Globe & Orbit Flashcards
1
Q
What type of orbit do carnivores have compared to herbivores?
A
Carnivores = open orbit (room for movement of the mandible due to open orbit - for catching prey etc)
Herbivores = closed orbit (protect skull and orbital contents - dominance rituals)
2
Q
What bridges the incomplete lateral orbit in carbivores? Where does it extend from/insert?
A
Orbital ligament (soft tissue) - extends from zygomatic process of frontal bone to frontal process of zygomatic bone.
3
Q
Which bones delimitate the orbit in cats and dogs?
A
Frontal bone - medial, separates orbit from nasal cavity
Sphenoid bone - caudal orbit, optic canal and orbital fissure pass through this bone and define caudal apex of orbit
Zygomatic and Maxillary bones - define the rostral and lateral limits of orbit.
Lacrimal bone also integrates into rostral limit of orbit.
4
Q
Which soft tissue structures surround the bony orbit?
A
Dorsal, lateral and ventral orbit bordered by muscle
Temporal muscle - dorsal and lateral
Masseter - lies ventro-medial to zygomatic arch and forms lateral border
Pterygoid- ventral floor of orbit
Orbital fascia - thin but tough connective tissue liner that envelops all the structures within the orbit and including bony fossa itself.
Fascia of the 4 rectii muscles are connected by periorbital fasical sheath which envelops them - this fascia borders caudally the optic canal and rostrally the globe.
Intraconal structures vs Extraconal structures (whether within orbital cone or adjacent)
5
Q
What are the intraconal structures of the orbit?
A
Extraocular muscles - 4 rectus, 2 oblique, 1 retractor bulbi
Cranial nerves - II, III (occulomotor), IV (trochlear), and ophthalmic branch of V (trigeminal), VI (abducens)
Orbital lacrimal gland
Orbital fat within cone
Autonomic veins, arteries and nerves
Smooth muscle enveloping the periorbita (discrepency between anatomy textbooks)
6
Q
What are the extraconal structures of the orbit?
A
Zygomatic salivary gland (dogs)
Base of nictitating membrane
Neurovascular structures transversing the orbital floor - maxillary artery (branch of external carotid arterty), maxillary branch of trigeminal nerve, palatine nerve, infraorbital nerve, parasympathetic nerve and ganglion
Orbital fat cushion inferior to orbital cone
7
Q
What is the orbital septum?
A
Extends from the bony orbit
Found across the base of the orbit and into the eyelids
Continuous with the periorbital fascia - is thicker laterally in species with an open orbit.
Separates the orbital structures from more superficial structures.
8
Q
What other structures can be relevant to orbital disease as they lie adjacent?
A
Nasal cavity and paranasal sinuses - thick bony wall separates usually from orbit but in disease can extend into orbit
Roots of maxillary 4th premolar and 1st/2nd molars - only thin layer of alveolar bone separates them from the soft tissue structures of the orbit. Abscessation of tooth roots or iatrogenic damage of the alveolar bone after dentistry can be a cause for orbital disease.
Central nervous system - orbital apex close to CNS and disease can extend to and from the orbit via the calvarial bone and through the foramina and canals
Muscular disease affecting temporal or masseters e.g immune mediated muscular myositis.
Salivary gland - zygomatic inflammation (sialoadenitis), increased activity (sialoadenosis) or sialoceles
9
Q
What are the key clinical signs of orbital disease?
A
Exophthalmos - rostral displacement of the globe along the orbital axis (differs from proptosis as globe remains behind eyelids!)
Enophthalmos - caudal displacement of the globe along the orbital axis
Globe deviation- rotation of the globe away from the normal axis (strabismus used for globe deviation of neurological origin, esotropia and exotropia can be used to identify medial and lateral globe deviation respectively)
10
Q
What other clinical signs may be seen with orbital disease?
A
Protrusion of nictitating membrane (TEL)
Periocular swelling
Conjunctival hyperaemia and/or chemosis
Epiphora/mucopurulent ocular discharge
Lagophthlamos +/- exposure keratopathy
KCS
Pain/difficulty on opening mouth
Inappetance/anorexia
Reduction in occulovestibular movements
Afferent or efferent nerve defecits from CN II to CN VI and or autonomic nerves within orbit
Mild elevation in IOP
Retinal folds
Scleral indentation
Solid retinal detachments
Papilloedema
11
Q
What does the rectus lateralis do? Which nerve innervates it?
