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Eq Special Topics > Equine Eyeballs > Flashcards

Equine Eyeballs Flashcards

1
Q

What is the corpora nigra/granulae iridica?

A

Extension of the posterior iris into the anterior chamber that acts as a “visor” for the pupil and helps control the amount of light reaching the retina

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2
Q

What does the auribulopalpebral nerve block? Why is it important for your ophthalmic exam?

A

Palpebral branch of the palpebral nerve (CN7)
Paralysis of orbicularis oculi muscle (mostly the upper eye)

Helps prevent blinking and clamping down

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3
Q

What are the supraorbital and frontal block anesthetizing? Why is this helpful?

A

Sensory innervation from V1 to elimination sensation to the central upper eyelid

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4
Q

T/F: Normal tear production for horses is over 20mm/min, but tear deficiencies are rare in horses.

A

True

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5
Q

Normal IOP in horses is _______mmHg

A

15-30

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6
Q

TonoPen (applanation tonometry) requires….

A

Topical anesthetic

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7
Q

Fluorescein stain is taken up on the medial aspect of the cornea. Where should you look first?

A

Beneath the third eyelid - looking for a FB resulting in corneal ulceration

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8
Q

What is a Jones test?

A

Fluorescein stain travels thru nasolacrimal duct to test patency

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9
Q

When is irrigation of the NLD indicated?

A

Epiphora, mucoid ocular discharge, nasal puncta discharge

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10
Q

By what two methods can you irrigate the NLD?

A

Normograde from the proximal eyelid puncta
Retrograde from distal nares opening

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11
Q

T/F: Normograde irrigation is easier than retrograde

A

False - retrograde is easier

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12
Q

Posterior synechia is indicative of…

A

Previous uveitis
ERU (Equine Recurrent Uveitis)

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13
Q

When performing indirect fundoscopy, how is the image presented?

A

Inverted (upside down) and reversed

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14
Q

Compare and contrast direct and indirect fundoscopy

A

Direct: smaller field of view w/ more magnification, upright image
Indirect: wider field of view w/ less magnification, inverted and reversed image

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15
Q

What bones compose the COMPLETE bony orbital rim?

A

Frontal
Lacrimal
Zygomatic
Temporal

Deep internal wall: sphenoid, palatine

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16
Q

Most EOM innervated by ______

A

CN3 (oculomotor)

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17
Q

What are the potential causes of a “sunken” appearing globe?

A

Enophthalmos
Microphthalmos
Phthisis bulbi

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18
Q

Causes of enophthalmos

A

Orbital fractures
Resorption of orbital fat
Dehydration in foals (entropion)
Sympathetic denervation (Horner’s)

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19
Q

Enophthalmos is usually secondary to ________

A

Loss of orbital contents

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20
Q

What is microphthalmia?

A

Congenital anomaly resulting in small globe

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21
Q

What is phthisis bulbi?

A

Gradual shrinkage of the globe d/t chronic inflammation and low IOP

Damage to CB results in decreased AH production

Non-visual

Enucleate if uncomfortable

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22
Q

Buphthalmos and exophthalmos result in a _________ appearance

A

Bulging

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23
Q

Buphthalmos is secondary to __________

A

Increased IOP secondary to glaucoma

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24
Q

What is the difference between buphthalmos and exophthalmos?

A

Buphthalmos involves a bigger globe
Exophthalmos is the anterior displacement of the globe

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25
Q

In addition to buphthalmos, what other ocular signs might you see?

A

Haab’s striae
Corneal edema

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26
Q

Potential causes of exophthalmos

A

Retrobulbar mass
Orbital cellulitis/abscess
Trauma

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27
Q

Most common location of orbital fractures?

A

Dorsal orbital rim and zygomatic arch d/t prominent location

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28
Q

How can you diagnose orbital fat prolapse?

