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Flashcards in SA Ophthalmology Deck (341)
1

What do the following terms refer to:
-blephar
-cor
-cycl
-dacryo
-hyal
-kerat
-papilla
-phak

-blephar- = lid
-cor- = pupil
-cycl- = ciliary body
-dacryo- = tears
-hyal- = vitreous
-kerat- = cornea
-papilla- = optic disc
-phak- = lens

2

What is anisocoria?

Unequal pupils

3

What is blepharospasm?

Sustained closing or excess blinking of the eye, usually implying pain and hence a variety of possible causes

4

What is buphthalmos?

"Ox eye"; an enlarged eye due to sustained glaucoma

5

What is chemosis?

Oedema of the conjunctiva

6

What is ectropion?

Outward rolling of the lid margin causing conjunctival exposure

7

What is entropion?

Inward rolling of the lid margin causing trichiasis (skin hairs abrading the eye)

8

What is endophthalmitis?

Inflammation of all of the interior of the eye, usually implying infection and a poor prognosis

9

What is enophthalmos?

Abnormally deep position of the eye in the orbit

10

What is epiphora?

Strictly: poor tear drainage leading to overflow but often used non-specifically for tear overflow of any cause

11

Where is the equator of the eye?

The area roughly over the ciliary body ie oriented vertically, not horizontally

12

What is exophthalmos?

Abnormal protrusion of the eye, either acquired or as a "normal" feature in some breeds e.g. Pekes (also called proptosis)

13

What is hyphaema?

Blood in the anterior chamber

14

What is hypopyon?

Pus in the anterior chamber, either either settling as a fluid line or in animals more usually as an irregular mass

15

What is lagophthalmos?

"Rabbit eye". Used to indicate an abnormally prominent eye such that the lids cannot close properly. The term is also used for neurological problems where the lids are not protecting the eye but where the globe is actually of normal size. Such an eye is at risk of “exposure keratitis"

16

What is microphthalmia?

An abnormally small eye, may be small but normal or accompanied by other ocular defects

17

What is miosis?

Abnormal constriction of pupil

18

What is mydriasis?

Abnormal dilation of pupil

19

What is panophthalmitis?

Inflammation of all parts of the eye (serious condition)

20

What is phthisis bulbi?

Shrunken soft "end stage" eye due to severe irreversible damage

21

Where are the poles of the eye?

Since the equator is vertical the poles of the eye are anterior and posterior and not North and South as in the Earth

22

What is ptosis?

Drooping of upper lid

23

What is staphyloma?

A defect in the coat of the eye which becomes lined with uveal tissue

24

What is synechiae?

Adhesion of the iris to adjacent tissues following inflammation

25

What is trichiasis?

Skin hairs in contact with the eye e.g. in entropion

26

Are systemic or topical drugs usually the first choice for treating eyes?

-Topical: always achieves higher concentrations on the ocular surface and in the anterior chamber than systemic medication.
-Oral medication is only used in the presence of a severe intraocular problem (inflammation/infection/if the posterior segment is involved where drops do not penetrate).

27

Compare eye drops to ointments

-Drops: better availability and do not affect vision but last a relatively short time
-Ointments: last longer on the ocular surface but human patients complain of smeary vision

28

Describe chloramphenicol

-Antibiotic
-Widely used for ocular surface infections as penetrates the eye well
-Doesn't act against pseudomonas species, so is not usually recommended for corneal ulcers if they may be infected

29

Describe fusidic acid

-Antibiotic
-Effective against Staph spp (which cause most non-specific conjunctivitis in dogs)
-Not suitable for corneal ulcers

30

Describe gentamycin

-Antibiotic
-Very good broad-spectrum inc gram -ves (eg pseudomonas)

31

Describe Ciprofloxacin and Ofloxacin

-Very broad-specturm antibiotics

32

Which corticosteroids are most commonly used to treat inflammatory eye conditions?

-Betamethasone
-Dexamethasone
-Prednisolone acetate

33

When should steroids not be used?

To treat corneal ulcers (except for rare conditions)

34

What is Maxitrol?

-Antibiotic/steroid combination
-Useful for symptomatic treatment of dry eye

35

What is cyclosporin used for?

-Anti-inflammatory
-Stimulates tear production
-Useful for dry eye and inflammatory conditions eg pannus and 3rd eyelid inflammation in the dog, and eosinophilic keratitis in the cat

36

When are NSAIDs typically used?
When should they be avoided?

-Mostly pre-cataract surgery
-Don't use on corneal ulcers

37

What are mydriatics?

-Dilate the pupil
-Indicated for treatment of uveitis and for lens and fundus examination

38

What kind of drug is atropine?
When is it used?

-Mydriatic (dilates the pupil)
-Used for treatment of uveitis only, but should be given to effect
-Very long lasting in non-inflamed eye so not used for examination
-Bitter taste

39

What kind of drug is tropicamide?

-Mydriatic (dilates the pupil)
-Lasts 4-6 hrs
-Aids fundus and lens examination

40

Which drugs are used to treat glaucoma?

-Dorzolamide and brinzolamide: topical carbonic anhydyrase inhibitors
-Latanoprost and travoprost: topical tx

41

What are lubricants used for?

Useful for dry eye but also useful in situations where the cornea needs to be protected and/or eye made more comfortable eg corneal ulcers/exposure problems

42

Give some examples of lubricants

-Lubrithal gel (4-6 times daily)
-Lacrilube ointment (longer duration than gel/drops)
-Artelac gel with added lipid
-Hycare gel

43

Which muscle encircles the lid margin and acts to close the eye?
What is it innervated by?

-Orbicularis oculi
-Innervated by facial nerve (CNVII)

44

Which muscles raise the upper eyelid?

-Levator palpebrae superioris (occulomotor nerve, CNIII)
-Muller's muscle (smooth muscle, sympathetic innervation)

45

Where do the tarsal/Meibomian glands lie?
What is their function?

-Lie at right angles to the lid margin (30 in each lid)
-Release lipid onto the pre-corneal tear film

46

What is the tarsal plate?

-A fibrous plate which stiffens and stabilises the lid margins in the terminal 4-5mm
-Tarsal glands found here

47

Do animals have eyelashes?

Only on upper lid

48

Do eyelids heal well?

-Yes as they have a very good blood supply
-Also therefore resist infection and necrosis

49

Which sutures should you use around the eye?

-Absorbable
-5/0 (dogs) or 6/0 (cats) vicryl or Polysorb for skin closures

50

How much hair should you clip for the following procedures:
-Enucleation
-Lid surgery
-Intraocular, cornea, 3rd eyelid surgery

-Enucleation: standard, playing card-sized area
-Lid surgery: minimal, surgical field only
-Intraocular, cornea, 3rd eyelid surgery: none (cover eye surface with gel and flush after surgery)

51

How do you prepare the surface of the eye before surgery?

