Ocular Injury Flashcards
1
Q
How can ocular trauma be classified?
A
Cause - blunt, sharp, chemical, thermal
Type - contusion, penetrating, perforating, rupture, laceration, intraocular foreign body
Structure/s involved - periorbita (facial bones, sinuses, skin), orbital, globe, eyelid, conjunctiva, nasolacrimal system, cornea, iris, ciliary body, vitreous, retina, optic nerve
2
Q
List some common causes of ocular trauma
A
Road traffic accidents
Balls, running into other dog etc
Dog/cat fights
Stick injuries
Non accidental injuries
Chemical injuries (cleaning products, detergents etc mostly)
Thermal (phacoemulsification, radiation)
Foreign bodies
Abrasion/ulcerations
3
Q
What is the ocular trauma terminology commonly used in humans called?
A
Birmingham Eye Trauma Terminology
4
Q
What is the definition of an eyewall injury according to the BETT system?
A
Sclera/corneal injury
5
Q
What is the definition of a closed globe injury according to the BETT system?
A
No full thickness wound of eyewall
6
Q
What is the definition of a open globe injury according to the BETT system?
A
Full thickness of the eyewall
7
Q
What is the definition of a contusion according to the BETT system?
A
No full thickness wound - injury results from direct energy delivery by an object e.g choroidal rupture or from changes in the shape of the globe (e.g angle recession)
8
Q
What is the definition of a lamellar laceration according to the BETT system?
A
Partial thickness of the eyewall (not through eyewall but into)
9
Q
What is the definition of a rupture according to the BETT system?
A
Full thickness wound of the eyewall caused by blunt object - impact results in momentary release of intraocular pressure, eyewall yields at its weakest point and wound is created by inside-out mechanism
10
Q
What is the definition of a laceration according to the BETT system?
A
Laceration = wound occurs at the impact in an outside-in mechanism
11
Q
What is the definition of a penetrating injury according to the BETT system?
A
Penetrating = entrance wound, if more than one wound present must have been caused by a different agent
12
Q
What is the definition of an intraocular foreign body according to the BETT system?
A
Retained foreign object within the globe
13
Q
What is the definition of a perforating injury according to the BETT system?
A
Perforating = entrance and exit wound, both caused by the same agent (one wound by outside in mechanism, other by inside out)
14
Q
How would you approach a history for a case of ocular injury?
A
History - BIOP, health, travel, vaccines etc as usual
Injury itself - date, time, how occurred (if known)
Previous trauma (NAI’s beware of inconsistent history)
If intraocular foreign body - composition
If chemical - pH, ideally product name/info, form (liquid, gel, powder)
15
Q
What things should you assess in a patient with ocular injury (some may come before the ophthalmic examination)
A
Check no other injuries (especially RTA) - stabilise life threatening injuries first before proceeding with ocular investigations - cover any damaged eyes with damp swab whilst doing this to try and preserve cornea.
Assess vision (if concious)
Dazzle
Menace
PLRs (direct and consensual) - if visible (may not always be possible if hyphema etc)
Open or closed globe? - has globe ruptured
If unable to visualise much then consider imaging
16
Q
What indications are there for radiography in ocular trauma?
A
Trauma e.g RTA - assess no diaphragmatic hernia, no other skeletal injuries
Skull/sinus fractures
Metallic foreign bodies
Emphysema (indicative of sinus fracture)
17
Q
What indications are there for ultrasound in ocular trauma?
A
Ultrasound = great for globe, especially when visualisation poor e.g due to hyphema
Globe integrity - integrity of ocular coats
Integrity of lens capsule
Lens luxation/subluxation
Vitreal haemorrhage
Retinal detachment
18
Q
If using ultrasound with traumatised eye how should you perform the ultrasound? What other method could you use to help detect trauma?
A
Avoid getting coupling gel directly onto corneal surface especially if suspect perforation - risk of uveitis.
Use water in glove as ultrasound stand off.
Can use microbubbles - IV to help show up areas of trauma especially subtle retinal/vitreal detachment
19
Q
When is CT indicated in ocular trauma cases?
A
Skeletal assessment - skull fractures
Metallic FB detection
Lung assessment
Faster then MRI and cheaper
20
Q
Which part of the orbit is most likely to fracture with trauma?
A
Medial wall of the orbit - thinnest part
21
Q
When is MRI indicated in cases of ocular trauma and when is it contraindicated?
A
Contraindicated - metallic FB
Soft tissue evaluation
Brain, optic nerve /CNS evaluation
22
Q
Is chemical trauma usually mild or severe in terms of threat to vision. What are the most common scenarios for chemical injury?
A
Severe threat to vision
Cleaning products/building works = most common injuries via this method
23
Q
Are acidic or alkaline agents more caustic to the eye and why is this? Describe their mechanisms of action.
A
Alkaline - worse
Acid agents tend to coagulate protein which limits penetration to just superficial structures.
Alkaline products 2 methods to cause damage
1. Cause saponification of triglycerides in the cell membrane leading to lysis of the cell.
2. Denaturation and hydrolysis of proteins leads to loss of structure as well as transport proteins and enzymes and cell death.