A

FNA or biopsy - will come back as just fat

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29
Q

Treatment for orbital cellulitis

A

Systemic antimicrobial agents
Aggressive NSAIDs
Lubricants
Drainage of abscess (if present)
Removal of FB (if present)
Enucleation

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30
Q

What is the most important diagnostic tool for orbital disease?

A

Imaging! CT, MRI, US

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31
Q

Important functions of the eyelid

A

Protection (blinking)
Entrapment and removal of material
Distribution of tears
Production of glandular secretions (meibomian glands)

32
Q

Movement of the third eyelid is __________, meaning the structure is not controlled by a muscle.

A

indirect

33
Q

In what population is entropion most common?

A

Congenital ocular abnormality in FOALS

34
Q

CS of entropion

A

Epiphora
Corneal ulcer
Conjunctivitis
Blepharospasm
Keratitis

35
Q

Describe a temporary tacking procedure

A

Vertical mattress suture using 4 to 6-0 non-absorbable monofilament suture left in for 2-3 weeks

36
Q

Though rarely required, describe how to permanently correct entropion

A

Hotz-Celsus procedure
Incision 2-2.5mm from and parallel to eyelid margin, extending slightly medial and lateral to region of entropion
Second incision defines amount of skin being removed
Excise skin and underlying strip of orbicularis
Simple interrupted skin closure (bisecting)

37
Q

How do we treat eyelid lacerations?

A

PROMPTLY
Standing under sedation or GA w/ local blocks
Clean wound w/ saline or dilute betadine
MINIMAL DEBRIDEMENT
Primary closure!!! 2 layer closure (tarsoconjunctival and musculocutaneous)

38
Q

Discuss post-operative care following eyelid laceration repair

A

Protective mask
Triple antibacterial ointment q8h for 1-2wk
Systemic NSAIDs (Banamine)
+/- systemic abx

39
Q

Consequences of improper eyelid repair

A

Corneal ulcer d/t suture rub
Poor tear film retention or dispersion leading to chronic keratitis

40
Q

CS of facial paresis/paralysis

A

Ptosis/diminished ability to blink
Ear droop and diminished motility
Nose deviation
Flaccid lip/diminished function

41
Q

Name some potential causes of facial paresis/paralysis

A

Trauma
Inflammation of inner ear, guttural pouch, salivary gland
Fracture of stylohyoid, petrous temporal bone, ramus of mandible

42
Q

Why is lubrication of the cornea so important with facial paresis/paralysis?

A

Tears are being produced but aren’t able to be distributed
Lubricant will cover the cornea and stick around for a bit

Should be doing 4-6x/d

43
Q

What can you do while waiting for eyelid function to be restored that will help prevent corneal ulcers?

A

Partial temporary tarsorrhaphy

44
Q

______________ is the inflammation of palpebral and/or bulbar conjunctive; this condition is usually _________

A

Conjunctivitis; secondary

45
Q

CS of conjunctivitis

A

Hyperemia
Chemosis
Ocular discharge

46
Q

_________ is the most common neoplasm of horses

A

A sarcoid

47
Q

Typical signalment associated with sarcoids

A

Young age (3-6y)
Increased risk in QH, Appaloosas, Arabians

48
Q

Prognosis of sarcoid

A

Metastasis is rare
Recurrence is VERY COMMON

49
Q

How do we treat sarcoids?

A

Surgical excision w/ adjunctive cryotherapy, hyperthermia, radiation
Chemotherapy (intralesional/topical)
Immunotherapy
Others

50
Q

You are examining a horse with a firm mass near its eyelid. You are highly suspicious of a sarcoid. You recommend excision to the owner.

What could you have done better?

A
  1. Unless sarcoids are compromising the eye, you should leave sarcoids alone. You don’t want to remove too much eyelid and they often recur.
  2. Excision alone has a high rate of recurrence

As long as the patient is clinically normal, don’t mess with it and continue to monitor. Typically, sarcoids are slow growing.

51
Q

_________ is the most common neoplasm of the equine eye and ocular adnexa

A

SCC

52
Q

What regions of the eye are most commonly affected by SCC?