Non-lathering aqueous povidone-iodine at a dilution of 1:50

52

Give 4 principles of good eyelid surgery

-Knots must never touch the eye
-Hairs must never touch the eye
-The cornea must be protected without exposure problems eg inability to blink
-Aim for good anatomical and aesthetic reconstruction

53

What is distichiasis?

-The growth of hairs from the tarsal gland openings on the lid margin -> can irritate the cornea
-Very common
-Congenital

54

How could you determine whether or not distichiasis hairs are irritating the dog?

Look for excess tear production and an increased blink rate

55

What are the treatment options for distichiasis?

-Plucking (waste of time)
-Electrolysis
-Cryo
-Tarsoconjunctival resection

56

Which dog breed is more prone to irritating distichiasis?

Weirmeraners

57

What are conjunctival (ectopic) cilia?

-Hairs which emerge through the conjunctival surface (a few mm from the lid margin) and impinge directly on the cornea
-More painful than distichiasis, less common
-Young dogs with painful eye and no obvious cause
-Often Bulldogs

58

Give the clinical signs of conjunctival (ectopic) cilia

-Often severe blepharospasm with refusal to open eye
-Pain
-Lacrimation
-May be a shallow corneal ulcer located opposite lesion
-Cilia are often difficult to see; cause problems as soon as they emerge through conjunctiva so are merely tiny dark stubs

59

Conjunctival (ectopic) cilia occur mostly on which lid?

Upper

60

How do you treat conjunctival (ectopic) cilia?

-Excise a deep wedge from the conjunctival surface around the cilium (electrolysis can also be used)
-No suturing needed
-Any ulcer should heal spontaneously

61

Entropion typically affects which dogs?

-Gundogs and larger breeds
-Assumed to be inherited
-Typically young dogs

62

Give the clinical signs of entropion

-Pain and watering of the eye (typically lateral lower lid)
-Corneal damage and ulceration can occur

63

When can entropion be secondary?

Can be secondary to pain -> retraction of globe -> entropion

64

How do you treat entropion?

-Dog must be conscious to evaluate how much tissue to remove
-Use your finger to support the lid from inside
-Incise 2mm from the lid margin and remove a strip of skin and underlying orbicularis muscle
-Suture closed starting with mid-point to give even closure

65

Should you perform entropion surgery in young pups?

-No as it is difficult to judge the correction required
-Use a temporary holding procedure eg 'tacking sutures' which last a few weeks and relieve pain. Can also use skin staples
-Surgery can be performed when dog is nearing adult size (4-5 months)

66

Give some negative features of the eyelids of Shar peis

-Downward angle to upper lid lashes
-Entropion from very young age
-360 degree entropion

67

Upper lid trichiasis/entropion affects which breed?

-Middle aged cocker spaniels
-Laxity of upper lid lashes -> turn downwards and abrade the eye -> discomfort, tear-straining

68

Which dogs are affected by medial entropion?

-Smaller/toy breeds
-Displaces the lower nasolacrimal duct opening -> poor tear drainage

69

Which dogs are affected by lateral canthus entropion?

-Breeds with broad heads eg Rottweilers
-Lateral canthal ligament insertion is too deep -> lateral canthus turns in -> entropion of lateral lower and upper lids

70

How do you treat upper lid trichiasis/entropion?

-Stades procedure: excise skin adjacent to lid margin and leave to granulate

71

What may occur as a result of ectropion?

-Conjunctivitis (through exposure)
-Poor tear drainage certainly occurs

72

What do most cases of ectropion result from?

Lid is too long

73

How can you treat ectropion?

Simple wedge excision to shorten the lid (where necessary or requested which is not often)

74

What is the most common eyelid tumour in the dog?

-Sebaceous epithelioma
-Arises from the tarsal/Meibomian glands and grows as a well-defined mass
-Benign, low metastsic risk

75

How do you treat a sebaceous epithelioma?

Local excision usually curative as low metastatic risk

76

What % of the eyelid can be removed before distortion occurs?

30-40%

77

When suturing the eyelid, where should you place the sutures?

-Holds best in the tarsal plate
-Knots must never contact the cornea

78

Which suture method is best for lid margin closure?

Figure of eight (takes the first knot away from the lid margin)

79

Which surgical procedures can you carry out on brachycephalics to reduce the incidence of corneal damage?

-Facial fold removal
-Medial entropion surgery
-Shortening the palpebral aperture (improves lid cover)

80

Do dogs scratch their eyes when they have eye pain/irritation?

No- likely to be a dermatological problem in the peri-ocular skin

81

Why is the deep surface of the nictitating membrance red and roughened?

Due to presence of numerous lymphoid follicles

82

What are the functions of the 3rd eyelid?

-Immunological
-Secretory
-Surface protection
-Tear film distribution

83

How can you protrude the 3rd eyelid?

Apply gentle pressure to the globe through the upper lid

84

How can you examine the deep surface of the 3rd eyelid?

-Local anaesthetic drops, pick up leading edge with forceps
-May need sedation/anaesthetic

85

Give some common differential diagnoses for prominence of the 3rd eyelid

-Non-pigmentation of the leading edge
-Prolapse of the gland ('cherry eye')
-Folding/kinking of the cartilage
-Plasma cell infiltration (GSD)
-Retrobulbar swellings
-Any condition causing pain and retraction of the globe
-Loss of retrobulbar fat
-Horner's syndrome

86

What is the most likely reason 'cherry eye' occurs?

Due to a weakness of the ligament stabilising the deep part of the membrane within the orbit

87

What is 'cherry eye'?

Prolapse of the third eyelid gland (nictitans gland)

88

Which dog breeds are more prone to 'cherry eye'?

Bulldogs, beagles, some giant breeds

89

How do you treat 'cherry eye'?

Pocket technique:
-Gland is buried (but preserved) in a fold of conjunctiva and sub-conjunctival tissue
-Quite expensive
Excision of gland:
-Lose 30% of tear capacity so is not recommended

90

Kinking of the 3rd eyelid typically occurs in which dogs?

Young dogs of larger or giant breeds

91

Give the clinical signs of kinking of the 3rd eyelid

Variable degree of prominence of 3rd eyelid, often with conjunctivitis and ocular discharge

92

How do you treat kinking of the third eyelid?

Only need to remove the kinked portion of cartilage, leaving the remaining cartilage in 2 pieces

93

Plasma cell infiltration of the 3rd eyelid affects which breed?

-GSD
-Immune-mediated inflammation of the 3rd eyelid

94

What are the clinical signs of plasma cell infiltration of the 3rd eyelid?

