VN September 2020

Vetnuus | September 2020 32 This is the term to describe the sudden forward displacement of the globe usually associated with the simultaneous entrapment of the eyelids behind the globe. This entrapment prevents the globe naturally repositioning itself. This condition is more common in brachiocephalic breeds such as Pugs and Pekinese, versus dolichocephalic breeds such as the Doberman where the globe is more deeply seated in the bony orbit. Themost common cause is trauma. Proptosis is a true ocular emergency requiring immediate medical and surgical management. Even if vision cannot be preserved, the globe often can be salvaged and this in many cases is what clients want for cosmetic reasons. The diagnosis of proptosis is simple to make but the prognosis for the globe is more difficult to speculate or assess. Use the following concepts to assist your decisionmaking: 1. The degree of proptosis may provide some idea of the extent of extraocular muscle damage. The medial rectus muscle usually is ruptured first, resulting in a dorsolateral strabismus of the globe. This is the shortest of the rectus muscles. This is usually followed by the ventral oblique and ventral rectus due to their anterior insertion. If three or more rectusmuscles avulsed then thevascular supplyand innervation to theglobe is seriously compromised, and in these cases the discussion with the client should be to have the globe enucleated. 2. The shape and turgor [firmness] of the globe can give an indication of whether the globe has been ruptured. It is not uncommon to have a tear through the very caudal sclera and this would result in the globe being softer as vitreous can leak into the retrobulbar tissues. A complete tear through the anterior segment of the globe would be easier to diagnose and, in these cases, iris prolapse often result and this usually resultsinapoorprognosisfortheglobeandoftenenucleation is the best option for the patient. Scleral rupture often is associated with focal subconjunctival bleeding. Ocular ultrasound can assist in the diagnosis of scleral rupture. 3. Globes that have extensive intraocular haemorrhage, especially if combined with avulsion of more than one extraocular muscle, may have a guarded prognosis. These eyes may be repositioned for later assessment. 4. Keratitis sicca and keratitis resulting from corneal exposure and corneal desensitisation may be a complicating factor and may make it more difficult to manage medially. It is important to discuss the long-term treatment and prognosis of such cases with the owner. In the authors experience, once exposure keratitis occurs the prognosis to save the globe becomes poor. 5. Eyes that havemildmuscle avulsion orminor hyphaemamay be repositioned andhave a better prognosis in the long term, but vision may still be compromised as the optic nerve itself is frequently affected. Regulars I Ophthalmology Column Dr Antony Goodhead & Dr Izak Venter Specialist Veterinary Ophthalmologists, Johannesburg and Cape Animal Eye Hospitals www.animaleyehospital.co.za Proptosis