What is an ophthalmic emergency and what to do with it (Proceedings)
True ophthalmic emergencies commonly seen in small animal practice include acute primary glaucoma, anterior lens luxation, traumatic globe proptosis, and progressive deep corneal ulceration. It is important that the general practitioner be able to recognize these sorts of emergencies. He or she must be able to assess correctly what must be done immediately, what can wait, and when referral is necessary.
Some ophthalmic emergencies can be handled very well on an emergency basis at the local level. Traumatic globe proptosis, for instance, is very time sensitive with respect to prognosis for vision and may actually be best addressed promptly at your facility. Globe replacement under brief anesthesia is fairly straight-forward, especially with the aid of a simple lateral canthotomy. Very seriously traumatized globes may be more appropriately addressed through enucleation, although it is recommended to err on the side of caution and replace the globe when in doubt. In this case, referral to an ophthalmologist should be recommended for follow-up a few days to a week later for assessment. In addition to being able to offer prognostic information with respect to vision and globe salvage, the ophthalmologist may discuss the usefulness of preventative medial canthoplasty (eyelid shortening) procedures for both eyes of brachycephalic dogs.
Another ophthalmic ER which may initially be addressed locally is acute canine glaucoma. Some tips will be given to differentiate true acute glaucoma from more chronic disease, but it is best to assume it is acute when there is any doubt. Hours make a huge difference in terms of prognosis for vision. Especially if you don't have an on-call ophthalmologist in your area, you must address this immediately or send the pet to an ER facility for prompt care- tomorrow may be too late and next week definitely will be. Fortunately, immediate glaucoma care is fairly straight-forward and has a simple goal- lower the intraocular pressure below 25 mm Hg and keep it that way until they can see an ophthalmologist. The use of topical (ex: latanaprost), oral (ex: methazolamide), and intravenous (ex: mannitol) medications for intensive glaucoma therapy are outlined, as are appropriate go-home medications. It is your obligation to encourage these patients to see an ophthalmologist the very next day if at all possible to monitor IOP, discuss prognosis and surgical options, and determine the etiology of the glaucoma if possible. An opthalmologist will assess for intraocular changes that may indicate secondary glaucoma and may recommend gonioscopy, a technique to assess risk for primary glaucoma. Dogs predisposed to primary glaucoma based on identification of an abnormal drainage angle are at risk of developing glaucoma in the other eye. Dogs with this hereditary abnormality, which is common in a number of breeds including Cocker Spaniels and Bassett Hounds, will benefit from prophylactic anti-glaucoma therapy of the as-yet-unaffected eye. Ultimately glaucoma is almost always blinding, but technology is advancing and there are options for dedicated clients and their pets- including placement of goniovalves and laser glaucoma therapy. Eyes which are blind and have persistently elevated IOPs must have their pain addressed- usually surgically by enucleation, evisceration with intrascleral prosthetic placement, or pharmacologic ciliary body ablation (gentamycin injection).Anterior lens luxation is another true ophthalmic emergency, and one which should be sent directly to a veterinary ophthalmologist if at all possible. The challenge for the GP here is in correctly identifying the condition. Tips will be given to help recognize the associated clinical signs. Lens luxations may occur primarily or secondarily. There is a very distinct breed predisposition to the primary condition, which involves gradual hereditary lens zonule breakdown. A Jack Russell terrier with an acutely painful eye, for instance, should be assumed to have an anterior lens luxation until proven otherwise. The acute pain and tendency for these eyes to promptly develop greatly elevated and ultimately blinding IOPs is what makes this an ophthalmic emergency. Although this sort of lens surgery is higher risk than elective cataract surgery, prompt lens removal may result in salvage of vision along with immediate lowering of the IOP. No artificial lens is placed with this surgery, but this only makes the dog far-sighted in that eye, not blind. Dogs with primary lens luxation are at-risk of the same thing occurring in the contralateral eye. Medications are initiated to keep the other lens more stable if there are any clinical signs indicating possible lens loosening. Secondary lens luxation may occur from chronic glaucoma with buphthalmia, chronic cataractous lens-induced uveitis, and other causes, and may indicate a different management approach.
Progressive corneal ulcerations, especially those extending greater than 50% corneal depth or progressing very rapidly deserve prompt attention by an ophthalmologist for best possible outcome. Usually this means surgical intervention, although sometimes very intensive medical therapy round the clock using some of the newer topical antibiotics is appropriate. Surgeries available include conjunctival grafts, corneconjunctival transposition flaps, corneal transplants, and biosynthetic grafts. Visual outcomes vary depending on the size of area to be grafted, degree of underlying ocular disease, species, and the surgery pursued.