Veterinary Medical Teaching Hospital, University of Missouri, Columbia, MO, USA
Ophthalmic emergencies are commonly seen by the small animal practitioner and 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 ophthalmic emergencies can be stabilized until consultation with, or referral to, a veterinary ophthalmologist is possible. The majority of ocular emergencies present due to significant ocular discomfort, loss of vision, or compromised globe integrity. Ocular emergencies can be thought of as having a traumatic (i.e., globe prolapse, conjunctival/corneal foreign body, corneal chemical burn, corneal wound and/or perforation, iris prolapse, and lens rupture with associated phacoclastic uveitis) or non-traumatic origin (i.e., 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.
Blunt or penetrating trauma may cause significant orbital trauma. Ocular proptosis results when the equator of the globe advances beyond the margin of the palpebral fissure. Proptosis carries a guarded to grave prognosis depending on breed-related conformational differences. When presented with a proptosis, assessment and stabilization of the entire patient is paramount in addition to treatment of the ocular abnormality. If the dog or cat has sustained a proptosis as a result of a severe concussive injury, the practitioner should first treat the patient for any signs of shock, cerebral edema or hemorrhage, and respiratory or cardiovascular compromise. Careful examination for facial deformities, epistaxis, crepitus, and subcutaneous edema will help determine the extent of the damage. Traumatic proptosis results in compromise of the globe's vascular supply and significant peribulbar swelling rapidly ensues. 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 may also adversely impact vision of the contralateral eye due to traction across the optic chiasm. Immediate ocular therapy should focus on keeping the globe moist; therefore, owners should be advised to lubricate the globe during transport. Negative prognostic indicators for salvage of the globe include rupture of 3 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. Providing the patient is stable for general anesthesia and the globe is deemed salvageable, surgery should be promptly undertaken to replace the globe. The eye and periocular tissues should be cleaned with a dilute (1:50) povidone-iodine solution and sterile saline. Lateral canthotomy should be performed to facilitate globe replacement in the vast majority of cases. Following globe replacement, 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 area (2–4 mm) 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 5–7 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 corneal ulceration. The canthotomy incision should be closed in two layers. This author advocates leaving all sutures in place for 10–14 days. Premature removal of the tarsorrhaphy sutures may result in re-proptosis due to significant peribulbar 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 4 times daily broad-spectrum antibiotics and 1–3 times daily topical atropine for uveitis is also recommended while the sutures are in place. Prognosis for return of vision is guarded to grave in any animal with traumatic proptosis.
Adnexa and Conjunctiva
Ocular emergencies involving the eyelid and conjunctiva are most frequently the result of concussive forces (motor vehicular accident or high-rise syndrome) or fighting injuries. While damage to the eyelids is usually obvious, injuries to 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. Untreated eyelid injuries or abnormalities result in a defective lid margin and function. Associated trichiasis or irregularity in eyelid contour can cause continual corneal surface irritation and ulceration. Eyelid lacerations should be treated by primary repair and every effort should be made to preserve as much eyelid tissue as possible. After minimal debridement, a simple interrupted, double layer closure with 7-0 to 5-0 suture (absorbable in the sub-conjunctival layer and non-absorbable in skin) is recommended. 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 8, suture provides good apposition of the lid margin. 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. Skin sutures may be removed in 10–14 days. Prognosis is excellent if proper surgical apposition has been achieved and the wound is not infected.
Disruption of the corneal epithelium with variable loss of corneal stroma defines corneal ulceration. Affected animals frequently present with acute, unilateral blepharospasm and epiphora. Variable degrees of aqueous flare (anterior uveitis) can be detected depending on the ulcer's severity and duration. Examination should be conducted in a dark room using magnification and a bright light source with slit beam capabilities. The practitioner should immediately suspect corneal ulceration when observing irregularity of the corneal reflection (Purkinje image), indicating corneal surface pathology. Variable degrees of corneal edema will also be present. Fluorescein stain will adhere to any exposed corneal stroma and is an essential diagnostic tool to fully delineate the ulcer's extent. When assessing corneal ulceration, the following questions should be answered: (1) What is the size, shape, depth, and duration or the corneal ulcer? (2) What is the underlying cause of the ulcer? (3) What is the health of the surrounding cornea (does this ulcer look infected)? (4)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 painful animals; however, topical anesthetics should be used for diagnostic purposes only since long-term use adversely affects corneal wound healing. Surgical repair of corneal ulcers is recommended in the following: 1) loss of 50% or more of the corneal stroma, 2) rapid progression of ulcer, 3) infected ulcer (as evidenced by yellow to white corneal cellular infiltrate, significant corneal edema, mucopurulent ocular discharge, and moderate to severe uveitis), 4) descemetocele, or 5) corneal perforation. Various surgical repair methods include conjunctival grafts, corneal-scleral transposition, cyanoacrylate glue, and penetrating keratoplasty. A pedicle graft is commonly performed and may be harvested from the bulbar conjunctiva and sutured into the corneal defect using 7-0 to 10-0 absorbable suture. The pedicle should be wide and long enough to cover the ulcer without tension so that the graft remains viable for 4 to 6 weeks. 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. Atropine solution is preferable to ointment if corneal perforation is imminent. Topical antiprotease agents 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 (NSAIDs) will ameliorate uveitis and ocular discomfort. Topical and systemic corticosteroids are contraindicated in complicated or infected corneal ulcers as they delay wound healing and increase collagenase activity. An Elizabethan collar is recommended to prevent self-trauma to the compromised globe while healing.
Uveitis and Glaucoma
See Dr. Giuliano's notes elsewhere in the 2015 WSAVA proceedings. (VIN editor: Other papers by this author are: The Complete Ophthalmic Examination, Uveitis – Simple, and Ocular Emergencies II)
References are available upon request.