Food Ani. Med- Opthamology

wilsbach's version from 2016-04-24 00:25


Question Answer
how is a cows vision set up- down fall?Prey animal= good vision off to the sides (not in front), means lack depth perception
what things dont cows like based on how they see?flapping objects, shadows/holes/puddles (cant tell depth), steps (cant see how high), dark places (dont know if predator), dead ends (no escape), barred gates (Can't tell how far away), dont like routine changes or new places, human noises, or bright sunlight (blinds them)
how do you know if a cow is blind?lack of menace response
causes of blindness?congenital, meningitis/septicemia, plant poisoning, lead poisoning, malig catarrhal fever, cerebrocortical necrosis (CCN), thromboembolic meningoencephalitis (TEME)
2 classifications of blindness, and how PLR differs with them, where the damage is(1) CENTRAL: normal PLR (since it goes through the optic chiasm before the brain), lesion of the lateral geniculate bodies (thalamus), optic radiations, or visual cortex. (2) PERIPHERAL: ABNORMAL PLR. lesion of retina/optic n, optic chiasm, potic tracts
congenital blindness is esp common in who? What dz can cause this?esp in holsteins, after BVD infection in utero- might see cataracts and microphthalmia too
meningitis causes blindness how? how do you tx/manage?inflammation and damage directly to optic nerves. (more severe in calves). tx with IV ABX (oxytet will cross BBB!!), IV NSAID, IV FLUIDS. place in a warm dark place (hypothermic, photophobia)
thromboembolic meningoencephalitis is caused by what? what parts of the body does it affect? tx/px?Caused by histophilus somni, which starts with a resp infection for 1-2 weeks and then moves to CNS---> meningitis. blindness, depression, recumbency ("sleeper" calves). Tx with LA oxytet (crosses BBB), effective if caught early (low incidence, high mortality)
how does septicemia lead to blindness?causes UVEITIS-->blindness. Uveitis= inflammation of choroid, ciliary body, iris. can be neonatal infection or toxic condition (like mastitis)
in UK, which plant causes blindness?ragwort (liver damage--> hepatic encephalopathy) (tox says: ragwort is senico species. pyrrolizidine alkaloids!! metabolized to pyrroles in liver, cross link DNA, prevent mitosis, hepatocellular necrosis)
****in US, which plant causes blindness?caused by astragalus sp (locoweed, milk vetches), which cause ~SELENIUM TOX IF CONSUMED, ONE OF THE SYMPTOMS IS BLINDNESS. (tox says: remember swainsonine, INDUCES NEURONAL DEGENERATION, also causes selenium tox (nitro-toxins) also inhibits alpha-mannosidase-->pseudo lysosomal storage dz)
CSs of lead poisoning/tx/ how do they find lead?lick old paint/car batteries--> show signs of blindness, headache/depression, fitting. Tx: IV CALCIUM EDTA (chelate), and VIT B INJECTIONS (sitm liver to help detox)
malig catarrhal fever: caused by what? Cs?usually only affects 1 ani but can get group outbreaks. caused by herpes virus from preg/lambing sheep. See pyrexia, corneal opacity, crusting of muzzle, mucopurulent nose/eye discharge, enlarged LNs, exudative dermatitis (inner thigh, udder), dies in 5-10d
cerebral cortical necrosis (CCN)/ PEM: caused by? CS? tx? associated with high conc feeding (high sulfur in them)--> inc thiaminase--> dec B1. CS: dull, isolated, high head carriage, stagger, blindness, headpress, bruxism, seizures. TX: IV thiamine hydrochloride
3 main causes of EXOphthalmosCongenital (common), retrobulbar neoplasia (lymphosarc. starts unilater-->bilat. BLV virus associated in adults), periorbital sinusitis (rare, direct trauma or 2* infected dehorning. large swelling front of head. systemic abx, analgesia, possibel trephination)
4 main causes ENopthalmosDehydration, emaciation, traumatic damage ( phthisis bulbi), advanced corneal ulcer causing eye to perforate (can be 2* to pinkeye)
3 main reasons eye is closed(1) PAIN (orbit or conjunctiva) (2) Nerve damage: often HORNERS from listeriosis. (3) SWELLING: if unilat, prolly conjunctival infxn/injury. bilat=anaphylaxis.
listeriosis caused by? CSs? Tx?Listeria monocytogenes, if infect inner ear can cause horner's. Silage is a common source--> enter wound in mouth--> up trigeminal nerve. inflammation of cochlea/surrounding structures--> unilateral paralysis of facial nerve. Symptoms: Dropped ear, closed eye, drooling, head tilt, depression, circling. Tx: HIGH DOSE OXYTET+antiinflammatories (cow walks in circles??? SAY LISTERIA)
which way does listeria cow circle?circle in direction of infection
tx differ between unilat and bilat swellingUnilat: abx/antiinflam. Bilat: prolly allergies= antihistamine or steroids
tactile response (palpebral reflex)= what nerve?trigeminal (and facial)
menace is..II and VI (thalamocortex and cerebellum too)
PLR is..II and III (pretty slow in food ani)
nerves responsible for eye movement?oculocephalic reflex (dolls eye) from III (occulomotor), trochlear (4, motor), vestibular choclear (8, sensory)
3 things which can cause nystagmus?LISTERIOSIS, PEM (CCN), or poisoning
if 3rd eyelid protruded/slow to move back, what are you thinking?TETANUS!! (look for hx of deep wound)
pink eye aka? caused by what/how are they infected? CS?aka infectious keratoconjunctivitis, aka new forest eye. caused by moraxella bovis, spread by flies. BActeria destroys corneal epithelium. Spot in eye-->corneal ulcer--> perforation. Causes pain (blepharospasm), lacrimation, corneal whitening, ulcers, poor vision. VS AVAIL
tx for pink eye?(moraxella bovis) abx cream, usually CLOXACILLIN. Also systemic OXYTET (good penetration of cornea), or systemic florfenicol, NSAIDs. IF SEVERE: cover ulcer by stitching eyelids together. (NOT TOO TIGHT OR CORNEA WILL HEAL TO EYELID). If cornea perforates- enucleate
entropion very common in?lambs
how might you tx entropion?mild= manual correction. Not mild= inject long acting oxytet under eyelid-->swelling-->brings it out
how bad are dermoids?not a prob
most common eye neoplasia? caused by? tx?SCC- sunlight + low pigmentation. can involve 3rd eyelid, conjunctiva, and globe. TX: if small: electrocautery/cryosx. big as of a margin as possible. If bigger, consider enucleation or culling.
3 common nerve blocks for enucleation?cornual, auriculopalpebral, infraorbital.
what is the peterson eye block?18g spinal needle directed into skull via the notch formed by the zygomatic arch, the ca rim of the orbit, and the coronoid of the mandible. Needle advanced until bony plate around foramen orbitorotundum is reached. withdrawl, aspirate, inject lidocaine. wait 5min for effect test
describe enucleation procedurestitch eyelids together--> cut around eye in continuous line--> blunt dissection around whole globe--> internal stitches to minimize dead space--> stitch eyelids together/infuse orbit with abx cream. systemic abx 3d. PAIN RELIEF
how can you try to differentiate wart vs SCC?warts have much less infiltration of the 3rd eyelid
inc tears might mean?early sign of infection
smelly yellow eye discharge might mean?might be sign of systemic condition (IBR, MCF)
2 things that can cause uveitis?MCF, septicemia
cataracts might mean what is in the herd?BVD