Opthamology Flashcards
Define exophthalmos
Protrusion of a normal size globe
What are the 2 most common ddx for exophathalmos?
- Retrobulbar cellulitis
- Retrobulbar neoplasia
Describe 3 clinical signs of orbital disease
- Exophthalamos
- Increased resistance to retropulsion
- Strabismus
Also pain on opening mouth, TEL protrusion and lagothalmos
Define strabismus
Deviation of the globe
Define lagophthalmos
Inability to complete a blink
How long should you treat a retrobulbar abscess with antibiotics and NSAIDs?
4-6 weeks (long course is indicated in diseases of the orbit)
What is the most common retrobulbar neoplasia?
Nasal adenocarcinoma
Masticatory myositis is an autoimmune disorder against which tissues?
Type II M myofibers
Abs target these muscle fibers
How do you treat masticatory myositis?
Long course (weeks) of systemic corticosteroids
Define traumatic proptosis
Protrusion of the globe with eyelids behind the equator of the globe
One step up from exophthalmos
Why is the prognosis of traumatic proptosis poorer in dolicephalic dogs and cats, compared to brachycephalic dogs?
Because they required a more severe force/trauma to pop the bulb out than brachycephalics (the greater the trauma the poorer the prognosis)
What procedure allows you to release the tension on the eyelids and allow them to be drawn over the cornea when replacing a proptosed globe?
A lateral canthotomy
How would you close the eyelids to keep the eye in place after replacing a proptosed bulb?
A temporary tarsorrhapy - passing suture through the eyelids at the level of the meibomian glands
Describe the steps of replacing a proptosed globe
6 steps
- Under GA, remove any debris by flushing with saline
- Check for ulcers with fluorescien
- Flush with saline once more
- Lateral canthotomy to reliver tension on the eyelids
- Temporary tarsorhaphy to close the eyelids
- Close the lateral canthotomy
How long should you leave tarsorrhapy sutures in place?
At least 2 weeks, or until swelling goes down
List 4 indications for enucleation
- A non visual, very painful eye
- Irreparable damage to the globe or optic nerve
- Proptosis with a torn optic nerve
- Neoplasia that can’t be taken out without damaging the eye
What would be a good choice of retrobulbar anaesthesia for an enucleation?
Bupivicaine
Long acting, good for post op too
Why shouldn’t you clamp or ligate the optic nerve when performing an enucleation?
Because the optic nerve is quite short, and the chiasm where to optic nerves from both eyes cross, if you pull on one nerve there is a high risk you damage the other and cause blindness in the ‘good’ eye
What is a special consideration when performing an enucleation in a rabbit?
They have a large orbital venous sinus, so there is a greater risk of hemorrhage
What is the universal method for enucleation?
Transpalpebral enucleation
Define enophtalmos
When the eye is sunken in the socket
What structures make up the adnexa?
The external and third eyelids, conjunctiva, lacrimal system, and orbit
Describe the procedure for a transpalpebral enucleation
- Make an circle incision around the eyelid margins
- Blunt dissection around the globe (don’t penetrate the conjunctival sac)
- Dissect all the way back to the posterior sclera, beyond the reflection of conjunctiva
- Dissect under the insertions of the EOM and cut
- Close the subcutical layer with absorbable suture (water tight)
- Close the skin layer
What are the 3 layers of the eyelid?
- Outer skin layer
- Middle muscle, gland and connective tissue layer
- Inner layer with palpebral conjunctiva
What is the caruncle?
A small pink nodule at the medial canthus, it is external to the third eyelid in the dog
What does the medial canthal tendon connect?
This one is shorter
The medial canthus to the frontal bone
What does the lateral canthal tendon connect?
The lateral canthus to the orbital ligament
This one is longer
Which nerve and muscle are responsible for closing the eyelids?
Nerve: CN VII
Muscle: orbicularis oculi
If a dog has facial nerve paralysis (CN VII) and can’t close its eyelids, how is the eye protected from corneal damage?
