Ocular Neoplasia & Systemic Disease

Question 1

List the primary and secondary types of orbital tumours seen in dogs and cats.

Answer 1

Primary - osteosarcoma, fibrosarcoma, chondrosarcoma, myxosarcoma, meningioma, neurofibrosarcoma, adenoma, adenocarcinoma, melanoma, lipoma, histiocytoma, mast cell tumour, feline restrictive orbital myofibroblastic sarcoma (previously known as pseudotumour)

Secondary - lymphoma, squamous cell carcinoma, nasal adenocarcinoma, cerebral meningioma

Question 2

Where do primary orbital tumours generally arise from and are they generally malignant & metastatic?

Answer 2

Primary orbital tumours = arise from bony orbital walls or soft tissue contents of the orbit

Primary tumours are generally locally invasive and may be metastatic but are slow to metastasise.

In both dogs and cats 90% orbital tumours are malignant.

Question 3

What age are dogs and cats most commonly when they present with orbital tumours?

Answer 3

Generally middle aged - older animals affected
Dogs average 8 years
Cats average 9 years

Question 4

Are primary or secondary types of orbital tumour more common in:

1. Dogs
2. Cats

Answer 4

1. Dogs - mostly primary orbital tumours
2. Cats - secondary metastatic orbital tumours pre-dominate

Question 5

What is the usual clinical presentation for an orbital mass?

Answer 5

Exophthalmos = often main presenting sign
Reduced globe retropulsion
Widened palpebral fissure
Chemosis
Exposure keratitis + epiphora

Mass outside the muscle cone formed by the retractor bulbi muscles then 3rd eyelid protrusion with strabismus may be seen.

If mass within the muscle cone formed by the retractor bulbi muscles then globe protrusion is usually axial and 3rd eyelid protrusion is minimal.

Secondary orbital tumours that involve the nasal passage (e.g nasal adenocarcinoma or SCC) may be associated with an ipsilateral nasal discharge or facial distortion.

Most orbital tumours slowly progressive and painless
Some may be associated with pain due to local compressive or inflammatory effects.
For this reason the presence or absence of pain cannot reliably be used to distinguish an orbital tumour from orbital abscessation.

Question 6

What diagnostic techniques can be used to diagnose and investigate suspected cases of orbital tumours?

Answer 6

Ultrasound - linear 7.5MHz scanner, B mode, transcorneal approach after topical anaesthesia.
Limitations = may not reveal the true extent of a mass or its margins, especially deep or extensive orbital disease extending intracranially or into adjacent soft tissues.
Ultrasound guided FNA under GA may allow for cytological diagnosis in 50% of cases, care to avoid iatrogenic penetration of globe, especially in cats.

Radiography - if suspect bony involvement
Lateral, dorsoventral, ventrodorsal and oblique views required
Skyline view if frontal sinus involvement is suspected
Dorsoventral/intraoral view to identify conditions involving the nasal turbinate bones.
Limitation = complexity of skull anatomy and superimposition of structures makes interpretation challenging.
May use chest radiography for staging purposes.

Advanced imaging - MRI or CT - give excellent detail of orbital structures
CT = better visualisation of bony structures of orbit
MRI = superior for soft tissue visualisation
Indicated when ultrasound inconclusive, possibility of extensive orbital and extra-orbital involvement or in cases where orbital surgery is being considered.

Question 7

What is the treatment of choice for primary orbital tumours?

What is the prognosis for primary and secondary orbital tumours?

Answer 7

Small and discrete tumours - orbitotomy (so that globe and associated structures can be preserved)

Large or infiltrative tumours - extenteration +/- chemotherapy or radiotherapy depending on tumour type

Secondary orbital tumours poorly amenable to surgical resection (already elsewhere in body also)

Dogs Primary = guarded prognosis, only 19% lived longer than 1 year in one study

Cats = prognosis grave, on average <1.9 months following diagnosis

Question 8

What are the 3 most common eyelid tumour types in dogs? What age do they typically start to appear?

Are they mostly benign or malignant?

Answer 8

Sebaceous gland (meibomian) adenoma (up to 60% all canine eyelid tumours)
Melanoma (17%)
Squamous papilloma (11%)

Typically >9 yrs

Dogs eyelid tumours mostly benign

Question 9

What types of malignant eyelid tumour are there in dogs?
Do they usually metastasise?

Answer 9

<10% of all canine eyelid neoplasms

Malignant melanoma
Sebaceous adenocarcinoma
Histiocytoma
Mast cell tumour
Lymphoma
Basal cell tumour

Locally invasive rather than metastatic in most cases
Exception = malignant melanoma which may metastasise.

Question 10

What are the most common types of eyelid tumour in the cat. Are they usually benign or malignant?