Alkaline = both stromal keratocyte and limbal cell death
Can also penetrate to deeper tissue structures e.g trabecular meshwork/ciliary body increasing risk of glaucoma, uveitis and phthisis bulbi.
24
Q
Why is limbal cell death due to alkaline agents so damaging for the eye and what may be a sign of this.
A
Blanching of limbus = likely limbal cell death
Limbus = corneal stem cell population in the crypts and palisades of Vogt - important for corneal healing and repair
Stem cells = self renewing to transient daughter cell, transient amplifying daughter cell also self renewing for finite number of divisions then becomes post mitotic terminally differentiated corneal epithelial cell.
25
What are the consequences of damage to the limbus? What other sequelae may we see with alkaline injuries?
Poor epithelial healing - persistent ulceration and pain, conjunctivalisation of the epithelium potentially affecting visual axis.
Sequelae include - ankyloblepharon (adhesions of upper/lower eyelids), symblepharon
Cicatricial entropion and trichiasis secondary to adhesions and fibrosis.
Pigmentation/vascularisation
Permanent corneal oedema
Damage to trabecular meshwork/ciliary body - uveitis/glaucoma
Pthsis bulbi
Damage to meibomian glands and loss of goblet cells
26
How may alkaline injuries cause damage to the lacrimal system and tear film?
Alkaline injuries can lead to secondary displacement of the meibomian gland orifices and loss of goblet cells - leading to tear film deficiencies as well as direct damage to the lacrimal system.
27
What are the acute clinical signs of a chemical injury?
Acute = blepharospasm, oedema of eyelids, chemosis, conjunctival hyperaemia, conjunctival ischaemia, whitish haze of corneal stroma (O's often report occurred suddenly), mild cornea oedema, uveitis signs.
28
What can damage of the corneal endothelium by alkaline agents cause?
Can lead to persistent corneal oedema and subsequent bullous keratopathy
29
What is the very first thing that should be done when a chemical injury has occurred to the eye? Why is this step important?
If client rings up and concern for chemical in eye tell them to lavage with tap water for at least 30 minutes
Tap water = low osmolarity
Hypotonic solutions preferred for lavage (high buffer capacity and can reduce intracameral pH)
Flushing should extend into cojunctival fornices (swipe with cotton bud/cellulose spear)
Lavage = dilute and remove chemical contact
30
How can you measure the success of lavaging in chemical injuries? When should lavage be continued until?
Can use urine pH strip to measure pH of tear film or litmus paper
Lavage should be continued until normal pH reached (7.4 = aim, normal tear film pH 7.2 to 8)
31
What other treatments should we consider for chemical injuries?
Necrotic tissue debrided - increased inflammatory mediators and stimulates neutrophils increasing risk of keratomalacia via production of collagenases.
Topical broad spectrum antibiotics
Collagenase inhibitors - topical autologous serum (also promotes epithelial healing)
Analgesia - systemic NSAID + 1% atropine to reduce ciliary body spasm, may also need opioids
?Oral tx with doxycycline - inhibit corneal vascularisation
AVOID topical steroids/NSAIDS as may worsen corneal ulceration, melting and perforation
32
What treatments may we used for chemical injuries in the intermediate stage (7-21 days post injury)
Encourage epithelialisation and control inflammation
Bandage contact lens, temporary tarrsorrhaphy, amniotic membrane graft (supports epithelialisation but also prevents symblepharon and reduces corneal vascularisation)
33
What treatments may be considered in the late phase management of chemical injuries?
Addressing permanent ocular surface damage
Superficial keratectomies
Limbal autograft (stem cell transplant using stem cells from other eye - 2 clock hours or cultured stem cells of amniotic membrane)
Penetrating keratoplasty
?Keratoprosthesis - failed in literature so far
Amniotic membrane grafts - anti-collagenase activity, resist infection, encourage healing, resist infection, analgesia, prevent adhesions
34
What are some sources for thermal injuries to the eye?
Thermal - burns e.g housefire, NAI e.g cigarrette burns, surgical (phacoemulsification), laser burns, radiation exposure (cancer treatment), lightning strike
35
What are the consequences of burns to the eyelids?
Cicatricial entropion (fibrosis)
May require cicatrix excision and blepharoplastic repair after initial healing
36
What should be the initial treatment for a burn injury?
Cooling
Occlusive dressing
Antibiotic therapy
Fluid therapy depending on surface area of burns and depth
Analgesia - associated with severe pain
(N.B Smoke inhalation may be life threatening and should take precedence over any ocular injury)
37
What are the consequences of burns to the cornea?
Corneal oedema +/-stromal fibrosis and contraction
Conjunctival hyperaemia and chemosis may also be present
38
Why may thermal burns occur with phacoemulsification?
Occur if lavage tip occluded allowing phacoemulsification needle to overheat and burns structures it contact (mostly cornea)
Corneal stroma contracts and opacifies making incision closure more difficult
Cover with advancement conjunctival graft if occurs as post operative shrinkage may lead to an aqueous leak and gape.
