Glaucoma (Plummer)

Question 1

Pertinent structures

Answer 1

• Ciliary body
• Iridocorneal angle (ICA)
• Retina and optic nerve

Question 2

Gonioscopy

Answer 2

• special lens to visualize drainage angle

Question 3

Aqueous production

Answer 3

• Active secretion by the non-pigmented ciliary epithelium
  
  • carbonic anhydrase
• Ultrafiltration of plasma

Question 4

Glaucoma def

Answer 4

• Group of diseases characterized by altered aqueous humor dynamics
• Elevation of IOP incompatible with health of optic nerve and eye
• CS
  
  • edema of cornea
  • depression of optic disc

Question 5

Types of glaucoma

Answer 5

• Primary
  
  • congenital
  • open angle
  • closed angle
• Secondary
  
  • inflammatory
  • lens lux
  • mechanical/neoplastic

Question 6

Congenital Glaucoma

Answer 6

• Usually due to a developmental defect
  
  • failure of rarefaction of drainage apparatus
• May produce profound buphthalmia
• May be inherited
• Usually a ‘fluke’ of development

Question 7

Primary open angle glaucoma

Answer 7

• Hereditary disorder in beagle, and others
• Most common form in people
• Normal drainage angle and pectinate muscles but slow increase in IOP…..?
• Open angle will progress to closed angle

Question 8

Primary closed angle glaucoma

Answer 8

• most common form in veterinary patients

Question 9

One part of body not covered by epithelial lining

Answer 9

• Iris has no anterior epithelium
  
  • makes it sticky: prone to synechia

Question 10

Lens lux is a cause of

Answer 10

• cause of secondary glaucoma

Question 11

Glaucoma

DX

Answer 11

• Clinical signs
  
  • mydriasis
  • scleral injection
  • corneal edema
• Index of suspicion
• Tonometry

Question 12

Acute presentation of glaucoma

Answer 12

• Ocular pain
  
  • epiphora
  • blepharospasm
  • ‘headache’
• Increased IOP
• Mydriasis
• Corneal edema
• Episcleral injection
• Visual loss or disturbance

Question 13

Chronic presentation

Answer 13

• Permanent vision loss
  
  • optic disc cupping
  • retinal degeneration
• Buphthalmia
• Permanent corneal edema
• Striate keratopathy
  
  • Haab’s striae
• Recurrent corneal ulcerations
• Lens lux/sublux
• cataract formation

Question 14

Equine Glaucomas

Answer 14

• Mostly secondary to
  
  • uveitis
  • ERU
• Primary in the appaloosa
• Tend to maintain vision longer than dogs

Question 15

Feline Glaucomas

Answer 15

• Mostly secondary to
  
  • uveitis
  • Intraocular neoplasia
  • aquous misdirection
• POAG in Siamese and Burmese

Question 16

Tonometry

Answer 16

• Via applanation or rebound
• Normal canine and feline IOP
  
  • 15-25
  • ideal target is low teens
  • can vary with eye/orbit conformation
    
    • brachycephalics higher
• Normal equine IOP
  
  • 23.3 +/- 6.9 mmHg
  • must be taken with head held up
    
    • down head can inc up to 87%

*digital tonomotry is not reliable

Question 17

Visual implications of early glaucoma

Answer 17

• Narrowing field of vision (peripheral loss)
• chronic and progressive

Question 18

Treatment of glaucoma

Answer 18

• Goals of therapy
  
  • treat primary cause
  • lower IOP
    
    • decrease prod AqH
    • inc outflow of AqH
  • Neuroprotection
• Medical
  
  • topical
  • systemic
• Surgical

Question 19

Glaucoma

Medical Therapy

Answer 19

• Classes of drugs
  
  • Hyperosmotic agents
    
    • Topicals: chronic therapy
    • systemics: emergency therapy
  • Cholinergic agonists
  • a₂ adrenergic agonists
  • B adrenergic antagonists***
    
    • used a lot
    • dec prod of AqH by a small amount
    • treat normal eye as well as abnormal eye
    • synergism
  • Carbonic anhydrase inhibitors***
    
    • Dorzolamide: made at UF (bigger than gatorade)
  • Prostaglandin analogues
    
    • cause inc in outflow of aqueous humor
    • causes profound miosis: worry about lens luxation

Question 20

Parasympathomimetics

Answer 20

• do not use as primary tx for glaucoma
  
  • can use as adjunct I think
• burns
• pH too low
• lowers intraocular pressure by causing profound myosis and uveitis

Question 21

The majority of AqH produced by

Answer 21

• Carbonic anhydrase in ciliary epithelium

Question 22

Prophylactic therapy

Answer 22

• Essentially all POAG and PCAG are bilateral
• Need to treat normotensive eye to delay onset of ocular hypertension
  
  • b-blocker
  • prostaglandin
  • miotic
• Mean time to develop glaucoma is 6 mos
  
  • Medical Tx can delay to a mean of 30 mos

Question 23

Glaucoma

Surgical treatment

Answer 23

• Gonioshunts***
• Cycloablation***
  
  • Cryotherapy: old school causes lots inflammation
  • Laser photocoagulation
    
    • transscleral
    • Endoscopic
• Other techniques to inc outflow
  
  • iridenclesis
  • cyclodialysis
  • corneoscleral trephination/posterior sclerotomy + peripheral iridectomy

Question 24

‘Safe’ IOP

Answer 24

• Once optic nerve is damaged, remaining axons more sensitive to further insult
• Lowering IOP to less than normal may be protective of ONH
• Sensitivity of optic nerve to an IOP may change

Question 25

Salvage procedure for glaucoma

Answer 25

* Once vision is lost * comfort first priority * enucleation * evisceration with intraocular prosthesis * pharmacologic ablation: if not blind will cause blindness

Question 26

Glaucoma take home

Answer 26

* Glaucoma painful and potentially blinding * Recognize clinical signs * Is an emergency * get pressure down ASAP * mannitol * Topical prostaglandin * referral * Goals of therapy * maintain vision as long as possible * keep pressures low enough for comfort * treat normal eye if primary glaucoma