Answer 10

Most feline eyelid tumours = malignant and locally invasive, some will metastasise although often slow

Squamous cell carcinoma (>65% of cases) - UV light/lack of pigmentation = risk factor
Fibrosarcoma
Adenocarcinoma
Lymphoma
Hemangiosarcoma
Melanoma

Benign types of eyelid tumour in the cat:
Basal cell carcinoma
Mast cell tumour
Apocrine hidrocystoma (Persians/Himalayans)

Question 11

Describe the typical clinical appearance of a sebaceous gland adenoma in the dog.

Answer 11

Focal mass on eyelid margin
Eversion of eyelid shows meibomian gland swelling beneath palpebral conjunctiva
May be associated with ocular discomfort due to corneal irritation - can lead to keratitis and corneal ulceration.

Question 12

How does apocrine hidrocystoma in cats present?

Answer 12

Single or multiple, round pigmented masses - may be unilateral or bilateral
Masses are cystic adenomas of the apocrine sweat glands (glands of Moll)
Persian and Himalayans predisposed.

Question 13

How do we diagnose the type of eyelid tumour?

Answer 13

Presumptive diagnosis is made on clinical examination
Haematology/Biochem not indicated unless lymphoma suspected
Diagnostic imaging not usually indicated unless suspect malignant - thoracic radiography
Impression smears poorly diagnostic for most tumour types
FNA can be more rewarding but does not allow for tumour grading

BIOPSY = modality of choice, often excisional biopsy with small masses.

Question 14

What are the options for treatment of eyelid masses?

What margins should we aim for with excision of eyelid masses?

How should we approach eyelid masses that we suspect are malignant?

Answer 14

Surgical resection (most cases)
Remove at early stage as only finite amount of eyelid margin
25% -1/3rd of eyelid margin = ok for surgical resection with primary closure
>1/3rd = blepharoplasty techniques to re-oppose the eyelid margins (often needed in cats with malignant eyelid masses that require margins)

Benign masses 1-2mm margins

Suspected malignant masses (often cats!) - FNA or biopsy followed by histological tumour grading recommended prior to surgery to aid planning - often need much wider margins and blepharoplasty techniques +/- adjunctive therapy.

Question 15

Apart from surgical excision what other techniques could be considered for removal of eyelid masses?

Answer 15

Cryotherapy - small eyelid tumours - thermal coupling within and adjacent to mass recommended during freezing. Application of petroleum based ocular lubricant to reduce risk of iatrogenic corneal freezing during procedure.

Carbon dioxide laser therapy
Photodynamic therapy
Carbon dioxide laser therapy

Question 16

Why is resection of canine eyelid mast cell tumours often more complicated than other types of tumour in this location.

Answer 16

Malignant
Current recommendation for MCT = 2cm margins and a fascial plane, impossible to do without losing eyelid margin and function completely.

Options
Surgical resection with limited margins and adjunctive therapy e.g chemotherapy or radiotherapy (little published evidence of effectiveness of chemo in MCT)
Grade III MCT radical surgical excision and exenteration.

Question 17

Which type of eyelid mass may benefit from chemotherapy as the primary treatment?

Answer 17

Lymphoma
(adjunctive therapy for mast cell tumours in dogs)

Question 18

What is the prognosis for…

1. Benign eyelid mass removal
2. Malignant eyelid mass removal

Answer 18

1. Benign eyelid mass removal = good prognosis, as long as removed with good margin
2. Malignant masses depends on type of mass and stage of malignancy
   Low rate of metastasis - early removal of SCC = favourable prognosis
   Invasive SCC = more guarded prognosis as can be difficult to achieve good margins of resection

Malignant melanoma = associated with metastatic disease so more guarded prognosis in both dogs and cats.

MCT = guarded prognosis due to difficulty in achieving adequate margins of excision

Question 19

List some of the types of tumour seen in the conjunctiva and third eyelid in dogs and cats.

Answer 19

Melanoma
Squamous cell carcinoma
Lymphoma
MCT
Papilloma
Histiocytoma

Alongside many others!

Question 20

What diagnostics can we perform to diagnose masses of the conjunctiva and third eyelid?

Answer 20

Biopsy - recommended if any doubt to the nature of the mass under investigation

Question 21

How does episcleral/limbal melanoma usually appear? What would be the other differential to consider?

What other step of the ophthalmic examination should be performed if suspect melanoma?

Answer 21

Focal dark swelling of varying size - most consistently originates from limbus or epibulbar region in dogs

Intraocular melanoma would be other differential - may extend externally through the limbus to mimic limbal melanoma.

Check iridocorneal drainage angle with gonioscopy to check for intraocular involvement.

Question 22

What other clinical signs can we see associated with conjunctival, third eyelid or limbal masses?

