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GLAUCOMA - Coggle Diagram

- - - - impairment or loss of vision
      - beware if applying pressure to neck or manual extension of eyelids during tonometry measurement as this will increase IOP
      - IOP reported to decrease with ageing
      - IOP may be affected by breed e.g. terriers have fluctuant IOPs
  - - - if IOP falls as a result of anterior segment inflammation, patients are at risk for 2ry glaucoma
- - - - in young animals (and those with slowly progressive cases e.g. open angle glaucoma) may be poss for useful vision to be retained
- - - - aqueous drainage ultimately fails
    - - spaniels
      - basset hound
      - bouvier des flandres
      - lab and golden/flat coated retriever
      - great dane
      - welsh terrier
      - dandy dinmont terrier
      - shiba inu
      - siberian husky
      - samoyed
      - chow chow
      - shar pei
      - boston terrier
  - - - the optic nerve seems to tolerate the prolonged, often marked elevations in IOP better than acute onset forms of glaucoma
      - in some cases useful vision can be retained through the late stages of the disease, despite the presence of pronounced buphthalmos
- - - - increased lacrimation
      - blepharospasm
      - enopthalmos/third eyelid protrusion
      - head shyness
      - does not respond well to NSAIDs, need to control IOP as pain relief
    - - 'steamy' bluish appearance
      - esp. in acute rise in IOP >40-50mmHg in dogs
    - - dilated or moderately dilated poorly responsive pupil
        
        results from pressure-induced paresis or paralysis of the iris sphincter muscle
      - consensual PLR in other eye should be assessed to determine if vision function present
    - - not all causes of episcleral congestion have glaucoma and vice versa
      - differential diagnoses
        
        glaucoma
        
        uveitis
        
        episcleritis
        
        retrobulbar space occupying lesion e.g. abscess, neoplasia
        
        horners syndrome
        
        hyper viscosity syndromes
        
        excitement
    - - initially occurs as a result of damage to the ganglion cell axons in the region of the optic nerve head
        
        due to the adverse effects of elevated IOP on the vascular supply to the optic nerve head and axoplasmic flow within the optic nerve axons
      - clinical signs indicative of unilateral blindness in glaucoma
        
        loss of menace response in affected eye
        
        loss of dazzle reflex to a bright light shone in affected eye
        
        loss of consensual PLR
        
        no constriction of the pupil in the constralateral eye when the affected eye is illuminated in a dimly lit room
        
        re-dilation of the pupil in affected eye on swinging flashlight test
        
        absence of tracking response to cotton wool ball with the contralateral eye covered
        
        inability to negotiate a maze with the contralateral eye covered