How common? Affect on vision? Resolution?

A

Fairly common (~16% of TB foals)
No affect on vision
Resolve on own in 10 days

26
Q

How does ischemic optic neuropathy occur in horses?

A

Ligation of the internal and external carotid, and the greater palatine artery, when trying to treat GP mycosis
(NOTE: the maxillary artery should be the ONLY artery occluded)

27
Q

Unlike small animals, where damage to the optic chasm is usually from enucleation, when does this occur in the horse?

A

Trauma to the occipital region, causing both globes to move anteriorly and stretching this area

28
Q

Equine Motor Neuron disease causes what changes to the retina?

A

A mosaic of light and dark d/t ceroid lipofusion in the pigmented area

29
Q

When can you get fungal optic neuritis in horses? (2)

A
  1. Crypto meningitis

2. Guttural pouch mycosis

30
Q

Retinal dysplasia in a HORSE has been associated with what process, and in what breed?

A

Anterior segment dysgenesis; Rocky Mountain of course

31
Q

When are peripheral retinal (ciliary) cysts seen?

A

Silver dapple coloration associated with multiple congenital ocular abnormality syndrome

32
Q

How should you advise owners of horses with peripheral retinal (ciliary) cysts?

A

No affect on vision, but don’t breed these horses

33
Q

What do peripapillary lesions represent?

A

Post-inflammatory lesions

34
Q

How common are bullet hole lesions?

A

VERY– like 80% of mature horses!

35
Q

What is thought to probably cause the bullet hole lesions?

A

Equine herpesvirus

36
Q

When are bullet hole lesions considered significant?

A
  1. When densely and widely distributed over entire pigmented fundus or when locally extensive
  2. distributed in a linear pattern across the circumpapillary or ventral peripapillary fundus
37
Q

What is associated with distributed linear distribution of bullet hole lesions across the circumpapillary or ventral peripapillary fundus?

A

Behavioral issues are associated, suggesting visual deficits (unknown why this location does that)

38
Q

What is the appearance of optic nerve atrophy?

A

Pale, granular, nonvascularized; blind in ONE eye

39
Q

What usually causes optic nerve atrophy

A

Space occupying lesion in the optic chiasm; can progress to bilateral blindness

40
Q

Describe bullet hole lesions?

A

Multiple small, circular focal areas of depigmentation with a central area of hyperpigmentation

41
Q

Describe fibrinous traction bands

A

White spike-like structures that radiate from the perimeter of the optic disc

42
Q

What should be your first thought if you see retinal detachment in a horse?

A

ERU

43
Q

Where is the pigment of the RPE the least concentrated in the equine retina?

A

Over the visual streak

44
Q

How does the pigment concentration change from the level of the visual streak?

A

The pigment gradually increases as the tapetum thins out

45
Q

How does the shape of the optic nerve change from foal to horse?

A

Rounder as a foal

46
Q

Where is the visual streak located?

A

Ventral tapetum, parallel to the edge of the bottom of the tapetum

47
Q

How does the tapetum appear when observed in bright light?

A

As a horizontal band (as opposed to triangular/semi-circular in shape)

48
Q

What is the horizontal band of tapetum thought to represent by some people?

A

The only functional part of the tapetum under normal (day or night) light conditions

49
Q

How do the visual streak and horizontal band of tapetum relate to the pupil?

A

All are horizontal = horizontal visual field

50
Q

Where in the eye is the optic disc?

A

ventrolateral

51
Q

How should you visualize the the optic disc in a horse?

A

Stand in front, at level of eye or slightly above, and look down

52
Q

What is the name for the age-related retinal changes in horses?

A

Senile retinopathy

53
Q

What is the appearance of senile retinopathy?

A

Hyper pigmented (black) streaks with depigmented (white) streaks on either side, within the non-tapetal fundus, mostly ventral to optic disc. This will be bilateral.

54
Q

What is the clinical significance of senile retinopathy?

A

None– no visual deficits

55
Q

What is the DDx for senile retinopathy?

A

Vit E deficiency/EMND

56
Q

What is the appearance for horses with Vit E deficiency and/or EMND?

A

Mosaic, honeycomb pattern of a dark brown to yellow-brown pigmentation in the tapetal zone, and a horizontal band of pigment at tapetal-non-tapetal junction

57
Q

What is the pigment that is deposited in Vit E deficiency/EMND?

A

Ceroid lipofuscin