Download Ocular Manifestations of Systemic Disease in Companion Animals

OCULAR MANIFESTATIONS OF SYSTEMIC DISEASE IN COMPANION ANIMALS PART I
Pennsylvania Veterinary Medical Association 18th Annual Spring Clinic 2017
Eric C. Ledbetter, DVM, DACVO
Cornell University, College of Veterinary Medicine,
Ithaca, NY, USA
Outline
1) General Concepts
2) Immune-mediated disease
3) Vascular and hematologic disease
4) Metabolic and endocrine disease
5) Neoplastic disease
6) Nutritional disease
7) Systemic toxicities
1) General Concepts
The ocular examination is a valuable diagnostic tool for a wide-range of systemic disorders and it
is frequently underused by clinicians for this purpose. Performance of a complete ocular exam requires
relatively simple and inexpensive equipment.
Ocular lesions are frequently observed with systemic disease. Examination of the eyes provides
a unique opportunity for direct visual examination of the nervous (optic nerve) and vascular (retinal and
uveal vessels) systems of the animal. Animals with systemic disease conditions are often first presented
for evaluation of their ocular problems as these lesions may be visually obvious to owners and clinical
signs of ocular disease are often more readily apparent, and difficult to ignore, than subtle systemic
abnormalities.
2) Immune-mediated Disease
Canine uveodermatologic syndrome (Vogt-Koyanagi-Harada-like syndrome) is an autoimmune
disorder of dogs targeting melanocytes. As the name suggests, clinical lesions primarily develop in the
eyes and skin. Ocular lesions include varying degrees of anterior and posterior uveitis, uveal
depigmentation, retinal detachments, and secondary glaucoma. Dermatologic lesions typically include
poliosis (whitening of the hair) and vitiligo (skin depigmentation). Breed predispositions include Akita,
Samoyed, Siberian husky, and Shetland sheepdog.
Granulomatous meningoencephalitis is an idiopathic, inflammatory disorder of the canine and
feline central nervous system. Disseminated, focal, and ocular forms of granulomatous
meningoencephalitis exist and all forms may be associated with ocular lesions. Ocular lesions of
granulomatous meningoencephalitis may include optic neuritis, papilledema, chorioretinitis, and retinal
detachment.
Numerous immune-mediated epidermal disease can result in blepharitis, including pemphigus
foliaceus, pemphigus erythematosus, pemphigus vulgaris, bullous pemphigoid, drug reactions, atopy,
and food allergies.
3) Vascular/Hematologic Disease
With systemic hypertension of any etiology, uveal hemorrhages, hyphema, retinal hemorrhage,
vitreal hemorrhage, subretinal fluid, tortuous retinal vessels, and retinal detachments may be observed.
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Thrombocytopenia and coagulopathies may be associated with periocular or intraocular hemorrhage.
With serum hyperviscosity, dilated tortuous conjunctival and retinal vessels, retinal hemorrhages, retinal
detachment, and papilledema may develop.
Severe anemia is associated with pale retinal vessels, retinal hemorrhages, and conjunctival
pallor. These changes are typically not seen until the hematocrit approaches 5-7% or lower.
4) Metabolic/Endocrine Disease
Diabetes mellitus is a common etiology of cataracts in the dog and a rare etiology in the cat.
Diabetic retinopathy (characterized by retinal microaneurysms and hemorrhages) may also develop with
chronicity, but is generally not vision-threatening in companion animals. Sustained hypocalcaemia
results in cataracts that appear as focal, punctate to linear lens opacities that begin in the posterior
cortex and clinically resemble snowflakes.
Hyperlipidemia may result in lipid keratopathy, lipemic uveitis, or lipemia retinalis. The sclera is
a classic location for the detection of subtle icterus/jaundice and intraocular structures may also be
affected by this color change.
5) Neoplastic Disease
Systemic neoplasms may concurrently or secondarily involve the eye, adnexa, or orbit. The uvea
is a common site of intraocular metastasis and this may been seen in companion animals with numerous
different malignancies (e.g., lymphoma, hemangiosarcoma, osteosarcoma, melanoma,
mammary/pancreatic adenocarcinoma, mast cell tumor, squamous cell carcinoma, transitional cell
carcinoma). Intraocular metastasis characteristically causes intense and medically-refractory uveitis
associated with nodular or diffuse uveal infiltrates.
Intracranial neoplasms may produce eyelid dysfunction, pupillary light reflex deficits, reduced
vision, and/or blindness. Papilledema or optic nerve extension of the tumor may be evident during
ocular examination.
6) Nutritional Disease
In addition to cardiomyopathy, taurine deficiency in cats causes a characteristic retinal lesion
called feline central retinal degeneration. The initial retinal lesion is located in the area centralis and
slowly progresses to a generalized retinal degeneration and blindness. Correction of the taurine
deficiency halts progression of the retinal disease.
7) Systemic Toxicities
Numerous systemic toxins and pharmaceuticals can result in ocular lesions. Examples include:
- Rodenticides causing ocular and periocular hemorrhage
- Etodolac, acetaminophen, and sulfa antimicrobials are potentially lacrimotoxic
- Ethylene glycol intoxication can cause retinal edema, degeneration, and detachment
- Enrofloxacin (and other fluoroquinolones) may produce retinal degeneration in cats
- Ivermectin is potentially retinotoxic
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