Ophth - Orbit and eyelids Flashcards
What species have open orbits?
Dogs and cats
What species have closed orbits?
Horses and cattle
What does having a closed orbit mean?
Space between the zygomatic bone and frontal bone is linked with orbital ligament
What are the extra-ocular muscles of the eyes?
4 cardinal rectus muscles
2 oblique muscles
Retractor bulbi
Where do all of the extra-ocular muscles attach?
All attached at equator - widest part of eyeball
Where do all the extra-ocular muscles meet at the back of the eye?
Annulus of Zinn
What cranial nerve innervates the majority of the extra-ocular muscles?
CNIII - oculomotor nerve
What are the thee muscles that are innervated by nerves other than CNIII?
Lateral rectus
Dorsal oblique
Retractor bulbi
What nerve innervates the dorsal oblique muscle?
CNIV - trochlear
What nerve innervates the lateral rectus muscle?
CNVI - abducens
What are some examination techniques for examining the eye?
Check the visual axis
Check the position of the eye in the orbit
Size of globe
Retropulsion - can eye move back in the orbit
Inspect oral cavity
Inspect the nasal/sinus cavities
What is the name for abnormal protrusion of the eye from the orbit?
Exophthalmos
What is the name for abnormal recession of the eye in the orbit?
Enophthalmos
What is lagophthalmos?
Incomplete eyelid closure and globe coverage
What is the name for deviation of the eyes from the axis so they arent aligned towards the same object?
Strabismus
What can cause exophthalmos?
Space occupying lesions
Neoplastic
Inflammatory
What are some common causes of space occupying lesions?
Foreign body
Infection from oral cavity
Infection from sino-nasal
Trauma
Haematogenous infection
What are some primary neoplasms in the orbit?
Mesenchymal tumours
Epithelial tumours
Orbital meningioma - nerve sheath tumours
What are some secondary neoplasms in the orbit?
Lymphoma
Metastasis
From adjacent tissues eg. SCC
What is orbital myositis?
Immune mediated disease affecting eye causing bilateral exophthalmos
What is it called when the eye pops out of the socket?
Globe proptosis (globe popped-out-is heheh)
What should you do if globe proptosis occurs?
Emergency
Must keep eye moist
Check systemic injuries
Supportive care
How do you treat proptosis?
Lift lids over globe to replace under GA
Flush conjunctival sac
Roll out lids and place temporary tarsorraphy
When should you perform enucleation in proptosis cases?
When globe is ruptures
3 or more extraocular muscles torn
Complete hyphaema - eye full of blood
What can cause enophthalmos?
Muscular atrophy
Dehydration
Reduced orbital fat
Ocular pain - retractor bulbi pulls back
Breed related - dolichocephalic dogs
Horners syndrome
What are the signs of horner’s syndrome?
Miosos
Third eyelid protrusion
Enophthalmos
Ptosis
What is miosis?
Small pupil
What is ptosis?
Drooping of the upper eyelid
When should you perform enucleation?
Irreversible loss of vision
Ongoing pain and discomfort
Chronic glaucoma
What are the two approaches of performing enucleation?
Transconjunctival - simpler
Transpalpebral
When should you perform a transpalpebral enucleation?
When there is infection or neoplastic cells on the surface
How do you perform a transpalpebral enucleation?
Suture lids
Dissect around
Dont pull - can affect other eye across chiasm
Remove eye
Homeostasis
What is different about a transconjunctival enucleation?
Lateral canthotomy - widen the palpebral fissure
Section extraocular muscles individually
What are the main muscles of the eyelid?
Levator palpebrae superioris
Orbicularis oculi
Medial palpebral ligament
What is the structural plate of the eyelid called?
Tarsus
What are the glands called that produce the lipid portion of tears?
Meibomian glands
What are the functions of the eyelid?
Mechanical protection
Produce/spread tear film
Part of lacrimal functional unit
What is the name for introversion of the eyelid?
Entropion
What is the name for excessive eyelid length?
Macroblepharon
What is the name for combined entropion and ectropion?
Diamond eye
What is the name for hairs of normal skin irritating the eye?
Trichiasis
What is the name for when cilia emerge from the meibomian gland and irritate the eye?
Distichiasis
What is the name for when the cilia arise from the meibomian gland but protrude through the conjunctiva (inside of the eyelid)?
Ectopic cilia
What is the difference between distichiasis and ectopic cilia?
They both grow out of the meibomian gland but
Distichiasis is through the meibomian gland orifice on the eyelid margin
Whereas ectopic cilia emerge through the palpebral conjunctiva
What is the term for when they cant blink properly?
Lagophthalmos
What are the 4 parts that make up brachycephalic ocular syndrome?
Macroblepharon
Lagophthalmos
Medial entropion
Reduced corneal sensitivity
How do you treat macroblepharon?
Frequent lubrication
Surgical correction to reduce palpebral fissure
What is the normal eyelid length? What is an oversized lid?
33-35mm - normal
40-50mm - oversized
How do you treat diamond eye?
Blepharoplasty - reconstructive surgery to shorten eyelid and stabilise lateral canthus
What indicates that an animal has entropion?
The eyelid margin is not visible
How do you treat entropion?
Hotz- celsus technique
Tacking sutures - in very young, can grow and correct
Refer in complex cases
What is the hotz-celsus technique?
Insize along parallel to lid as long as the lid inversion
Remove a semicircle of skin
Undertreatment is better than taking too much
What does ectropion cause?
Frequent conjunctivitis - cant spread tear film
How do you treat ectropion?
Eyelid shortening - wedge resection
How do you treat distichiasis/ectopic cilia?
Check eyelids thoroughly
Can pluck but will grow back
Permanent surgical removal en bloc - cryosurgery and electrolysis
What are the most common eyelid tumours?
Meibomian gland epithelioma
Adenoma
Adenocarcinoma
Melanoma
Squamous papilloma
When should you surgically remove eyelid tumours? How is it done?
When the mass is <1/3 of the eyelid length
Chalazion clamp stabilises the lid
Wedge resection
Close with figure-8 suture