As long as CN VI (the abducence nerve) is intact and the dog has good tear production, the eye can still retract enough for the third eyelid to sweep over it and distribute the tear film + promote drainage
What is distichiasis?
When cilia emerge from the lid margin
What is conjunctival/ectopic cilium?
When the hair emerges through the conjunctiva of the upper eyelid
You are presented with a young patient with a dorsal corneal ulcer, what are you suspicious of?
Ectopic cilia
What is trichiasis?
Normally located hairs abnormally directed to irritate the ocular surface
Define entropion
When the lid margins turn inwards towards the cornea so there are skin hairs in contact with the cornea, causing pain
List 3 signs of occular pain
- Lacrimation
- Globe retraction (3rd eyelid protrusion)
- Photosensitivity
In which breeds do we most commonly see medial canthal entropion?
Brachycephalic breeds
What is the most prominent sign of medial canthal entropion and why?
Corneal pigmentation - because of chronic irritation from the tight medial canthal ligament pulling the lower eyelid inwards
Why do corneal ulcers in brachycephalics deteriorate so quickly?
I.e., why do they take so long to heal
They have reduced corneal sensation (because their corneas are always so exposed and their tear film evaporates quickly), which slows healing time
What is a medial canthoplasty, and what would it fix?
A procedure that shorterns the length of the palpebral fissure
It would fix medial canthal entropion and reduce corneal exposure, especially in brachycephalics
It would also help flatten nasal folds than can rub against the eye
What is spastic entropion?
A form of secondary entropion where a form of ocular pain is causing the globe to retract, causing entropion and worsening the ocular pain
How would you address entropion in a newborn sharpei puppy?
Temporary tacking with vertical mattress sutures (temporary)
Can put under longer GA and fix surgically once 3-4 months
What is the name of the technique used for definitive surgical correction of entropion?
Hotz-celsus repair
Describe a Hotz-celsus repair for the correction of entropion
You remove an ellipse of skin below the lid margin at the affected site and close with simple interrupted sutures
What is an atonic/senile entropion?
When there is lack of tone in the upper eyelid, causing the skin to droop and hairs to irritate the cornea
What are 2 corrective procedures for atonic/senile entropion?
- Rhytidectomies (face lift)
- Stades procedure (remove an ellipse of skin from the upper eyelid and leave to heal by secondary intention)
What tx is indicated for a cosmetic ectropion?
None - leave it be
What is a coronal rhytidectomy?
Excision of redundant skin
Which facial features are indicative of lateral canthal instability?
When the lateral canthus presents lower than the medial canthus because of long eyelids, heavy ears and excessive brow skin
What are 3 tx options for meibomian gland inflammation?
- Warm compress
- Topical/systemic abx (not a first choice, but sometimes needed)
- Corticosteroids
What causes a chalazion to form?
Rupture of meibomian glands and the release of meibum into tissues causes a foreign body reaction and a pyogranulomatous response
What are your tx options for a chalazion?
Warm compress in the early stages, but then cut it off under GA and give abx for 7-10 days
What is the most common eyelid tumor in the dog?
Tarsal gland adenoma (adenocarcinoma)
What is the most common eyelid tumor in the cat?
Squamous cell carcinoma
What is the 3rd eyelid supported by?
T cartilage
What are the functions of the 3rd eyelid?
- Wind screen wiper for the tear film
- Immune response to pathogens entering through mucous membranes of the eye
When would you see ‘flicking’ of the 3rd eyelid?
With tetanus or rabies
List 5 cases in which you will have 3rd eyelid prominence
- Orbital mass lesions
- Retraction of globe
- Reduction in globe size
- Reduction in orbital contents
- Horner’s, tetanus, rabies (NS dysfunction)
How would you fix a cherry eye?
Replace it using the pocket technique
Do not excise it
Define nictitans plasmacytic conjunctivitis
Plasma cell infiltration of the 3rd eyelid
How would you treat a plasmoma?
Long-term topical cyclosporine
List 2 tumors of the 3rd eyelid
- Haemangioma
- Lymphoma
