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LA DX & TX II > Final Exam - Equine Glaucoma & Lens > Flashcards

Final Exam - Equine Glaucoma & Lens Flashcards

1
Q

what is normal equine vision?

A

large visual field with monocular & binocular vision

great at detecting motion - adapted to dim & bright light

dichromatic

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2
Q

what are your treatment options for a blind horse? what should be prioritized above everything?

A

euthanasia, pasture pet, limited capacity use of the horse

prioritize the security/welfare of the horse & safety of handlers!!!

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3
Q

what considerations should you think about when taking on management of a blind horse?

A

horse’s temperament, adaptation to vision loss, training, safety, economics, owner’s dedication, & presence of a safe & predictable environment

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4
Q

T/F: horses have better vision than most domestic animals

A

true

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5
Q

what is nuclear sclerosis?

A

age related change seen in animals 15-20 years old

nucleus & lens becoming more dense with the tapetal reflection still visible

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6
Q

what is the most common glaucoma type in horses?

A

secondary more common than primary

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7
Q

when is tonometry contraindicated for horses?

A

in horses with deep corneal ulcers & lacerations/perforations

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8
Q

when is tonometry performed in your ophthalmic exam?

A

done before pupil dilation & after the auriculopalpebral nerve block

with head above the heart - IV sedation may decrease pressures

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9
Q

what tonometry readings indicate glaucoma?

A

pressures > 30 mmHg with clinical signs/vision loss

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10
Q

what are normal tonometry readings for horses?

A

10-25 mmHg is normal, under 30 mmHg

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11
Q

what acute clinical signs are associated with glaucoma? what about chronic signs?

A

acute (<48-72 hours) - blepharospasm, epiphora, episcleral injection, transient corneal edema, & mydriasis

chronic - permanent corneal edema, haab’s stria, lens luxation, optic nerve atrophy, blindness, uveitis, buphthalmos, & narrowed/compressed ICA

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12
Q

what is primary glaucoma?

A

abnormality of aqueous humor outflow & absence of concurrent ocular disease - rare in horses

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13
Q

what is secondary glaucoma? what are some examples of causes?

A

obstruction caused by concurrent ocular disease

ERU, neoplasia, trauma, lens luxation, & after cataract surgery

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14
Q

when considering therapy options for a horse with glaucoma, what must you consider?

A

think about their vision, ocular disease, age/purpose of the horse, economics, & ease of treatment

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15
Q

what topical medication is most effective in reducing intraocular pressures in horses?

A

dorzolamine/timolol

DON’T USE LATANOPROST

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16
Q

when is surgery indicated for a horse with glaucoma?

A

when medical therapy is not effective

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17
Q

how is laser cyclophotocoagulation used for treating glaucoma?

A

surgery that destroys the ciliary body epithelium to reduce aqueous humor production

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18
Q

how are gonioimplants used for treating glaucoma? what complications are associated with it? what’s the prognosis?

A

aqueous humor shunted to the subconjunctival space

risks - corneal edema, worsening uveitis, corneal ulceration, fibrosis around the implant, & uncontrolled glaucoma

prognosis is guarded for long-term maintenance of vision

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19
Q

when are salvage procedures indicated for equine glaucoma?

A

medical therapy is inadequate & the horse has blind, painful eyes

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20
Q

what is chemical ciliary body ablation? what complications are associated with this procedure?

A

gentamicin destroys the ciliary body epithelium

worsening uveitis, hyphema, & uncontrolled IOP

phthisis bulbi is expected!!!

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21
Q

how is enucleation used as a salvage procedure for equine glaucoma?

A

fast recovery & a very low complication rate - also allows for histopathology

intraorbital silicone implant minimizes the sunken appearance of skin & is purely cosmetic

22
Q

what are cataracts?

A

true opacity of the lens classified by age, location, maturation, & etiology

23
Q

what are the different ages of onset that are seen with equine cataracts?

A

congenital, juvenile, adult, & senile/geriatric

24
Q

what horses are predisposed to congenital cataracts?

A

thoroughbreds, quarter horses, morgans, & rocky mountain horse

usually present with other anomalies

25
Q

what is the importance of location of cataracts in the equine eye?

A

need to specify where in the lens the opacity is for classification purposes!!!

