01 Canine orbit, enucleation and Eyelids (part 1)

LO: To be familiar with the clinical signs of orbital disease, and how clinical signs may be useful in distinguishing neoplastic from inflammatory causes LO: To be aware of how exophthalmos may be investigated further in first opinion practice, and treatment of retrobulbar bacterial infection LO: To recognise and treat traumatic proptosis in the dog LO: Know the common indications for enucleation in the dog LO: Be familiar with the trans-palpebral technique for enucleation LO: To have a basic knowledge of the anatomy and function of the external eyelids LO: Know how to examine the external eyelids in the first opinion practice setting LO: Be able to define distichiasis, conjunctival cilia, and trichiasis and understand how these conditions present

canine orbit typeexophthalmos

open

opent type orbit

Incomplete in the temporal or dorsal temporal region—> continuous with the temporal fossa

canine orbit is divided into

Intraconal space

• extraocular muscles, CN II, III, IV, V(1), VI)

Extraconal space

• neurovascular structures

• nictitating membrane

• zygomatic salivary gland

neighbouring structure of canine orbit?6 what is the significance?

• caudal nasal cavity,

• paranasal sinuses,

• masticatory muscles,

• caudal maxillary molar teeth,

• pharynx

• zygomatic salivary gland

diseas may extent into orbit

Hallmark clinical sing of orbital disease

exophthalmos

exophthalmos

anterior displacement of globr along orbital axis

how do you derernmine exophthalmos

viewing the patient from above

exopthalmos often associated with

increased resistance to digital retropulsion of the globe

Other Clinical signs of orbital disease

x increase resistnace

x exophthalmos

• Strabismus: rotation of the globe away from the normal optical axis e.g. exotropia or esotropia

• Pain on opening the mouth (esp. nflammatory conditions) or reluctance to eat and chew

• Protrusion of the nictitating membrane

• Periocular swelling

• Chemosis (swelling) and conjunctival hyperaemia

• Epiphoramucopurulent ocular discharge

• Keratoconjunctivitis sicca

• Visual and afferent pupillary defects

• Decreased ocular motility

• Decreased eyelid and periorbital sensation

• Lagophthalmos +/- exposure keratopathy /corneal ulceration

• Swelling, induration or fistula of the oral mucosa in the pterygopalatine fossa (caudal and medial to the
  second maxillary molar tooth)

• Retinal folds / scleral indentation / tortuous engorged retinal blood vessels / papilloedema

Lagophthalmos

condition preventing eyelid from closing completely

common ddx diagnosis: exophthalmos

Retrobulbar cellulitis or abscess

Retrobulbar neoplasia

less common ddx: exophthalmos

• Myositis of masticatory or extraocular muscles

• Adenitis of the zygomatic salivary gland (sialoadenitis)

• Retrobulbar haemorrhage

• Cystic space-occupying lesions of the nictitans gland/ zygomatic mucocoele

• Dacryops

• Dermoid cyst

unilateral or bilateral orbital disase more comon

unilateral

bilateral involvement suggest

• myositis

• bilateral sialoadenitis

Retrobulbar abscess/cellulitis

aetiopathogenesis

inflammatory disease of neighouring periorbital structure or space

can be

• direct inoculatoion

• or secondary to orbital FB or septicaemia

Retrobulbar abscess/cellulitis

clinical sign

• Acute onset / rapid progression

• expophthalmos

• Discomfort on opening the mouth + globe retropulsion

• perorbital swelling sensiticity

• marked conucntical hyperaemia

• Pyrexia, anorexia and neutrophilia with left shift may be present

Retrobulbar abscess/cellulitis

investigation

Orbital ultrasonography

Radiographs of the caudal maxillary molar tooth roots

• evidence of periodontal or endodontic disease

Examination of the oral cavity

• particular attention to the pterygopalatine fossa and the maxillary molar teeth

• may need GA

• period of stabalisation may be needed in systemically unwell px

On ultrasound, retrobulbar abscesses often have

vs orbital cellulitis

a well-defined hyperechoic wall surrounding a uniformly

orbital cellulitis: subtle changes in the
normal retrobulbar space

• distortion or obliteration of the normal retrobulbar architecture

• retrabnormal mixed echogenicity

Retrobulbar abscess/cellulitis

SHOULD BE TREATED AS EMEGENCY

urgent investigation and instigation of
appropriate management to preserve the globe and its function

Retrobulbar abscess/cellulitis

management: emergency

if abscess is not seen on ultrasound

1. Initial treatment with a potentiated-
   penicillin (amoxicillin/clavulanic acid) or cephalosporins while waiting on C+C result

   • usually mixed aerobic and anaerobic

2. empirical broad-spectrum antibiotics (3-4 weeks) and NSAIDS

   • generally results in rapid improvement.