Answer 22

Visible mass or erosive lesion
Secondary conjunctivitis
Ocular discharge
(Diffuse conjunctival lymphoma may mimic chronic conjunctivitis)

Question 23

What other diagnostic steps may be considered for conjunctival, third eyelid or limbal/epsicleral masses?

Answer 23

Ocular ultrasound - if suspect local invasion of tissues
Chest radiography - possibility of malignant disease
Biopsy - indicated in most cases = useful to distinguish neoplasia from nodular granulomatous episclerokeratitis (small masses may choose to perform excisional biopsy)

Question 24

Describe limbal melanoma in the dog vs cat. How is it usually treated?

Answer 24

Dogs - limbal melanoma usually benign and slow growing
Surgical excision followed by cryosurgery or laser photocoagulation usually curative.

Cats - limbal melanoma rare, usually also benign but metastatic disease has been reported so do consider imaging to check if diagnosed with limbal melanoma.

Question 25

How does conjunctival melanoma differ from limbal melanoma?

How is it treated?

Answer 25

Conjunctival melanoma at site distant to limbus = uncommon

Behaviour can be aggressive and malignant in dogs - local recurrence and possible metastasis
Cats almost always malignant with local recurrence and distant metastasis

Dogs = wide surgical excision with cryosurgery advised
Cats = often already metastasised by time diagnosed, 3 in 4 cats have metastatic disease.

Question 26

Are conjunctival mast cell tumours and tumours of the third eyelid usually benign or malignant?

Answer 26

Dogs - conjunctival mast cell tumours = benign (grade 1-2)
Cats - single report of mast cell tumour in third eyelid was benign and surgical excision was curative.

Question 27

What is squamous cell carcinoma of the third eyelid or conjunctiva usually associated with?

Answer 27

Usually associated with extension from the eyelids and the tumour may also invade the orbit.

Surgical excision in combination with other modalities may be indicated.
If local invasion extensive then exenteration may be indicated.

Question 28

What are the most common intraocular tumour types in dogs and cats?

Answer 28

Primary = Melanoma & Ciliary body adenoma/adenocarcinoma (dogs)
Melanoma & Intraocular sarcoma (cats)

Secondary = Lymphoma (cats preferential area of metastasis for primary lung adenocarcinomas), eye can be a target for metastatic spread of any tumour.

Question 29

Describe anterior uveal melanomas in dogs and cats.

Answer 29

Most common primary intraocular tumour in both species

Arises from anterior uveal tract (iris or ciliary body) - choroidal melanoma = very rare.

?possible breed predisposition Labradors/Persians

Older animals most commonly affected

Dogs - usually discrete focal mass of the iris
Cats - may also be a focal mass or make also show as a diffuse thickening and darkening of the iris.

Question 30

What differentials could be considered for anterior uveal melanoma?

Answer 30

Chronic uveitis (which can cause progressive iris darkening)
Benign iris pigmentation (nevi or freckles)
Iris cyst (spherical and can be transilluminated)
Pigmented epithelial cell tumour
Pigmentary uveitis in Golden Retrievers
Ocular melanosis in Cairn Terriers
Intraocular histiocytic sarcoma (can resemble an amelanotic melaoma both clinically and histologically = IHC often required to differentiate the two. Important as metastatic risk for histiocytic sarcoma in dogs higher than for melanoma and in some breeds e.g Burmese Mountain Dog may be associated with systemic histiocytosis.

Question 31

How does the biological behaviour of anterior uveal melanoma vary between dogs and cats?

Answer 31

Dogs - 75% primary anterior uveal melanomas are benign
25% histologically malignant with metastatic rate of 5% - liver and lungs main target organs. Both histologically benign and malignant types however are locally invasive with fewer than 10% remaining inside the sclera

Cats - anterior uveal melanoma more likely to be malignant with local invasion and metastasis common. Reported metastatic rate of up to 63%, although more recent paper suggests 19%. Guarded prognosis with risk of metastasis to the liver and lungs.

Question 32

What index can be a reliable indicator of malignancy in anterior uveal melanoma for both dogs and cats?

What other indicators of malignancy have been reported in cats?

Answer 32

Mitotic index
Both species positive association between mitotic rate and local invasiveness and between mitotic rate and survival times.

Other indicators of malignancy = extrascleral extension, necrosis within the neoplasm, choroidal invasion and increased E-cadherin and melan-A intensity.

Question 33

What options are there for the treatment/management of anterior uveal melanoma in dogs?

