Overview

Ophthalmic emergencies are commonly seen by the small animal practitioner and can be said to include any ophthalmic condition that has rapidly developed or is the result of trauma to the eye and/or periocular structures. With proper treatment, most emergencies can be stabilized until consultation with, or referral to, a veterinary ophthalmologist is possible. Most ocular emergencies present due to significant ocular discomfort, loss of vision or compromised globe integrity, and can be classified as being either traumatic or non-traumatic in origin. The first category includes problems such as globe prolapse, conjunctival/corneal foreign body, corneal chemical burn, corneal wound and/or perforation, iris prolapse, and lens rupture with associated phacoclastic uveitis, whilst the second category includes conditions such as orbital cellulitis/abscesses, acute keratoconjunctivitis sicca (KCS), corneal ulcers, acute congestive glaucoma, uveitis, anterior lens luxation, retinal detachment, SARD (sudden acquired retinal degeneration), optic neuritis, and endophthalmitis. Prompt intervention and proper treatment are essential to preserve vision and restore ocular comfort. This article reviews the initial approach to canine ocular emergencies and discusses some of the more common problems, including conditions affecting the orbit and globe, adnexa, conjunctiva, and cornea. Uveitis, glaucoma, and lenticular diseases are other significant ocular diseases that may present as an emergency but are not discussed in detail in this brief review.

Initial approach

I recommend examining all patients initially from a distance. This will help determine if the problem is unilateral or bilateral (if it is an externally visible problem). Observe the relationship of the globe to the orbit and eyelids, and to the other globe, and ask yourself the following questions: 

• What is the size of the eye — small, normal or enlarged?

• What is the position of the eye — protruding or sunken into the orbit?

• Is there a difference between the axes of the two eyes?

• Is there any evidence of periorbital swelling?

• Is there any ocular discharge and if so, what is its character (serous, mucoid, or sanguineous)? 

Canine ocular emergencies most frequently present as the result of trauma to the eye or periocular structures, or any ophthalmic condition that has developed rapidly. Trauma to the orbit or globe may result from a variety of insults, including concussive forces (vehicle accidents or falling from a height), penetrating foreign bodies, fight wounds, and chemical and thermal burns, to name just a few. Sudden onset eye problems include retrobulbar processes leading to altered globe position and/or swelling of periocular tissues, rapidly progressive corneal ulcers with impending perforation, uveitis, or sudden blindness. As with any ophthalmic condition, concern for the patient’s vision and ocular comfort should guide your diagnostic and therapeutic plan. 

Regardless of the nature of the emergency, a complete ophthalmic examination should be performed to ensure that both the correct diagnosis is reached and that any concurrent ocular disease is recognized and treated appropriately. For example, when presented with a corneal ulcer, if the lids and intraocular structures are not also carefully examined, the underlying cause for the ulcer (e.g., an eyelid abnormality with distichiasis) may be missed. Furthermore, if the intraocular structures are not carefully examined, any reflex uveitis resulting from the corneal ulceration may be missed. If the eyelid abnormality is not addressed, the ulcer will likely not heal and may progress in severity. If the concurrent uveitis is not treated, more serious vision-threatening sequelae may ensue, such as synechia, cataract, or glaucoma. Thorough examination of all external and internal ocular structures of both eyes, even if the patient presents with a unilateral problem, should be attempted on all ophthalmic emergencies. A minimum ophthalmic database, to include menace response (Figure 1), pupillary light reflex, tear testing, fluorescein staining (Figure 2), and intraocular pressure measurement (Figure 3), should be acquired whenever possible 1. Occasionally an aspect of the exam may need to be forfeited due to circumstances, e.g., tonometry should not be performed on an eye with a descemetocele due to risk of globe rupture. 

Orbital conditions

Blunt or penetrating trauma may cause significant orbital damage. Ocular proptosis (Figure 4), whereby the equator of the globe advances beyond the margin of the palpebral fissure, is not uncommon, and carries a grave prognosis in dogs with a dolicocephalic (e.g., sight-hound breeds) conformation versus brachycephalic (e.g., Pekingese and Shih Tzu). This is due to the physical force required to proptose a globe that is well-situated in the orbit compared to the relative ease with which brachycephalic canine globes can be extruded.

