CANINE & FELINE

Definition and Epidemiology:

• Definition: A cataract is any opacity of the ocular lens or its capsule, resulting from changes in lens protein composition or lens fiber arrangement. It is a prevalent ocular abnormality in dogs and occasionally seen in cats.

• Species Affected: Both dogs and cats, with a significant breed and age-related predisposition in dogs.

• Breed Predisposition:

  • Dogs: Smooth fox terrier, Havanese, Bichon frisé, Boston terrier, various poodle types, silky terrier, American cocker spaniel, miniature schnauzer. Diabetes mellitus is a significant secondary cause, showing a genetic predisposition in some breeds.

  • Cats: Persian, Birman, Himalayan, domestic shorthair (mostly presumed congenital).

Clinical Presentation:
  •    Forms/Subtypes: Classified by age at onset (congenital, juvenile, senile), location (capsular, cortical, nuclear), and severity (incipient, immature, mature, hypermature, Morgagnian).
  •    Symptoms: Vision disturbances, cloudy white pupil appearance, potentially associated with pain, redness, or epiphora if leading to secondary anterior uveitis.

Etiology and Pathophysiology:
  •    Inherited Factors: Autosomal recessive traits in many breeds.
  •  Secondary Causes: Diabetes mellitus (especially in dogs), intraocular diseases (uveitis, glaucoma), trauma, nutritional deficiencies, hypocalcemia, radiation exposure, medication effects (e.g., ketoconazole), toxins (e.g., dinitrophenol), electric shock.
  •   Mechanisms: Altered glucose metabolism in diabetic animals leads to sorbitol accumulation, increasing intra-lens osmotic pressure and opacification.

Diagnostic Overview:
  •    Initial Examination: Presence of a cloudy pupil, assessed further with complete dilation using 1% tropicamide.
  •   Differential Diagnosis: Includes nuclear sclerosis (age-related change without vision loss), hyperlipidemia, diffuse corneal edema, other causes of secondary cataracts like retinal diseases.

Advanced Testing:
  •    Confirmatory Tests: CBC, serum biochemistry, urinalysis to exclude systemic causes; ocular ultrasound and electroretinogram to evaluate eye health before surgical interventions.

Treatment Strategies:
  •    Non-Surgical Management: Monitoring for nonprogressive or early-stage cataracts; manage secondary uveitis and potential glaucoma.
  •    Surgical Intervention: Phacoemulsification with intraocular lens (IOL) implantation for vision restoration, significantly reducing risks of complications such as uveitis, glaucoma, and retinal detachment.
  •    Postoperative Care: Frequent monitoring, topical antibiotics, and anti-inflammatories; potentially long-term anti-inflammatory therapy especially in diabetic patients.

Prognosis and Outcome:
  •    Success Rates: High success rates (90-95%) with early surgical intervention and diligent postoperative care.
  •    Long-Term Monitoring: Regular follow-ups essential to assess the surgical outcome and manage any long-term complications.

Preventive Measures and Client Education:
  •    Breeding Considerations: Screen potential breeding animals for hereditary cataracts; encourage breeding of non-affected individuals.
  •    Management of Diabetes: Critical for delaying cataract formation in diabetic animals, although most will eventually develop cataracts despite optimal management.
  •    Public Awareness: Educate clients on the differences between cataracts and lenticular sclerosis, and the importance of early diagnosis and management.