Answer 33

Surgical resection (iridectomy) - local small iris melanomas (for both diagnostic and treatment purposes) - specialist procedure requiring operating microscope and wet-field cautery

Diode laser photocoagulation - small local iris melanomas

If above approaches are not an option a “watch and wait” poloicy if often advised with regular e.g 6 monthly ophthalmic examinations

Monitoring of suspected anterior uveal cases:
Slit lamp exam - magnification of tumour and any intraocular changes
Gonioscopy to look for invasion of the drainage angle
IOP measurement
Pharmacological dilation of the pupil to allow examination of the ciliary body and posterior segment
General physical examination (particularly palpation of submandibular LN’s)
Ocular ultrasound in selected cases - posterior segment difficult to examine or if mass has grown significantly
Abdominal ultrasound +/- chest radiography - any signs of systemic disease

Enucleation if any of the following:
Suspicion of malignancy based on behaviour of the tumour
Mass enlarges causing invasion of the iridocorneal drainage angle or sclera/adjacent tissues
Secondary intraocular problems develop - glaucoma, uveitis, blindness, intraocular haemorrhage, retinal detachment

Question 34

Describe how you would approach monitoring of a cat with iris pigmentation (ddx iris melanosis vs iris melanoma)

Answer 34

Higher risk of metastatic disease with cats with iris melanoma therefore early enucleation often recommended

However unable to tell iris melanosis (benign) from iris melanoma (malignant) on just examination alone without histology therefore risk of enucleating normal eye.

Approach generally recommended in these cases is to monitor for signs of malignancy and enucleate if displaying these signs or progressing:
1.Significant change in colour/darkening of the mass over time
2. Associated thickening of the iris stroma and/or loss of normal iris architecture “velveting”
3. A significant increase in tumour size/area affected
4. Pigment shedding into the anterior chamber
5. Invasion of the iridocorneal drainage angle or other areas of the eye
6. Pupil distortion (dyscoria)
7. Pupil dilation relative to the contralateral pupil
8. Increase in IOP
9. Secondary uveitis, glaucoma, hyphaema, or other severe intraocular disease

Question 35

What should always be performed when enucleating a globe with an intraocular tumour? (especially anterior uveal melanoma suspicion!)

Answer 35

Abdominal ultrasonography + chest imaging (radiography or CT) - check for metastasis before procedure

Eye submitted for histopathology for complete diagnosis (including assessment of mitotic index) = allows for accurate prognosis.

Question 36

Describe ciliary body/iris adenoma/adenocarcinomas.

Answer 36

Second most common primary intraocular tumour in dogs
Uncommon in cats

Middle aged to older dogs predisposed
Adenoma:adenocarcinoma = 5:1

Usually arise from non pigmented epithelium of ciliary body (occasionally pigmented epithelium)

Adenomas = well differentiated, slow growing and although do infiltrate the ciliary body and iris stroma do not invade the sclera.

Adenocarcinomas = less well differentiated, increased numbers of mitotic figures, locally invasive

Metastatic potential extremely low but metastasis to the lungs has been documented.

Typical appearance = focal, mostly non pigmented mass protruding through the pupil or infiltrating the iris

Question 37

How should you examine and work up a dog with a suspected iris/ciliary body adenoma/adenocarcinoma?

Answer 37

Complete ophthalmic exam including IOP, gonioscopy (evidence of iridocorneal drainage angle involvement)
Dilation of the pupil to examine posterior segment and posterior extent of tumour
Ocular ultrasonography may help to determine the size of the mass and also allows you to measure and monitor its growth.

General physical exam - rule out any systemic disease

Question 38

What are the main differentials for an iris/ciliary body adenoma/adenocarcinoma?

Answer 38

Amelanotic anterior uveal melanoma
Ciliary body cyst (usually thin walled and can be transilluminated)
Metastatic tumour

Question 39

Why is biopsy of the iris or ciliary body unable to differentiate an adenoma from an adenocarcinoma?

Answer 39

Biopsy alone unable to distinguish between adenomas and adenocarcinomas as key differentiating factor between these types of tumour is invasion of the sclera.

True histopathological diagnosis can therefore only be made on an enucleated eye.

Question 40

What approach is generally taken with suspected ciliary body adenoma/adenocarcinomas? When is enucleation indicated?

Answer 40

As low metastatic risk for this type of tumour often “watch and wait” approach taken

Enucleation considered if:
1. Tumour enlarges or begins to invade other parts of the eye (e.g sclera, iridocorneal drainage angle, posterior segment) or if the iris and pupil become progressively distorted.
2. If the tumour leads to secondary intraocular problems such as blindness, glaucoma, uveitis, hyphaema or retinal detachment.

Enucleated eye should be sent for histopathology and determine if adenoma/adenocarcinoma.

Question 41

Describe intraocular sarcoma in cats. What is a prediposing factor for its development?

Answer 41

Second most common primary intraocular tumour in cats
Previous ocular trauma = predisposing factor (especially if lens involvement)
Middle aged to older cats at risk
Time from traumatic injury to development of sarcoma = 5 years on average (long lag time)
Secondary uveitis and glaucoma common

Highly malignant with both local invasion and metastasis - usually to the CNS
Often metastasied by time diagnosed
Poor prognosis with mortality rate exceeding 90%

Question 42

What is the most common secondary type of intraocular tumour in dogs and cats? What other types may we see?