39
How can radiation exposure cause injury to the eye?
May be seen with radiotherapy where eye not excluded from the radiation field - can cause blepharitis, lacrimal gland damage (tear film deficiency), lens damage resulting in cataract formation and retinal damage leading to degeneration and blindness.
40
What type of damage may a lightning strike cause?
Retinal and cataract formation + thermal burns at strike site
41
List some examples of blunt force trauma in animals.
RTA, ball injuries, collisions with other animals/people/furniture.
NAI - beatings
42
What else should you consider in terms of assessment when presented with an animal with blunt force trauma?
No other injuries - life threatening get priority over oculr injuries
Cover eye with damp swab and lubricant if exposed
43
What happens to the cornea and globe when a blunt force trauma occurs and what are the consequences of this?
Blunt trauma to cornea causes deformation of the cornea and subsequent equatorial expansion of the globe. As the corneal deformation resolves the axial globe length then may expand.
Expansion = intraocular haemorrhage, iridodialysis (peripheral iris shears away from cornea), iris tears, lens luxation, ciliary body dialysis (ciliary body separation from sclera), retinal dialysis (retinal tear at ora serrata - ora serrata = most anterior extension of retina, junction between choroid and ciliary body), retinal schisis (splits in retinal layers) and retinal detachment.
Intraocular pressure may also rise to such an extent that ocular coat ruptures - most commonly at posterior pole and adjacent to optic nerve head in dogs/cats.
44
What may you see presentation wise in animals with scleral rupture? What step would you do next to confirm?
360 subconjunctival haemorrhage - ocular ultrasound to confirm
45
List other types of injury we may think about with blunt force trauma.
Proptosis, Globe rupture, facial and oral fractures, sinus fractures, optic nerve avulsion, optic neuropathy
46
How does the equatorial lengthening that occurs with blunt force trauma lead to lens subluxation/luxation?
Equatorial lengthening may rupture lens zonules allowing for lens luxation/subluxation.
47
What is angle recession and how does it occur in severe blunt trauma? How would you identify this injury? What would you expect to see as a consequence.
Rare but has been reported
Seen with very severe blunt trauma
Iridocorneal angle appears shifted posteriorally and widened
Believed to occur due to aqueous being forced into iridocorneal angle and causing split in ciliary body
Longitudinal ciliary muscle still attached to sclera but circular muscle of ciliary body and the iris root forcefully separated.
Gonioscopy required for identification
Glaucoma as a consequence
48
What is a retinal tear? How do they occur and what is the definition of a giant retinal tear.
Form when hole ripped into retina
Giant tear = >2 clock hours
Hole allows vitreous (especially if liquidified) to move underneath the retina and increase the retinal detachment (progression)
Retinal tears largely due to disruption of vitreoretinal adhesions
Peripheral retinal tears more commonly as adhesions cause increased shearing forces on peripheral retina (vitreous gel pivots on this adhesion)
Dorsal retinal tear often more significant than ventral - gravity and greater pivot force acting.
49
When do we usually see traumatic cataracts following a blunt trauma?
Weeks-months after incident
Trauma require to dislocate a lens (except in cases of primary lens luxation where lens zonules already weakened) usually results in concurrent retinal detachment or scleral rupture giving poor prognosis for vision.
50
Where may intraocular haemorrhage originate from?
How long does haemorrhage take to clear in each segment?
What may be associated with posterior segment haemorrhage?
Iris, ciliary body, choroid or retina
Anterior chamber- usually quick to clear if no further bleeds occur
Posterior segment - slow to clear (weeks to months), may be associated with vitreal floaters
51
What other type of rupture can we see in humans with blunt force trauma?
Choroidal rupture/detachment
Associated with macula - immediate vision loss
Some vision may return with resolution of haemorrhage if not in macula area
May see delayed vision loss either due to epiretinal membane formation (glial proliferation through trauma breaks internal limiting membranes of retina) or choroidal neovascularisation (angiogenesis stimulated by hypoxia)
52
What signs of blunt force trauma may we seen in birds?
Prone - RTA/flying into windows
Scleral rupture, choroidal rupture, retinal detachment, pre-retinal membranes, iridodialysis, ciliary body dialysis, cataracts, lens luxation, traumatic uveitis, intraocular haemorrhage, chronic corneal ulcers/erosions.
Pecten haemorrhage and disruption also seen.
53
What may sinus fractures result in and how should they be treated?
Emphysema - treated as open fractures
Broad spectrum AB cover should be provided systemically
54
What may happen to the extraocular muscles in cases of facial fracture?
Can get extraocular muscle entrapment - strabismus or ocular motility disorders as consequence
Needs to be dealt with within 5 days to prevent permanent damage
55
How should facial fractures be dealt with depending on their size?
Small non displaced fractures - conservative management (analgesia, AB cover, cold compresses)
Small displaced bony fragments may cause sequestra and should be removed
Large displaced fractures - reduced
Involvement of the cranium in any fractures may result in severe neurological signs and require priority treatment and stabilisation.