When presented with a proptosis, assessment and stabilization of the entire patient is paramount. If the dog has sustained a proptosis as a result of a severe concussive injury, always first treat for any signs of shock, cerebral edema or hemorrhage, and respiratory or cardiovascular compromise. Careful examination for facial deformities, epistaxis, crepitus, and subcutaneous edema can help determine the extent of the ocular damage. Traumatic proptosis results in compromise of the globe’s vascular supply and rapid, significant peribulbar swelling. Extraocular muscles may be avulsed, resulting in permanent strabismus. The optic nerve will have been stretched, potentially resulting in blindness of the affected eye, but vision in the contralateral eye can also be adversely affected due to traction across the optic chiasm. Immediate therapy should focus on keeping the globe moist, and owners should be advised to lubricate the eye during transport wherever possible; any over-the-counter ocular lubricant is suitable. Negative prognostic indicators for salvage of the globe include rupture of three or more extraocular muscles, lack of a consensual pupillary light reflex to the contralateral eye, corneal laceration that extends past the limbus, and extensive hyphema 2. Providing the patient is stable for general anesthesia and the globe is deemed salvageable, surgery should be undertaken promptly. The eye and periocular tissues should be cleaned with a dilute (1:50) povidine-iodine solution and sterile saline, and a lateral canthotomy performed to facilitate globe replacement. Once achieved, temporary tarsorrhaphy is performed by placing three or four horizontal mattress sutures of 4-0 or 5-0 silk with stents (e.g., sectioned IV tubing) to prevent eyelid tissue necrosis. A small (2-4 mm) area at the medial canthus may be left open to facilitate application of topical medications. Proper placement of mattress sutures requires careful attention; the needle should be inserted 4-5 mm from the eyelid margin and exit at, or just external to, the opening of the meibomian glands but inside the cilia. If sutures are placed too far external, entropion will result; however sutures that are placed internal to the opening of the meibomian glands will rub on the cornea and cause severe ulceration. The canthotomy incision should be closed in two layers. I advocate leaving all sutures in place for 10-14 days, as premature removal of the tarsorrhaphy sutures may result in re-proptosis due to significant peri-bulbar edema and hemorrhage. Intravenous broad- spectrum antibiotics and systemic anti-inflammatory corticosteroids are recommended at the time of surgery to prevent secondary infection and reduce both periocular and intraocular inflammation. Many ophthalmologists also advocate the use of broad-spectrum oral antibiotics and a tapering dose of oral corticosteroids for 7-10 days after surgery. Topical treatment (instilled at the medial canthus) with broad-spectrum antibiotics (4 times daily) and topical atropine (1-3 times daily) for the uveitis is also recommended while the sutures are in place. 

Exophthalmos (abnormal protrusion of the eye) may have a sudden onset or be a slowly progressive disease that the owner appreciates as a sudden change in the dog’s appearance (Figure 5). Exophthalmos is caused by an accumulation of air, fluid (edema, hemorrhage) or cells (inflammatory, neoplastic) within the intraconal or extraconal space (Figure 6). The location and nature of the infiltrate will alter the appearance of the eye and may affect the overall health of the animal at presentation 3. Orbital cellulitis and retrobulbar infections are usually associated with severe pain upon opening the mouth or when retropulsion of the globe is attempted. Dogs may be febrile, anorexic, and lethargic. Thorough oral examination is essential in such cases, to look for evidence of tooth root abscessation or fluctuant swelling behind the last molar tooth in the upper arcade. If the latter finding is noted, drainage may be attempted under general anesthesia via a small mucosal stab incision into the pterygopalatine fossa and careful insertion of a closed hemostat into the orbit, with slight opening of the hemostat upon withdrawal. Any obvious foreign body protruding from this space can be gently removed (Figure 7). Gentle lavage with sterile saline may promote drainage, and cytology and bacterial culture with sensitivity should be obtained, with appropriate systemic antibiotic therapy for 2-4 weeks.