A
Moves eye laterally - abducens
12
Q
What does the rectus medialis do? Which nerve innervates it?
A
Moves eye medially - oculomotor
13
Q
What does the rectus dorsalis do? Which nerve innervates it?
A
Moves eye dorsally - oculomotor
14
Q
What does the rectus ventralis do? Which nerve innervates it?
A
Moves eye ventrally - oculomotor
15
Q
What does the dorsal oblique do? Which nerve innervates?
A
Rotate eye inwards - trochlear
16
Q
What does the ventral oblique do? Which nerve innervates?
A
Rotates eye outwards - oculomotor
17
Q
What does the retractor bulbi do? Which nerve innervates?
A
Retraction of the globe within the orbit - abducens
18
Q
What type of strabismus (misalignment of the eye from the usual visual axis) is seen with oculomotor nerve disease?
A
Lateral or ventrolateral strabismus +/- mydriasis (parasympathetic innervation form oculomotor)
19
Q
What type of strabismus is seen with trochlear nerve disease?
A
Intortion of the globe (only seen in non rounded pupils) or when evaluate fundus and see tilted
20
Q
What type of strabismus is seen with abducens nerve disease?
A
Medial strabismus
Lack of retractor bulbi = absent corneal reflex
21
Q
How can you differentiate a globe deviation such as strabismus from a mechanical impediment within the orbit?
A
Traction test - done under sedation with local anaesthetic
Can you rotate globe manually
If mechanical impediment - feel traction
22
Q
What are the steps to follow for work up of a patient with suspected orbital disease?
A
Full history - duration, onset, previous ocular disease, tendency to play with foreign objects, sticks, bones etc
PE
Head/skull examination
Orbital palpation
Oral examination (if patient allows)
Ophthalmic examination (including neuro-ophthalmic assessment)
Localisation of intraconal or extraconal process
Haematology/Biochemistry
Orbital imaging
23
Q
What can you do on physical exam to try and help determine if an eye if exophthalmic?
A
Examine from above
Resting hands over both eyes and feeling advancement of one of them or gently retropulsing globes can help
24
Q
When performing an examination of the head for a patient with suspect orbital disease what should you focus on?
A
Palpation of temporal muscles (pain response - acute masticatory muscle myositis)
Crepitus/emphysema - may indicate bony fracture
Auscultation of orbit - bruit = orbital vascular anomaly
Oral examination - ptergopalatine fossa (look for swelling or fistulas), dental disease (esp caudal maxillary teeth), stoma of zygomatic gland duct - opens in oral cavity opposite to 1st molar tooth (eryhema/swelling/discharge - zygomatic disease)
25
What steps of the ophthalmic exam should be performed when suspecting orbital disease?
All of them!
STT
Corneal sensation
Slit lamp exam
Fundic examination (looking for engorgement of retinal vasculature, papilloedema - optic nerve obstructed, globe impingement - orbital disease indenting globe), retinal detachment
Fluorescein staining
Tonometry
Neuro-ophthalmic evaluation also - PLR. menace, dazzle, vestibulocular reflex, palpebral,
26
What are the clinical characteristics of intraconal orbital disease (space within the muscle cone formed by the extrocular muscles)? What are the most common diseases of this type.
Axial exophthalmos
Absence or minimal protrusion of TEL
Absence or minimal strabismus
Limited ocular mobility in some instances
Most common - neoplasia of optic nerve, inflammatory myopathies
27
What are the clinical characteristics of extraconal orbital disease? (space outside the muscle cone but within the orbit)
What are the most common disease of this type?
Exophthalmos (non axial)
Globe deviation (deviation can provide information regarding location of the disease)
Protrusion of the TEL
Limited ocular motility
28
What is the difference between exophthalmos and buphthalmia?
Exophthalmos = globe deviated rostrally within orbit
Buphthalmia = globe bigger in diameter, globe itself larger
29
What options are there for orbital imaging?
Radiography (conventional and dental), Ultrasound, CT/MRI
30
When may radiography be a suitable imaging method for suspected orbital disease?
Suspicion of skull fractures (oblique views as well as standard)
Identification of radio-dense foreign bodies
Evaluate osteolysis (neoplasia)/bone remodelling
Can be difficult to interpret so cross sectional imaging (CT/MRI) generally preferred for orbital disease investigations.