56
How are facial fractures classified in people?
Le Fort classification
Le Fort 1 = lower aspect of maxilla (floating palate fractures)
Le Fort 2 = pyramidial fracture - maxilla, nasal bone, inferior orbital rim, medial orbital walls and lacrimal drainage system
Le Fort 3 = craniofacial dysjunction - nasal bones, medial and lateral orbital walls, zygomatic arches with the facial skeleton only attached to the cranium by soft tissue structures (floating face fractures)
57
What may accompany facial fractures clinically?
Epistaxis or CSF Rhinorrhea - leakage of CSF through nose
58
What is optic neuropathy? What may it be associated with?
Shearing forces on the optic nerve within the optic canal - may be associated with basal skull fractures and other cranial nerve defecits (occulomotor, trochlear, trigeminal, abducens and facial nerves), also possibility of brainstem injuries.
59
What is optic nerve avulsion?
Seen with severe blunt trauma - optic nerve is pulled posteriorally
60
Which type of injury carries a poorer prognosis generally? Blunt or sharp trauma?
Blunt trauma - force can affect multiple ocular structures with generally more severe vision threatening consequences.
61
List some common sharp injuries seen in veterinary patients.
Cat claw
Sticks
Thorns/brambles
62
How can sharp injuries be further classified?
Laceration
Penetrating
Perforating
63
What shape of injury do we typically see with claw lacerations? What else may we see?
Cat claw = distinctive C shaped injury
May see halle's comet of fibrin (Indicative of full thickness penetration) + sometimes dyscoria of pupil if anterior synechiae.
64
What potential sequelae may we see as a result of sharp trauma?
Uveitis
Endophthalmitis (inflammation of all/multiple internal structures of the eye)
Panopthalmitis (inflammation of all structures of eye including ocular coats)
If trauma to orbit alone - orbital cellulitis/abscess formation
65
What may cause microbial endophthalmitis? How would we treat?
Secondary to bacterial/fungal contamination
Claws/bites/plant foreign body
Removal of FB
Broad spectrum AB cover (based on C+S if possible)
Intracameral/intravitreal injections can be used - vancomycin/cefuroxime
Poor prognosis/very painful disease.
66
What is the most common form of iatrogenic sharp trauma in veterinary practice and what consequences do we often seen?
Endophthlamitis due to iatrogenic sharp trauma during dentistry - either slipping with elevators when extracting caudal maxillary teeth or performing regional anaesthetic blocks.
Contamination with oral bacteria to globe +/- orbit as well as trauma.
Prognosis = poor, often require enucleation
67
What may we see with extensive full thickness lacerations of the cornea?
Can see loss of intraocular structures - iris prolapse, entrapment of vitreous, choroid or retina within ocular coat
68
What may we see if the lens capsule is damaged by a penetrating trauma?
Phacoclastic uveitis - must be addressed as complications = glaucoma/phitsis bulbi
Most cases require surgical removal of lens fibres (phacoemulsification) although smaller lens capsule rents may self seal (fibrin, fibrosis and pigment deposition from posterior iris) - inflammation may be controlled medically in those cases.
69
What condition has been seen in cats with a history of sharp lens trauma?
Post traumatic sarcoma formation - poor prognosis if occurs so always be more cautious with cats
70
Why is identifying the composition of an intraocular foreign body important?
Some substances have ocular toxicity
Iron containing FB - Siderosis bulbi
Choice of imaging modaility for further investigations - avoid MRI where ferrous metallic FB suspected
71
What imaging modalities are typically used for foreign body penetration investigation?
Ultrasound - assessment of intraocular structures (especially if visibility poor), integrity of ocular coat, may help locating FB's
MRI (non ferrous) /CT (ferrous) - locating FB's
72
Define proptosis.
Proptosis = forwards displacement of the globe combined with entrapment of the eyelids posterior to the globe equator.
Eyelid entrapment prevents the globe from returning to normal position.
73
Which types of dogs are more prone to proptosis and why?
Brachycephalics - shallow orbit, much less force required to displace compared to doliocephalics and cats.
Cats = often poorer prognosis than dogs, more severe trauma required to proptose eye.
74
What would you advise an owner do before coming down to the clinic if proptosis is suspected?
Keep globe moist and protected - damp flannel or swab over eye
Once at clinic antibiotic ointment can be applied to keep moist and protect against infection until repositioning.
75
What is the general prognosis for vision in cases of proptosis?
20% visual
Some may still be salvaged for cosmetic reasons
76
Which types of cases have a poorer prognosis for replacement in proptosis?
Which extraocular muscle is the first to be avulsed in proptosis.
Multiple extraocular muscles avulsed
Total hyphema
PLR - pupil size not prognostic indicator for vision although eyes with direct/indirect PLR and or positive menace response have better prognosis for vision.
Medial rectus first to be avulsed as shortest extraocular muscle.
If in doubt about visual prospects of eye replace - can always enucleate later. Evaluate 10-15 days later.