 

Note that retrobulbar neoplasia is typically more slowly progressive and not associated with severe acute pain upon opening the mouth. Advanced imaging techniques (e.g., orbital ultrasound, computer tomography scan or magnetic resonance imaging) are often required to effectively delineate the extent of involvement and to aid in surgical planning for biopsy or debulking 4 5 6, and therapy depends on the type of neoplasia, extent of local involvement, and overall health of the animal. While orbital neoplasia does not usually represent a true emergency per se, adverse sequelae from prolonged globe exposure may lead to secondary conditions such as corneal ulceration which can threaten the health of the eye. 

Adnexal and conjunctival problems

Ocular emergencies involving the eyelid and conjunctiva are frequently the result of concussive forces (vehicle accident or “high-rise syndrome”) or fighting injuries. While damage to the eyelids is usually obvious, injuries to the third eyelid (Figure 8) or deeper ocular structures may be difficult to detect if significant chemosis or conjunctival hemorrhage is present. Careful examination of the intraocular structures is critical, since concurrent globe penetration is potentially more threatening to the long-term health of the eye. Intraocular involvement should be suspected if dyscoria or a shallow anterior chamber is observed, or if intraocular pressure is low. A clear ocular discharge may indicate aqueous humor leakage and can be confirmed by performing a Seidel test 1. This involves applying fluorescein stain to the corneal surface; prior to rinsing the eye with sterile eyewash, carefully observe for a clear rivulet of fluid emanating from the corneal wound and diluting the fluorescein stain, confirming the presence of corneal perforation.

Untreated eyelid injuries or abnormalities result in a defective lid margin and function. Lacerations should be treated by primary repair and every effort should be made to preserve as much eyelid tissue as possible. I recommend minimal debridement followed by closure using a simple interrupted, double layer method with 7-0 to 5-0 suture (using absorbable material for the subconjunctival layer and non-absorbable in the skin). Closure of the eyelid margin must be meticulous to avoid any long-term “step” irregularities and subsequent corneal abrasion; a modified cruciate or figure-of-eight suture provides good apposition of the lid margin 7 8. If eyelid trauma near the medial canthus damages any part of the nasolacrimal puncta, canaliculi, or duct, reconstruction should be undertaken with microsurgical instrumentation and magnification. Topical and systemic antibiotics for 7-10 days and an Elizabethan collar to prevent further self-trauma are recommended for eyelid wounds, with skin sutures removed after 10-14 days. Prognosis is excellent if proper surgical apposition has been achieved and the wound is not infected.

Conjunctival damage may manifest as chemosis, hemorrhage, and/or localized swelling. As with eyelid trauma, intraocular structures should be critically examined for evidence of involvement. In most cases, treatment requires only protection from corneal desiccation and the prevention of secondary infection; topical broad-spectrum antibiotic (applied 3-4 times daily for 7-10 days) is adequate. A single dose of systemic anti-inflammatory medication may also be considered to help reduce acute swelling.

Corneal ulceration

When assessing corneal ulceration, ask yourself the following questions:

• What is the size, shape, depth, and duration of the corneal ulcer?

• What is the underlying cause of the ulcer?

• What is the health of the surrounding cornea (i.e., does this ulcer look infected)?

• What is the proximity of the ulcer to the limbus (from which a neovascular response promoting healing may occur)?

Initial therapy is directed at determining and correcting the underlying cause of ulceration. Prevention of corneal infection and treatment of reflex uveitis should be initiated through broad-spectrum topical antibiotic therapy (4-6 times daily) and mydriatic cycloplegia with atropine to effect in superficial, uncomplicated corneal ulcers. Systemic analgesics will improve comfort in animals in pain; but topical anesthetics should be only used for diagnostic purposes since long-term use adversely affects corneal wound healing. Surgical repair of corneal ulcers is recommended in the following: 

• Loss of 50% or more of the corneal stroma

• Rapidly progressing ulcers 

• Infected ulcers (as evidenced by yellow/white corneal cellular infiltrate, significant corneal edema, mucopurulent ocular discharge, and moderate to severe uveitis (Figure 11)