31
What scenarios may you choose to use CT/MRI respectively for orbital disease work up?
CT - generally better if suspect bone involvement e.g extension of nasal neoplasia, orbital fracture, nasolacrimal involvement etc
MRI - better imaging modality for soft tissues
Downsides = cost, accessibility, and need for sedation/GA respectively.
32
When may ocular ultrasonography be helpful for orbital disease
7.5-10HZ transducer recommended
Can be performed conscious - corneal or temporal approach
Visual assessment of orbital cone and help visualise abnormalities within/outside cone
Can use contralateral orbit as reference
Will not help identify tissue or origin or malignancy or lesion
Good at detecting free fluid e.g orbital abscess/cellulitis
Ultrasound guided trucut biopsy may be possible in some cases where neoplasia suspeced.
Not helpful for disease affecting orbital apex
33
What is anophthalmos?
No globe developed (very rare) - most animals will have a primitive non functional ocular structure on histological exam
34
What is microphthalmos and what abnormalities are associated with it?
In which breeds is it associated as a hereditary defect?
Abnormally small eye with abnormalities
Other abnormalities present include - anterior segment dysgenesis, cataracts, persistent hyperplastic primary vitreous/persistent hyaloid artery, retinal dysplasia
Doberman - microphthalmia with anterior segment dysgenesis and retinal dysplasia
Minature Schnauzer - with cataracts, microphakia, posterior lenticonus, nystagmus and retinal dysplasia
Cavalier - cataracts, nystagmus, posterior lenticonus and persistent hyaloid artery
Australian Shepherd - equatorial staphyloma, persistent pupillary membrane, iris colobomas, retinal dysplasia (linked to merle gene)
35
What is nanophthalmos?
Abnormally small eye without other abnormalities
36
What can be done in cases of microphthalmos where protrusion of the third eyelid limits vision?
If causing significant visual deficits then can consider shortening of the cartilage
(Never recommended to remove the whole nictitating membrane)
37
What is hydrophthalmos?
Associated with congenital glaucoma and can be unilateral or bilateral due to abnormalities in AH outflow pathway.
Enlargement of globe occurs and is dramatic in young animals
(Has been used synonomously in vet med with buphthalmos)
38
What is the difference between microphthalmia and a phthysical globe?
Microphthalmia = congentially small globe
Phthisis bulbi = atrophied globe and is acquired
39
Which breeds can have an enophthalmos (abnormal posterior position) as a developmental abnormality - deep orbit and small globe?
Dolichocephalic breeds typically - English Bull Terrier, Rough and Smoot Collies, Dobermann, Flat coated retrievers
Often have prominent nictitating membrane and medial canthal pocket syndrome due to gap or pocket at medioventral canthus where mucus and debris accumulate.
No specific treatment - just management with routine hygeine
40
Which breeds have an exophthalmic conformation? How can their conformation be managed?
Typically brachycephalic - extreme conformation
Incomplete blink/patient sleeps with eyes partially open or only partially closed
Tear replacement substitutes recommended even if normal tear production (paraffin based at nights)
Also consider surgical reduction of macropalpebral fissures - medial or lateral canthoplasties to improve blink and facilitate corneal protection.
41
What is an orbital arteriovenous fistula? (OAV fistula)
Rare congenital or acquired (spontaneous, post traumatic or vascular neoplasia) conditon
Abnormal communiciation between orbital arteries and veins
Increased venous (may also see pulsatile jugular) and orbital pressure - pulsatile exophthalmia or bruit auscultatable over temporal region
Diagnosis confirmed colour flow Doppler or CT angiography
No successful treatment to preserve globe.
42
What are orbital varices?
Congential disease of orbital veins.
Exophthalmos that worsens with exercise but can eventually become persistent
Coil emobilization reported in one dog
Significant exophthalmia and advanced intervention not possible - careful exenteration is indicated - careful pre-op planning due to risk of intra op haemorrhage.
43
What are orbital dermoids?
Dermoids are developmental choristomas (normal ectoderm tissue developing in abnormal location)
Orbital dermoids can contain many tissue types.
Confirmation with histopathology
Dermoids slow growing and this can determine age/presentation
Leakage of keratin/lipids can occur from dermoids causing secondary inflammation and complicating removal.