77
Discuss how you would re-position a proptosed globe.
Anaesthetise patient - done under GA (ensure any other injuries stabilised first e.g if RTA)
Globe cleaned with sterile saline
Eyelids grasped with allis tissue forceps and gently pulled up and away from globe
Lateral canthotomy can help with repositioning of eyelids due to the tightness of eyelids and traumatic swelling.
Temporary tarsorrhaphy may be indicated also - retrobulbar swelling/haemorrhage may result in exophthalmic globe. Tarsorrhaphy helps to protect ocular surface whilst resolves and reduces risk of re-proptosis.
Medial canthus usually left a fraction open to allow topical medications to be applied
Tarsorrhaphy left in place for 1-2 weeks depending on degree of swelling an the need to assess/treat ocular surface disease.
78
When would you advise enucleation of a proptosed globe?
Globe rupture
Total avulsion
>2 extraocular muscles torn then reduced vascular integrity of globe (prognosis for vision poor)
If going to enucleate ideally defer for 24-48hrs to allow tissue swelling to subside - less chance of wound breakdown/necrosis.
79
What are the long term potential complications following proptosis replacement?
Permanent blindness
Strabismus (which can lead to double vision - diplopia)
Lagopthalmos (incomplete closure of the eyelids)
KCS
Neurotrophic keratitis
Pthisis bulbi
80
Which facial fractures are most commonly encountered?
What may be indicators of facial fracture on physical exam?
Frontal, zygomatic and temporal
Indicators - facial asymmetry, skin lacerations, eyelid swelling, conjunctival haemorrhages, excessive lacrimation, exophthalmos, enophthalmos, lagophthalmos, exposure keratitis.
Globe contusion common and therefore intraocular haemorrhage, scleral rupture, lens luxation and retinal detachment can also be seen.
81
What is optic neuropathy and how may that occur wuth facial fractures?
Optic neuropathy - shearing forces on optic nerve within optic canal, results in axonal damage
Initial ocular exam (if fundus visible) may not initially show any abnormalities
Optic nerve degeneration and retinal degeneration commonly seen 6-8 weeks post injury
82
Which imaging modalities can be used to identify facial fractures?
Radiography - oblique views required
CT = best modality when suspect facial fractures
MRI - indicated if intracranial damage also suspected
Ultrasound - for assessing integrity of globe/ocular structures only, no good for identifying facial fracture
83
Which reflex may be stimulated by zygomatic fracture?
Occulocardiac reflex - bradycardia and AV block
84
Within what time frame should facial fractures be stabilised and what methods might we use to protect the globe when preservation is desired and while awaiting a reduction in swelling.
Must address facial fracture within 5-7 days as fibrosis may hinder reduction/stabilisation of fractures.
Temporary tarsorrhaphy or TEL flap may be considered to protect globe whilst awaiting for any swelling to subside.
85
What are the possible sequelae to facial fractures?
Blindness
Lagophthalmos/Strabismus
Corneal sensory deficits - trigeminal supply (relative KCS due to lack of stimulation for tear production)
Occulomotor paralysis - fixed and dilated pupil
Damage to lacrimal gland - KCS
Secondary glaucoma and phthisis bulbi
86
What are the signs of an orbital cellulitis/abscess?
Penetrating orbital injury can lead to cellulitis/abscess formation.
Signs = exophthalmos, eyelid swelling, axial or non axial strabismus, pain on opening the mouth, episcleral venous congestion and conjunctival hyperaemia/swelling. Extraconal - TEL raised.
Intraocular examination itself may be unremarkable
Frequently accompanied by pyrexia (but not always)
87
What are some of the causes of orbital cellulitis/abscesses
Penetrating FB (through skin, conjunctiva, oral mucosa)
Dental procedure
Extension from other localised structures e.g tooth root/sinus infections
Salivary gland/duct trauma
Haematogenous spread
Secondary to panophthalmitis
88
What is the most common bacteria in cases of orbital abscesses?
Staphylococcus - 25%
E.coli - 17%
Pasturella - 8%
Anaerobic (Clostridium/Bacteroides) - 30%
89
What imaging modality is excellent for assessment of the retrobulbar space and to investigate possible retrobulbar abscesses/cellulitis?
Ultrasonography - visible a hypoechoic material behind globe
Can also obtain FNA's for cytology, C+S
90
How would you manage and treat a case of an orbital abscess/cellulitis?
Frequent topical lubrication and antimicrobial ointments due to exposure from exophthalmos
Broad spectrum systemic AB's (may decide to base on cytology/C+S if FNA has been taken)
NSAIDS
Hot packs
Oral drainage
+/- temporary tarsorrhaphy to protect corneal surface
Should expect improvement within a week unless retained FB.
Prognosis generally good.
91
Where would you aim for with oral drainage of a suspected orbital abscess?
Via pterygopalatine fossa behind the last molar
Performed under GA with intubation and throat packing
Oral mucosa caudal to last molar incised and closed haemostat gently inserted into retrobulbar space then opened and withdrawn whilst open.
