Eye Opener: Pathology - Common diseases

Common diseases

Conjunctivitis

Figure 1: Allergic conjunctivitis with hyperemia and mucoid discharge in a dog.

Source: Gelatt K.N. (2008) Essentials of veterinary ophthalmology, 2nd edn., USA: Blackwell Publishing.

Figure 2: Viral conjunctivitis in a dog with canine distemper.

Source: Gelatt K.N. (2008) Essentials of veterinary ophthalmology, 2nd edn., USA: Blackwell Publishing.

Figure 3: Viral conjunctivitis with chemosis and hyperemia in a cat with feline herpesvirus.

Source: Gelatt K.N. (2008) Essentials of veterinary ophthalmology, 2nd edn., USA: Blackwell Publishing.

Inflammation of conjunctival membrane

Red eye with discharge

Serous discharge

Physical irritants
Allergy
Viral agents
Treatment: Flush eye with sterile saline eyewash or artificial tears 3-4 times a day

Mucoid discharge

Follicles on underside of third eyelid
Eye irritant
Infection
Treatment: Antibiotic and corticosteroid eye ointments

Purulent discharge

Infection
May crust eyelids
Treatment: Remove mucus and pus from eyes and apply antibiotics

Bilateral - allergy or systemic disease
Unilateral - foreign body in the eye

Clinical signs

Hyperemia
Chemosis
Ocular discharge
Harmorrhage
Follicle formation
Pruritis
Pain/discomfort

Cats: twitching
Dogs: no discomfort

Classification

Infectious

Bacterial

Dogs: usually caused by Streptococcus and Staphylococcus
Cats: Chlamydophila Felis, Bordetella bronchiseptica

Viral

Dogs: canine distemper virus
Cats: feline herpesvirus-1, Feline calicivirus

Fungal
Rickettsial

Rickettsia rickettsii

Parasitic

Cats: Thelazia californiensis

Noninfectious

Allergic
Follicular

Cats

Lipogranulomatous
Eosinophilic

Ocular squamous cell carcinoma

Figure 1: Limbal squamous cell carcinoma in a horse. Carcinoma is seen as a light pink lobulated mass on the limbus extending to the cornea and conjunctiva.
Source: Hendrix D.V.H. (2005) 'Equine Ocular Squamous Cell Carcinoma', Clinical Techniques in Equine Practice, 4(1), pp. 87-94.

Figure 2: Third eyelid replaced by squamous cell carcinoma in a horse.
Source: Hendrix D.V.H. (2005) 'Equine Ocular Squamous Cell Carcinoma', Clinical Techniques in Equine Practice, 4(1), pp. 87-94.

Figure 3: Ulcerated squamous cell carcinoma in the medial canthus of a horse.
Source: Hendrix D.V.H. (2005) 'Equine Ocular Squamous Cell Carcinoma', Clinical Techniques in Equine Practice, 4(1), pp. 87-94.

Figure 4: Limbal squamous cell carcinoma in a cattle.

Source: Tsujita H. and Plummer C.E. (2010) 'Bovine Ocular Squamous Cell Carcinoma',Veterinary Clinics of North America: Food Animal Practice, 26(3), pp. 511-526.

Figure 5: Corneal squamous cell carcinoma in a cattle.

Source: Tsujita H. and Plummer C.E. (2010) 'Bovine Ocular Squamous Cell Carcinoma',Veterinary Clinics of North America: Food Animal Practice, 26(3), pp. 511-526.

Tumour of the eye and ocular adnexa

Nictitating membrane/third eyelid
Conjunctiva
Eyelids
Cornea
Limbus

Cattle

7-9 years old
Herefold

Kept in subtropcal areas - environmentally favourable
White faced and pink skin around eyes
Incidence: 0.8-5%

Holstein
Whole-carcass slaughter

80% of bovine tumors reported at slaughter

Pigs, goats and sheep - low incidence
Horses

10-11 years old
Lack of periocular pigmentation and ultraviolet light exposure
Draft breeds

Colorado
Belgians
Clydesdales

Light breeds

Appaloosa
Albino
Colour dilute

Clinical signs

Conjunctiva or limbus: small white to light pink mass
Limbal to corneal: multilobulated and compacted
Eyelid: ulcerative mass

Treatment

Surgical excision
Cryosurgery
Radiofrequency Hyperthermia
Irradiation therapy
Radiotherapy
Laser ablation
Immunotherapy
Topical and intralesional chemotherapy

Uveitis

Figure 1. Uveitis of a cow

Source: Bruce H.G., Cheryl L.C. and Robert L.P. (2004) Veterinary ophthalmology essentials, 1st edn., Philadelphia: Elsevier.