44
Which breeds may be affected by craniomandibular osteopathy and what is this disease?
Non neoplastic proliferation of tissue
WHWHT, Cairn Terriers and Scottish Terriers
Affects mandible, tympanic bullae and other bones of skull including the occipital, temporal, sphenoid and/or parietal bones
Skull radiography best for demonstrating lesions.
No curative tx.
45
What are buphthalmos/hydrophthalmos associated with?
Enlargement of globe secondary to persistently elevated IOP
Thinning of fibrous tunic of the eye can become obvious on ophthalmic examination
Haab's striae - linear lesions on cornea, pressure high enough to cause breaks in descemet's membrane
46
When is phthisis bulbi seen? Why does it occur?
Acquired shrunken blind eye
End stage response to severe ocular injury or disease
Reduction in size due to damage of the ciliary body and the reduction of aqueous humour - marked decrease in IOP
Lack of IOP = ocular tissue shrink and leads to small size non functional globe.
May be comfortable (although debated) but secondary entropion and medial canthal pocket syndrome can cause problems.
Often enucleated.
47
Which is associated with a worse prognosis - blunt or penetrating trauma?
Blunt
48
What sequelae can be seen as a result of a blunt trauma?
Contusion of the uvea - hypotony, miosis, iridial congestion, presence of fibrin and debris or hyphema within globe.
Scleral rupture/haemorrhage
Retinal detachment via coup contra coup effect
49
What imaging modality is useful for blunt trauma cases?
Ultrasonography - check continuity of posterior sclera, look for retinal detachments, assessment of intraocular structures
Temporal approach if concerned about globe integrity.
50
What options are there for treatment of blunt trauma?
Depends on level of injury to ocular structures
Assess vision - PLR (consensual helpful if hyphema make visualisation impossible), Dazzle, Menace
Haemorrhage but no damage to intraocular structures on U/S = anti-inflammatories (NSAID orally, topical steroid or NSAID as long as no ulceration), cycloplegics (atropine)
Anterior scleral rupture but intraocular structures in place = reconstruction can be attempted with reserved prognosis
Posterior scleral rupture/intraocular structures displaced = enucleation performed.
51
What clinical signs are seen associated with penetrating type traumas?
+/- Uveal prolapse (dark to tan tissue protruding through corneal or scleral wound
Iritis
Fibrinous clots
Haemorrhage
Miosis
Dyscoria
May have shallow anterior chamber with perforation
Leaking of aqueous (+ve Siedel test)
52
What may occur if there is rupture of the lens capsule associated with a penetrating trauma?
Phacoclastic uveitis
Small rents <2mm may develop fibrosis and self seal
Larger capsular lacerations require phacoemulsification
53
What is the prognosis for lacerations affecting limbus/posterior to limbus?
If full thickness = poor prognosis
Evaluate other intraocular structures
Likely requires enucleation.
Can try repair limbus/anterior sclera via direct replacement of uveal tissue into eye but prognosis for vision poor.
54
How should lacerations/perforataing corneal wounds be managed after surgery?
Topical antibiotic treatment with good ocular penetration e.g chloramphenicol
Systemic broad spectrum antibiotics
Systemic anti-inflammatories
Topical steroids once corneal wound have re-epithelialised
Cycloplegics
55
Define orbital abscesses vs orbital cellulitis.
Orbital abscess = accumulation of purulent material within the soft tissues of the orbit
Orbital cellulitis = diffuse inflammation of the soft tissues of the orbit, can be aseptic (uncommonly)
Both associated with aerobic and anaerobic bacteria and tend to be unilateral in presentation,
Cellulits = spread within the soft tissue
Abscess = walled off by reactive fibrous tissue
Starts in extraconal space and progressively tends to affect intraconal space.
56
What are the usual aethopathogenesis for orbital abscesses/cellulitis?
Infectious or non infectious inflammatory disease of contagious periorbital structures or spaces - endodontic disease, sinuses, dacryoadenitis, sialoadenitis or panophthalmitis
Inoculation of infection into orbital space via transconjunctival, transpalpebral or transoral routes
Secondary to orbital foreign bodies
Haematogenous spread/septicaemia
57
What are the clinical signs seen associated with orbital abscess/cellulitis?
