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Ophthalmology > Glaucoma > Flashcards

Glaucoma Flashcards

1
Q

Glaucoma

A

Increased intraocular pressure causing damage to optic nerve and retina

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2
Q

Normal IOP dog

A

10-20 mmHg

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3
Q

How close should the IOPs of two different eyes be?

A
  • Within 5 mmHg
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4
Q

Cat and horse IOP normal

A

12-30 mmHg

  • Not hard and fast for them
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5
Q

Flow of aqueous in the eye (3 steps)

A
  1. Aqueous produced by ciliary body
  2. Passes through the pupil into the anterior chamber
  3. Exits the eye through the iridocorneal angle
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6
Q

WHat determines IOP?

A
  • Volume of aqueous
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7
Q

Can IOP ever be high due to over-production of aqueous?

A
  • No, we say never
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8
Q

When does intraocular pressure increase?

A
  • WHen aqueous cannot escape the eye through the ICA

- i.e. the ICA is closed

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9
Q

What are the two categories of causes of glaucoma?

A
  • Primary glaucoma (hereditary)

- Secondary glaucoma (other ocular disease)

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10
Q

Who gets hereditary/primary glaucoma?

A
  • Cocker SPaniels
  • Siberian husky
  • Bassett hound
  • Many others
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11
Q

Age of onset with hereditary glaucoma

A
  • Any age

- As young as 2 years of age in huskies

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12
Q

Secondary glaucoma causes

A
  • Lens induced uveitis, instability, luxation
  • Uveitis any cause
  • Neoplasia (ocular or metastatic)
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13
Q

Most common cause of secondary glaucoma?

A
  • Cataracts –> LIU –> glaucoma
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14
Q

Mechanism of secondary glaucoma

A
  • Inflammatory cells, blood, or tumor cells in ICA
  • Pre-iridial fibrovascular membrane from uveitis or retinal detachment covers the ICA
  • Peripheral anterior synechia
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15
Q

How can anterior lens luxation lead to glaucoma?

A
  • Pressure increase due to physical obstruction, disturbance of intraocular environment, and/or induction of uveitis
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16
Q

How does diabetic cataracts lead to glaucoma?

A
  • Intumescent lens can push iris forward against the cornea and close the ICA
  • Or lens induced uveitis from lens proteins
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17
Q

Acute glaucoma - how quickly should yo utreat?

A
  • Emergency to save vision
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18
Q

Signs of acute glaucoma

A
  • Corneal edema (not as much in cats)
  • Dilated, sluggish pupil
  • Decreased/absent menace
  • Pain/epiphora/blepharospasm
  • Episcleral vessel congestion
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19
Q

Mechanism of corneal edema acute glaucoma

A
  • High IOP causes endothelial cells to be paralyzed and can’t pump fluid out –> corneal edema
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20
Q

Why is the pupil dilated in glaucoma?

A
  • Pressure is high enough to paralyze pupil –> dilated
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21
Q

Main features to distinguish glaucoma from uveitis

A
  • High IOP - dilated pupil
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22
Q

Heelers and glaucoma

A
  • Tend to get high pressures but not corneal edema with glaucoma
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23
Q

How do you diagnose IOP?

A
  • Tonovet pen
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24
Q

Treatment of acute glaucoma principles

A
  1. Rapidly decrease IOP
  2. Neuroprotection (optic nerve - can get damaged with reperfusion injury)
  3. Treat primary problem if secondary glaucoma
  4. Primary glaucoma usually presents with blind eye- treat fellow eye preventatively
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25
Q

What is the mainstay to decrease IOP with glaucoma?

A
  • Dorzolamide/timolol
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26
Q

Dorzolamide/timolol MOA

A
  • Carbonic anhydrase inhibitor (slows production of aqueous)
  • Beta blocker (vasoconstriction to decrease aqueous production)
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27
Q

Which species can you use dorzolamide/timolol on?

