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Rumi Ophthalmology

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sihirlifil's version from 2018-04-29 13:39

Ophthalmic anatomy, exam, abnormalities

Question Answer
Outer layer =Fibrous (protection, transmission, refraction)
Cornea, sclera, limbus
Middle layer =Vascular (nutrition, immunity, accommodation)
Iris, ciliary body (produce fluid), choroid
Inner layer =Nervous (signal in response to light)
Retina
(list of associated anatomical structures)Conjunctiva
3rd eyelid
Optics (tear film, cornea, lens)
Anterior (btw cornea & iris) & posterior (btw iris & vitreous) chambers
Vitreous
Tapetum
Optic nerve
Glands
What’s this?
Corpora nigra! normal in camelids
Step 1 of eye examStart w/ observation! can see head carriage, appearance/symmetry of face, periocular swelling or alopecia, discharge, redness…
After distance exam…?Good restraint required!
Cattle: head catch, halter, +/- sedation
SR & camelids: Manual, sedation
Pigs: ANX or really heavy sedation
**Visual exam: need what? checking for?Local & topical ANX. Magnification can help
Check PLR, cranial nerves. Fluorescein stain (need dim light). Check under 3rd eyelid & upper lid for FB (hold eyelids apart & press gently on globe, 3rd eyelid pops out)
(Visual exam: things we don’t really use)(Schirmer tear test, Tonopen/slit lamp, Fundic exam difficult if outside, tropicamide is short acting)
Local/topical ANX: motor fxn to eyelids =Auriculopalpebral
Local ANX: Which nerves are blocked?Cornual, auriculopalpebral, optic
Local ANX: optionsRing block
Retrobulbar block
How is the retrobulbar block performed?1-4 needle insertion sites, 10-20cc 2% lidocaine per site
Don’t stick needle through tumor or anything near! Stay close to orbital bones as you advance needle behind the eye. use curved spinal needle
Ophthalmic meds: go-to? others?Oxytetracycline parenteral or topical, not in subconjunctival bleb
Ciprofloxacin drops ILLEGAL in FA in USA! PO = VFD restrictions (only to tx, not prevent)
Gentamycin = prolonged withdrawal time
PPG topical (leaks out of bleb, bathes surface)
Macrolides: Tulathromycin, tylosin, gamithromycin
Florfenicol
Most common abnormalities (5)Red eyes (surface, diffuse)
Cloudy eyes
Ocular dmg
Asymmetry
Visual defects/blindness
1st CS of a problem usually..?Excessive lacrimation/epiphora
What’s going on here?
Excessive lacrimation! cleaning mechanism for eye, mechanical & immunological
Attracts flies!
Excessive lacrimarion: DdxIBR
Infx bovine keratoconjunctivitis (IBK)
MCF
Entropion
Clogged/incomplete/inflamed ducts or puncta
FB
SR: pink eye
Blepharospasm =Involuntary eyelid spasm (painful, light sensitive)
Conjunctivitis: looks like?Unilateral or bilateral. Hyperemic, injected; ocular d/c; blepharospasm
+/- lymphoid hyperplasia
Causes of conjunctivitisTrauma, irritation
Inxn (Chlamydia, IBK, IBR, MCF)
Allergies
Neoplasia (SCC)
Tx of conjunctivitisID & Tx 1ry cause (Culture, scraping, biopsy if not resolving)
Anti-inflam, antibx
Protection: patch, 3rd eyelid flap, fly control
This eye was just stained w/ fluoroscein. what happened? what does it tell you?
Not fluorescein positive- no dye uptake! Means internal structure is abnormal (2ry ulcers, something going on w/ 3rd eyelid? etc)
Causes of cataractsBVDV, juvenile
Causes of ophthalmic nerve hypoplasiaVit A deficiency in dam
Causes of uveitis/iritisInfection, sepsis
Silage eye
Malignant catarrhal fever
Uveitis: CSOcular d/c
Enopthalmos
Blepharospasm
Scleral & conjunctival injection
Corneal edema, aqueous flare
Sluggish PLR
Synechia formation
Uveitis: TxID & Tx 1ry problem!
Antibx; NSAIDs or steroids
Parasympatholytic (mydriasis): Atropine, tropicaminde (lasts a long time! keep them somewhere in the shade)
What’s this??
Hypopyon (pus in eye)
Hypopyon usually happens inNeonates (FPT, sepsis)
memorize