Acute onset with rapidly progressive signs
Pain and difficulty opening mouth
Hyporexia/anorexia
Swelling of periocular tissues
Ophthalmic exam:
Pain on retropulsion of globe/opening of mouth
Exophthalmos (often TEL protrusion as extraconal)
Erythema and oedema of eyelids
Chemosis + conjunctival hyperaemia (+/- mucopurulent discharge) - sometimes severe enough swelling precludes visualisation of the globe.
Visual and afferent light reflexes abnormalities
Reduction in oculo-cephalic movements
Exposure keratitis
Mild increase in IOP
+/- swelling or fistula in the ipsilateral pterygopalatine fossa
+/- Pyrexia with neutrophila and left shift
58
How should suspected cases of orbital abscess/cellulitis be approached and why?
Seen as emergency - close association of the orbit with CNS - infective processes risk causing meningoencephalitis and potentially can be life threatening.
59
What imaging modality can help with the identification of cases of orbital abscesses/cellulitis?
Ultrasound - compare to normal orbit as control
Retrobulbar abscesses tend to have well defined hyperechoic wall surrounding a uniform hypoechoic region
Cellulitis = more subtle change including distortion of normal retrobulbar architecture and decreased definition of the structures with mixed echogenicity.
Cross sectional imaging may be indicated if suspicious of potential foreign body and need further help with localisation.
60
How would you treat a case of orbital cellulitis?
Hospitalisation
IV fluids (as often pyrexic)
Analgesia - systemic NSAID +/- opioid
Soft food to encourage to eat
Broad spectrum antibiotics - cephalexin/amoxy-clav
Consider topical treatment if ocular surface affected - management of any corneal ulceration as a result of exposure, lubrication
Consider temporary tarrsorhaphy if severe exposure to protect globe and protect against exposure keratopathy.
Monitor - should see an improvement in swelling within 24-48hrs post treatment
Re-evaluate case if re-lapse occurs (?underlying foreign body)
Drainage is NOT INDICATED for cellulitis
Should be able to differentiate from abscess based on previous imaging
61
How would you drain an orbital abscess?
If abscess focal and can be assessed through pterygopalatine fossa or somewhere else safe then drainage is indicated.
Induration or fistulation of the pterygopalatine fossa = highly suggestive of orbital abscessation.
General anaesthesia required - ensure patient stable enough before drainage (may start medical therapy e.g IV fluids + analgesia + anti-inflammatories first)
Instruments = non sterile swabs, mouth gag, scalpel blade, straight mosquito forceps, microbiology swab
1. Patient anaesthetised and ET tube in place cuffed
2. Patient placed into lateral recumbency with non affected side to table
3. Pharynx packed with moist swabs of known number
4. Mouth gag placed
5. Prep minimally with chlorhexidine over pterygopalatine fossa (behind last maxillary molar)
6. Incise gingiva with blade - will be some bleeding
7. Enter closed mosquito forceps longitudinal to skull
8. Open forceps and remove whilst they are open (never close blindly in orbit - risk could damage optic nerve/maxillary artery inadvertently)
9. Attempt to reach area of interest and wait for abscess to drain - very gently pressure can be applied to globe to help this process but never whilst forceps are in orbit
10. Take sample for microbiology C+S
11. Once drainage has occurred remove moist swabs from phayrnx and wake patient up. Leave incised area open to drain/heal by itself.
Any suspicion of dental/endodontic disease may take dental radiographs at same time.
62
What is masticatory muscle myositis?
Canine immune mediated disorder affecting muscles derived from 1st brachial arch and innervated by mandibular branch of trigeminal nerve and containing 2M myofibres.
Bilaterally symmetrical condition and leads to inflammation then fibrosis of the masseter, temporal and pterygoid muscles.
63
What antibody is generated as part of the immune response to canine masticatory myositis?
Patient will develop cellular and humoral autoantibody against 2M fibres.
64
What are the clinical signs of masticatory myositis?
Acute phase = swelling of temporalis muscle leading to signs of extraconal disease
Exophthalmos + protrusion of TEL
Pyrexia/Anorexia
Pain on attempting to open mouth and on palpation of masticatory muscles
Chronic stage = fibrosis or atrophy of masticatory muscles leading to enophthalmos with secondary entropion.
Trismus (spasm of jaw muscles) can be present in both acute and chronic phase although more typical of chronic.
65
How is a diagnosis of masticatory myositis usually made?
Typically suspected based on clinical signs
Serum creatinine kinase may be increased and neutrophilia may be present.