Figure 2. Uveitis of a guinea pig

Source: Bruce H.G., Cheryl L.C. and Robert L.P. (2004) Veterinary ophthalmology essentials, 1st edn., Philadelphia: Elsevier.

Figure 3. Uveitis of a horse

Source: Bruce H.G., Cheryl L.C. and Robert L.P. (2004) Veterinary ophthalmology essentials, 1st edn., Philadelphia: Elsevier.

Figure 4. Uveitis of a rabbit

Source: Bruce H.G., Cheryl L.C. and Robert L.P. (2004) Veterinary ophthalmology essentials, 1st edn., Philadelphia: Elsevier.

Inflammation of the uveal tract: iris, ciliary body and choroid

Anterior uveitis: Iris and ciliary body
Posterior uveitis: choroid and retina

Inflammation mediated by vascular impairment
Animals with uveitis are susceptible to secondary infection
Causes

Infection

Parasites
Fungi
Bacteria

Trauma
Metabolic disease
Cancer
Tumor

Clinical signs

Blepharospasm
Conjunctival hypermia
Chemosis
Corneal edema
Aqueous flare (proteins and cells leaking into anterior chamber due to impaired blood-aqueous barrier)
Miosis (small sized pupil)
Unique clinical signs in cats

Nodular accumulation of inflammatory cells within the iris storma

Treatment

Must be treated aggressively to prevent further development (e.g. glaucoma, scarring or loss of vision)
Aspirin
Corticosteroid- injection under the eyelid, eyedropper or oral medication
Atropine

Cataracts

Figure 4: Cataracts in a foal.

Source: Brooks D.E. (2002) 'Equine Ophtalmology', American Association of Equine Practitioners Proceedings, 48, pp. 300-313.

Figure 5: Mature senile cataract of a dog.
Source: Mitchell N. (2006) 'Treatment of canine cataracts using phacoemulsification Part 1: When to refer', Companion Animal, 11(3), pp. 83-87.

Opacity in the lens of the animals giving the animal a blurry vision
Vacuoles in equatorial region
Proceeding to lens nucleus becoming more opaque and spreading to the entire lens
Occurrence due to

Disease
Old age
Trauma to the eye
Inheritance
Can be produced by diets deficient in riboflavin or tryptophane

Clinical signs

Change in colour of the eye
Behaviour of animal changed due to increasing loss of vision i.e clumsiness

Treatment

Surgery

Phacoemulsiﬁcation cataract surgery = high success rate in foals

Topical antibiotics after surgery:

Chloramphenicol, gentamicin, ciproflaxacin, tobramycin ophthalmic solutions
1% atropine = maintain blood-aqueous barrier, minimize pain from ciliary muscle spasm and dilation of pupils.
Corticosteroid = prevent inflammation

References

Brooks D.E. (2002) 'Equine Ophtalmology', American Association of Equine Practitioners Proceedings, 48, pp. 300-313.
Bruce H.G., Cheryl L.C. and Robert L.P. (2004) Veterinary ophthalmology essentials, 1st edn., Philadelphia: Elsevier.
Eldredge D.M., Carlson L.D., Carlson D.G. and Giffin J.M. (2007) Dog owner's home veterinary handbook, 4th edn., New Jersey: Howell Book House.
Gelatt K.N. (2008) Essentials of veterinary ophthalmology, 2nd edn., USA: Blackwell Publishing.
Hendrix D.V.H. (2005) 'Equine Ocular Squamous Cell Carcinoma', Clinical Techniques in Equine Practice, 4(1), pp. 87-94.
King T.C., Priehs D.R., Gum G.G. and Miller T.R. (1991) 'Therapeutic management of ocular squamous cell carcinoma in the horse: 43 cases (1 979-1 989)', Equine Veterinary Journal, 23(6), pp. 449-452.
Kinoshita J.H., Kador P. and Catiles M. (1981) 'Aldose reductase in diabetic cataracts', The Journal of American Medical Association, 246(3), pp. 257-261.
Mitchell N. (2006) 'Treatment of canine cataracts using phacoemulsification Part 1: When to refer', Companion Animal, 11(3), pp. 83-87.
Richter C.P. and Duke J.R. (1970) 'Cataracts produced in rats by yoghurt', American Association for the Advancement of Science, 168(3937), pp. 1372-1374.
Tsujita H. and Plummer C.E. (2010) 'Bovine Ocular Squamous Cell Carcinoma',Veterinary Clinics of North America: Food Animal Practice, 26(3), pp. 511-526.
Turner S.M. (2008) Small animal ophthalmology, 1st edn., Saunders Elsevier.