Common Ophthalmic issues

Question Answer
Types of ulcers/perforations1ry (FB) or 2ry (sequela to various diseases)
What can happen if an ulcer goes on for too long?Descemetocele
About to rupture
What happened
Corneal perforation
Loss of aqueous humor, iris moves forward to plug hole, can lose lens
**Corneal ulcers: TxTreat 1ry problem
Do well with parenteral antibx, NSAIDs
Topical serum
(3rd eyelid flap: patches make it impossible to see what’s going on or do topical tx)
What’s happening to this eye
Healing corneal perforation. Can see neovascularization from dorsal aspect, fibrin
What’s this procedure? complications?
Cubconjunctival bleb
Squirting procaine penicillin G/steroids (NOT OXYTET). Penicillin is thick, will probably squirt back at you
SC oxytet is just as effective and easier (secreted in tear film)
What’s this procedure? benefits?
3rd eyelid flap (protect cornea, easier to install meds, more direct contact bandage)
How is a tarsorrhaphy done?Horizontal mattress sutures placed through stent, partial-thickness bites of lower & upper eyelids (approx 5-10 sutures). Need apposition of lid margins, avoid inversion
How is a 3rd eyelid flap done? when?Temporary bandage (ulcerative keratitis)
Suture nicitans to dorsolateral fornix of upper lid with 1-2 simple interrupted horizontal mattress. Remove as soon as dz has resolved
**Pink eye in CATTLE: top ddxMoraxella bovis
Infx bovine keratoconjunctivitis
IBR
IBK vs IKC: diagnosticsLesion location
Check 3rd eyelid for FB
Fluorescein
Culture if don’t respond
IBK: who gets it? how?Younger > older CATTLE (hence the ‘B’ for bovine)
Transmitter via face fly; dust, trauma, feed abrasions can also initiate
IBK: which bacteria involved?Moraxella bovis/bovoculi, Mycoplasma
IBK: vax?Efficacy is iffy
IBK: characteristic lesion locationstarts at center of eye
IBR (BHV-1) & MCF: characteristic lesion locationstarts peripheral
(BHV-1 usually doesn’t cause ulcer unless concurrent IBK; also other systemic signs w/ IBR & MCV)
IBK: where found? CS?Worldwide!
All typical corneal signs, +/- scarring or rupture, lens/iris prolapse (econ & welfare impacts)
IBK: any predisposition?May be genetic susceptibility (Herefords vs. ocular margin-pigmented breeds). genetic links being ID’d
IBK: contributing agents?Moraxella bovis/bovoculi
Other viruses & bacteria: BHV-1, Mycoplasma, Branhamella, etc
Flies, solar irritation, mechanical trauma
How does Moraxella bovis cause dmg?Produces various enzymes (esp. pilli & cytotoxin proteins)
Allow adherence, pore formation, hemolysis
Moraxella bovis: Tx?Variety of antibx. protect eye as needed
Moraxella bovis: control(Vax efficacy is sketchy)
Fly control: ear tags, face rubbing devices, topicals
Pasture management: reduce grass awns
Cu & Se supplementation
Bovine iritis: aka? how does it happen?Sileage eye
Microtrauma from poor quality silage/haylage (mold, stems, poor preserved: Listeria monocytogenes!!
Hypersensitivity reaction
Bovine iritis: CSEpiphora --> mucopurulent
Blepharospasm, photophobia
Blue-white opacity --> yellow with pus
Iris bulges, corneal opacity w/in 2-3d. Lesions take weeks to resolve w/o tx (looks just like Moraxella at this stage)
Bovine iritis: Tx optionsSilage management, antibx, protect eye (stall, eye patch, 3rd eyelid flap), NSAIDs or steroids, Fly repellant, atropine (not set schedule, base on response)
Methods of antibx deliveryDorsal bulbar subconjunctival bleb
Subconjunctival dorsal/ventral eyelid
Systemic or topical
(Subpalpebral lavage: not recommended… have to then tx 2nd ulcer, especially in camelid)
**Pink eye in SR: 2 big onesChlamidophila pecorum, Mycoplasma spp. (other organisms can also cause ICK/pink eye)
Condition? Tx options?
Pink eye! Can do systemic & local antibx, serum eye drops, 3rd eyelid flap
How common is fungal keratitis? Dx? Tx?
Relatively uncommon. Dx on conjunctival scrapings, topical antifungals to tx
What’s going on with these babies
Entropion
Entropion: common in who?Lambs & kids (hereditary links if see at birth) (also pot-belly pigs)
How does entropion happen?Secondary to dehydration, trauma, weight loss, painful (globe withdraws) --> eyelid rolling in. Lower > upper
Entropion: txMedical: tx the ulcer & inflammation
Fix the eyelid if not due to illness (manual eversion, SQ penicillin/benzathine or lidocaine, vertical mattress, *superglue*) (surgical: Holz-Celcus, only if temporary not successful)
Ddx for this?
SCC, wart, dermoid, other neoplasia
(where is it attached? lid, cornea, 3rd eyelid? dark pigmented animal have ocular SCC?)
How do warts happen? Tx?Papillomavirus (contagious, self-limiting, less invasive than SCC)
Tx: Leave & monitor, or debulk (thermocautery); tx 2ry effects trauma, abrasion. Fly control!
memorize

