Large animal ophthalmology Flashcards
What do sunken eyes commonly indicate in large animals?
Dehydration
What effect do toxicity or septicaemia commonly have on the eyes?
Lead to congestion of mucous membranes, including the conjunctiva
What can be assessed in aqueous/vitreous samples of the eye?
- Calcium or magnesium in cases of sudden death
- Urea
- Beta hydroxybutyrate
What is meant by blaines in large animals and what does this suggest?
Swelling of the eyelids, hives/pohtosensitisation as an allergic reaction
Briefly outline besnoitiosis
- Protozoal parasite with severe effect on skin
- Very pathognomic lesions in the eye, almost cyst like appearance without conjunctival inflammation
List the ophthalmic conditions commonly affecting cattle
- New Forest eye (IBK)
- Silage eye (bovine iritis)
- Squamous cell carcinoma
- Systemic viral infections e.g. IBR ad MCF
- BVS/catarats
- Hypovitaminosis A
- Ringworm
List diseases of young stock/calves that may have ophthalmic presentations
- Lead poisoning
- Cerebrocortical necrosis
- Meningitis
- Listeriosis
- Tetanus
What causes New Forest eye in cattle?
- Aka infectious bovine keratoconjunctivitis
- Moraxella bovis G-ve aerobic bacterium
Describe the clinical signs of New Forest eye
- Seen in group setting, young stock at pasture, transmission by flies in summer
- Severe pathology in cornea, blood vessel infiltration, opacity
- Significant pain
- May get perforation of cornea
- Old lesions may be visible as pigmented scars
Describe the treatment of infectious bovine keratoconjunctivitis
- Topical cloxacillin ointment (impractical,, stressful)
- Tetracycline (often get secondary Mycoplasma infection)
- Bulbar conjunctivitis injection as depot source, IM can also be used
- NSAIDs
- Suture eyelids to control pain and reduce risk of performation
Why should topical steroids not be used in the treatment of IBK?
Risk of ulceration
Outline the prevention of IBK
- Fly control and pasture control
- Some age related immunity so do not mix stock of different ages
What is iritis?
Inflammation of the iris
Describe the clinical signs of iritis in cattle
- Severe intraocular inflammation without systemic illness
- Blindness
- Yellow cornea
- Fibrin and collagen accumulations in anterior chamber and cornea
- Signs of anterior inflammation
- May see foreign body in some cases, or evidence of physical trauma
Outline the cause of silage eye in cattle
- Is iritis
- Pathogenesis poorly understood
- Some association with Listeria
- May be a contaminant of silage and poor silage handling
- To prevent, consider feeding method
Outline the treatment of silage eye in cattle
- Usually just steroids rather than antibiotics
- If just silage eye, then only nneed anti-inflamma
- Bulbar subconjunctival injection to act as depot
What is ocular squamous cell carcinoma commonly known as?
Cancer eye
Describe the appearance of ocular squamous cell carcinoma in cattle
- Ocular surface
- small mass, typically affects eye ball at limbus
- Looks like wart-like mass
- Can affect eyelid and third eyelid, usually lighter coloured skin
- Some may bleed
Outline the treatment of ocular squamous cell carcinomas in catle
- Depends on extent, may require enucleation if globe is not salvageable or if orbit is affected
- Enucleation can be performed standing
- Or under local, can clamp and remove mass
How does IBR cause ocular disease in cattle
- Infectious bovine rhinotracheitis, BHV-1
- Affects upper resp. tract and eyes
- Eye and mucous membranes around there are sites of viral replication and damage
Describe the ocular signs of IBR
- Conjunctivitis (hyperaemia and chemosis)
- Bilateral serous ovular discharge
- Diffuse corneal oedema possible
- In immunological naiive first signs maybe pyrexia and conjunctivitis
- Secondary bacterial infection leading to purulent discharge and ulceration
- Can be fatal
Describe the appearance of the respiratory tract with IBR
Ulceration in upper and lower resp. tract
What are the causative agents of malignant catarrhal fever?
Rhadinovirus genus of Gammaherpesviridae subfamily of Herpesviridae
Outline the pathogenesis of MCF
Lymphotrophic herpesviruses that are commonly associated with lymphoproliferation
