Prominent Eyes - Part 1 March 2013

Many see a prominent eye, and think it must be an enlarged (buphthalmic) globe and jump to a
diagnosis of glaucoma. This is one possible cause, but there are other possible aetiologies for a
prominent eye.

Clinical signs of a prominent eye

Proptosis: the globe looks prominent. In severe cases this is quite obvious, but in early cases this can be hard to define. Try looking from on top, even slight proptosis can usually be identified.

Chemosis: swelling of the conjunctiva is seen when orbital disease leads to reduced venous return. The swollen conjunctiva can dry out, and can also reduce eyelid movement resulting in corneal
exposure. A prominent eye with chemosis of the eyelid and or third eyelid conjunctiva suggests
retrobulbar disease.

Corneal Exposure: when the globe is quite prominent, the cornea can develop exposure problems. This may be seen as slow healing ulceration, vascular keratitis, and/or pigmentary keratitis.

Reduced Retropulsion: with orbital disease eg tumour, or abscess, or cellulitis, the eyeball cannot be pushed back into the orbit. Compare the affected eye with the normal eye.

How to approach a prominent eye

History: sudden onset, could be glaucoma but for the globe to become enlarged the IOP needs to be increased for some time. Acute onset of a prominent eye suggests either trauma, retrobulbar abscess or cellulitis. Slow progressive exophthalmia in an older animal without pain suggests an orbital
tumour.

Check the PLRs: In most cases of orbital disease the PLR is still intact and is usually normal. A
normal PLR suggests that the IOP is not increased!

Measure the IOP: The IOP with orbital disease is usually normal at 10 to 25 mmHg. With a
glaucomatous, buphthalmic eye the IOP is increased.