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Ophthalmology Rotation > Glaucoma > Flashcards

Glaucoma Flashcards

1
Q

What is glaucoma?

A

A diverse group of diseases united by a common theme in which IOP is too high for the optic nerve to function properly resulting in the loss of some or all vision

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2
Q

Intraocular Pressure

A
  • Generated by aqueous humor production and outflow normally in balance
  • Elevated in glaucoma due to decreased outflow (NOT overproduction)
  • Prevalence of glaucoma in dogs 1.7% in last decade (similar to 1-2% in man)
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3
Q

Glaucoma Diagnosis

A
  • Signalment, history and clinical signs
  • Menace responses, cotton ball tracking, and maze testing to assess vision
  • PLRs and dazzle reflexes to assess visual pathway
  • Ophthalmoscopy
  • Tonometry (normal IOP 15-25mmHg)
  • Gonioscopy (referral procedure)
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4
Q

glaucoma (rankin)

Primary glaucoma - breed related

A

– American Cocker Spaniel
– Basset Hound
– Chow Chow
– Shar Pei
– Boston Terrier
– Fox Terrier, Wire
– Norwegian Elkhound
– Siberian Husky

(43 breeds)

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5
Q

glaucoma (rankin)

Owner may report:

A

– Blepharospasm
– Nictitating membrane protrusion
– Red eye
– Cloudy eye
– Mydriasis
– Decreased vision

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6
Q

glaucoma (rankin)

Clinical Signs of Glaucoma

  • Ophthalmic findings
A

– Red eye (episcleral injection)
– Corneal edema (blue)
– Mydriasis
– Lens subluxation/luxation
– Painful!!! (blepharospasm)
– Buphthalmia
– Retinal and optic nerve changes
– Decreased vision

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7
Q

Diagnosis

A
  • Tonometry (normal 15-25mmHg)
    • Ideally both eyes should have roughly the same IOP (>5mmHg (or > 20%) difference should make you wonder why…)
  • Gonioscopy
    • Use of a special lens to visualize the iridocorneal angle
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8
Q

IOP can be affected by…

A
  • Normal diurnal variation (highest in the morning)
    • 2-4 mmHg in normal dog
  • Sedatives, 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

glaucoma (rankin)

Primary Glaucoma

A
  • Breed related
  • Always bilateral
  • “Good” eye will be lost in median of 8 months
  • With prophylactic therapy, median time to onset of glaucoma is 31 months
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10
Q

glaucoma (rankin)

Secondary Glaucoma Signs/Causes

A
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11
Q

glaucoma (rankin)

  • *Acute vs. Chronic?**
  • *▪ Acute**
A

– Less than 24 hours old
– Potential for vision?

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12
Q

glaucoma (rankin)

  • *Acute vs. Chronic?**
  • *• Chronic**
A

– >>24 hours old
– Buphthalmia (big, blue…..

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13
Q

glaucoma (rankin)

Glaucoma Therapy

  • goals
  • control of intraocular pressure
A
  • Goals
    – Save or regain, and maintain vision
    – Achieve and maintain comfort
  • Control of intraocular pressure
    – Target “safe” level
    – Avoid progressive optic nerve and retinal damage with associated visual deficits
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14
Q

glaucoma (rankin)

Therapy for Acute Glaucoma

A

Treat aggressively if chance for vision!!!
Referral

  • Emergency treatment
    – Topical prostaglandin analogues
  • Latanoprost 0.005% (Xalatan®)
  • Travaprost 0.004% ( Travatan ®)
    – Topical carbonic anhydrase inhibitors
  • Dorzolamide 2% ( Trusopt ®)
  • Brinzolamide 1% ( Azopt ®)
    – Beta blocker
  • Timolol 0.5 & 0.25%
  • Betaxolol 0.5%
  • Hyperosmotic agents
    – Dehydrate vitreous
    – Last about 6-10 hours
    – IV mannitol
  • Dosed at 1-2 grams/kg
  • Administered slowly over 20 30 minutes
    – Glycerin
  • 1-2 g/kg orally
  • May produce emesis
    – Withhold water for 4 hours
  • Contraindications
    – Renal disease
    – Cardiovascular disease
    – Dehydration
    – Diabetes (glycerin)
    – Other debilitating disease
  • Ophthalmologist referral
  • Maintenance therapy
    – Latanoprost 0.005% q12 to 24 hr
    – Dorzolamide 2% q6 to 8 hr
    – Timolol 0.5% q12 hr
  • **Treat the “normal
    – Timolol 0.5% q12 hr
  • Frequent IOP checks for monitoring of BOTH eyes
    – 1 day, 3-5 days, then weekly, monthly, q2 to 3 months
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15
Q

glaucoma (rankin)

Chronic Glaucoma

  • signs
  • treatment
A
  • Irreversibly blind (duration >72 hours)
  • Buphthalmic (big, blue…blind)
    – Except puppies
  • Absent dazzle reflex
  • Absent consensual PLR to fellow eye
  • Palliative procedure
    – Enucleation
    – Evisceration
    – Chemical ablation
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16
Q

glaucoma (rankin)

Glaucoma Medications

A
  • Topical prostaglandin derivatives
  • PGF2α derivatives
    – Latanaprost 0.005% (Xalatan®)
    – Travoprost 0.004% ( Travatan ®)
    – Increase uveoscleral outflow
    – Species specific
  • Causes miosis but does not lower IOP in cats
  • Ineffective in horses
    – Used SID (in evening) or twice daily
  • Carbonic anhydrase inhibitors
    – Dorzolamide 2% ( Trusopt ®)
    – Brinzolamide 1% ( Azopt ®)
    – TID to QID treatment
    – Decrease aqueous humor production
    – May be topically irritating
  • Dorzolamide pH 5.6 vs brinzolamide pH 7.5
    – Oral CAI rarely used due to systemic side effects
  • Sympatholytic agents (adrenergic antagonists) Beta blockers
    – 0.25% & 0.5% Timolol (ß1 and ß2), Betaxolol (ß1)BID
    – Inhibits ß 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
  • Cholinergic miotics
    – 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
    – I do NOT recommend using topical pilocarpine (too irritating!)
    – Demecarium bromide for prophylactic therapy SID
    ▪ Often administered with topical steroid SID
17
Q

glaucoma (rankin)

Therapy for Secondary Glaucoma

A

Treat the underlying problem!
– Lens luxation - refer for surgery if still visual
– Uveitis - treat the inflammation
– Intraocular neoplasia - enucleation?
– Hyphema - determine cause of hyphema

18
Q

glaucoma (rankin)

Surgical Therapy for Glaucoma

  • goals
A

Increase aqueous humor drainage

Decrease aqueous humor production

19
Q

glaucoma (rankin)

Surgical Therapy - Increase Outflow

A
  • Gonioimplants
    – Tube in AC drains fluid to subconjunctival space
    – Fibrosis leads to early failure
  • Filtering procedures:
    – Creating holes in iris, sclera, ciliary body
    – Low success rate in veterinary patients
20
Q

Surgical Therapy Decrease 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…increase “success” rate to 58% visual in 1 year

Ophthalmology Rotation (20 decks)

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