Ophthalmology > Glaucoma > Flashcards

Glaucoma Flashcards

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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
What is the mainstay to decrease IOP with glaucoma?
- Dorzolamide/timolol
26
Dorzolamide/timolol MOA
- Carbonic anhydrase inhibitor (slows production of aqueous) - Beta blocker (vasoconstriction to decrease aqueous production)
27
Which species can you use dorzolamide/timolol on?
- Dogs, cats, horses
28
What can you use dorzolamide/timolol to treat?
- Primary glaucoma - Lens luxation - Uveitis
29
Caution for dorzolamide/timolol
- Asthmatic cats
30
Mannitol MOA
- Osmotic diuresis to dehydrate the eye
31
When to use mannitol?
- If IOP >40 mmHg | - Primary glaucoma only
32
How to use mannitol?
- IV slowly over 15-30 minutes - Give once - WIthhold water and fluids for 4 hours
33
Contraindications for mannitol?
- Uveitis | - If eye is inflamed, mannitol goes into vitreous and draws fluid in which is bad
34
Latanoprost MOA
- 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
Species for latanoprost
- DOGS ONLY | - Not cats or horses
36
Contraindications for latanoprost
- Uveitis or anterior lens luxation (traps vitreous in pupil)
37
Who can use latanoprost?
- ONLY opthalmologists
38
Solu-medrol and solu-delta purpose
- Prevent reperfusion injury
39
Solumedrol and solu-delta MOA
- Calcium channel blocker to stop cytotoxic effects of ischemia - Like amlodipine but IV
40
Prognosis for glaucoma
- Always grave
41
Treatment for glaucoma
- 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
Secondary glaucoma treatment principles
- MUST treat the underlying problem | - Generally associated with uveitis
43
Drug of choice for secondary glaucoma
- Dorzolamide/timolol is the drug of choice
44
Chronic glaucoma urgency
- Not an emergency to lower pressure, as the eye is already blind
45
How to know when looking at the eye if it's secondary or primary glaucoma?
- I guess you're looking for signs of uveitis or something else going on - Flare, swollen iris, synechia
46
Signs of chronic glaucoma
- 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
Process of glaucoma and blindness
- Pressure destroys ganglion --> lose optic nerve --> retinal degeneration --> ruined corneal endothelium --> corneal edema --> painful eye
48
Medical management for chronic glaucoma
- Not appropriate in a blind, painful eye
49
Options for a blind, painful eye
- Enucleation - Enucleation with an implant (not for cats) - Evisceration with prosthesis - Chemical cytoablation
50
What is the best treatment for a blind, painful eye?
- Enucleation
51
Why not put an implant in the socket for cats?
- They get cancer
52
Contraindication for evisceration with prosthesis?
- Not for intraocular tumor or corneal disease
53
Contraindication for chemical cytoablation
- - Not for cats or anyone you like | - Associated with secondary ocular neoplasia (traumatic sarcoma)
54
Description of chemical cytoablation
- 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
Issues with cytoablation
- Persistently increased IOP - Ocular neoplasia may develop - LIU
56
Feline glaucoma causes
- 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
Treatment for feline glaucoma
- Requires removal of the lens | - Referral procedure
58
Prognosis for feline glaucoma
- Grave | - You always lose
59
Treatments to reduce pressures in cats
- Dorzolamide/timolol - Do not use timolol in asthmatic cats - Latanoprost not useful - Usually no point
60
Microphthalmia
- Congenitally small globe - may or may not be visual
61
Who gets traumatic proptosis most often?
- Brachycephalic dogs, Pekingese
62
- Definition of proptosis
- Eyelids are trapped behind the globe
63
How quickly to correct traumatic proptosis?
- Very quickly | - Prior to referral
64
Treatment for traumatic proptosis
- Replace the globe - Warm compress, systemic and topical antibiotics - Oral anti-inflammatory - 14-21 day suture removal when globe retropulses
65
How to replace the globe with traumatic proptosis?
- 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
Tarsorrhaphy
- 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
Potential complications of proptosis?
- Blindness, exophthalmos, lagophthalmos, ulceration | - Lateral deviation of the globe
68
Follow up care for proptosis
- 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
Proptosis in dogs that are dolichocephalic - prognosis
- Worse than in brachycephalic dogs | - Enucleation is the best choice
70
Prognosis for proptosis in cats
- Poor prognosis
71
Prognosis for proptosis in horses or any species with a closed bony orbit
- Poor
72
Other indications of poor prognosis
- Hyphema - Soft globe - 2 orbital muscles ruptured (medial rectus ruptures first) - No direct or consensual PLR
73
Pthisical eyes
- Clinically, it is characterized by a soft atrophic eye with disorganization of intraocular structures.
74
Exophthalmosis vs proptosis vs buphthalmos
- Make sure you can distinguish
75
Some characteristics of exophthalmos
- Third eyelid is up | - Mass effect in orbit and globe is pushed out
76
Differentials for exophthalmos
- Inflammation - Cellulitis - Neoplasia - Hemorrhage
77
Orbital cellulitis causes
- Peridontal disease (abscess) - Penetrating foreign body - Unknown etiology
78
Treatment of periorbital cellulitis
- Localize with oral exam - Ultrasound, MRI - Remove abscessed teeth - Remove FB - Systemic antibiotics - Systemic NSAIDs - Topical antibiotics - Surgical drainage only if US guided
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