How do they spread to the eye?

Answer 42

Lymphoma = most common secondary intraocular tumour

Haematogenous spread or local invasion

Local extension rare due to tough fibrous coat of the globe - (example = meningioma via optic nerve sheath)

Haematoenous spread = most secondary intraocular tumours
Lymphoma, mammary/lung adenocarcinoma/carcinoma, haemangiosarcoma, osteosarcoma, oral malignant melanoma.

Question 43

What percentage of dogs with systemic lymphoma will show ocular signs.

Answer 43

37% of dogs with systemic lymphoma will show ocular signs

Ocular disease = second most common sign after lymphadenopathy!

Anterior uveitis and intraocular haemorrhage = most common findings

Lymphoma with intraocular involvement = poor prognosis, stage V disease

Question 44

How does ocular lymphoma typically present in cats?

Answer 44

Infiltration of tumour cells into the uveal tract, anterior chamber and cornea.
Anterior uveitis and secondary glaucoma are common.

Question 45

If suspecting ocular lymphoma and aqueous flare is present what other diagnostic test may you consider performing? What are the risks involved with this technique?

Answer 45

If suspicious for ocular lymphoma and aqueous flare is present - consider aqueocentesis

Specialist procedure - risk of intraocular damage including lens trauma, intraocular haemorrhage, iris damage and infection.

Question 46

Which type of tumour can cause a condition called ischaemic chorioretinopathy?

Answer 46

Primary lung carcinoma in cats - metastasis to the eye as a predilection site

Tumour emboli lodge within choroidal arteries
Choroidal blood supply sectorial in nature (single arteriole supplies one distinct wedge shaped area of choroid with no collateral blood supply) blockage of such an arteriole will lead to necrosis of an entire section of choroid

Characteristic appearance of wedge shaped areas of tan discolouration in the tapetal fundus.

Question 47

Which mnemonic can be used to help remember the causes of systemic diseases that can affect the eye and nervous system?

Answer 47

Vitamin D

V= vascular
I = Infectious, idiopthic
T = trauma
A = Autoimmune
M = Metabolic
I = Immune mediated
N = Nutritional, neoplastic, neurological
D = Dermatological, degenerative

Question 48

What ocular signs can canine distemper virus cause?

Answer 48

Conjunctivitis, keratoconjunctivitis sicca, chorioretinitis and optic neuritis

Early stage = acute conjunctivitis as the virus targets mucous membranes

KCS occurs when the virus targets the lacrimal glandular tissue causing dacryoadenitis (in most dogs spontaneous recovery of tear film over 4-8 weeks)

Chorioretinitis is characterised by multifocal areas of inflammation over the fundus. Post inflammatory lesions highlighted by hyper-reflective areas that persist for life.

Optic neuritis - sudden onset blindness, unilateral or bilateral, often associated with encephalomyelitis.

Question 49

What type of ocular signs can canine adenovirus 1 (CAV-1) cause?

How does this pathology occur?

When can we see it not as a consequence of the disease directly?

Answer 49

Acute anterior uveitis with corneal oedema (blue eye)
Usually self resolving over period of weeks
Unilateral most common but can be bilateral

Corneal oedema due to antibody-antigen complexes depositing on corneal endothelium which blocks the Na-ATPase pump

Can be seen with live vaccinations for CAV-2 (which confer protection against both CAV-1 and CAV-2)

CAV-2 = isolated from cases of idiopathic canine conjunctivitis.

Symptomatic treatment of the uveitis usually leads to resolution over 2-3 weeks

Question 50

What type of ocular disease can canine herpevirus (CHV-1) cause?

Answer 50

Newborn puppies - keratitis, panuveitis, retinal necrosis/dysplasia and optic neuritis

Adult dogs - self limiting conjunctivitis

Dendritic, punctate and geographic corneal ulceration has been associated with naturally occurring canine herpes virus variants also.

Question 51

What type of ocular disease can feline herpesvirus (FHV-1) cause?

Answer 51

FHV-1 = dendritic and geographic corneal ulceration, associated with corneal sequestrum formation and eosinophilc keratitis/keratoconjunctivitis, conjunctivitis, symblepharon formation.

Also causes signs of upper respiratory tract disease

Widespread within feline population
Latent infections and recrudescence

Question 52

What is the most common ocular manifestation of feline infectious peritinotitis (FIP)?

What other ocular signs may it cause?

Answer 52

Anterior uveitis - 30% non effusive cases (more common with non effusive vs effusive forms)
More chronic disease course with dry FIP.
Occurs due to vasculitis - immune complex deposition within blood vessel walls of iris allows breakdown of blood-ocular barrier.

