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.