A

TE and medial canthus
Limbus
Eyelid

53
Q

T/F: Surgical excision for treatment of SCC is associated with recurrence rate of 50-60%

A

T: Need some form of adjunctive therapy

Exception - TE removal is typically curative for TE SCC

54
Q

Nasal lacrimal duct atresia is….

A

Imperforate nasal punctum

Most common congenital nasolacrimal abnormality in foals

55
Q

How can we diagnose NL duct atresia or imperforate nasal punctum?

A

Nasal punctum not visible
Inability to flush NL duct
Contrast radiography
Culture/susceptibility (most have secondary bacterial dacryocystitis)

56
Q

Treatment for imperforate nasal puncta

A

Create nasal punctum by passing catheter and cutting
Prevent re-obstruction by leaving catheter in place for 4-6wk
Treat secondary infection (dacryocystitis)

57
Q

What is the role of the corneal endothelial cells?

A

Pump fluid out of cornea to prevent build up (corneal edema)

58
Q

Dysfunction of endothelial cells or disruption of epithelium will lead to

A

Corneal edema

Can’t pump fluid out or too much fluid being let in

59
Q

Potential etiology behind ulcerative keratitis

A

Trauma
FB
Exposure/Paralytic keratitis
EHV (uncommon to rare)
KCS (rare)

60
Q

3 major ulcer categories

A

Superficial

Stromal (Superficial, mid, or deep stromal)

Desmetocoele

61
Q

Describe the appearance of a desmetocoele

A

Perfect clear lesion (basement membrane) in the middle of a cloudy lesion

Loss of stroma and fluid can’t accumulate

62
Q

What do we mean by “complicated” ulcers?

A

Secondary infection (bacterial, fungal)

Stromal degradation

Iridocyclitis (uveitis)

63
Q

You come across an ulcerated cornea with snotty material that gets stuck to your cotton swab. What likely is this material?

A

Lytic corneal stromal collagen indicating a “melting” ulcer

64
Q

What’s the best way to evaluate whether or not a corneal ulcer has healed?

A

Stain!

If the cornea is no longer taking up stain, you can stop treatment

65
Q

Define cycloplegia and what medication can we use to achieve this

A

Paralysis of the ciliary body to prevent spasm

Atropine

66
Q

CS of corneal perforation

A

Iris prolapsed/fibrin
Corneal edema
Hyphema/hypopyon

67
Q

T/F: In most cases, corneal perforation can be managed conservatively

A

False - almost always a surgical disease

68
Q

Describe the appearance of a corneal abscess

A

Yellow-white stromal opacity

69
Q

Are corneal abscesses painful?

A

Yes and they are often accompanied by secondary uveitis

70
Q

What is band keratopathy and what disease is it associated with?

A

Corneal mineralization/calcification

ERU and chronic uveitis

Typically non-painful unless ulceration occurs d/t sloughing mineral

71
Q

T/F: IMMK is a very painful condition

A

False - typical non to minimally painful chronic disease

72
Q

Clinical findings associated with eosinophilic keratoconjunctivitis

A

Ocular discomfort
Raised pink-white necrotic corneal plaque
Variable corneal ulceration

73
Q

What is the best diagnostic tool for eosinophilic keratoconjunctivitis?

A

Cytology - will see eosinophils

74
Q

What is the only kind of ulcer you should ever use steroids on?

A

Ulcers associated with eosinophilic keratoconjunctivitis

75
Q

Describe the appearance of corneoconjunctival squamous cell carcinoma

A

Typically raised fleshy/verrucous appearance

Usually lateral limbus

76
Q

How can you differentiate corneoconjunctival SCC from stromal invasive SCC?

A

White stromal infiltrates present

Not raised like typical superficial SCC

77
Q

Treatment for corneoconjunctival SCC

A

Surgical excision
Laser ablation
Cryotherapy
Photodynamic therapy
Radiation therapy
Topical chemotherapy

Eq Special Topics (3 decks)

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