Serum autoantibody 2M testing
Biopsy of temporalis muscle - definitive diagnosis to confirm inflammation and fibrosis of muscle fibres.
Electromyography can be helpful and show reduced denervation of affected muscle.
66
What is the treatment for masticatory myositis?
Immunosuppressives - prednisolone maintained until resolution of clinical signs then gradually tapered whilst monitoring for recrudescence.
Azathioprine may also be used concurrently or as an alternative immunosuppressant long term.
Nursing care - food prehension can be limited, softer foods
Physiotherapy regime may improve jaw opening in some cases.
67
What is extraocular myositis? Which breed/sex is predisposed? What factors may be triggers.
Canine immune mediated inflammatory disease of just the extraocular muscles (intraconal disease) - bilateral presentation.
Young dogs - entire females predisposed
Golden retriever - over-represented.
Potential triggers - oestrus, ovariohysterectomy, boarding in kennels/stress.
68
What are the clinical signs of extraocular muscle myositis?
Bilateral condition
Exophthalmos without TEL protrusion (intraconal disease)
360 degrees scleral show and retraction of upper eyelid
Reduction in oculovestibular movements bilaterally
May be painful on retropulsion
Generally non painful on palpation of periorbital structure/opening mouth
No systemic signs
69
How is extraocular myositis diagnosed?
Clinical signs generally enough
Ultrasound - thickening of EOM
CT/MRI - EOM thickening
70
What is the treatment for extraocular myositis?
Immunosuppression - prednisolone +/- ciclosporin +/- azathioprine
Recurrence is common long term
71
Describe fibrosing extraocular muscle myositis with restrictive strabismus.
Rare canine condition of young dogs
Enophthalmos and severe unilateral or bilateral ventral/ventromedial globe deviation leading to visual deficits.
Diagnosis = Traction test, muscle biopsy of EOM and lymphocytic/plasmacytic inflammation seen.
Responds poorly to immunosuppressives (often diagnosed too late and too much fibrosis)
Surgery may be considered to restore visual axis by specialists.
72
Describe feline restrictive myofibroblastic sarcomas (orbital pseudotumours)
Chronic, non specific and fibrosing inflammation of orbit
Affects orbit and periocular tissues and in the long term the contralateral side of the face including gingiva.
Oral cavity thought to be involved with infiltrative disease.
Middle aged to elderly cats
73
What are the clinical signs of a cat with feline restrictive myofibroblastic sarcoma?
Chronic non healing ulceration
Absent palpebral reflex and lack of spontaneous eyelid movement (unilaterally or bilaterally)
Marked fibrosis of eyelids and loss of normal eyelid tone
Variable degrees of exophthalmia with reduced oculovestibular movements.
Exposure keratitis can be severe and lead to perforations requiring enucleation.
74
How are feline restrictive myofibroblastic sarcomas diagnosed?
Advanced imaging and periocular skin biopsy with immunohistochemistry
Alternatively if eye enucleated should be sent to histopath
(Invasive squamous cell carcinomas can mimic)
75
What is the treatment for feline restrictive myofibroblastic sarcomas?
No curative treatment
Palliation only
Radiotherapy suggested but lacking studies to support
Often euthanised due to poor prognosis.
76
How are orbital neoplasias divided?
Primary (originating from the orbit)
Secondary (metastasis from elsewhere in the body usually local extension from adjacent structures)
77
Where can primary orbital tumours arise from?
Epithelial, glandular, osseous, neural, haemolymphatic or connective tissues.
78
Where do secondary orbital tumours originate from?
Brain, nasal cavity, globe (local extenson)
Multicentric/metastatic - lymphoma/adenocarcinoma
79
What type of prognosis do orbital tumours generally have?
Poor prognosis - often malignant and often in advanced stage by time detected.
80
What are the clinical signs of orbital tumours?
Generally affect middle age/older patients (lymphomas/MCT may affect younger patients)
Insidious onset (slowly progressive) generally - few types may present more acutely and mimic inflammatory disease.
Long hx of exophthalmos (mostly unilateral)
Ophthalmic findings:
Extraconal - exophthalmos (non axial), protrusion TEl, strabismus, conjunctival hyperaemia
Optic nerve tumours (intraconal) - axial exophthalmos
81
How are orbital neoplasias generally diagnosed?