Retrobulbar abscess/cellulitis

management: emergency

if lagophthalmos are apparent

1. Initial treatment with a potentiated-
   penicillin (amoxicillin/clavulanic acid) or cephalosporins while waiting on C+C result

   • usually mixed aerobic and anaerobic

2. empirical broad-spectrum antibiotics (3-4 weeks) and NSAIDS

3. appropriate topical treatments to manage or prevent exposure keratitis are indicated

Retrobulbar abscess/cellulitis

management: emergency

if ultrasound indicate abscess

drain pus through oral approach (pterygopalatine fossa)

periapical( tooth root) abscessation:

• extraction of tooth

• Gentle probing of the alveolar bone may reveal direct communication with the orbit and allow drainage of the orbital abscess

• if not then sx pterygopalatine fossa drainage

If radiographs of the maxillary dental arcade reveal evidence of periapical
abscessation

extraction of the affected tooth is indicated

entle probing of the alveolar bone may reveal a direct
communication with the orbit

• allow drainage of the orbital abscess.

• If drainage inadequate, surgical drainage via pterygopalatine fossa

7yo MN Border Collie with right orbital cellulitis. Clinical signs included painful exophthalmos, strabismus, third eyelid protrusion and exposure keratitis

dental radiographs identified periapical abscesses of the maxillary molar teeth.

Retrobulbar abscess/cellulitis

prognosis

generally good,

• rapid improvement on appropriate antibiotics

• combined with orbital drainage when orbital abscessation is present.

If recurs on completing the course of treatment

• foreign body may be implicated

• referral for advancing imaging

• surgery should be recommended

Retrobulbar neoplasia

aetiopathogenesis

primary

• arises from orbital structures

secondary

• local extension from
  adjacent structures or metastasis from distant sites

generally affects older patients (> 8 years)

often follows a more insidious course
leading to a late presentation when tumours are well-advanced

most common orbital tumour

Nasal adenocarcinoma

Retrobulbar neoplasia prognosis

late presentaion, 90% malignant,

guarded or grave

Retrobulbar neoplasia

clinical sign

Hx:

• slowly progressive
  unilateral exophthalmos

• strabismus

• third eyelid protrusion

• without pain on opening the mouth or on palpation of periocular tissues

• reduced air flow through the nostril of the affected side (common originate from nsal cavity)

• importance to check for disseminted diseas and sample non orbital diseae

Retrobulbar neoplasia

Investigaton

Physical exam importatnt

• Lymphadenomegaly or organomegaly —> increase suspicion of disseminated disease

• Sampling of more accessible non-orbital tissues may be more appropriate

• orbital US (most tumours appear variably hyperecoic)

plain film radiography : abd and thorax

• extension from the nasal cavity, loss of orbital bone

• both are poor prognostic indicators.

Sample: FNA/ US biopsy

• typing tumor

• grading needs: Rx thorax and abdo, abdo ultrasound

(if tx considered)

CT or MRI

• demonstrate the extent of the neoplasia more fully, and frequently indicate the origin of the tumour.

Retrobulbar neoplasia

pronosis

generally guarded

unless advance img suggest sx can be curative

Traumatic proptosis

Protrusion of the globe with eyelids behind equator of globe

• only occurs as a result of trauma where it often becomes entrapped

• orbicularis oculi muscl spasm—> exaccerbated

• minor trauma posisble in brachy: better chance retain vision

• evaluateion of concurrent craniofacial and CNS injury

Traumatic proptosis

• evaluateion of concurrent craniofacial and CNS injury

• Strabismus from torn extraocular muscles is common (medial rectus typically affected)

  • lateral strabismus.

• Chemosis and corneal ulceration

• uveitis,

• glaucoma or

• hypotony and hyphaema.

• Neuro-ophthalmic examination

  • visual deficits

  • pupillary abnormalities

prognostic indicator for cision

when is enucleation indicatied in traumatic proptosis

• damage to the globe, extraocular muscles and / or optic nerve is severe

• prognosis for salvaging even a non-functional globe is poor

Replacement of proptosed globe sx steps

1. GA, clean ocular surface with povidone iodine (1:50 solution), fluorescein, flush again

2. gentle forward traction applied to the eyelids, lateral canthotomy —> tension release

   • eyelids drawn forward over the ocular surface

   • protect the cornea as the sutures are tightened.

