• 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: dysecdysis, subspectacular abscess, corneal lipidosis secondary to hypercholesteremia, uveitis, corneal ulceration, general corneal trauma, trauma from prey, topical irritation, foreign body, keratitis, keratoconjunctivitis sicca, hypovitaminosis A, 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 – sudden onset corneal opacity.
• Blepharospasm.

• Worldwide.

• Reptiles incubated at incorrect temperatures may hatch with abnormalities such as microphthalmos and corneal edema.
• Otherwise no age predisposition noted.

• None reported.

• None reported.

• 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.
• Cost of investigations for underlying cause such as fluorescein staining needs to be discussed with the owner.
• A thorough husbandry review should always be performed, in particular assessing humidity levels.

• Care should be taken handling carnivorous reptiles such as snakes when in pain – vision with corneal edema is likely to be compromised and animals may strike.

• 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.

⚠️Aquatic reptiles may experience ocular irritation if placed in chlorinated water.

• Reptiles: Fungal keratitis, hypovitaminosis A resulting in keratitis and corneal edema, especially when chronic, corneal erosion and ulceration, dysecdysis Ecdysis/dysecdysis due to environmental deficiencies such as humidity issues, trauma resulting from being dropped, blunt trauma or bites from prey, eg crickets seeking moisture, rodents striking at snakes:
  • Corneal lipidosis/xanthomatosis/corneal arcus: deposition of cholesterol. Start as small foci becoming denser and progressing to raised, central opacities Corneal/spectacle opacity which can lead to blindness.
  • Neoplasia such as eyelid fibropapillomas leading to recurrent corneal irritation, ulceration and scarring.

⚠️The feeding of live vertebrate prey is discouraged in the UK unless done for welfare reasons, eg animal will not feed otherwise.

General

• Husbandry deficiencies such as inadequate environmental humidity predisposing to dysecdysis.
• Premature removal of spectacles leading to loss of proteinaceous fluid and damage of cornea with scarification.
• Live vertebrate feeding.

Specific

• Hypovitaminosis A Hypovitaminosis A.

• 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.
• An increase in intra-ocular pressure with glaucoma can also lead to corneal edema.
• Microphthalmos Microphthalmos/anophthalmos and corneal oedema present in hatchlings may develop because of too high an incubating temperature. This may increase the metabolic rate and lead to hypoxia compromising normal development.
• Hypovitaminosis A Hypovitaminosis A leads to conjunctival disruption by desquamated cells. This metaplasia leads to hyperkeratosis which may affect the ocular surface.

• 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

• Masi M, Selleri P & Moore B (2022) Reptilia. In: Wild and Exotic Animal Ophthalmology. Volume 1: Invertebrates, Fishes, Amphibians, Reptiles and Birds. Springer Nature, Switzerland. pp 145-319. Website: SpringerNature
• Lawton M (2019) Ophthalmology. Eds: Divers S & Stahl S. In: Mader’s Reptile and Amphibian Medicine and Surgery. 3rd edn. Elsevier, USA. pp 721-35.
• Williams D (2019) The Reptile Eye. In: BSAVA Manual of Reptiles. Eds: Girling S & Raiti P. 3rd edn. BSAVA, UK, pp 273-283.