i'm really super-duper proud of myself today. i diagnosed a sneaky little eye disease. of course, i was nearly bitten in the process (and badly), but i dodged the bullet this time. just a reminder that i REALLY need to get that rabies vaccination, especially considering that this dog had not been vaccinated for rabies recently. but that wasn't the point. this was a little blue heeler dog of indeterminate age and definitely determinate temperment (nasty). he had a history of an acute onset of cloudiness about 3 months ago in his left eye. his right eye was gone, but the current owner wasn't sure of the circumstances under which the eye was lost. they suspected trauma. at any rate, after nearly losing a hand to "chopper" - as i will affectionately refer to him, i muzzled the dog and preceded with my ophthal exam. i was thrilled when, upon examining the eye with a transilluminator, i saw what looked like the lens hanging out in the front of the eye.
now for a brief lesson in eye anatomy. everyone knows what the pupil is, right? the black spot in your eye, surrounded by the colored portion of the eye (the iris). well, the iris is actually a muscle surrounding that pupil, which is nothing more than an opening into the back of the eye that allows light in so that it can be detected by the retina. the lens, a basketball shaped clear object that is responsible for the refraction of light, sits back there. it's kept in place by thousands of tight little - for lack of a better word - pseudo-ligaments - called zonules. sometimes these rupture. there are a variety of causes, the most common being an inherited defect, as seen in jack russell terriers. glaucoma (increased pressure in the eye) can also cause this, as can trauma to the head (less frequently). at any rate, when i first looked in the dog's cornea (the clear part at the front of the eye/where you put your contact lens), i was 100% sure i saw the lens in front of the pupil. this represents a total luxation, where all the zonules are broken, and the lens has floated forward into the anterior chamber of the eye. i was SO excited. for my diagnosis, not so much for the dog. when the lens comes forward into the eye, it blocks a crucial angle that exists more or less solely for the purpose of draining aqueous humor (the fluid in your eye - NOT tears). when that angle is blocked, the aqueous can't get out and pressures in the eye begin to rise, leading to glaucoma. when i measured this dog's pressure, it was definitely elevated (normal is 15-25mmHg, this dog had 33mmHg). the 2nd time i looked, i had a harder time seeing the lens. after all, in a normal, cataract-free eye, the lens is crystal clear - and really hard to see, even when it's misplaced.
the doctor came and examined the dog and confirmed my diagnosis. i swelled up like a japanese blowfish, i swear to god. i was so happy to make such a definitive (and to me) difficult diagnosis. so our recommendation for this poor dog (already blind on the right side due to -- well -- not having an eye and all) was that the owner take him home, try to bring down the pressure in that eye with glaucoma medications, and that the eye be dilated with mydriatic drugs (tropicamide) to encourage the lens to fall back into the posterior chamber behind the lens (it poses less of a threat there to vision, although it still ain't good). the other option was surgery to remove the lens, but with the problem lasting 3 months already, and the pressure in the eye elevated, and the dog already experiencing visual deficits in that eye, it is unlikely that the dog will have restoration of vision (10-15% chance). he's already lost some, so the probability of ever being even 50% visual in that eye is very, very poor. those are not great odds for a surgery that costs $1000.
the owner elected medical therapy, and we sent "chopper" - the first dog to nearly take my hand off, home. he was quite the patient. we had to muzzle him to do a proper ophtho exam. it was not fun. well, the part about being right was. the rest wasn't. a cat also tried to bite me today. i must taste particularly yummy...
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