Advanced imaging indicated when orbital neoplasia suspected
Locate lesion, evaluate extension and help formulate possible treatment plan e.g FNA/biopsy (ultrasound may also be useful for this)
Chest x-rays/abdominal ultrasound for metastasis check
FNA of any enlarged lymph nodes or organs for staging
82
How may orbital tumours sometimes be treated?
Surgical excision (if chance curative or aimed to palliate e.g exophthalmic globe with severe exposure keratopathy).
Referral often best practice for multi-disciplinary approach to tx/management.
Rare instances if well defined mass orbitotomy sparing the eye may be possible.
Infiltrative masses - exenteration or orbitectomy so long as mass does not extend beyond orbit.
83
Define proptosis. Which breeds are predisposed? Which breeds have worse prognosis?
Traumatic event where globe displaced rostrally in the orbital cavity with eyelids trapped between equator of globe and orbital rim.
Brachycephalics predisposed due to shallow orbits and large palpebral fissures - less force to displace.
Mesocephalic/dolicocephalic/cats = more severe trauma required and therefore poorer visual prognosis.
84
What are the clinical signs of a proptosis?
Severe chemosis and haemorrhagic conjunctiva at 360 degrees
Globe deviation (generally laterally as medial rectus shortest EOM so ruptures first)
Hyphaema
Corneal ulceration
Eyelids behind equator of globe
+/- craniofacial trauma
+/- CNS trauma
85
What are the first steps in approaching a patient with proptosis.
Stabilise first if other injuries (ABC's assessment)
Assess any other injuries e.g skull fractures primarily
Keep globe covered with moist swab whilst assessing other injuries/stabilising.
Analgesia
86
What factors can we use to assess prognosis for an eye post proptosis and help to decide whether to replace or enucleate?
Visual prognosis generally poor but may be able to replace for cosmetic appearance.
PLR (may not be able to directly visualise if hyphema so look at indirect PLR) - better visual prognosis if PLR intact
Cannot rely on dazzle or menace due to position of eyelids.
How many extraocular muscles intact - >2 torn = poor prognosis due to lack of vasculature to eye and will lead to phthisis over time.
If lateroventral deviation/laterodorsal position >2 EOM affected.
87
If in doubt as to the prognosis for a proptosed eye what can you do?
If unsure about prognosis then can replace and re-evaluate eye at later stage once swelling subsided (10-15 days later) and then choose to enucleate at later stage.
88
What are the long term complications we can see with a proptosed eye post replacement?
Blindness
Lagophthalmia
Neutrotrophic keratitis
Dry eye
Permanent strabismus
Phthisis bulbi
Control owner expectations if going to replace globe!
89
Describe how you woud replace a prolapsed globe.
Perform under GA (after patient stabilised) - ET tube in place and analgesia already instigated.
1. Patient in sternal position.
2. Prep affected eye with povidone iodine 1:50 for ocular surface, 1:10 for skin
3. Try and flush conjunctival fornices with povidone iodine 1:50 although due to eyelid positioning may not be possible
4. Sterile gloves on and drape patient
5. Flush globe with cold saline to try and reduce swelling
6. Lateral canthotomy (incision on lateral canthus to enlarge palpebral fissure, 4mm length generally enough
7. Sterile ultrasound gel placed over cornea and gently push eyelids outwards whilst pushing globe inwards towards orbit
8. Once globe back into position eyelid margins should be visible along full length. Evaluate for any conjunctival tears or foreign material and flush with saline.
9. Close lateral canthotomy with figure of 8 on eyelid margin and 2 planes for s/c and skin - use no bigger than 4/0 polyglactin suture material
10. Temporary tarrsorrhaphy (or TEL flap) to prevent re-prolapse (tarrsorrhaphy preferred for visualisation/medication of ocular surface). Nylon 3/0/4/0 can be used for this with stents
90
What are the signs of an orbital fracture?
Facial asymmetry
Instability/crepitation on palpation
Communication with rostral sinus = periorbital emphysema
91
What is the modality of choice for orbital fractures?
CT
92
How are the majority of orbital fracture cases managed?
Majority = conservatively
Unless bone fractures compromise globe/vision then surgery may be indicated.
93
What are zygomatic mucoceles?
Zygomatic gland = located on ventral floor of orbit in dog
Leakage of saliva from the gland or duct can lead to accumulation within the orbit (orbital mucocele)
94
What are the clinical signs of a zygomatic orbital mucocele?