FIP can also affect posterior segment - chorioretinitis, retinal blood vessel changes particularly affecting the retinal venules may be particularly marked with FIP

Chronic antigenic stimulation may also lead to hyperglobulinaemia and hyperviscosity syndrome = fundic changes e.g increased thickness and tortuorosity of retinal vessels

FIP = mutation of feline coronavirus
Young cats <1 year mostly
Dry form - may also present with neurological signs/non specific signs e.g lethargy, GI signs etc
Wet form - often ascites/effusions

Remdesivir = treatment of choice.

Question 53

What are the ocular signs of FeLV infection? Why do they occur?

Answer 53

Retinal dysplasia - newborn kittens, diffuse intraocular inflammation, progressive retinal disorganisation and necrosis.

Adult cats - only direct ocular sign = pupillary abnormalities, hemi-dilated pupil (D shaped or reverse D shaped)

Hemi-dilated pupil result of viral infiltration of the malar or nasal branches of the short ciliary nerves.

Question 54

What ocular signs are associated with FIV infection?

Answer 54

Anterior uveitis
Self resolving conjunctivitis

Predisposes to secondary infections that can also cause uveitis e.g toxoplasma (opportunistic infections)

Assoacited with intermediate uvieits (pars plantitis) also - inflammation of posterior ciliary body, manifests as white opacities within the posterior vitreous just behind the lens.

Retinal perivasculitis and haemorrhages also reported.

FIV = higher risk of developing lymphoma (FIV immunosuppression and resultant reduced immune surveillance) + increased risk of opportunistic infections

FIV shown to prolong or worsen signs in cats with both FIV and toxoplasma/chlamydophila infections.

Question 55

What ocular signs can be seen with feline panleukopaenia?

Answer 55

In utero or early neonatal infection - retinal necrosis and dysplasia and optic nerve hypoplasia

Also associated with non ocular - cerbellar hypoplasia amd immunosuppression.

Question 56

What type of ocular disease can feline cowpox virus lead to?

Answer 56

Eyelid lesions in association with generalised skin disease and in some cases pneumonia

Question 57

What type of ocular disease does chlamydophila felis cause?

Answer 57

Conjunctivitis - often with severe chemosis
Primarily local pathogen with most cats showing no systemic signs of disease
Some cases will have mild upper respiratory tract signs

Excreted by genitourinary and GI tracts which may act as source of infection for other cats.

Question 58

What type of tick borne diseases can we see causing ocular disease?

Answer 58

Ehrlichia cania - tick vector Rhincephalus sanguineous
Not endemic to UK but seen in imported animals
Acute infection - conjunctival hyperaemia, chorioretinitis, retinal haemorrhages, optic neuritis
Chronic infection - thrombocytopaenia, monoclonal gammopathy - hyperviscosity syndrome

Rocky Mountain Spotted fever - Rickettsia

Cyclic Thrombocytopaenia - Anaplasma

Borrelia burgdorferi - tick transmitted spirochete - Lyme disease
Ocular signs = anterior uveitis, chorioretinitis, orbital myositis.

Question 59

What ocular manifestation may we see with Brucella canis?

Answer 59

Anterior uveitis (chronic and recurrent)
Not endemic to UK - imported dogs
Associated with epididymitis and abortion in dogs

Question 60

What is the most common ocular manifestation of Leptospirosis?

Answer 60

Spirochaete bacteria - L icterohaemorrhagiae and canicola = most common

Uveitis = most common ocular pathology

Question 61

What ocular sign is associated with bartonella?

Answer 61

Bartonella = cat scratch fever in humans

?possibly anterior uveitis - recent study showed no difference in seroprevalence between healthy cats and those with uveitis and large study looking at naturally occuring uveitis failed to find any bartonella DNA = significance in feline uveitis aetiology debatable.

Question 62

What are the most common ocular manifestations of toxoplasma gondii in cats and dogs?

Answer 62

Transplacentally and neonatally infected kittens - chorioretinitis often associated with severe and often fatal systemic toxoplasmosis

Adult cats - signs may develop due to tachyzoite spread following acute primary infection or via latent reactivation of tissue cysts following immunosuppression - anterior uveitis and chorioretinitis. are the principal manifestations.

Adult dogs - chorioretinitis, anterior uveitis, optic neuritis

Protozoal disease - cats = definitive host, rodents/birds = intermediated host

Question 63

What are the most common ocular manifestations of neospora caninum in the dog?

Answer 63

Protozoal disease - dogs = definitive host
Intermediate host = cattle, deer, sheep

Ocular signs of neospora are often associated with neurological disease
Blindness, anisoscoria, optic neuritis, chorioretinitis, anterior uveitis and extraocular myositis.

Question 64

What are the most common ocular manifestations of leishmania in the dog vs in the cat?