-Depigmentation of the leading edge
-Membrane becomes strikingly red and inflamed with a rough surface
-May be distinct follicle-like structures on the surface

95

How do you treat plasma cell infiltration of the 3rd eyelid?

-Steroids: unpredictable
-Ciclosporin: lifelong treatment

96

Give the clinical signs of Horner's syndrome

Disruption to sympathetic supply
-Ptosis (drooping of upper lid)
-Enophthalmos (abnormally deep position of eye in orbit)
-Miosis (pupil constriction)
-Protrusion of 3rd eyelid)

97

Horner's syndrome is recognised as idiopathic in which breed?

Older Golden Retrievers
Usually spontaneous improvement over a few months

98

What is the only reason you'd excise the entire nictitating membrane or leading edge?

Neoplasia

99

Which cells does the conjunctiva contain?

Goblet cells - contribute to the mucus fraction of the tear film

100

How would you recognise conjunctivitis?

Diffuse redness on all surfaces

101

How would you distinguish bacterial infection from normal mucus?

-Bacterial infection: causes a purulent, yellow-green discharge which adheres to lid margins
-Normal mucus: is off-white when fresh, and darkens to grey/brown when exposed to air

102

How would you distinguish simple conjunctivitis from something more severe?

Check the cornea, anterior chamber and pupil as these are not affected in simple conjunctivitis

103

Which pathogen is the most common cause of non-specific conjunctivitis?

Staph intermedius

104

How would you treat non-specific conjunctivitis?

-Fusidic acid once daily (antibiotic)
-Or gentamycin/chloramphenicol (broad-spectrum antibiotics)

105

How would you recognise follicular conjunctivitis?

-Numerous lymphoid follciles appearing as circular raised pink swellings
-Mild/no irritation, no purulent discharge

106

What are the different layers of the tear film?

-Deep muscous layer (produced by goblet cells of conjunctiva)
-Aqueous layer (produced by lacrimal gland and gland of 3rd eyelid)
-Lipid layer (produced by tarsal glands)

107

What causes keratoconjunctivitis sicca (dry eye)?

-Deficiency in aqueous tear production
-Majority of cases are immune-mediated
-Inflammation of glands -> reduced secretion -> progressive fibrosis and atrophy
-Other causes: sulphonamides, trauma, distemper

108

Give the clinical signs of keratoconjunctivitis sicca (dry eye)

-Loss of corneal reflex
-Corneal ulceration (not often in chronic cases)
-Superficial keratitis with oedema and neo-vascularisation
-Corneal pigmentation
-Diffuse conjunctivitis
-Mucopurulent ocular discharge (green/yellow)

109

Which dog breeds are more prone to keratoconjunctivitis sicca (dry eye)?

-WHWT
-English cocker spaniel
-Brachycephalics esp bulldogs but including CKCS

110

How can you diagnose keratoconjunctivitis sicca (dry eye)?

-Clinical signs
-Schirmer tear test strips (measure tear flow for > 1 min)

111

What value for the Schirmer tear test would indicate keratoconjunctivitis sicca (dry eye)?

10-15mm= moderate dry eye
<10mm= moderate to severe dry eye
(Minimum for normal eye=15mm)

112

How would you medically manage dry eye?

-Ciclosporin bid (tear stimulant; reduce cautiously after a length of time)
-Lubricants eg Lubrithal 4-6x daily (tear film replacement)

113

How many nasolacrimal puncta are there?

2 on each eye, visible as fine slits situated inside the lids near the medial canthus

114

How can you diagnose and investigate tear drainage problems?

-Rule out causes of painful lacrimation
-Check for entropian and 2 normal nasolacrimal puncta
-Check for discharge or foreign bodies
-Instil 1 drop of fluorescein into both eyes, flush with saline and time the flow to the nares
-Normal time=3-4 mins (can be seconds in some dogs)

115

Why may a fluorescein flush test be negative in brachycephalics?

Have caudal drainage into the pharynx

116

Which breeds are more prone to congenital micropuncta and imperforate puncta?

Golden retrievers and cocker spaniels

117

What are the clinical signs of tear drainage problems?

Tear overflow without pain

118

What is dacryocystitis?

-Infection and inflammation of the tear duct as a result of a foreign body which may be visible at the punctum
-Quite rare
-May be the primary cause of a persistent unilateral conjunctivitis

119

How can you treat epiphora (tear overflow) due to permanent naso-lacrimal duct obstruction?

-Bypass surgery to the nose or mouth
-Difficult, rarely justified

120

What are the 4 layers of the cornea?

-Outer epithelium
-Collagenous stroma (fine collagen fibrils arranged in lamellae -> transparent appearance)
-Descemet's membrane (acellular)
-Endothelium (pumps fluid out of cornea into aqueous)

121

Which cranial nerve innervates the cornea?

Ophthalmic branch of trigeminal

122

How does the cornea obtain its nutrition?

-Avascular
-From the tear film, perilumbar capillaries and aqueous

123

Why is the normal cornea transparent?

-No keratin
-No pigment
-Avascular
-Precise arrangement of collagen fibrils in stroma

124

Which factors can disturb the lamellar arrangement of the collagen fibris in the stroma?
What does this result in?

-Oedema
-Inflammatory tissue
-Scar tissue
-Other infiltrates (eg lipid, calcium)
-Results in opacity of cornea

125

What is a corneal ulcer?

A full-thickness defect in the epithelium

126

Why should corneal ulcers always be taken seriously?

-Very painful
-Potential for deeper progression and full-thickness perforation

127

How do you diagnose a corneal ulcer?

-Fluorescein (stains the stroma green)
-The flush with saline

128

What are the clinical signs of a corneal ulcer?

-Redness
-Pain
-Lacrimation
-Photophobia
-May not all appear as a deep crater (if quite superficial)

129

What does a clear, non-fluorescein-staining area in the centre of a positively staining cornea represent?

-Descemet's membrane
-Check for perforation (the anterior chamber collapses to a potential space between the iris and cornea)

130

How do melting uclers occur?

-Enzymatic breakdown of corneal stroma -> proteolysis
-Proteolyrtc enzymes may be released by gram -ve bacteria (eg pseudomonas), inflammatory cells, corneal cells

131

How do corneal ulcers heal?

From the outside in

132

Why may a corneal ulcer be fluorescin-negative?

-Down to Descemet's membrane
-Already healed

133

Give some primary causes of a corneal ulcer

-Factors causing direct mechanical damage (trauma, foreign body, entropion etc)
-Factors contributing to an unhealthy superficial corneal environment (KCS, any cause of corneal exposure)
-Inherent corneal defects (indolent ulcers, chronic corneal oedema)
-Unknown/multifactorial (brachycephalics)

134

Why is chloramphenicol not used to treat corneal ulcers?