26
Q

what are the 4 maturation categories for equine cataracts?

A

incipient - small opacity & <15% of the lens affected

immature/incomplete - not 100% affected, still visual

mature/complete - 100% of the lens is affected, the horse has a negative menace, no tapetal reflection

hypermature/resorbing - lens cortex liquifies, lens shrinks, tapetal reflection can return, vision may return, & uveitis is present

27
Q

what is brunescence?

A

yellow lens - normal aging & seen with some cataracts!

28
Q

what is the most frequent cause of cataracts in horses? what are some other causes?

A

chronic uveitis!!!!!!

inflammatory, inherited, metabolic, trauma, nutritional, toxic, etc

29
Q

what are the sequelae associated with cataracts?

A

visual impairment, lens-induced uveitis, lens luxation, glaucoma, & retinal detachment

30
Q

what topical drug is required for life for horses with cataracts?

A

topical NSAIDS to control uveitis

31
Q

what is phacoemulsification? what complications are associated with this procedure?

A

surgical procedure done to restore vision in horses with cataracts - high frequency vibrations emulsify cataract & it is then removed by aspiration through a small corneal incision

poor success rate in horses!!!! corneal ulceration, uveitis, endophthalmitis, glaucoma, & retinal detachment

32
Q

why are horses not great candidates for phacoemulsification?

A

there is a poor success rate - ERU horses are not good candidates for this!!! extensive post-op care is required!

vision after surgery is still compromised!!! may not be a safe animal!!!

33
Q

what horses may be a good candidate for phacoemulsification?

A

foals with congenital cataracts

34
Q

what horses do you especially need to do tonometry on?

A

horses with:

corneal edema, red/painful eye, orbital/blunt ocular trauma, exophthalmos, buphthalmos, history of glaucoma in other eye, lens luxation/subluxation

35
Q

what lesion is shown here? what condition is it associated with?

A

haab’s stria (striate keratopathy)

chronic glaucoma

36
Q

what lesion is shown here? what condition is it associated with?

A

buphthalmos (visible enlargement of the eyeball)

chronic glaucoma

37
Q

which photo of the iridocorneal angle is normal?

A

left photo is normal

right is narrow & compressed

38
Q

which optic nerve is abnormal? how do you know?

A

optic nerve on the right is atrophied & abnormal!

loss of myelin reveals reticulated lines of lamina cribosa

39
Q

what lesion is shown here? what does it mean?

A

phthisis bulbi - end stage ocular disease

shrunken eye

40
Q

this foal has congenital glaucoma - what causes it?

A

developmental abnormality of the anterior segment

41
Q

what is your target IOP for a horse with high IOP?

A

wat it < 20 mmHg

42
Q

what horses are surgical candidates for glaucoma?

A

horses that have glaucoma but still have visual eyes!!!!

still must control inflammation, IOP, & prevent infections after surgery

43
Q

in this photo, do you see nuclear sclerosis or cataracts? how do you know?

A

nuclear sclerosis - tapetal reflection remains intact, no affect on vision, & nucleus of the lens becomes more dense/apparent

44
Q

does age of onset = etiology for cataracts in horses?

A

nope

45
Q

what type of cataract is shown here? how do you know?

A

incipient cataract - small opacity with <15% of the lens affected

still visual & you can see the tapetal reflection

46
Q

what type of cataract is shown here? how do you know?

A

immature cataract - larger than incipient, but smaller than mature!

tapetal reflection is variable, but horse is menace positive

47
Q

what type of cataract is shown here? how do you know?

A

mature - 100% of the lens is affected, tapetal reflection isn’t visible, & animal has lost its menace

48
Q

what type of cataract is shown here? how do you know?

A

hypermature - lens cortex liquifies, lens shrinks (wrinkles, deep anterior chamber)

tapetal reflection may return, vision may return, & uveitis is often present

49
Q

what is this?

A

brunescence - increased yellow discoloration of the lens that occurs as a normal part of aging

can also be seen in some equine cataracts

50
Q

what is the pathophysiology of chronic uveitis causing cataracts in horses?

A

mediators of inflammation diffuses into the eye & alters the lens structure/metabolism

changes in aqueous humor production & synechiae

51
Q

what kind of cataracts are these?

A

mature cataracts from ERU

LA DX & TX II (44 decks)

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