Eye Procedures Flashcards
Do ruminants have a tapetum?
- Yes
Do camelids have a tapetum?
- No
Eyelid trauma primary cause
- Trauma
Laceration in the eye repair
- Fluorescein to see if there are ulcers
- Visually you can usually see it
- They can get fibrosis
What is the agent of most infectious bovine keratoconjunctivitis?
- Moraxella bovis
- To a lesser extent Moraxella bovocoli
Transmission of Moraxella bovis
- Direct or fomite transmission
- Face flies can transmit
Keratoconjunctivitis in sheep and goats
- Chlamydophilia and Mycoplasma
- ZOONOTIC
Moraxella bovis
- Carrier animals
- Ultraviolet rays (bright sun, snow glare)
- Dust
- Face flies transmit
Appearance of pink eye
- Can progress to corneal ulceration
- Neovascularization at the limbus
- Clouded over cornea
- Often heal well
- Neovascularization from the limbus and vasculature regresses
Moraxella bovis appearance
- Lesions are always symmetric
- If it’s off to the side, you should think that it’s something else
Treatment for Moraxella bovis
- Oxytetracycline
Oxytetracycline usage
- Effective against pinkeye, pneumonia, footrot, bacterial scours, metritis, and wound infections
How often does oxytetracycline need to be dosed?
- One dose delivers 3 days of sustained therapy
Oxytetracycline in dairy cows - okay or not?
- Yep, it’s fine
- Even in lactating dairy cows
Milk withdrawal time for oxytetracycline
- 96 hour milk discard (4 days)
Meat withdrawal time for oxytetracycline
28 days
Draxxin
- Macrolide made for food animals initially
- Tulathromycin
Indication for Draxxin
- Injectable solution indicated for the treatment of infectious bovine keratoconjunctivitis associated with Moraxella bovis
Draxxin species indication
- Beef cattle (including suckling calves), non-lactating dairy cattle (including dairy calves), veal calves, and swine
- Not for use in female dairy cattle 20 months of age or older
Keratoconjunctivitis of sheep and goats definition
- infectious/contagious ocular disease characterized by keratitis, conjunctivitis, and visual impairment
Clinical course of KCS in sheep
- Self-limiting often
- 7-14 days
- Improvement by day 3-4
Treatment for KCS
- Self-limiting
- Recurrence is common
- Treatment considerations:
1. Animal comfort
2. Decrease severity of disease 3. Control or eliminate carrier state (limit spread of disease in naive flock difficult)
4. Tetracycline ophthalmic (and eventually Draxxin)
5. Systemic oxytetracycline, Draxxin (tulathromycin)
Blocks for eye surgery
- Auriculopalpebral is most important (over the zygomatic arch)
- Cornual also
- Infraorbital
Primary differential for pink eye?
- Trauma or foreign body
- If it’s asymmetrical, that’s more likely
How are most corneal lesions treated?
- Medically not surgically
Indications for lid closure
- Gain stability and protect the cornea
- Common uses in Ag-animals for keratitis, corneal injuries, and ulcers
How long do antibiotics in the eyes last?
- A couple of minutes
- You can do sub-conjunctival blebs of antibiotics
Post-op care for eye surgery
- Bandage the eye
- Don’t seal it all the way around
Tarsorrhaphy
- He will do an auriculopalpebral block for this too
- Closing the eyelids shut so that the suture line doesn’t rub on the cornea
- Leave some of it open
Purpose of Tarsorrhaphy
- Gain stability and protection for underlying corneal structures
- Provides pressure as well as warmth and vascular supply
Conditions that can benefit from tarsorrhapy
- Corneal ulcers, corneal lacerations, keratoconjunctivitis
Anesthesia for tarsorrhaphy
- Palpebral nerve block (motor to eyelids)
- Local infiltration of lidocaine along lid margins
How long to leave tarsorrhaphy in place?
- 7-10 days
Third eyelid flap indications
- Same indications as tarsorrhaphy (corneal ulcers, corneal lacerations, and KCS)
Anesthesia for third eyelid flaps
- Palpebral nerve
- Local lid infusions
- Topical
Technique for third eyelid flap
- Pass up away from the eye
- Take a good bite of the lid with a simple mattress type suture
- Tension techniques often used
- Pass back up through the eye and tie together
What are three locations of squamous cell carcinomas?***
- The third eyelid
- The limbus (junction of the cornea and the sclera)
- The lower lid
What is the most common third eyelid issue?
- Squamous cell carcinoma
Squamous cell carcinoma other information
- Malignant
- Can be described in early stages as aggressively local with very indistinct margins
- Later on can be metastatic (reason for carcass condemnation)
Third eyelid excision anesthesia
- Palpebral nerve
- Topical (lidocaine or proparacaine in the eye)
- Can infuse anesthetic (lidocaine) deep to the base of the third eyelid
Third eyelid excision technique
- palpebral nerve block and topical anesthetic
- Try to avoid cutting cartilage
- Crush with a carmalt or hemostat just below lesion and remove it
- No sutures
- If extensive, you remove the entire third eyelid including cartilage, lymphoid tissue, and gland of Harder
- Blunt pair of scissors are used to cut around the edge and entire 3rd eyelid removed
Dermoid cyst
- Hairy cyst in the eye
- Congenital growth containing hair, teeth, fluid, glands, etc.