Cancer

Question Answer
Ocular SCC: aka? who gets it?Aka cancer eye
Herefords predisposed (change in pigment style), see in all livestock w/ high UV exposure
**Ocular SCC: txComplete resolution is difficult! warn O about recurrence, sx easier if caught early! (range cattle are a problem)
What dis
Ocular SCC (cornea, 3rd eyelid… anywhere they want to be really)
Which one of these is SCC?
Both! can just look like epiphora early on. (rubbing --> bleeding, fly problems)
** SCC: treatments?(All with topical & regional ANX! NSAIDs, antibx vary)
Thermocautery
Cryotherapy
3rd eyelid resection
Enucleation/exenteration
SCC: when to do thermocautery?Early & small! Large a margin as possible
SCC: how does cryotherapy work?2-3 30sec freeze cycles: Freeze --> tap w/ scalpel handle/wooden Qtip (should feel frozen solid) --> Wait 30-60sec --> Reapply cryotherapy applicator
Thawing is what kills the cells (ice ruptures cytoplasm)
What are we doin
Cryotherapy! (top L = debulk)
SCC: aftercare for cryotherapy?Topical/parenteral antibx if extensive lesion
NSAIDs (cryo causes some corneal edema & conjunctivitis)
Recheck in 3-4w, may refreeze. Then routine followup q2-4m
3rd eyelid resection: basically doing what?Remove entire 3rd eyelid. Lidocaine at base, remove w/ scissors, can use cryo too
Eyelid tumors: tx optionsDebulk & freeze (often recur, touch to get every cancer cell frozen when liquid N2 in deep wound)
Sx removal w/ wide (>.05cm) borders
Sliding flap techniques
Enucleate if tumor removal would cause inadequate lid coverage of cornea
Enucleation =Remove only the globe & conjunctival sac, leaves the muscles
Exenteration =Remove entire contents of orbit
Enuc/Exent: preparation?(Speed is critical!) Risks for pregnant cows due to blood loss
Sedation, analgesia, ANX if doing recumbent (SR & camelids) (standing in cattle)
Enuc/Exent: procedureTowel clamp/suture eyelids together
Plan cutting margins (tumor size, enough tissue to close)
Blunt dissection & snip w/ scissors around globe (AVOID SCALPEL)
Leave no gauze behind (use roll) Don’t close over gauze or suture quickly

Enuc/Exent: If have to remove so much the eyelids can’t close?Pack w/ gauze, suture in tightly, remove in 2-3d
Enuc/Exent: post medsAntibiotics! e.g. Long acting oxytet. Blood is great growth media
NSAIDs (Flunixin & PO meloxicam)
Fly control: wound spray & ear tag
memorize

 

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