-Not active against gram -ves (which can infect deeper ulcers -> melting)

135

Which antibiotics can you use to treat a corneal ulcer?

Gentamycin, fluoroquinalones

136

Why is Isathal (fusidic acid) not used to treat corneal ulcers?

Active against staphs only (gram -ves are what cause deeper infection)

137

How should you medically manage a corneal ulcer?

-Broad spectrum antibiotics (eg gentamycin, fluoroquinalones) every 4-6 hours initially
-Lubrithal (lubricant) qid
-Atropine 1 drop to effect (relieves painful pupil spasm)
-Serum? (from dog's own blood)

138

Why should you never use steroids on a corneal ulcer?

-Predispose to infection
-Inhibit epithelial healing
-Potentiate the action of collagenases -> melting

139

Why should you never use local anaesthetic for ongoing pain relief of a corneal ulcer?

-Only lasts 1 hour
-Toxic to epithelium
-Prevents blinking (causes surface damage)

140

Why should you not use topical NSAIDs on corneal ulcers?

Associated with stromal melting

141

Why are 3rd eyelid flaps no longer recommended for corneal healing?

-Obscure the eye (vet can't see what's happening)
-Applies pressure to a weakened eye
-Interferes with medication
-Not adequate for really deep ulcers
-Not a treatment for indolent ulcers

142

What is an indolent ulcer?

-Non-healing ulcer (but non-infected)
-The epithelium at the edge of the ulcer is loose -> wont 'stick down' and heal the defect

143

How do we treat indolent ulcers?

-Remove the loose epithelium (gently rub it away with a cotton bud and phenol)
-Grid/punctate keratotomy (scratches are made on the corneal surface to allow the epithelium to spread across and 'stick down')
-Or superficial keratectomy (GA, remove top layer of corneal ulcer)

144

When would surgery be required to treat a corneal ulcer?

-Large deep ulcers with no vascular ingrowth, where there is a mechanical weakness and a risk of perforation
-Mostly pugs

145

Which dog breeds are more at risk of indolent ulcers>

Boxers, beagles

146

How would you identify an indolent ulcer?

-Painful eye
-Very shallow ulcer with only the epithelium lost (no stromal loss), and under-running of the epithelium at the margins
-Stain well with fluorescein
-Go months without healing
-Mild oedema

147

What are the 2 types of corneal foreign bodies?

-Adherent to surface (embedded in/on surface, can be wiped off under LA)
-Intracorneal (eg thorns)

148

What is pigmentary keratitis?

-Pigment is carried in from the limbus in response to superficial damage (eg chronic KCS, entropion, pannus etc)
-Common in the medial cornea in brachycephalics
-Doesn't regress once primary lesion is resolved, but rarely causes a problem

149

What is a dermoid?

-A congenital malformation where a patch of skin grows on the ocular surface, usually lateral limbus
-Carries long hairs which irritate the cornea
-Don't invade deeper structures

150

How do you remove a dermoid?

Superficial keratectomy

151

What is senile corneal endothelial dystrophy?

-In some older dogs, progressive degeneration of the endothelium -> chronic corneal oedema
-Fluid may accumulate -> bullae
-Bullae may rupture -> ulcers

152

Which species are more prone to senile corneal endothelial dystrophy?

English springer spaniels and wire-haired fox terriers

153

How would you recognise lipid depositions?

Milky or crystalline appearance

154

What is pannus?

-Inflammatory and vascular tissue advances across the cornea, always from a ventrolateral direction
-GSD

155

How do you treat pannus?

Topical ciclosporin (bid) or topical steroids 6x daily for first week, then reduce over several weeks

156

What does the anterior uvea consist of?

Iris and ciliary body

157

What is the posterior uvea?

Choroid

158

What is special about the uvea?

Is the most vascular, most pigmented, and most immunologically reactive tissue in the eye

159

What is the function of the iris?

Controls the amount of light entering the eye

160

Which nerves innervate the dilator and constrictor muscles of the iris?

-Dilator: sympathetic nerves
-Constrictor: parasympathetic portion of occulomotor nerve

161

What is the function of the ciliary body?

-Comprised of ciliary muscle (controls shape of lens) and the ciliary epithelium (produces aqueous humour)
-Also acts as the attachment of the zonule supporting the lens

162

What are Persistent Pupillary Membrane (PPM) remnants?

-In the embryo a mesodermal membrane covers the pupil, providing an external vascular system for the developing avascular lens
-This should regress soon after birth but remnants may persist for weeks/months/life
-The strands arise from the mid-iris and may run to the lens, usually with a cataract at the point of attachment, or to the cornea (focal corneal opacity) or across the pupil sometimes in a web-like pattern
-No treatment necessary

163

What is anterior uveitis?

Inflammation of the iris and ciliary body

164

Give some clinical signs of anterior uveitis

-Pain (blepharospasm, photophobia, lacrimation)
-Aqueous flare (no longer clear)
-Red eye (circumlimbal deep vascular congestion)
-Miosis (constricted pupils)
-Hypotonia (decreased aqueous production)
-Hypopyon (pus in anterior chamber)
-Keratic precipitates (yellow +/or pigmented)
-Iris changes (dull, swollen)
-Corneal oedema (mild)
-Loss of vision (variable)
-Syncehiae (adhesion of iris to anterior lens or cornea)
-Iris rests (patches of pigment on anterior lens as a result of previous synechiae)
-Iris may be darker
-Glaucoma
-Cataract

165

Why does aqueous flare occur with uveitis?

-Breakdown of blood-aqueous barrier -> protein release -> aqueous no longer clear

166

Give some possible causes of anterior uveitis

-Corneal injury and ulceration
-Blunt/penetrating trauma
-Release of antigenic lens protein
-Intra-ocular infection
-Septicaemia
-Intra-ocular neoplasia
-Leukaemia/lymphoma
-Pyometra
-Idiopathic/immune-mediated

167

How do you treat anterior uveitis?

-Mydriatics eg atropine. Dilate pupil (reduces the risk of adhesions), relieve pain from ciliary muscle spasm
-Topical steroids-reduce inflammation eg dexamethasone, prednisolone acetate, use every 2-4 hours initially

168

What is 'iris bombe'?

Ballooning forward of the iris tissue

169

Which is the only species to have myelinated nerve fibres in the fundus?

Rabbit

170

How would you describe a rabbit's fundus?

-Merangiotic- long, horizontal streak (giving it good vision along the horizon to spot predators)
-Myelinated nerve fibres appear as white streaks extending medially and laterally

171

Give some differential diagnoses for masses in the anterior uvea

-Uveal cysts
-Naevi
-Myeloma
-Ciliary body adenoma
-Others inc lymphoma, metastatic tumour

172

Where do uveal cysts arise from?

