• Cause: corneal edema is the increase in corneal thickness due to accumulation of extracellular fluid in the epithelium and stroma resulting in a loss of corneal transparency. There will be an underlying cause such as corneal lipidosis secondary to hypercholesteremia, uveitis, corneal ulceration, general corneal trauma, topical irritation, foreign body, keratitis, keratoconjunctivitis sicca, exposure to toxic substances, increased intra-ocular pressure, eg with glaucoma.
• Signs: corneal opacity, often with a ‘blue’ tinge. There may be associated blepharospasm, blephredema, exophthalmos, buphthalmos depending on the underlying cause.
• Diagnosis: presentation, confirm opacity to be affecting cornea, identify underlying cause
• Treatment: variable, dependent on underlying cause and often chronicity at time of presentation
• Prognosis: good to poor for resolution depending on nature and cause of opacity.

• Corneal edema – corneal opacity, often with a ‘blue’ tinge.
• Accompanying blepharospasm, blepharedema, exophthalmos
• Corneal edema should not be confused with heterotropic bone formation Heterotopic ocular bone formation.

• Corneal edema – sudden onset corneal opacity.
• Blepharospasm.

• Worldwide.

• No age predisposition noted.

• None reported.

• None reported.
• Guinea pigs appear particularly prone to ocular trauma with resultant corneal ulceration and corneal edema due to ‘hay pokes’ from foreign bodies such as hay or straw. Feeding hay from a height rather than on surface level may predispose to these types of injuries. Breeds predisposed to distichal and ectopic cilia include the Teddy Teddy and Rex Rex breeds.

• In cases of simple trauma, cost of repeat consultation and medication needs to be considered.
• In some cases, depending on underlying cause, enucleation may be needed and the client may need to be counselled on the costs and potential welfare implications of this Enucleation.
• Cost of investigations for underlying cause such as fluorescein staining needs to be discussed with the owner.

• Any animal with corneal edema may have impaired vision and so may be more stressed and therefore likely to bite or attempt to flee.

• Corneal edema is defined as the increase in the thickness of the cornea due to accumulation of extracellular fluid in the epithelium and stroma resulting in loss of corneal transparency. The cornea may also appear ‘blue’ in color.
• Edema may be secondary to trauma or underlying pathology such as hypercholesterolemia, changes in intraocular pressure, etc.

General

• Feeding guinea pigs hay from a height may predispose to ocular trauma.

• Any situation affecting the integrity of the cornea leading to an increase in extracellular fluid accumulation within the epithelium and stroma.
• Trauma is one of the most common causes of this Traumatic injuries.
• An increase in intra-ocular pressure with glaucoma can also lead to corneal edema.

• Timecourse variable depending on underlying cause.
• May be congenital and chronic, but often seen as acute in cases of sudden ocular trauma.

Refereed papers

• Recent references from PubMed and VetMedResource.

Other sources of information

• Quesenberry K, Orcutt C, Mans C & Carpenter J (2021) Ferrets, Rabbits, and Rodents: Clinical Medicine and Surgery. Elsevier, USA.