Answer 64

25% of leishmania infected dogs display ocular signs or periocular signs

Anterior uveitis, periocular dermatitis, keratoconjunctivitis.

Chronic leishmania = hyperglobulinaemia - hyperviscosity associated retinal signs.

Cats - leishmania = rare
Anterior uveitis, panuveitis and corneal ulceration associated.

Question 65

What types of mycotic and algal disease can cause ocular signs and what are the most common manifestations?

Answer 65

Not very common
Cryptococcosis and disseminated aspergillus - found in uk
Blastomycosis, coccidiomycosis, histioplasmosis, protothecosis - generally imported animals

Systemic mycoses = pyogranulomatous uveitis with signs of chorioretinitis predominating over the signs of anterior uveitis

May also be associated with non healing corneal ulcers

Disseminated aspergillosis = predisposition for GSD

Aspergillosis = rare in cats but may be associated with retrobulbar granuloma formation.

Question 66

Which parasites can cause ocular disease and how do they manifest?

Answer 66

Migrating parasitic larvae - may gain access to the anterior or posterior segment of the eye leading to anterior or posterior uveitis.

1. Angiostrongylus vasorum - subconjunctival haemorrhage (early presenting sign) - secondary to parasitic induced coagulopathy. Aberrent migration of L3 larvae into anterior or posterior segment can lead to severe granulomatous uveitis
2. Toxocara canis - aberrent migration of L2 larvae can cause focal granulomatous chorioretinitis and possibly more extensive retinal degeneration
3. Dirofilaria immitis (not endemic to UK) - anterior uveitis in imported dogs
4. Onchocerca - canine and feline ocular disease (but no cases reported in UK)
5. Dipteran larvae e.g Cuterebra species - rarely may affect ocular tissues (again no UK cases reported)

Question 67

Which vascular disease may affect the eye and how do they present?

Answer 67

1. Haemorrhage - any systemic bleeding disorder will predispose to subconjunctival and intraocular haemorrhage
   Causes - systemic hypertension, coagulopathies-thrombocytopaenias, clotting factor deficiencies, vasculitis and hyperviscosity.
2. Anaemia - anaemia will cause retinal vessels to look pale and narrowed, increased blood vessel fragility associated with chronic anaemia may lead to retinal haemorrhages
3. Hyperviscosity - e.g due to elevated serum protein levels
   due to hyperglobulinaemia - multiple myeloma, infection or inflammtory conditions OR polycythaemia
   Ocular abnormalties may be the presenting complaint of a hyperviscosity syndrome.

Signs mostly seen on fundic examination - retinal vessel tortuosity, retinal haemorrhages, severe cases - retinal detachment and intraocular haemorrhage +/- glaucoma

4. Hyperlipidemia - elevated triglyceride levels (particularly hyperchylomicronemia) = blood milky appearance that can be visualised within the retinal vessels (lipaemia retinalis)
   Anterior uveitis with this condition - triglycerides may leak through iridal blood vessels to cause lipid laden aqueous in anterior chamber.
   Primary hyperlipidemia = inherited in minature schnauzer
   Secondary - lipid rich diets or raised due to diabetes mellitus, pancreatitis, hypothyroidism and liver disease.
5. Systemic hypertension - eye = major target for hypertension
   Most common ophthalmic lesion in both dogs + cats = retinal blood torturosity, focal retinal oedema and bullous retinal detachment with retinal haemorrhage.
   As disease progresses can lead to total retinal detachment and intravitreal haemorrhage may develop.

Question 68

What inherited types of systemic disease may manifest in the eye also?

Answer 68

1. Lysosomal storage diseases
   Rare - deficiency of specific degraditive enzymes with resultant accumulation of their substrate.
   Ophthalmic signs depend on substrate but may include - corneal clouding, retinal infiltrates and progressive neurological signs.
2. Chediak Higashi syndrome
   Autosomal recessive disease of cats - affects cytoplasmic granules in wide range of cells including platelets, neutrophils and melanin containing cells - characterised by bleeding tendency, increased infection susceptibility and partial albinism.
   Ophthalmic signs = pale irises, retinal hypopigmentation, degeneration, absence of a tapetum, cataracts and nystagmus.
3. Ehlers-Danlos syndrome
   Autosomal dominant disease of connective tissue causes fragile skin and joint laxity in dogs
   Ophthalmic signs = abnormal limbus, corneal clouding, lens luxation and cataract.
4. Oculo-skeletal dysplasia
   Autosomal dominant disease with incomplete penetrance
   Short limbed dwarfism in dogs
   Ocular signs = retinal dysplasia
   Labradors + Samoyeds (not currently seen in UK population)

Question 69

What immune mediated systemic disorders can affect the eye and how do they manifest?