-Posterior surface of iris or from ciliary body
-They break free and move into the anterior chamber

173

What do uveal cysts look like?

-Pigmented (black)
-Spherical
-Not solid
-Transilluminate (let light through)

174

Which dog breeds are most prone to uveal cysts?

Middle-aged labradors and staffies

175

Do you treat uveal cysts?

No

176

What is the most common intra-ocular neoplasm in all species?

Anterior uveal melanoma

177

How would you recognise an anterior uveal melanoma?

-Appear as solid masses in the iris or ciliary body
-Usually heavily pigmented (can vary)
-May be trans-scleral extension
-Often exhibit benign beahviour with slow growth
-Variable metastasis

178

How would you treat an anterior uveal melanoma?

Enulceation usually curative

179

How would you recognise a limbal melanoma?

-Heavily pigmented tumour arising within the wall of the eye at the limbus
-Invade the cornea and sclera

180

How would you recognise a ciliary body adenoma?

-Pink mass protruding into the pupil from behind the iris
-More aggressive ones may invade forward into the iris -Cause less intraocular disturbance than melanomas as there's less interference with the drainage angle

181

How do you treat ciliary body adenomas?

Enucleation

182

What is the most common 'metastatic' tumout of the eye?

Lymphoma

183

What is glaucoma?

An abnormal rise in intra-ocular pressure due to a problem with drainage of aqueous

184

Describe the path of aqueous

-Produced by ciliary body
-Passes through the pupil into the anterior chamber
-Drains at the irido-corneal angle (between the base of iris and the peripheral cornea)
-Enters general circulation

185

Give the clinical signs of acute glaucoma

-Red eye
-NORMAL globe size
-Severe pain and general lethargy
-Mild 'steamy' corneal oedema
-Unresponsive mid-dilated pupil
-Blindness
-Palpably hard globe

186

Give the clinical signs of chronic glaucoma

-Enlarged eye
-Blindness
-No response to light
-Tears in Descemets membrane (white lines across cornea)
-Variable corneal opacoty, vascularisation and pigmentation
-Lens (sub)luxation
-Visible retinal degeneration and optic disc cupping
-Variable degree in pain

187

What is the difference in globe size with acute and chronic glaucoma?

-Acute: normal globe size
-Chronic: enlarged globe size

188

Give the primary causes of glaucoma

-Breed disposition
-Dysplastic drainage angles, maintain normal pressure for several years -> sudden decompensation -> acute glaucoma

189

Give some conditions which can lead to secondary glaucoma

-Lens luxation
-Anterior uveitis
-Hyphaema
-Intumescent and hypermature cataracts
-Tumours
-Retinal detachment
-Trauma and perforated ulcers
-Chronic retinal detachment
-Intraocular haemorrhage

190

How can you medically treat acute glaucoma in an emergency?

-Hyperosmotic agents eg Mannitol 10% or 20% iv, 1-2g/kg over 30 mins (dehydrate and contract the vitreous)

191

How can you medically treat acute glaucoma (non-emergency)?

-Carbonic anhydrase inhibitors eg dorzolamide ('Trusopt') or brinzolamide (Azopt)
-Latanoprost
-Both

192

How can you surgically treat acute glaucoma?

Laser, cryo etc, to reduce aqueous secretion/improve drainage

193

How is the lens supported?

By the ciliary body via the zonular fibres which attach at the lens equator

194

How can you examine the lens?

-Distant direct ophthalmoscopy (light source + magnification)
-Mydriasis often essential (pupil dilation)

195

How can lens luxation occur?

-Primary
-Secondary to chronic glaucoma
-Trauma
-Hypermature inflexible cataracts

196

How does chronic glaucoma lead to lens luxation?

Glaucoma -> rupture of the zonules -> subluxation

197

Which dog breeds are more prone to primary lens luxation?

-British terrier breeds eg Jack Russell, Lancashire Heeler, Tibetan Terrier
-Primary abnormality of the zonule -> subluxation -> luxation

198

Give the clinical signs of primary anterior lens luxation

-Sudden onset poor vision
-Glaucoma
-Some degree of anterior uveitis
-In time: focal sub-central corneal opacity

199

Give the clinical signs of primary posterior lens luxation

-Iridodonesis (vibration of iris with eye movement)
-Deep anterior chamber
-Edge of lens may be visible
-Lens may fall out of sight (to floor of vitreous cavity)
-Aphakic crescent may be visible at early stage (visible gap between edge of lens and pupil margin due to lens moving to one side)

200

How would you manage lens luxation?

-Lens removal
-Carbonic anhydrase inhibitors (eg Trusopt/Azopt) and topical steroids will buy time
-Posterior luxation doesn't usually cause glaucoma so the lens can be left ventrally in the vitreous
-Sub-luxation: best to remove lens

201

What is a cataract?

Any opacity of the lens

202

Does a cataract affect the pupillary light reflex?

No

203

Describe the pathogenesis of cataracts

-Disruption of fibre (cell) arrangement
-Accumulation of insoluble proteins
-Oedema due to accumulation of osmotically active substances

204

What are the classifications of cataracts?

-Hereditary
-Congenital
-Diabetic
-Seondary to uveitis
-Trauma (blunt or penetrating)
-Spontaneous/senile/idiopathic

205

What are the classifications of stages of development of cataracts?

-Incipient=earliest stage, small opacities only
-Immature=more extensive opacities, good tapetal reflex
-Intumescent=rapidly developing, may swell sufficiently to obstruct drainage and/or leak lens protein -> uveitis
-Mature=total opacity, no fundic reflex
-Hypermature=lens may contract -> wrinkled surface, may leak protein -> uveitis, may become so inflexible -> rupture of zonular fibres

206

What is the most common cause of intumescent cataracts?

Diabetes

207

How would you distinguish nuclear sclerosis from a cataract?

-Affects the nucleus only
-Does not noticeably affect vision
-No opacity is present on distant direct ophthalmoscopy (although there may be a refractile ring around the nuclear outline)

208

Nuclear sclerosis affects dogs of what age?

7yrs +

209

How would you recognise nuclear sclerosis?

-Blue/grey pearly opalescence of nucleus caused by a condensation of the nucleus

210

How would you identify a diabetic cataract?

-Wet appearance to cataract, sometimes with clearer zones along the suture lines
-Total cataracts
-Impaired vision
-Can get lens-induced uveitis
Lens can rupture

211

How is pupillary light reflex related to vision?

It's not- a blind animal can still have a positive PLR

212

How do you manage cataracts?