• Descemetocoeles, or 

• Corneal perforations

There are various surgical repair methods including conjunctival grafts, corneal-scleral transposition, cyanoacrylate glue, and penetrating keratoplasty, and these procedures are described in greater detail elsewhere 7 10 11. In complicated corneal ulcers, topical and systemic antibiotic therapy should be based on microbial culture and sensitivity results obtained from the ulcer bed. Topical antimicrobials may be administered hourly in infected or rapidly progressive ulcers during the initial stages of treatment. Topical atropine should be administered 2-4 times daily until pupillary dilation is achieved and then given only as needed to affect mydriasis. I recommend topical solutions (rather than ointments) if corneal perforation is imminent, and owners should be educated as to the correct technique to administer drops (Figure 12). Topical anti-protease agents (e.g., Nacetylcysteine, fresh serum, EDTA) may also be applied topically (every 2-6 hours) to inhibit progression of corneal malacia. Systemic antibiotic therapy is beneficial if conjunctival grafting has been performed or if corneal perforation has occurred. Systemic nonsteroidal anti-inflammatory drugs will ameliorate uveitis and ocular discomfort, but care must be taken to avoid excessive use in dogs due to their association with gastric ulceration, hemorrhage, vomiting and diarrhea 12. Topical and systemic corticosteroids are contraindicated in complicated or infected corneal ulcers as they delay wound healing and increase collagenase activity 13 14. An Elizabethan collar is recommended to prevent self-trauma to the compromised globe while healing.

Corneal foreign bodies

Corneal foreign bodies (e.g., plant material, metal fragments) result in acute blepharospasm and epiphora (Figure 13). Following application of topical anesthesia, superficial foreign bodies may be removed by aggressive flushing with sterile eyewash or gentle manipulation with a moistened cotton-tipped applicator. Foreign bodies embedded deeper within the stroma frequently require surgical removal under general anesthesia. Care must be taken to avoid inadvertently pushing the foreign body more deeply into the eye, resulting in corneal perforation. A 25-27 G hypodermic needle may be used to engage the foreign body at 900 to its long axis which can then be removed in a direction retrograde from which it entered the cornea. Following removal, treatment consists of standard corneal ulcer management. Prognosis for canine corneal foreign bodies is generally good providing the iris and lens have been spared, but note that removal of firmly implanted corneal foreign bodies or those entering the anterior chamber require microsurgery for removal (Figure 14) and should be referred to a veterinary ophthalmologist if possible. Foreign body perforation of the lens capsule may cause phacoclastic uveitis, resulting in the demise of the globe. 

Uveitis

A thorough review of the clinical findings, diagnosis and treatment of canine uveitis is beyond the scope of this article, but uveitis and its sequelae (cataract, glaucoma, lens luxation) represent a significant threat to vision and ocular comfort. Clinical findings depend on the cause (endogenous versus exogenous factors) and duration, but the hallmark features of uveitis include pain, episcleral and associated conjunctival vascular congestion, corneal edema, aqueous flare, fibrin and hemorrhage in the anterior chamber, keratic precipitates, rubeosis iridis, miosis, and hypotony (Figure 15). Posterior uveitis may result in retinal detachment and blindness. Identification of the underlying cause dictates specific therapy, but symptomatic therapy consists of mydriatic cycloplegics and anti-inflammatory agents.

 

Other problems

Glaucoma can occur as a primary disease in dogs, but may also be secondary to uveitis, hyphema, or neoplasia (Figure 16). Similarly, lens luxation occurs as a primary disease in dogs, especially in terrier breeds, or secondary to chronic uveitis, and readers are referred to more complete discussions of glaucoma and lenticular diseases elsewhere 15.

 

 

Further reading

• Stades FC, Wyman M, Boevé MH, et al. Ophthalmology for the Veterinary Practitioner. Hannover, Schlütersche GmbH & Co, 1998.

• Williams DL, Barrie K, Evans TF. Veterinary Ocular Emergencies. Marnickville, Australia, Elsevier Science/Harcourt, 2002.

• Nasisse MP. (ed): Surgical management of ocular disease. Philadelphia: W.B. Saunders Co. Vet Clin North Am Small Anim Pract 1997;27(5).