Answer 69

1. Uveodermatological syndrome (UVD) - also known as Vogt-Koyanagi-Harada like syndrome

Alaskan Malamute, Siberian Husky, Japenese Akita all predisposed
Anterior + posterior uveitis are often earliest presenting signs - progress to secondary glaucoma and retinal detachment in many cases.
Associated skin changes - ulceration of muco-cutaneous junctions, poliosis, vitiligo

2. Pemphigus, Lupus erythematosis - may cause erosive periocular disease
3. Granulomatous meningoencephalitis
   GME = non suppurative inflammatory disease of unknown origin that affects central nervous system of dogs
   Ocular signs = optic neuritis, chorioretinitis, anterior uveitis and retinal detachment.

Question 70

Which metabolic disease can affect the eye - how do they manifest?

Answer 70

1. Diabetes mellitus
   Cataracts - most common manifestation (80% of diabetic dogs) will develop within 16 months of diagnosis.
   Cataracts form due to changes in osmotic potential within the lens as it becomes saturated with glucose.
   Glucose converted to sorbitol by aldose reductase which attract water into lens leading to osmotic disruption and cataract formation. Oxidative stress also plays important role

(Cataracts not seen commonly in cats - lower capacity for conversion of glucose to sorbitol in older adults)

Chronic hyperglycaemia may also lead to damage of retinal blood vessels and diabetic retinopathy may occur in affected dogs.

2. Hyperadrenocorticism & hypothyroidism
   Little evidence cause direct ocular signs but dogs affected by these do seem more prediposed to KCS, corneal lipidosis, corneal ulceration, cataracts, lipaemia retinalis and hypertensive retinopathy
3. Hyperthyroidism
   Hypertensive retinopathy seen relatively frequently in hyperthyroid cats
4. Hypoparathyroidism
   Primary or secondary may lead to hypocalcaemic cataract formation.

Question 71

What nutritional diseases may have an impact on the eye?

Answer 71

1. Taurine deficiency
   Cats - central retinal degeneration ( focal area of degeneration in area centralis), over time progresses to diffuse retinal degeneration resulting in irreversible blindness
2. Thiamine deficiency
   Rare but usually due to long term ingestion of thiaminase rich foods e.g raw fish or thiamine deficient foods
   Progressive neurological defecits - fixed and dilated pupils, peripapillary retinal haemorrhages, papilloedema and optic nerve head neovascularisation
3. Zinc deficiency
   Zinc responsive dermatosis uncommon disease in dogs - asolute or relative deficiency in zinc
   Alaskan Malamutes and Siberian Huskies
   Common ocular signs = periocular dermatitis, periocular alopecia, scaling and crusting.
4. Vitamin E deficiency
   Retinal degeneration in addition to neurological signs (ataxia and weakness)
   English Springer Spaniels (RPED) - inherited form of vitamin e deficiency due to abnormal metabolism of vitamin e.
   Progressive visual deficits, accumulation of yellow/brown spots throughout tapetal fundus. Significant no of dogs also neurological.
5. Hypocalcaemia
   Young animals - inadequate diet, nutritional secondary hyperparathyroidism and resultant hypocalcaemia
   Older animals - hypoparathyroidism
   Systemic signs - lethargy, poor growth, bone weakness
   Ocular - hypocalcaemic cataracts - characteristic punctate appearance within anterior and posterior cortex of lens.

Question 72

Which dermatological diseases may affect the ocular area?

Answer 72

1. Atopic dermatitis - periocular and ocular signs are present in 60% of dogs with atopy
2. Infectious and parasitic skin disease
   Demodex
   Sarcoptes scabei
   Dermatophytosis (microsporum canis/trichophyton mentagrophytes/microsporum gypseum)
   Juvenile cellulitus/pyoderma - staphylococcus - abscess formation within meibomian glands and potential for marked trauma, oedema, pustules, papules and crusts periorally, periocularly, on chin/muzzle or in ears.

Question 73

Describe systemic histiocytosis - which breed does it mainly affect?

Answer 73

Non neoplastic histiocytic proliferative disease
Signs = eyelid masses, episcleral nodules, anterior and posterior uveitis

Systemic lesions = nodules and plaques affecting head/face, trunk and limbs. Erythema, swelling and depigmentation of the nasal planum/nares.

Differentiate from malignant histiocytosis which carries a more guarded prognosis.

Question 74

Describe dysautonomia - what ocular signs may it present with?

Answer 74

Seen in both dogs and cats.
Degeneration of neurons within the autonomic ganglia - dysfunction of both parasympathetic and sympathetic nervous systems.
Systemic signs = V+, D+, weight loss, depression, GI disturbances and dysuria

Ocular signs = reduced to absent PLR, elevated nictitans membrane, reduction in tear production due to loss of parasympathetic innervation to the lacrimal glands.