Top 5 Canine Ophthalmic Emergencies offers a useful review of the initial diagnostic plan and first aid that a general practitioner should provide when confronted with these devastating diseases, which can result in blindness or enucleation. As Dr. Haeussler notes, after the initial consultation, these cases (with the possible exception of traumatic proptosis) should ideally be referred to a board-certified ophthalmologist for further diagnostic investigation and treatment. Unfortunately, however, such referral centers may not be available in some countries or in remote areas. When referral is simply not an option, practitioners can consider the following:
Descemetocele
Progression of ulcers to descemetocele and corneal rupture is largely caused by degrading activity of the corneal stroma by proteases and collagenases. The most effective inhibitor of these destructive enzymes is serum, which can be obtained from the patient or another animal. The serum also contains growth factors that promote corneal healing. In cases of melting ulcers, the patient should be hospitalized so serum can be administered as often as every 30 minutes.Practitioners should remember that every corneal ulcer triggers secondary uveitis. The descemetocele may be successfully treated, yet the patient may lose the eye to the inflammation. Unless contraindicated by keratoconjunctivitis sicca, atropine should be prescribed to reduce the risk for adhesions of the iris to the lens and to provide analgesic effects. Although topical NSAIDs are probably best avoided, systemic NSAIDs may be considered for the uveitis. Of course, topical and/or systemic antibiotics should also be prescribed.The eye should not be covered with a third eyelid flap, which does not contribute to corneal healing and prevents monitoring and topical treatment of the covered eye.Finally, it is important to look for the cause of the descemetocele. Removal of a foreign body or ectopic cilia should facilitate healing.
Corneal Laceration
As Dr. Haeussler notes, corneal lacerations are usually caused by cat claws, and the trauma is potentially grave when the claw perforates the anterior lens capsule. Phacoemulsification is ideal in such cases, but it is not always available and may not be necessary,1 especially when the length of the capsular laceration is <1.5 mm.2However, if the lens is not removed, the clinician should remember that the claw may have introduced infectious organisms into the lens. One long-term potential complication of this is septic lens implantation, a slowly progressive endophthalmitis caused by traumatic lens capsule rupture and formation of a lenticular abscess.3 Signs, which can present weeks to months after the trauma, include fibrinous exudate on the lens capsule, especially associated with a focal cataract.Lens material may be present in the anterior chamber and/or adhered to the lens capsule; if the lens is not removed, the patient should be closely monitored for signs of uveitis and/or endophthalmitis for months after the trauma.
Anterior Lens Luxation
If referral is not possible, the lens may be pushed from the anterior chamber back to the posterior part of the eye (reclination, transcorneal reduction). This is a noninvasive procedure that may be facilitated by sedation (to reduce globe tension caused by the extraocular muscles) and administration of hyperosmotic agents (to decrease the volume of the vitreous body). After reclination, permanent miotic therapy is instituted to increase the likelihood that the lens remains in the posterior part of the eye, although return of the lens to the anterior chamber is not uncommon. A recent study reports that reclination was successful in 17/20 eyes; vision was maintained (median follow-up of 1 year) in 6/11 eyes that were visual before the procedure.4In animals with unilateral lens luxation, the unaffected eye should be carefully examined for early signs of lens instability. Clients should be educated about signs of possible lens luxation and glaucoma in the unaffected eye. Appropriate prophylactic miotic treatment with latanoprost or dermecarium bromide should be considered.
Acute Glaucoma
In cases of unilateral glaucoma, it is critical to determine whether the disease is secondary (eg, caused by uveitis or lens luxation) or primary (ie, genetic), as hereditary glaucoma may affect one eye months before the other. If no veterinary ophthalmologist is available and if there is no obvious intraocular disease causing secondary glaucoma in the affected eye, it is advisable to suspect hereditary glaucoma and to initiate prophylactic treatment in the unaffected eye. Such treatment will not prevent the glaucoma in the second eye but can delay onset by almost 2 years.5