A
  • Dogs, cats, horses
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28
Q

What can you use dorzolamide/timolol to treat?

A
  • Primary glaucoma
  • Lens luxation
  • Uveitis
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29
Q

Caution for dorzolamide/timolol

A
  • Asthmatic cats
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30
Q

Mannitol MOA

A
  • Osmotic diuresis to dehydrate the eye
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31
Q

When to use mannitol?

A
  • If IOP >40 mmHg

- Primary glaucoma only

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32
Q

How to use mannitol?

A
  • IV slowly over 15-30 minutes
  • Give once
  • WIthhold water and fluids for 4 hours
33
Q

Contraindications for mannitol?

A
  • Uveitis

- If eye is inflamed, mannitol goes into vitreous and draws fluid in which is bad

34
Q

Latanoprost MOA

A
  • Synthetic prostaglandin
  • Decreases aqueous production
  • Increases uveoscleral outflow
  • Either decreases IOP in 20 min or doesn’t work for that patient
  • Maximal effect in 1 hour
35
Q

Species for latanoprost

A
  • DOGS ONLY

- Not cats or horses

36
Q

Contraindications for latanoprost

A
  • Uveitis or anterior lens luxation (traps vitreous in pupil)
37
Q

Who can use latanoprost?

A
  • ONLY opthalmologists
38
Q

Solu-medrol and solu-delta purpose

A
  • Prevent reperfusion injury
39
Q

Solumedrol and solu-delta MOA

A
  • Calcium channel blocker to stop cytotoxic effects of ischemia
  • Like amlodipine but IV
40
Q

Prognosis for glaucoma

A
  • Always grave
41
Q

Treatment for glaucoma

A
  • Surgical procedure when medical therapy fails
  • Surgical procedures are not successful long term (micropulse, valve implant, diode laser cyclophotocoagulation, etc.)
  • May preserve vision in the short term
  • Very expensive medical treatment, with lots of drugs
  • Long term medical treatment will not be effective
42
Q

Secondary glaucoma treatment principles

A
  • MUST treat the underlying problem

- Generally associated with uveitis

43
Q

Drug of choice for secondary glaucoma

A
  • Dorzolamide/timolol is the drug of choice
44
Q

Chronic glaucoma urgency

A
  • Not an emergency to lower pressure, as the eye is already blind
45
Q

How to know when looking at the eye if it’s secondary or primary glaucoma?

A
  • I guess you’re looking for signs of uveitis or something else going on
  • Flare, swollen iris, synechia
46
Q

Signs of chronic glaucoma

A
  • Corneal edema
  • Dilated pupil with absent PLR
  • Absent menace
  • Pain
  • Episcleral injection
  • Corneal striae (breaks in Descemet’s)
  • Retinal degeneration (hyperreflectivity)
  • Cupped optic disc (lost myelin and vessels)
  • BUphthalmic - enlarged globe
47
Q

Process of glaucoma and blindness

A
  • Pressure destroys ganglion –> lose optic nerve –> retinal degeneration –> ruined corneal endothelium –> corneal edema –> painful eye
48
Q

Medical management for chronic glaucoma

A
  • Not appropriate in a blind, painful eye
49
Q

Options for a blind, painful eye

A
  • Enucleation
  • Enucleation with an implant (not for cats)
  • Evisceration with prosthesis
  • Chemical cytoablation
50
Q

What is the best treatment for a blind, painful eye?

A
  • Enucleation
51
Q

Why not put an implant in the socket for cats?

A
  • They get cancer
52
Q

Contraindication for evisceration with prosthesis?

