Glaucoma

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Glaucoma

• Björn Ekesten
• Department of Clinical Sciences, SLU
• 2006

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What is glaucoma?

• A condition with elevated, abnormal intraocular
  pressure (IOP)?
• The abnormal IOP damages different ocular
  structures
• Impaired function

• An optic neuropathy with a certain type visual
  field loss?
• Elevated IOP is only a risk factor

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Aqueous humor

• Transparent
• Ultrafiltrate of plasma
• Very few cells
• Low protein content
• Function
• Nutrition
• Eliminates wastes
• Maintains the shape of the globe
• Required for normal refraction

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Production

• Formed in the ciliary body
• Diffusion
• Lipophilic substances
• Ultrafiltration
• Passage over a cell membrane hydrostatic
  pressure
• Active secretion
• Carbonic anhydrase
• Rate of formation
• Dog 2,5 µl / min
• Cat 15 µl / min

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Elimination

• Conventional outflow
• Bulk flow - plexus aqueous
• Normal dog 85
• Normal cat 97
• Non-conventional (uveoscleral) outflow
• Normal dog 15
• Normal cat 3
• Glaucomatous dog 3
• What is the normal rate of elimination / min?

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Kammarvinkeln
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Intraocular pressure (IOP)

• (Pa-Pi) Cin (Pi-Pe) Cout U
• Cin inflow facility µl / min / mm Hg
• Cut outflow facility µl / min / mm Hg
• Pa ciliary artery pressure mm Hg
• Pi intraocular pressure (IOP) mm Hg
• Pe episcleral venous pressure mm Hg
• U uveoscleral outflow µl / min

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Glaucoma

• Cause of elevated IOP
• Impaired aqueous outflow
• Not increased production
• Primary - without predisposing ocular disease
• Secondary - complication to other ocular diseases

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Pupillary block

• Primary
• Relative pupillary block (angle-closure glaucoma)
• Sekundary
• Total posterior synechia / iris bombé (seclusio)
• Inflammatory debris in the pupil (occlusio)
• Fakomorfic (intumescent catarakt / swollen lens)
• Lens(sub)luxation, vitreous prolaps

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Closed iridocorneal angle
Iris touches the corneal endothelium

• Primary
• Angle-closure glaucoma (effect of the relative
  pupillary block)
• Secondary
• Iris bombé (together with pupillary occlusion)
• Anterior uveitis - peripheral anterior synechiae
• Forward displacement of peripheral iris -
  neoplasia, iridociliary cysts?

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Reduced opening to ciliary cleft

• Primary
• Angle-closure glaucoma (collapse of ciliary
  cleft)
• Dysplasia of the pectinate ligamentet
• Secondary
• Anterior uveitis / preiridal membranes
  (predisposed individuals)
• Neoplasia

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Pectinate ligament dysplasia

• Increased risk for glaucoma if excessive PLD
• 100 90 risk
• 75 11 risk
• 50 0,2 risk
• Polygenic inheritance
• Triggering factor?

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Outflow block inside the ciliary cleft

• Primary
• Open-angle glaucoma
• Sekundary
• Anterior uveitis - inflammatory debris
• Intraocular hemorrhage
• Melanocytosis / neoplastic cells
• Viscoelastics

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Primary glaucoma

• Open-angle glaucoma
• Beagle (AR)
• Norwegian Elkhound
• Angle-closure glaucoma
• Samoyed
• Springer spaniel
• Pectinate ligament dysplasia
• Samoyed
• Springer spaniel
• Flat Coated Retriever

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(No Transcript)
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Secondary glaucoma

• Anterior uveitis
• Peripheral anterior synechiae
• Posterior synechiae
• Debris
• Lens associated
• Catarakt
• Luxation / subluxation
• Intraocular neoplasias
• Intraokular hemorrhage
• Intraokular melanocytosis
• Iridociliary cysts

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Acute glaucoma

• Sudden onset and dramatic
• Signs of pain
• Blepharospasm
• Epiphora
• Altered behaviour
• Episcleral congestion
• Corneal changes
• Cloudiness / edema
• Striae
• Mydriasis - no response to light
• Impaired vision
• Elevated IOP

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Sequels - short-term

• Ganglion cell damage
• Optic nerve head excavation and cupping
• Visual impairment
• Secondary uveitis
• Synechiae formation
• Rapid!

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Open-angle glaucoma

• Insidous!
• Obvious clinical signs rare initially
• Visual field loss
• Slightly - moderately elevated IOP (30 mm Hg)
• Optic nervehead alterations
• Obvious signs when ciliary cleft has collapsed

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Chronic glaucoma

• Chronic pain
• Impaired vision / blindness
• Buphthalmos
• Chronic uveitis
• Cataract
• Lens luxation
• Retinal degeneration
• Elevated IOP

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Diagnosis

• Eye examination
• Tonometry
• Gonioscopy
• Primary / secondary?

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Treatment
Medical
Filtration surgery
Cyclo- destructive surgery
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Acute medical treatment

• Mannitol 1-2 g/kg iv
• Transient decrease in IOP
• Not horse
• Miotics (topical)
• Pilocarpine 2 x 3-4
• Avoid in horses
• Beta blockers (topical)
• Timolol 0,5 x 2
• Prostaglandins (topical)
• Latanoprost x 1-2
• Not in horses
• Carbonic anhydrase inhibitors (topical)
• Dorzolamid
• Brinzolamid

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Maintenance

• Miotics (topical)
• Pilocarpine 2 x 3-4
• Avoid in horses
• Beta blockers (topical)
• Timolol 0,5 x 2
• Prostaglandins (topical)
• Latanoprost x 1-2
• Not in horses
• Carbonic anhydrase inhibitors (topical)
• Dorzolamid x 2-3
• Brinzolamid x 2-3
• Surgical intevention?

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When is surgery needed?

• When medical treatment is insufficient
• Does it help
• Shunts
• Cyclodestructive treatments
• Laser
• Cryo
• Enucleate if the IOP cannot be controlled properly

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Gonioscopic findings in ESS
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Selective breeding
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Summary

• Several mechanisms
• Primary / secondary
• Mode of inheritance?
• No DNA-tests available
• Emergencies!
• Guarded prognosis, at best.