3. tissue swelling— not possible to return globe to normal position in whiere corneal surface will be protected—> Temporary tarsorrhaphy

   • Pass suture upper eyelid first ~ 5mm from lid margin exiting eyelid margin at level of meibomian gland openings

   • Direct needle through meibomian gland opening on opposite lid, exit through skin

4. routinely closed (figure 8), eyelids sutured together for 14 days

   • simple interrupted

   • partial thickness horizontal mattress sutures emerging through the lid margins

   • ensure suture material not contacting the cornea

Replacement of proptosed globe sx

aftercare

how long does the suture have to stay in?

• B/S systemic antibiotics if wound open and contaminated

• nsaids & analgesia

• Appropriate topical antibiotics applied via small gap left open at medial canthus

• Leave sutures in place at least 2 weeks

prolapse globe treatment complicaion

long term complications leading to patient morbidity

• permanent blindness

• lagophthaalmos

• neurotrophic keraitits

• KCS

• permanent strbismus

• phthis bulbi

indications for enucleation

• Unmanageable ocular disease associated with pain or risk to the patient

• Intraocular neoplasia/neoplasia— cannot be removedc without sacrificing globe

• Non visual eye + intractable pain

• Chronic glaucoma, irreversible loss of vision + evidence of discomfort

• Panophthalmitis (inflammation of all intraocular structures and sclera) refractory to treatment

• Severe ocular trauma – e.g. proptosis with ON transection

importance: enucleation post op care

often best welfare option for O with money contraint

what to do post enucleatiokn

1. access demeaanour following removal

2. histo assessment

3. store glbe in formalin in case later prob

enucleation

Magnification and lighting

Magnification ranging from ____ Working distance of_____

Magnification: 1.5 to 8x;

Working distance: ~ 20 - 50 cm

Major disadvantages of loupes include: (4L)

lack of variability in magnification

limited magnification

limited field of view (smaller at higher mag)

limited depth of field

enucleatio pre op prep

1. instrument set: personal pref. bishop harmon forcep; 4/0 monocryl 6/0 vicryl)

2. meticulous haemostasis: Clamp bleeding vessels Ligate larger vessels Thermal cautery Bipolar cautery Care with monopolar cautery – esp in orbit

3. px postition: vacuum positioning. px insulatied from cold table, resistant to infectant

4. hair clipping: avoid rash, prep aseoptically (1:50 ocular serviei; 1:10neyelid)

enucleation anaesthesia

• retrobulbar nerve block prior to enucleation reduce postoperative pain and anaesthetic requirements.

  • cureved retrobulbar needle
    

• Alternatively, a splash block of the orbit once the eye has been removed can help with post-operative discomfort

enucleation species and breed consideration

CATs

• Short optic nerve

• Tractional injury to contralateral Optic nerve via chiasm

• DO NOT clamp or ligate the ON

Rabbit

• Large orbital venous sinus

• Retrobulbar lobes of tear glands

• Risk for haemorrhage

goal of transpalpebral enuceleation

• Removal of globe, eyelids and conj sacs in one unit

• Not entering conj sac (Infectious/neoplastic contamination of orbit)

• Eyelids sutured together or held by Allis tissue forecps

Transpalpebral enucleation technique

The eyelids are held together with Allis tissue forceps and the skin incised around
them.
• Use scissors to section the lateral canthal tendon, and dissect back to the
conjunctival reflection.
• Once posterior to this, work as close to the globe as possible, sectioning each of
the rectus and oblique muscles in turn at their tendons of insertion (this will
drastically reduce haemorrhage as the muscle bellies are very vascular). The retractor
bulbi muscles surround the optic nerve and usually obscure it
• Continue the plane of dissection medially, sectioning the short tight medial canthal
tendon to free up the outer surface of the third eyelid
• Avoid at all costs applying tension to the optic nerve (ON), as this may damage the
chiasm and blind the patient in the remaining eye (traumatic optic neuropathy).
Rotate the globe medially to expose the retractor bulbi muscles surrounding the
optic nerve rather than using traction. Section the retractor bulbi muscles and optic
nerve without clamping them first. Clamping the ON increases the risk of
contralateral traumatic optic neuropathy
• If there is any residual bleeding apply digital pressure with a gauze swab (for 5
mins). Close deep orbital tissue, then place a continuous layer in the deep tissue
attached to the lids (try to make this layer watertight). Finish with skin sutures.
• Maintaining even pressure over the closed wound with an ice pack (covered by a
cloth moistened with sterile saline) for 10-20 minutes during the recovery period
will reduce haemorrhage into the orbit/eyelids and subsequent swelling.
• Provide good post-operative analgesia and systemic NSAIDs