Possible complications - optic and ciliary nerve damage
92
What are potential long term sequelae for orbital abscesses/cellulitis?
Permanent orbital structure damage e.g KCS due to lacrimal gland adenitis and fibrosis
93
Discuss which types of foreign bodies are likely to be detected by different imaging modalities?
Radiography - metallic FB's (likely to miss other materials)
CT - if FB potentially metallic, improves localisation (3D reconstructions), dense FB materials (plastic, stone, glass, bone)
MRI - superior soft tissue contrast and is modality of choice for looking for organic matter FB's e.g grass seeds
Ultrasonography - good for assessment of retrobulbar space but air can be problematic and can be difficult to localise.
94
What surgical procedures/approaches may be required in order to remove retained FB's in the retrobulbar space?
Orbitotomy +/- removal of zygomatic arch
Oral approach
Percutaneous approach (via lateral orbital ligament)
95
Why may salivary retention cysts occur?
Oral trauma to the excretory duct leads to obstruction
Addressing cause of obstruction essential to treat.
96
What is a sialocoele?
Secondary to zygomatic gland trauma and escape of saliva inducing tissue fibrosis and encapsulation.
Sialocoeles best excised along with associated gland.
97
With eyelid lacerations why do we see so much swelling? What types of lacerations are there?
Eyelids highly vascularised and innervated so post trauma swelling can be significant
Due to this good vascular supply minimal debridement is often necessary for eyelid lacerations
Types of laceration - full thickness, partial thickness, involve lid margin (or not), involve lacrimal system (or not)
98
Why is primary surgical repair strongly recommended for any full thickness eyelid laceration?
Correct alignement of eyelid margin essential for healthy cornea (spread of tear film)
Secondary intention healing can lead to distortion, fibrosis, cicatricial entropion and ultimately corneal pathology and conjunctival exposure/pathology.
99
Discuss approach to the repair of eyelid lacerations.
Hair around area clipped and prepared with povidone-iodine solution and conjunctival sac thoroughly irrigated 1:50 dilution.
Magnification (surgical loupes) + good illumination
Lid margin suture performed first to get correct alignment - figure of 8 suture
2 layer closure in full thickness lacerations as better alignment of tissues, reduce internal gap of conjunctival wounds and increases comfort.
Sutures must not penetrate conjunctival surface - risk of corneal ulceration
Coated vicryl - as absorbable and soft improving comfort post op. 6-0 vicryl appropriate size but may consider 5-0 for large dog cases and 7-0/8-0 for pediatric cases.
100
What other repair techniques may be considered if there is a loss of facial/eyelid tissue?
Blepharoplastic techniques
H-plasty
Sliding Z cathoplasty
More extensive loss of tissue may require axial pattern grafts to close.
101
How can you identify a lacerated end of a canaliculus as part of the nasolacrimal system?
What are the clinical implications of laceration to the upper canaliculus vs lower canaliculus?
Cannulate adjacent puncta and inject saline or air or viscoelastic with bubbles to identify the flow of the air/saline/bubbles at the lacerated end of the canaliculus.
Upper = often heal without clinical implications
Lower = persistent epiphora
102
How would you repair a damaged canaliculus surgically?
Passage of silastic tubing
Meticulous accurate apposition without direct suturing of the canaliculus itself as fibrotic healing could result in stricture formation.
Subcutaneous tissue adjacent to canaliculus is sutured to appose the lacerated ends.
Perform under operating microscope for accurate visualisation.
Silastic tubing left in place for 3-6 weeks to reduce likelihood of stricture formation and facilitate re-epithelialisation of the canaliculus.
103
What imaging modalities are useful for identification of compression of the nasolacrimal system e.g in cases of facial fractures.
Radiography/contrast dacryocystorhinography
CT
Diagnosis and surgical planning
104
How are facial fractures that compress the nasolacrimal system dealt with?
Damage within lacrimal or maxilla bones requires apposition of bony fragments and removal of small fragments as may form sequestra.
Post op silastic tubing left in for 4-6 weeks to prevent strictures
If repair not possible then alternative route for tear flow can be devised - conjunctival rhinostomy, cojunctival maxillary sinusotomy or conjunctival buccostomy.
105
What type of foreign body is most common within the lacrimal system? Where can they get lodged?
Organic plant matter e.g grass awns - migrate into lacrimal puncta with barbs preventing backwards movement.
Can become lodged in the canaliculus with tip visible at punctum or more commonly become retained within lacrimal sac.
Another site of retention = entrance to nasolacrimal bony canal where duct is at its narrowest.
106
What other type of obstruction can occur to the nasolacrimal system?
Granuloma formation and strictures (within lacrimal sac or canaliculi) - secondary intention healing of lacerations or if good apposition not achieved surgically or sutures placed into nasolacrimal system mucosa.
107
How might we remove foreign bodies from the lacrimal system?
Flushing (anterograde and retrograde)
Incision into lacrimal sac (dacryocystotomy) or nasolacrimal duct may be required.
