Please enable JavaScript.

Coggle requires JavaScript to display documents.

Cataracts - Coggle Diagram

- - - - genetic tests are available
    - - can be congenital
  - - - hyperglycaemia leads to sorbitol accumulation in the lens and causes osmotic draw and disruption of lens fibers
      - begins as vacuoles at the equator most easily visible following pharmacologic dilation
        
        progress quickly and become swollen
        
        can produce visible Y sutures and phacolytic uveitis and creates a risk for lens capsule rupture
        
        diabetic patients develop water clefts due to the increase in lens volume (intumescence) that occurs as fluid enters across the lens capsule
        
        the cleating tends to occur across the suture lines because these are the weakest points of the lens structure
      - classic presenting complaint = acute blindness with eyes 'clouding over'
      - most diabetic dogs (75%) develop cataracts within 6-12 months of disease onset
        
        topical aldose reductase inhibitor has been shown to reduce or delay the onset of cataract formation in diabetic patients
        
        once the cataract has formed it cannot be reduced medically
    - - intraocular inflammation of any cause can result in cataract development
      - all cataracts may cause phacolytic uveitis
        
        hard to determine if cataract is the cause or the result of uveitis
        
        if uveitis preceded the cataract then systemic diagnostics are required
        
        rule out infectious, neoplastic and inflammatory disease
    - - commonly secondary to metabolic disease (rather than nutritional deficiency)
        
        e.g. 1ry hypoparathyroidism
      - present as classic multifocal white pinpoints or 'field of stars' within the lens cortices
        
        care to differentiate from asteroid hyalosis in the vitreous
    - - age-related, dx by exclusion and signalment
      - suspect in large breeds over 6 or small breeds over 10
    - - penetrating trauma from a sharp object e.g. cat claw, thorn
      - severe uveitis 2ry to blunt trauma, corneal trauma or foreign material in anterior chamber can cause cataract development
        
        in some animals severe uveitis may occur after a period of quiescence --> septic implantation syndrome
      - electrocution 2ry to lightning or chewing wires
    - - when fed exclusively inappropriate milk replacers that are amino-acid deficient --> cataracts in puppies (most often isolated to the nucleus)
      - supplement with dam milk/appropriate puppy milk replacer prevents formation and progression
      - once puppy on a balanced diet - nuclear cataracts will often condense as new lens fibres are laid down
    - - 6-12 m after insult
      - other signs e.g. conjunctivitis, keratoconjunctivitis sicca, keratitis, retinopathy may also occur 2ry to radiation
    - - during retinal regeneration, progressive retinal atrophy and retinal detachment, dying photoreceptor cells are hypothesised to produce toxic aldehyde metabolites that progressively damage the lens
      - certain medications e.g. ketoconazole administration at high doses, dimethyl sulfoxide long term can cause lenticular damage
      - may be transient
      - increased levels of free radicals in lens e.g. substituted hydrocarbons --> transient hyperglycaemia --> cataract
    - - metabolic products of retinal degeneration (oxidation products) in vitreous --> lens abnormalities
    - - increased intra-ocular pressure or altered intra-ocular environment --> cataract
      - phagocytic glaucoma 2ry to lens-induced uveitis