by Noelle La Croix, DVM, Dip. ACVO
A traumatic proptosis is an ophthalmic emergency which can ignite both panic and revulsion in a client. However, a systematic and sympathetic approach from a veterinarian can often calm the client and encourage a positive outcome.
The prognosis for the retention of vision by a proptosed eye is usually poor. In a brachycephalic dog a minimal amount of force, such as that received in an altercation between dogs, can result in a proptosis. Proptosis in longer-nosed animals typically requires a larger amount of force applied in a major traumatic incident (e.g., vehicular trauma). Subsequently, the prognosis for vision and globe retention is especially grave following proptosis in a mesocephalic or dolichocephalic dog. These animals usually suffer concurrent skull and mandibular fractures. They must be stabilized and accessed for other defects prior to ophthalmic examination.
In stabilized animals globe replacement surgery can be attempted. However, clients should be informed that 60% of canine and 100% of feline proptosed eyes will be left blinded. Brachycephalic dogs have the highest rates of visual retention following globe replacement, as they have generally suffered the least forceful trauma. During proptosis the medial rectus, ventral rectus, and ventral oblique muscles are often torn at their insertions to the globe. This will typically result in strabismus after globe replacement (Figure 1). Globe replacement surgery should never be attempted if more than 3 extraocular muscles have been torn, as it is sure to fail (Figure 2).
Proptosis can also generate collateral damage to the lachrymal glands and the ophthalmic branch of cranial nerve V which connects with the corneal nerves. These corneal nerves are responsible for signaling reflexive tearing and are involved in corneal epithelial wound healing. Therefore post-operative dry eye and corneal ulceration can follow globe replacement. Other post-replacement complications include lagophthalmos and exophthalmos that can lead to corneal ulceration and scarification.
Prior to globe replacement surgery, the surface of a proptosed eye is liberally lubricated with antibiotic ointment to prevent corneal desiccation and to protect the corneal surface. In surgery, the orbit of the anesthetized animal is first flushed with 0.2% povidone iodine. Four to six 3-0 to 4-0 non-absorbable interrupted horizontal mattress sutures are pre-placed in the eyelids with stents of IV tubing. These temporary tarsorrhaphy sutures exit the eyelid margins either rostrally to or from the openings of the meibomain glands. If these sutures exit the eyelid margins caudal to the meibomain gland openings, the suture will rub against the corneal surface. The stents redistribute the force of the sutures to prevent them from tearing through the eyelid margin.
A 5 mm lateral canthotomy is performed to expand the palpebral fissure to accept the globe. The tarsorrhaphy sutures are then tightened and tied to replace the globe caudal to the orbital rim. A small opening at the medial canthus will allow for the application of ocular medications. The canthotomy is then closed with 4-0 to 5-0 absorbable suture in a simple continuous pattern within the orbicularis oculi layer. All suture knots are placed anterior to the suture plane to prevent contact with the cornea. The skin is then closed with simple interrupted non-absorbable sutures.
Post-operative medications include topical and oral antibiotics to prevent infection; topical atropine to prevent posterior synechiae and secondary glaucoma; oral anti-inflammatories to reduce uveitis, swelling, and pain; and pain medications to improve comfort. An E-collar will prevent self-trauma and the tarsorrhaphy sutures can be removed in 10 to14 days.
Globe replacement is a relatively simple procedure following proptosis. The possible outcomes and complications should be presented to the client prior to surgery. If you have any questions about proptosis and globe replacement surgery, please feel free to consult with your veterinary ophthalmologist.
Noelle La Croix, DVM, Dip. ACVO
Veterinary Medical Center of Long Island
75 Sunrise Highway
West Islip, New York 11795
(631) 587-0800; fax (631) 587-2006
Figure 1: Dorsal and lateral strabismus in the right eye of a King Charles Spaniel following proptosis and globe replacement surgery.