If FB reaches bony nasolacrimal canal - much more difficult requiring lacrimal or maxillary bone removal
Post op stent placement required to allow healing of incised canaliculus without stricture formation
Stent removed after 4-6 weeks and topical antibiotic-corticosteroid treatment maintained until stent removal.
108
Why is nasolacrimal retrograde flushing challenging?
Nasal punctum located on the ventromedial border of the alar cartilage of the nostril - challenging to visualise
Cannulation with suture material first then threading silastic tubing over can facilitate placement.
109
Where may foreign bodies become lodged in the conjunctiva?
Conjunctival sac, behind third eyelid or even trans/sub conjunctivally
Examined under local anaesthesia carefully to find these FB's
Palpation with clean non gloved finger can help to identify small foreign bodies
Rolling eyelid outward to expose posterior palpebral conjunctiva important - especially those in dorsal/ventral cornea with classically linear abrasion.
110
What clinical signs would we see with contact irritants to the conjunctiva? What is the primary treatment?
Blepharospasm
Rubbing/pawing at eye
Conjunctival hyperaemia
Epiphora
Conjunctival swelling/chemosis
Primary treatment = irrigation/flushing
111
Which topical medications may cause conjunctival irritation?
Gentamicin
Neomycin
Benzalkonium Chloride (preservative)
Cases may develop medial canthal ulceration, blepharitis (including marginal depigmentation and swelling)
Discontinuation of medication usually sufficient to resolve clinical signs.
112
What may be the causes for conjunctival haemorrhages?
Sharp or blunt trauma
Coagulopathy
113
How are conjunctival lacerations treated?
Many will heal ok without surgical intervention - vascular tissue
Should be explored/flushed to ensure no deeper laceration of the sclera/foreign material
Very large lacerations (>1cm) can be closed with 6-0-8-0 vicryl (polyglactin) in simple continuous or interrupted pattern. Burying knots reduced post op irritation.
114
How are lacerations of the third eyelid treated?
Small lacerations not involving the free margin may heal spontaneously
Large lacerations or those involving free margin can be repaired using 6-0-8-0 polyglactin (Vicryl). Sutures/knots must not contact corneal surface so buried patterns are preferred
Removal only justified for cases where repair is impossible (rare)
115
What clinical signs do we usually see with a corneal perforation/full thickness laceration?
Aqueous will initially leak through the perforation site.
Sudden hypotony = very painful and many patients will yelp in pain
Aqueous will initially clot the wound followed by formation of a fibrin clot as a result of breakdown in the blood-aqueous barrier associated with the acute hypotony (allows leakage of plasma fibrin into the anterior chamber)
Rush of aqueous out of the eye will often cause the iris to move forwards and plug the wound (iris prolapse)
Prolapsed iris will develop fibrinous cover that may make it appear more of a tan/grey colour as opposed to yellow/blue (cat) or brown/blue/amber (dog)
Advised to leave the fibrin clot/iris/aqueous alone to maintain the corneal seal until patient is anaesthetised for surgical repair.
If iris tissue viable (retained blood supply, not dried out or necrotic) then can be replaced
116
Discuss how the cornea heals following laceration.
Descemet's membrane highly elastic and will retract from wound on laceration
Corneal stroma when hydrated swells and may help to occlude small wound initially
Within few hours (5hr) leucocytes migrate to wound largely from tear film but also aqueous and infiltrate wound edges.
Epithelial cells will attempt to slide across wound from 1hr post injury. Later mitosis will re-establish epithelial thickness.
Mononuclear cells arrive 12-24hrs later and act as scavengers but may also change into fibroblasts and continue fibrosis of the wound (production of collagen and glycosaminoglycans)
Fibrosis remodelling (reorientation of collagen fibrils to reduce light scatter and increase corneal transparency) starts at 7 days post injury but may not complete for several months post healing.
Endothelium begins to heal from 24hrs post injury by sliding and enlargement of adjacent cells (limited regenerative ability) with reduction in endothelial cell density.
Endothelial cells responsible for production of their basement membrane (descemet's membrane) and injury may result in duplication of descemet's membrane in some areas following full thickness wounding.
At critical level endothelial cells cannot maintain confluent layer and corneal oedema occurs (may progress to bullous keratopathy with increasing stromal hydration).
117
What process causes keratomalacia (corneal melting)?
Overzealous proteinase activity - proeinases released from corneal epithelial cells, fibroblasts, inflammatory cells (esp neutrophils/macrophages) and micro-organisms.
Proteinases important for normal cell turnover and maintenance of the cornea but imbalance encourages stromal degradation and potential for corneal rupture.
118
How should corneal lacerations be approached surgically?
Suitable illumination/magnification - operating microscope
8-0 to 10-0 suture material (polyglactin/Vicryl)
Suture placement 75-90 per cent corneal depth - reduced chance of gaping, poor healing and corneal oedema.
Avoid full thickness placement (aqueous leakage, potential for intraocular contamination/endophthalmitis)
Sutures placed perpendicular to wound edges with equal and close enough placement of continuous sutures that compression forces will be overlapping and equal in force (so minimal shifting of wound edge occurs).