What type of margins with SCCa?
- VERY WIDE margins
Corneal neoplasia location
- Pre-cancerous or cancerous lesions most commonly occur at the sclero-corneal junction (limbus)
Superficial neoplastic lesion blood supply
- Derive blood supply from the bulbar conjunctiva
Invasive neoplastic lesion blood supply
- Deep structures
- Worse prognosis
What to do for a corneal neoplastic lesion?
- Cryosurgery
Goal of cryosurgery
- Irreversible damage to treated tissue by intracellular ice formation
What determines the degree of damage with cryosurgery?
- Rate of cooling and minimum temperature achieved
- Inflammation 24 hours post treatment contributes to lesion destruction via immune mediated mechanisms
What type of freeze and thaw do you want to use for a corneal lesion
- FAST freeze and SLOW thaw to damage and kill tissues
How many cycles of fast freeze/slow thaw?
- Three cycles
Technique for cryosurgery on corneal lesion
- ) Palpebral nerve block
- ) topical anesthetic to eye
- ) Proptose eye or fix in position
- ) Tumor debulking as necessary
- ) Irradiation historical but rarely used now
- ) Hyfrecator (thermocautery)
- ) Cryosurgery
- ) trying to destroy the blood supply
Invasive corneal lesion treatment
- Eye ablation
- Radiation
Why are squamous cell carcinomas often on the bottom lid?
- More exposed to UV light
Eyelid neoplasia goals
- Evaluate extent of lesion
- Anesthesia
- Cryosurgery and lesion excision with or without primary closure
- Ocular ablation
Closing eyelid repair
- If you had a tumor and chopped it out, you can sew the edges together OR slide it up
- Take out some wedges and move it up
- You can also do an H plasty
Techniques for cryosurgery
- Probes, swabs, evaporative
Eye ablation
- Taking out the orbit and the adnexa (surrounding tissue)
What are reasons for eye ablation?
- Severe ocular damage due to injury, infection, or neoplasia
- Salvage vs surgery
- SCC metastasize late to regional LN
Slaughter regulations for Squamous cell carcinomas
- If the tumor has spread to the extent that it has destroyed the eye, the animal is condemned on ante-mortem inspection
- If it is small, it is tagged suspect and slaughtered. Public Health veterinarian will look at it post-mortem
- If significant spread around the eye (visible after removal of skin), or if there has been metastasis to LN of the head, the entire animal is condemned - head, carcass, viscera
- If the tumor is localized, the head is condemned and the carcass and viscera passed, assuming no other condemnable diseases or conditions are found
Eye ablation
- Thorough examination to determine type and extent of lesion
- Restraint
- Prepare surgical field
- Anesthesia (palpebral nerve, topical, lid infusion, + RETROBULBAR infusion with a Three or four point or Peterson block)
Peterson block
- He doesn’t do this
- Trying to hit the foramen orbitorotundum
- If you sneak the bevel of the needle underneath the dura you can kill the animal immediately
His blocks for eye ablation
- Auriculopalpebral and ring block around the eye
Common reasons for eye ablation
- Extensive squamous cell carcinoma
- Panophthalmitis
- Irreparable ocular damage or trauma
- Ocular lymphosarcoma
Technique of total ocular ablation
- Close eyelids with towel clamps
- Elliptical incision around orbital fissure, encompassing the skin tumor if present
- Sharp dissection toward the orbital rim staying retroconjunctival
- Free the periorbita from the orbital rim (strongest attachment at commisurae)
- Now using scissors - serrated edge scissors, dissect free
- Can ligate or emasculate ocular pedicle with angiotribe
- Remove all suspect tumorous tissue
- Tension relieving pattern (horizontal mattress; simple interrupted, etc.; simple continuous oversew)
Entropion definition
- Eyelid rolls in and rubs the cornea traumatically
How does entropion occur?
- Genetic condition of sheep or eyelid injury
Surgical techniques for entropion
- Local lid infusion with air or penicillin
- Local crush technique
- Surgical resection of excessive tissue (May take a lot of time)
Tracheotomy indications
- Upper airway obstruction
- Larynx (necrotic laryngitis, common)
- Nasal cavity
- Tracheal collapse (uncommon)
- Surgery in area
Ruminant trachea type of tracheal rings: complete or incomplete?
- Incomplete
Rules for tracheotomy tube
- First rule to stay on midline and cut down to trachea
- Retractors are good if you have time
- He will cut across the tracheal rings
- Junction of upper and middle third of trachea
- Select proper tracheotomy tube (can use endotracheal tube in a pinch)
- Surgical prep if possible
- Local or general anesthesia
- Incise between two rings
Post op care for tracheotomy tubes
- Daily maintenance of tube
- Stall and environment (make sure you are not in shavings)
What to do when you’re ready to take the tube out?
- Take it out and let it heal by second intention
- Keep them in a clean area
Complications of tracheotomy
- Tracheal collapse
- Tracheal obstruction
- Aspiration pneumonia
- Chondritis
- Larynx may never heal