-Phacoemulsification: delivers high frequency US to fragment the cataract so it can be aspirated, all through a tiny incision
-Specialist procedure

213

Give some desirable conditions for cataract surgery

-Significantly impaired vision
-No history of impaired vision before the cataracts
-Patient should ideally be easy to handle
-Good pupillary light reflex (indicating normal retinal function)

214

What is the vitreous comprised of?

-98% water
-Collagen
-Hyaluronic acid

215

What are persistent hyaloid remnants?

-In the embryo, the hyaloid artery extends from the optic disc to the posterior lens to provide a good blood supply to the developing lens
-Parts of the hyaloid system may persist in adults
-Appears as a vermiform appendage on posterior lens/projects from optic disc to a complete remnant which may contain blood

216

Are persistent hyaloid remnants of clinical significance?

No

217

What is PHPV?

-Persistent hyperplastic primary vitreous
-Hyaloid system may persist and undergo hyperplasia
-Dogs are born with a vascular mass around posterior lens, posterior cataracts, and lens rupture
-Congenitally poor vision

218

How would you recognise asteroid hyalosis?

-Numerous minute opaque spheres in a gel vitreous
-Older dogs

219

Asteroid hyalosis may be seen in the presence of which other conditions?

-Tumours
-Systemic hypertension
-May be an otherwise normal eye

220

How many layers does the retina have?
What are they?

-2
-Neuroretina: light-sensitive (rods and cones) and integrating layer
-Retinal pigment epithelium

221

How does the inner retina receive its blood supply?

Retinal arteries and veins

222

How does the outer retina receive its blood supply?

Choriocapillaries across the retinal pigment epithelium

223

What are the functions of the retinal pigment epithelium?

-Phagocytosis of discarded discs from rods
-Delivery of nutrients to the photoreceptors

224

What is the choroid?

A very vascular and pigmented layer between the retinal pigment epithelium and sclera

225

Which cells make up the neuroretina?

-Outermost layer= rods and cones
-Inner retina= ganglion cells (axons comprise the optic nerve)

226

What is the function of the tapetum?

Aid vision in low light conditions, by reflecting light which has passed through the retina back onto the photoreceptors for additional stimulation ensuring optimal use of available light

227

The sclera consists mostly of what?

Collagen

228

Where is the tapetum in relation to the optic disc?

Dorsal

229

How long after birth does it take for the tapetum to gain its adult colour?

10-12 weeks

230

What is the only instance where hyper-reflectivity of the tapetum is normal?

Some dogs have a hyper-reflective crescent/cone around the optic disc where the retina is thinner= conus

231

Describe hyper-reflectivity of the tapetum

If the retina is atrophic (thinner), the tapetum is seen through a thinner layer than normal so appears brighter and more metallic

232

When does vascular attenuation of the retina occur?

Secondary to retinal degeneration as the metabolic demands of the reduced tissue mass decline

233

Describe the different kinds of retinal haemorrhage

-Sub-retinal haemorrhage appears as small dark round spots
-Superficial retinal haemorrhage is streaky and radial as it follows the nerve fibre layer
-Pre-retinal (intra-vitreal) haemorrhage settles under gravity and assumes a boat shape

234

How would you recognise retinal detachment?

Appears as billowing grey folds with blood vessels on the surface progressively out of focus

235

What is GPRA?

-Generalised progressive retinal atrophy

236

Which breeds are most affected by GPRA?

-English cockers and miniature poodles
-Middle-aged
-Prone to secondary dense cataracts

237

What are the clinical signs of GPRA?

-Night-blindness/fear of the dark -> day and total blindness
-Later stages may be accompanied by cataracts

238

Give the ophthalmoscopic signs of GPRA

-Generalised hyper-reflectivity followed by vascular attenuation as the retina atrophies
-Non-tapetal fundus undergoes a blotchy depigmentation

239

Collie eye anomaly affects which breeds?

Rough collie, sheltie, border collie, smooth collie

240

What is collie eye anomaly?

-Hypoplasia/dysplasia and hypopigmentation of the RPE and choroid in the area lateral to the optic disc
-Non-progressive

241

How does collie eye anomaly appear ophthalmoscopically?

Pale patch with abnormal choroidal blood vessels against the white of the sclera

242

When does retino-choroiditis occur?

With distemper and toxoplasmosis

243

How does retinitis appear?

-As circumscribed grey dull areas
-Result of oedema and inflammation
-In time, the retina in these areas is destroyed giving circumscribed areas of hyper-reflectivity and abnormal pigmentation

244

Retinal haemorrhage may be seen with which conditions?

•Coagulopathies
•Hypertension
•Septicaemia
•Hyperviscosity syndrome (plasma cell myeloma)
•Leukaemia
•Trauma
•Sometimes in association with retinitis
•In association with retinal detachment

245

How does hypertension affect the retina?

-Retinal haemorrhages
-Papilloedema
-Retinal detachment

246

Give the clinical signs of SARD (sudden acquired retinal degeneration)

-Sudden onset loss of vision
-Bilaterally dilated fixed pupils
-Ophthalmoscopically normal eye

247

What is the cause of SARD?

Toxins

248

What is the prognosis for SARD?

-No treatment
-Permanent total blindness is inevitable

249

Describe papilloedema

-Oedematous sweling of the optic disc due to increased intra-cranial pressure, hypertension or pressure on the retro-bulbar optic nerve (eg by tumour)
-Disc appears swollen, indistinct outline

250

Give the clinical signs of optic neuritis

-Similar appearance to papilloedema (swollen optic disc)
-Sudden loss of vision
-Fixed dilated pupils

251

How do you treat optic neuritis?

-High doses of systemic steroids for several weeks is sometimes effective if started early
-Long-term prognosis is guarded

252

When does atrophy of the optic nerve occur?

Usually as a result of advanced retinal degeneration

253

How does the optic disc apear with optic atrophy?

Either small and pale (due to decreased blood flow) or small and dark (due to demyelination)

254

What is meant by the orbit?

The anatomical region containing the eye, optic nerve, lacrimal gland, extraocular muscles and associated nerves and blood vessels

255

The bony orbit is complete laterally by what?

Orbital ligament (runs from frontal to zygomatic bone)

256

How may nasal tumours enter the orbit?

Through the medial wall of the orbit, which is very thin where it overlies the ethmoturbinates

257

Where is the lacrimal gland situated?

Deep to the orbital ligament

258

Where is the zygomatic salivary gland situated?