119
What are the most common causes of scleral rupture/perforation/penetration?
Dental extractions - slipping of periosteal elevator when extracting caudal maxillary teeth
Infraorbital nerve blocks
Gunshot/air rifle pellets
Migrating plant material
Bites
Blunt trauma - equatorial expansion followed by axial expansion
Some small scleral ruptures may self seal and retain blind but cosmetic eye
Others = chronic inflammation (endophthalmitis) - enucleated control pain
Can get entrapment of vitreous, lens, retina, choroid or ciliary body through scleral ruptures.
120
What type of repair has been described in the literature for a scleral rupture?
Autogenous fascia lata graft - cosmetic/comfortable eye but non visual
121
What is the most common type of corneal foreign body?
Plant material - thorns etc
Labradors/Springers over-represented.
Plastic, metal and glass also recorded.
122
How can you recognise a full thickness corneal foreign body penetration?
Fibrin clot usually adhered to distal tip of the foreign body
123
What may be the consequence of decemet's membrane stripping/endothelial damage from surgical trauma?
Endothelium highly vunerable to trauma from surgical instruments and irrigating fluids.
Endothelium= limited regenerative ability so permanent corneal oedema may result if endothelial cell density drops below certain threshold.
Cell density naturally declines with age so critical threshold may be reached some months/years after intraocular surgery meaning clinical signs associated with this trauma may be significantly delayed.
124
What types of trauma usually result in lens luxation? What often accompanies it? What modality is best for investigation?
Blunt trauma - generally severe
Intraocular haemorrhage with retinal detachment often accompanies. Scleral rupture may also be a feature.
Ultrasound = excellent at detecting lens luxation
125
What types of trauma can result in a traumatic cataract and can they progress?
Both blunt and sharp trauma can cause
Sharp trauma - may be limited to capsule only (if seals) or extend into cortex. Some will be static whilst others progress.
Blunt force = typical petal/sunflower shape, may also progress.
126
What type of trauma typically causes lens ruptures?
Either sharp (although typically penetration) or blunt force
Minimal trauma required for rupture when tumescent cataracts (e.g diabetic cataracts) present as lens capsule already under increased tension.
127
In puppies who undergo phacoemulsification following lens rupture post claw injury what are the possible consequences?
Altered growth of globe post operatively
Microphthalmia
Increased risk of secondary glaucoma.
128
What is septic implantation syndrome?
Laceration of the lens capsule by cat claw or other foreign material may lead to implantation of microbes within the lens. Intralenticular microbes may lead to lenticular abscess formation and endophthalmitis.
129
What cases are linked to post traumatic sarcoma formation?
What is the prognosis?
Cats and rabbits
Previous ocular trauma involving the lens
Previous lens surgery (phacoemulsification)
Intravitreal gentamicin injection (cycloablation for glaucoma)
Aggressive malignant tumour with metastatic spread to CNS - poor prognosis (survival 7-11 months post diagnosis)
3 variants - spindle cell, round cell (lymphoma), osteosaroma/chondrosarcoma
Local invasion through sclera and along the optic nerve are described - cases may have neurological signs where brain is involved.
Cases typically present as solid white/tan/pink mass occupying most of anterior chamber or globe some with transscleral expansion.
Mean age 11yrs
Mean time since trauma = 6 yrs
130
Define retinal dialysis.
Retinal tear at the ora serrata - usually a result of vitreous traction at the vitreal base here.
Disinsertion of the retina from the underlying RPE whilst still attache to vitreal base.
Can be associated with rhegmatogenous retinal detachments - where retinal tear allows vitreous to pass under retina into the subretinal space (between sensory retina and RPE)
131
How may retinal tears occur?
Secondary to vitreous traction (e.g partial posterior vitreal detachment resukting in remaining attached vitreous exerting increased tension on that portion of the retina)
Vitreal traction band (fibroblastic epiretinal membrane that may contract over time and pull on retina)
Direct tear from penetrating or perforating injury.
132
Define a giant retinal tear.
Giant retinal tear = >2 clock hours.
132
What is rhegmatogenous retinal detachment often secondary to?
How else may retinal detachment occur with trauma?
Secondary to retinal dialysis or tears (giant or otherwise) - vitreous passes under retina into subretinal space separating sensory retina and RPE.
Especially case for dorsal retinal tears due to effect of gravity on the vitreous.
Ventral retinal tears - better prognosis.
May also occur secondary to blunt trauma through combination of equatorial expansion and contrecoup wave of energy.
133
Which types of surgeries have been attempted for retinal detachments?
Vitreoretinal surgery - not common in veterinary patients at present
Scleral buckling - uses a buckle placed against sclera at site of detachment to push the RPE towards the detachment
May be combined with laser therapy, cryotherapy or retinal tacks.
Diode retinopexy along margins of retinal detachment to attempt to bond the retina to RPE and choroid along series of laser burn sites also been trialled.
Row of 2 lines along length of detachment using diode 810nm laser system.