A
  • Not for intraocular tumor or corneal disease
53
Q

Contraindication for chemical cytoablation

A
    • Not for cats or anyone you like

- Associated with secondary ocular neoplasia (traumatic sarcoma)

54
Q

Description of chemical cytoablation

A
  • Aspirate fluid from vitreous, avoid the lens, inject gentocin and dexamethasone intravitreally
  • must manage post-op uveitis and pressure
  • Multiple treatments may be needed
55
Q

Issues with cytoablation

A
  • Persistently increased IOP
  • Ocular neoplasia may develop
  • LIU
56
Q

Feline glaucoma causes

A
  • Usually secondary to uveitis, lens luxation, neoplasia, trauma, senile change
  • Primary reported in Siamese cats
  • Ultimately fluid goes into the vitreous and pushes the iris and lens forward
57
Q

Treatment for feline glaucoma

A
  • Requires removal of the lens

- Referral procedure

58
Q

Prognosis for feline glaucoma

A
  • Grave

- You always lose

59
Q

Treatments to reduce pressures in cats

A
  • Dorzolamide/timolol
  • Do not use timolol in asthmatic cats
  • Latanoprost not useful
  • Usually no point
60
Q

Microphthalmia

A
  • Congenitally small globe - may or may not be visual
61
Q

Who gets traumatic proptosis most often?

A
  • Brachycephalic dogs, Pekingese
62
Q
  • Definition of proptosis
A
  • Eyelids are trapped behind the globe
63
Q

How quickly to correct traumatic proptosis?

A
  • Very quickly

- Prior to referral

64
Q

Treatment for traumatic proptosis

A
  • Replace the globe
  • Warm compress, systemic and topical antibiotics
  • Oral anti-inflammatory
  • 14-21 day suture removal when globe retropulses
65
Q

How to replace the globe with traumatic proptosis?

A
  • Anesthesia, lubricate, protect cornea
  • Stain cornea to make sure there’s no ulcer
  • Lateral canthotomy
  • Flat scalpel handle across cornea
  • Place mattress sutures
  • Strabismus hook to lift lids
  • Temporary tarsorrhaphy
66
Q

Tarsorrhaphy

A
  • Pre place sutures
  • Go through rubber band and through Meibomian gland
  • Tie them
  • Close the eyelids
  • Can leave a little open at the medial canthus
67
Q

Potential complications of proptosis?

A
  • Blindness, exophthalmos, lagophthalmos, ulceration

- Lateral deviation of the globe

68
Q

Follow up care for proptosis

A
  • Put an E-collar on
  • Check in a few days because the suture will loosen up and don’t want it rubbing on the cornea
  • Usually she leaves for a couple of weeks
69
Q

Proptosis in dogs that are dolichocephalic - prognosis

A
  • Worse than in brachycephalic dogs

- Enucleation is the best choice

70
Q

Prognosis for proptosis in cats

A
  • Poor prognosis
71
Q

Prognosis for proptosis in horses or any species with a closed bony orbit

A
  • Poor
72
Q

Other indications of poor prognosis

A
  • Hyphema
  • Soft globe
  • 2 orbital muscles ruptured (medial rectus ruptures first)
  • No direct or consensual PLR
73
Q

Pthisical eyes

A
  • Clinically, it is characterized by a soft atrophic eye with disorganization of intraocular structures.
74
Q

Exophthalmosis vs proptosis vs buphthalmos

A
  • Make sure you can distinguish
75
Q

Some characteristics of exophthalmos

A
  • Third eyelid is up

- Mass effect in orbit and globe is pushed out

76
Q

Differentials for exophthalmos

A
  • Inflammation
  • Cellulitis
  • Neoplasia
  • Hemorrhage
77
Q

Orbital cellulitis causes

A
  • Peridontal disease (abscess)
  • Penetrating foreign body
  • Unknown etiology
78
Q

Treatment of periorbital cellulitis

A
  • Localize with oral exam
  • Ultrasound, MRI
  • Remove abscessed teeth
  • Remove FB
  • Systemic antibiotics
  • Systemic NSAIDs
  • Topical antibiotics
  • Surgical drainage only if US guided

Ophthalmology (8 decks)

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