Sialoceles lead to signs consistent with extraconal orbital disease (exophthalmos with TEL protrusion)
Usually minimal pain on opening mouth and not usually difficulty on retropulsion (swelling ventral).
Oral exam = swelling in region of pterygopalatine fossa and swelling/redness of zygomatic papilla
95
How may a zygomatic mucocele be diagnosed?
Ultrasonography may show well demarcated hypoechoic or anechoic cavitary lesion in ventral orbit
Advanced imaging - MRI detailed images of location and extent of salivary mucocele.
FNA - viscous fluid consistent with saliva
Cytology to rule out neoplastic process with cystic component and infectious disease.
96
How are zygomatic mucoceles treated?
Drainage through ptergopalatine fossa as described for orbital abscess.
If drainage not possible a fistula can be created through the same fossa connecting the mucocele with the oral cavity.
Drainage + anti-inflammatories usually lead to resolution of the disease.
Recurrent cases orbitotomy and excision of zygomatic gland might be indicated.
97
What are dacryops? How are they treated?
Dacryops = cysts of lacrimal tissue due to developmental abnormalities or trauma
Reported in third eyelid and orbit
Surgical excision = treatment of choice
98
When may orbital fat pad and temporal muscle atrophy be seen?
Might be seen in cases of severe weight loss or as a result of senile processes.
Enophthalmia with secondary entropion often occurs
Often requires surgical correction for the entropion.
99
What 2 techniques are there for enucleation?
Transconjunctival and transpalpebral
Aim to remove whole globe, conjunctiva, nictitating membrane and its gland and eyelid margins.
100
Describe the approach to a transconjunctival enucleation?
Access the globe through the bulbar conjunctiva in order to identify the 7 extraocular muscle tendons attached to the globe and section them as close to the globe as possible to avoid haemorrhage
101
Describe the transpalpebral approach for enucleation.
Eyelids sutured together and access to the insertions of the EOM made through the skin
102
When is the transconjunctival approach contraindicated?
Contraindicated if ocular infection or neoplasia on ocular surface
Transpalpebral approach can be performed in all instances.
103
Which block can be performed as additional analgesia for enucleations? What are the risks associated with this?
Retrobulbar block
Bupivicaine generally used - 20 mins to act but 6-8hrs post op pain relief
Risks - intra-thecal injection (need for ventilation), globe perforation, retrobulbar haemorrhage
104
What other local anaesthetic technique may be considered for enucleations?
Splash block into orbit post enucleation for post op analgesia
105
Why should rostral traction never be applied to the globe during enucleation? Why should we not clamp/ligate retrobulbar structures?
Rostral traction = optic nerve and chiasm trauma and risk of blindness in contralateral eye
Increased risk in cats as optic nerve shorter.
No need to clamp or ligate any retro-orbital structures or vessels
Contraindicated to clamp optic nerve due to potential development of neurofibroma
106
What is the most common longer term complication of enucleations?
Orbital cystic cavities due to secretory tissue left during enucleation (generally conjunctiva)
Examine orbital cavity thoroughly before closure.
107
Can orbital prosthesis be used post enucleation?
Can be used with caution - ethics debated!
Aim is to prevent sinking of skin over orbital rim.
Silicone black prostheses
Brown should be avoided as interfere with MRI due to iron being present in colouring.
Complications = infection, extrusion and reactions to foreign material.
Many will not use as feel not in best interest of patient.
108
What is evisceration?
Removal of the contents of the globe leaving intact the fibrous tunic (cornea and sclera) then inserting silicone prosthesis to fill the emptied globe.
Aesthetic procedure- globe motility remains intact
Ethics widely debated and not really performed in UK.
109
When is evisceration contraindicated?
Corneal pathology
Globe rupture
Intraocular or surface neoplasia
110
What complications are seen with eviscerations?
Prostheses black but with time and fibrosis can appear grey (less ideal cosmetic appearance)
Scleral wound dehiscence
Corneal mineralisation
Ulceration
Dry eye
Prosthesis reaction
Reduction in corneal sensation = chronic corneal ulcerations
111
What should be done after all enucleations/eviscerations?
Globe/tissues sent for histopathology
Helps understand aetiology of disease, implications for other eye, neoplastic processes etc.