In a recess of the maxilla, rostroventral to the globe

259

Give some clinical signs of orbital disease

-exophthalmos
-protrusion of the nictitating membrane
-strabismus
-orbital swelling
-conjunctivitis/chemosis
-lagophthalmos
-pain or difficulty in opening the mouth

260

Give some differential diagnoses of retrobulbar swellings

-retrobulbar abscess/cellulitis
-retrobulbar neoplasia
-masticatory myositis

261

Describe the clinical history of a dog with a retrobulbar abscess/cellulitis or masticatory myositis

Sudden onset retrobulbar swelling with pain and difficulty opening mouth

262

Describe the clinical history of a dog with a retrobulbar neopasia

Gradual onset retrobulbar swelling with slow progression and little pain

263

How can you distinguish between exopthalmus and buphthalmos?

-Buphthalmos (enlarged globe) is more obvious from in front but causes little anterior displacement when viewed from above
-Exophthalmos (protrusion of globe) is more obvious from above than in front
-Try retropulsion of globe (simple pressure through upper lid)- little resistance with buphthalmos, but considerable resistance with exophthalmos caused by a retrobulbar mass

264

What does a unilateral retrobulbar swelling suggest?
What about bilateral?

-Unilateral: neoplasia or abscess
-Bilateral: myositis

265

What does exophthalmus with a deviation of the globe (squint, strabismus) indicate?

Focal mass eg tumour deviating the eye to the opposite direction

266

What does exophthalmus without a deviation of the globe indicate?

Abscess or masticatory myositis

267

Give the clinical signs of a retrobulbar abscess/cellulitis

-Sudden onset pain, swelling, exophthalmos, pain and difficulty in opening the mouth and reluctance to eat
-Conjunctivitis, ocular discharge, exposure keratitis and protrusion of the third eyelid are secondary signs

268

Give some possible causes of retrobulbar abscess/cellulitis

-Penetration of the skin/oropharynx with/without a foreign body
-Extension from sinus/tooth root infection
-Most cases:idiopathic

269

How do you treat a retrobulbar abscess/cellulitis?

-Broad spectrum antibiotics for 3-4 weeks
-Lubricant for cornea
-Good prognosis

270

Where may retrobulbar tumours arise from?

-Within tissues of the orbit
-Extension from nasal neoplasia

271

What is the most common retrobulbar neoplasia type?

-Optic nerve meningioma
-Grows as a partly-mineralised mass surrounding the optic nerve

272

Give the clinical signs of retrobulbar neoplasia

-Exophthalmos
-Swelling and protrusion of the nictitating menbrane
-Often deviation of the globe
-Difficulty repelling globe into orbit
-Check nasal air-flow and other evidence of nasal neoplasia

273

How do you treat a retrobulbar neoplasia?

-Some focal masses can be removed with the eye
-(rare to be able to remove an orbital tumour and retain a fully functional eye)
-Some conditions eg inflammatory masses, mast cell tumour and lymphoma can be treated medically, hence do tissue histology where possible

274

Give the clinical signs of extraocular myositis

-Bilateral swelling of the retrobulbar tissues -> exophthalmus and obvious 'bulging eyes'
-If untreated, the muscles may fibrose -> strabismus

275

How do you treat extraocular myositis?

Oral steroids (taper off gradually)

276

Extraocular myositis affects which kinds of dogs?

Young dogs of larger breeds (about a year old)

277

Is any treatment required for enophthalmos?

(Abnormally deep globe position)
No

278

Give some causes of enophthalmos

-Horners syndrome
-Retraction of a painful eye
-Normal in some nreeds eg rough collie

279

Give some causes of phthisis bulbi

-Primary or secondary glaucoma
-Severe intraocular inflammation
-Severe penetrating/blunt trauma

280

How do you treat phthisis bulbi?

Untreatable

281

How does prolapse of the globe occur?

-RTA
-Dog attack
-Trauma by man

282

Which changes occur with prolapse of the globe?

-Traction on the optic and other nerves and blood vessels
-Immediate oedema of conjunctiva and globe
-Lids go into spasm behind the equator -> reduction becomes more difficult and increases oedema and congestion

283

How should you respond to a prolapsed globe?

-True emergency
-Attempt to replace the globe immediately (apply pressure on eye surface with wet cotton wool, hold eye in a more normal position until permanent repair can be made)
-Lubricate cornea
-Aneasthetise patient
-If simple reduction not feasible: lateral canthotomy/ traction sutures/ Alliss forceps on lid margin while gently repelling globe
-Once prolapse is reduced, suture lids together for 14 days
-Give systemic corticosteroids and antibiotics

284

What is the prognosis like for prolapse of the globe?

Guarded

285

Prolapse of the globe may cause traction damage to which structures?

-Optic nerve -> blindness
-Trigeminal nerve -> desensitised ocular surface
-Medial rectus muscle -> avulsion and lateral strabismum

286

What does buphthalmos imply?

-Severe irreversible damage and a blind eye

287

How does chronic glaucoma affect sight?

Irreversible retinal and optic nerve damage therefore no communication between eye and brain -> blind

288

Briefly describe how you'd carry out an enucleation

1. Clamp the lids with Allis forceps
2. Use an assistant to help manoeuvre the eye
3. Cut the canthal ligaments
4. Work close to the sclera and cut all attachments to the eye
5. Cut optic nerve
6. Place a continuous suture in the tissue deep to the lids

289

Which eyelid tumour is most common in cats?

-Squamous cell carcinoma
-Usually ulcerative/erosive or nodular
(Lid tumours in general are uncommon)

290

'Cat flu' is caused by which agent?

-Feline herpes virus
-Causes severe conjunctivitis and respiratory tract infection
-Can lead to ulceration and perforation in young cats

291

Hpw do you treat 'cat flu'?

-Famiciclovir (Famvir)
-Young cats: also clean the eye, broad-spectrum antibiotics, adequate diet
-Surgery may be required for serios ulcers

292

How may chlamydophila present?

-As part of a respiratory tract infection or as conjunctivitis alone
-All ages of cats

293

How do you treat chlamydophila infection?

Oral doxycycline or synulox (amoxycillin)

294

What is symblepharon?

-Permanent adhesions of conjunctival surfaces following inflammation, particularly herpes infection in young cats (herpes -> ulceration of cornea and conjunctiva -> adhesions)
-3rd eyelid may be permanently protruded

295

Is symblepharon usually treated?

No as doesn't seem to cause a serious problem

296

Which kind of cats have poor tear drainage?

Brachycephalics

297

Corneal sequestrum is unique to which species?

Cat

298

How would you recognise a corneal sequestrum?

-Black plaque on the cornea following a non-healing ulcer
-Black material= sequestered necrotic corneal stroma
-Plaqu acts as a foreign body -> irritation

299

What causes a corneal sequestrum?

Chronc injury eg a non-healing ulcer

300

How do you treat a corneal sequestrum?

-May eventually slough spontaneously if undermined by granulation tissue
-Most require surgery: superficial keratectomy to remove the sequestrum
-Reconstruction eg grafting may then be required

301

How would you describe eosinophilic keratosis in the cat?

