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Medicine I > Glaucoma > Flashcards

Glaucoma Flashcards

1
Q

What is Glaucoma?

A

Diverse group of diseases which all have an IOP too high for the optic nerve to function properly resulting in the loss of some or all vision

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2
Q

How is Intraocular Pressure maintained?

A
  • Generated by aqueous humor production and outflow in balance
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3
Q

Why is IOP elevated in glaucoma

A

Decreased outflow! - not overproduction

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4
Q

How is Glaucoma diagnosed?

A
  • Signalment, history, clinical signs
  • Menace responses, cotton ball tracking, and maze testing to assess vision
  • PLRs and dazzle reflexes to assess visual pathway
  • Ophthalmoscopy
  • Tonometry (normal 15-25 mmHg)
  • Gonioscopy (referral procedure)
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5
Q

What breeds are commonly affected by Primary glacoma?

A
  • American Cocker Spaniel
  • Basset Hound
  • Chow Chow
  • Shar-Pei
  • Boston Terrier
  • Fox Terrier, Wire Terrier
  • Norwegian Elkhound
  • Siberian Husky
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6
Q

What are the clinical signs of glaucoma?

A
  • Red eye (episcleral injection)
  • Corneal edema
  • Mydriasis
  • Lens subluxation/luxation
  • Painful (blepharospasm)
  • Buphthalmia (enlargement of eyeball)
  • Retinal and Optiv Nerve changes
  • Decreased vision
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7
Q

How is Glaucoma diagnosed?

A
  • Tonometry:
    • Ideally both eyes should have roughly the same IOP
      • >5mmHg (or >20%) difference should make you wonder why
  • Gonioscopy
    • special lens to visualize the iridocorneal angle
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8
Q

What things can affect IOP for Glaucoma diagnostics?

A
  • Normal Diurnal variation (highest in morning)
    • 2-4 mmHg change in normal dog
  • Sedative, tranquilizers, and anesthetic drugs can lower IOP
    • ketamine may increase IOP
  • Patient cooperation
    • minimize pressure applied on eyelids and neck
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9
Q

What is Primary Glaucoma?

A
  • Breed related
  • Always bilateral
  • “good” eye will be lost in median for 8mo
    • With prophylactic therapy - median time to onset of glaucoma is 31mo
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10
Q

What are causes of Secondary Glaucoma?

A
  • Anterior lens luxation
  • Anterior uveitis
  • Neoplasia
  • Hyphema
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11
Q

What determines if Glaucoma is Acute or Chronic?

A
  • Acute - less than 24 hrs old
  • Chronic - >24hrs old
    • Buphthalmia (Big, Blue = Blind)
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12
Q

What are the goals of Glaucoma Therapy

A
  • Save or regain, and maintain vision
  • Achieve and maintain comfort
  • Control Intraocular Pressure
    • target “safe” level
    • avoid progressive optic nerve and retinal damage w/ associated visual deficits
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13
Q

What is the Treatment for Acute Glaucoma?

A
  • Emergency treatment:
    • Topical prostaglandin analogues
      • latanoprost 0.005%
      • Travaprost 0.004%
    • Topical carbonic anhydrase inhibitors
      • Dorzolamide 2%
      • Brinzolamide 1%
    • Beta blocker
      • Timolol 0.5 & 0.25%
      • Betaxolol 0.5%
    • Hyperosmotic agents
      • Dehydrate vitreous
      • Lasts ~6-10hrs
      • IV mannitol 1-2 g/kg
        • slowly over 20-30min
      • Glycerin 1-2 g/kg PO
        • may produce emesis
      • Withhold water for 4 hrs
  • Maintenance therapy:
    • Latanoprost 0.005% SID to BID
    • Dorzolamide 2% TID to QID
    • Timolol 0.5% BID
  • Treatment of “normal” eye
    • Timolol 0.5% BID
  • Frequent IOP checks of both eyes
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14
Q

What are the counterindications for hyperosmotic agents as treatment for acute glaucoma

A
  • Renal disease
  • Cardiovascular disease
  • Dehydration
  • Diabetes (glycerin)
  • Other debilitating disease
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15
Q

What are signs of Chronic Glaucoma?

A
  • Irreversibly blind (duration >72hrs)
  • Buphthalmic
    • except puppies
  • Absent dazzle reflex
  • Absent consensual PLR to fellow eye
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16
Q

What is the treatment for Chronic Glaucoma?

A
  • Enucleation
  • Evisceration
  • Chemical ablation
17
Q

What glaucoma medications are there?

A
  • Topical Prostaglandin derivatives
  • PGF2a derivatives
  • Carbonic anhydrase inhibitors
  • Sympatholytic agents (adrenergic antagonists) Beta blockers
  • Cholinergic miotics
18
Q

What PGF2a derivatives are used to treat Glaucoma?

A
  • Latanaprost 0.005%
  • Travoprost 0.004%
  • Increase uveoscleral outflow
  • Species specific
    • Causes miosis but does not lower IOP in cats
    • Ineffective in horses
  • Use SID or BID
19
Q

What Carbonic anhydrase inhibitors are used for Glaucoma treatment?

A
  • Dorzolamide 2%
  • Brinzolamide 1%
  • TID to QID treatment
  • Decrease aqueous humor production
  • May be topically irritating
    • dorzo pH 5.6 vs brinzo pH 7.5
  • Oral CAI rarely used due to systemic side effects
20
Q

What are the Sympatholytic agents used for Glaucoma treatment?

A
  • 0.25% & 0.5% Timolol (B1 & B2), Betaxolol (B1)
  • BID
  • Inhibits B receptors on ciliary epithelium
  • Decrease aqueous humor production
  • may also increase aqueous humor outflow
  • Mild miosis
  • Potential adverse effects
    • Bradycardia
    • Exacerbation of asthma in cats
    • Mild decrease in tear production
21
Q

What Cholinergic miotics are used for Glaucoma Treatment

A
  • Direct-acting parasympathomimetic agent
    • 2% pilocarpine
  • Indirect-acting parasympathomimetic agent
    • 0.25% or 0.125% demecarium bromide (compounded)
  • increase aqueous humor outflow
  • Usually not effective alone
  • Contraindicated in uveitis and anterior lens luxation
  • Topical pilocarprine - very irritating
  • Demecarium bromide for prophylactic therapy SID
    • often administered with topical steroid SID
22
Q

How are the underlying problems of Glaucoma treated?

A
  • Lens luxation - refer for surgery if still visual
  • Uveitis - treat the inflammation
  • Intraocular neoplasia - enucleation?
  • Hyphema - determine cause
23
Q

What are the surgical options for increasing outflow of aqueous humor?

A
  • Gonioimplants:
    • Tube in AC drains fluid to subconjunctival space
    • Fibrosis leads to early failure (high rates)
  • Filtering procedures:
    • Creating holes in iris, sclera, ciliary body
    • Low success rate in veterinary patients
24
Q

What are the surgical options to decrease Aqueous Humor Production?

A
  • Destruction of ciliary body
    • Cyclophotocoagulation-diode or YAG laser
      • Transcleral
      • Endolaser
  • Both-postoperative pressure spike, cataract formation, inflammation
  • Can perform both cyclophotocoagulation and gonioimplant at the same time increases “success” rate to 58% visual in 1 year

Medicine I (43 decks)

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