SYMPTOM
Enlarged eye
Owners may observe enlarged eye in their pet.
Various conditions
This symptom can occur in multiple conditions and warrants further assessment.
Buphthalmos From Chronic Glaucoma
Long-standing elevation in intraocular pressure gradually stretches the collagen fibres of the globe, producing a genuinely larger eye rather than one displaced forward. This develops over weeks to months and is associated with the same breeds prone to primary glaucoma, including Cocker Spaniels and Basset Hounds. The eye is typically firm on gentle palpation and may show corneal clouding from long-term stretching.
Orbital Space-Occupying Disease (Exophthalmos)
A mass behind the eye, such as a retrobulbar abscess, cellulitis, or a tumour, pushes a normal-sized globe forward within the orbit, which can look similar to true enlargement from the front. The third eyelid is usually also protruding, and opening the mouth can be uncomfortable if the swelling involves the muscles behind the jaw. Retrobulbar abscesses often follow a penetrating injury from a foreign body such as a grass awn or stick.
Traumatic Globe Proptosis
The eyeball can be forced partly out of the orbit by a blow to the head, a fall, or restraint around the neck, with the eyelids then trapping it in that forward position. Brachycephalic breeds such as Pugs, Shih Tzus, and Boston Terriers have shallow orbits and prominent eyes, so this can occur with comparatively minor trauma, including firm handling or a scuffle with another dog. The exposed surface of the eye dries quickly once proptosed.
Breed-Related Globe Prominence
Some breeds, particularly brachycephalic types such as Pugs, Pekingese, and Boston Terriers, have naturally shallow orbits that leave a normal-sized eye looking proportionally larger and more prominent than in longer-nosed breeds. This is a conformational feature present from a young age rather than a change over time, and the globe remains soft and mobile on gentle examination. It reflects normal anatomical variation rather than an underlying change to the eye itself.
Why timing matters
Early observation
Early recognition allows prompt assessment and intervention if needed.
Later presentation
Persistent or worsening signs may indicate progression requiring attention.
The significance of this symptom depends on its context, duration, and associated findings.
Conditions commonly associated
Glaucoma
Chronic pressure elevation stretches the globe, causing visible enlargement (buphthalmos).
Feline Herpesvirus (FHV-1)
Feline herpesvirus infection can cause inflammation of the conjunctiva and other eye structures, leading to swelling that may make the eye appear enlarged. This ocular involvement often occurs alongside other upper respiratory signs such as sneezing and nasal discharge.
Feline Calicivirus
Feline calicivirus infection may cause conjunctivitis and periocular inflammation, which can result in visible swelling around the eye. The ocular changes typically occur as part of a broader respiratory illness affecting the nose, mouth, and airways.
Hyperthyroidism in Cats
Hyperthyroidism in cats can lead to elevated blood pressure, which in turn may cause bleeding or fluid accumulation within or behind the eye, sometimes resulting in visible enlargement. Retinal changes and other ocular complications are recognised sequelae of poorly controlled hypertension in affected cats.
Chronic Kidney Disease in Cats
Chronic kidney disease in cats often leads to systemic hypertension, which can cause haemorrhage or oedema within the eye or orbit, occasionally manifesting as apparent enlargement. Hypertensive ocular damage is a well-recognised complication in cats with advanced or unmanaged renal disease.
Lens Luxation
The eye can appear larger than normal as pressure builds within it once the displaced lens blocks the normal drainage of fluid.
When to explore further
When the symptom is persistent or worsening
When other signs are present alongside
When daily activities or quality of life are affected
When there is uncertainty about the cause
Noting when this symptom occurs, any triggers, and how it changes over time can provide useful information for veterinary discussions.
Last reviewed: 24 April 2026 · Dr Alastair Greenway MRCVS