-A proliferative pale pink irregular mass of inflammatory tissue advancing across the cornea, often with a thick white discharge
-May be uni- or bilateral

302

How do you treat eosinophilic keratitis in cats?

Topical steroids (reduce over several weeks)

303

Where does the herpes virus of cat flu remain dormant?

Trigeminal ganglion

304

How may herpes virus affect adult cats?

-Ulcerative keratitis without conjunctivitis or respiratory infection
-Superficial dendritic or serpentine pattern in eye

305

How do you treat herpatic ulcers in adult cats?

Debridement and lubrication alone are ususally successful

306

Anterior uveitis in the cat is an indicator of what?

Systemic/viral disease inc FIV, FeLV, FIP, tuberculosis, toxoplasmosis

307

Retinal vasculitis in the cat is very suggestive of what condition?

FIP

308

What is the most common form of uveitis in the cat>

Lymphoplasmacytic

309

Which kinds of cats does lymphoplasmacytic uveitis occur in?

Male, older, outdoor or ex-stray, often FIV+ve

310

What has been implicated as the cause of lymphoplasmacytic uveitis?

Bartonella but cause unproven

311

How would you recognise lymphoplasmacytic uveitis?

-Chronic uveitis with grey lymphoid nodules in the iris and keratic precipitates on the deep cornea
-May also be clouds of particles in the vitreous
-Usually bilateral but not symmetrical

312

Give some possible secondary changes that may occur due to lymphoplasmacytic uveitis

-Glaucoma
-Lens luxation
-Cataracts

313

How would you treat lymphoplasmacytic uveitis?

-May respond to steroids in the early stages
-Doxycyline
-Tropicamide BID/TID (pupil dilator)

314

How does most glaucoma occur in the cat?

Due to obstruction of the drainage angle from acute or chronic anterior uveitis

315

What is the most common intraocular tumour in the cat?

Melanoma

316

What are naevi?

-Two-dimensional areas o fpigment on the iris surface without thickening
-No action required

317

What is the prognosis for intraocular melanoma in the cat?

-Worse than dog
-Metastases more likely
-Consider referral

318

Give a possible consequence of lens luxation in the cat

-Cataracts
-Does not usually cause glaucoma

319

Describe the fundus in tha cat

-Optic disc is circular, dark grey-pink, often some pigment and conus surrounding it
-Vessels do not anastomse on the surface of disc
-Tapetum is yellow-green, bright
-Sub-albuminism is common in white and siamese cats with blue irises

320

Generalised retinal atrophy is hereditary in which cat breeds?

-Siamese and Abyssinian (but not common)
-Photoreceptor degeneration

321

A deficiency in what can cause degenerative retinal atrophy in cats?

-Taurine
-Severe vit E or A deficiency (dogs and cats)

322

How would you identify generalised retinal atrophy in cats?

-Slow progression to complete blindness
-Extreme hyper-reflectivity (-> retinal thinning)
-Vascular attenuation (loss in intensity)

323

Retinal detachment in cats may be associated with which systemic diseases?

-FIP
-FeLV
-Hypertension (eg primary, CRF, hyperthyroidism)

324

Give some presenting signs of hypertension in the eye in cats

-Hyphaema
-Blindness
-Vitreous haemorrhage
-Retinal exudation, haemorrhage and detachment

325

Excess doses of which drug can cause sudden irreversible blindness in cats?
How?
Which dose should you not exceed?

-Enrofloxacin (Baytril) (fluoroquinalone)
-Toxic damage to retina
-Don't exceed 5mg/kg/day, use prolonged courses or give IV

326

Why should you never pull the eye when performing enucleation in the cat?

-Excessive traction to the eye can damage the opposite optic nerve at the chiasm

327

How should you treat a corneal laceration/penetration?

-Mydriatic eg atropine BID to dilate pupil to minimise risk of adhesions, reduce pain and expose lens for examination
-Topical broad-spectrum ABs QID
-Oral broad-spectrum ABs

328

How can a wound with iris prolapse be repaired?

-Excise non-viable iris
-Viable iris should ne irrigated and replaced and cornea sutured (vicryl/monofilament nylon)

329

How many tear duct openings do rabbits have?

-One per eye
-Situated deep in the fornix between the third eyelid and the lower lid

330

What is the usual cause of tear duct infections in rabbits?

Pasteurella spp

331

How do tear duct infections in rabbits present?

-Chronic ocular discharge and secondary corneal inflammation
-Discharge material can usually be milked out of the single tear duct opening

332

Explain the difference between primary and secondary tear duct infections in rabbits

-Primary: manifestaation of uncomplicated pasteurella infection (since pasteurella may ne found in the nasal cavity)
-Secondary: elongation/displacement of tooth roots -> damage tear duct -> chronic inflammation and bacterial infection

333

How do you treat tear duct infections in rabbits?

-Initially: can flush ducts with dilute 1:50 povidone-iodine antiseptic
-Topical and systemic ABs
-Regular flushing of ducts
-In some cases, the inflammation/tooth roots may cause duct stenosis -> incurable

334

What is a conjunctival membrane in rabbits?

-Conjunctiva from the limbus grows over the cornea in a centripetal manner
-Makes cornea appear vascularised and opaque
-Unknown cause

335

How does Encephalitozoan cuniculi affect the eye of rabbits?

-Lens luxation
-Severe chronic reaction -> large solid yellowish mass in one quadrant (looks like a tumour), eventually fills anterior chamber
-Eye is red and painful

336

How do you treat Encephalitozoan cuniculi infection in rabbits?

-Potentially treatable with fenbendazole
-Phakoemulsification to remove lens material and inflammatory mass
-Some result in enucleation

337

What should you do when performing enucleation in rabbits?

-Give IV fluids
Section all anterior attachments before working on posterior globe
-Work as close to eye as possible

338

Why should you be careful when performing enucleation in rabbits?

-Rabbits have large venosu sinuses in orbit
-If these are ruptured, haemorrhage can be profuse and life-threatening

339

What focus would you set the ophthalmoscoep to when looking at the:
-Retina
-Lens
-Anterior chamber
-Ocular surface

-Retina: -1/0/+1
-Lens: +8-12
-Anterior chamber: +12-15
-Ocular surface: +15-20

340

The 'arms length method' of distant direct ophthalmoscopy is useful for identifying what?

-Opacities in the eye (cast a shadow over tapetum)

341

What is the difference between exophthalmos and buphthalmos?

Exophthalmos: normal-sized globe that is being pushed forward by a space-occupying lesion in the orbit eg neoplasia
Buphthalmos: normally-positioned globe that is enlarged due to increased intra-cranial pressure eg glaucoma