Flashcards in SA Ophthalmology Deck (341)
What do the following terms refer to:
-blephar- = lid
-cor- = pupil
-cycl- = ciliary body
-dacryo- = tears
-hyal- = vitreous
-kerat- = cornea
-papilla- = optic disc
-phak- = lens
What is anisocoria?
What is blepharospasm?
Sustained closing or excess blinking of the eye, usually implying pain and hence a variety of possible causes
What is buphthalmos?
"Ox eye"; an enlarged eye due to sustained glaucoma
What is chemosis?
Oedema of the conjunctiva
What is ectropion?
Outward rolling of the lid margin causing conjunctival exposure
What is entropion?
Inward rolling of the lid margin causing trichiasis (skin hairs abrading the eye)
What is endophthalmitis?
Inflammation of all of the interior of the eye, usually implying infection and a poor prognosis
What is enophthalmos?
Abnormally deep position of the eye in the orbit
What is epiphora?
Strictly: poor tear drainage leading to overflow but often used non-specifically for tear overflow of any cause
Where is the equator of the eye?
The area roughly over the ciliary body ie oriented vertically, not horizontally
What is exophthalmos?
Abnormal protrusion of the eye, either acquired or as a "normal" feature in some breeds e.g. Pekes (also called proptosis)
What is hyphaema?
Blood in the anterior chamber
What is hypopyon?
Pus in the anterior chamber, either either settling as a fluid line or in animals more usually as an irregular mass
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"
What is microphthalmia?
An abnormally small eye, may be small but normal or accompanied by other ocular defects
What is miosis?
Abnormal constriction of pupil
What is mydriasis?
Abnormal dilation of pupil
What is panophthalmitis?
Inflammation of all parts of the eye (serious condition)
What is phthisis bulbi?
Shrunken soft "end stage" eye due to severe irreversible damage
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
What is ptosis?
Drooping of upper lid
What is staphyloma?
A defect in the coat of the eye which becomes lined with uveal tissue
What is synechiae?
Adhesion of the iris to adjacent tissues following inflammation
What is trichiasis?
Skin hairs in contact with the eye e.g. in entropion
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).
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
-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
Describe fusidic acid
-Effective against Staph spp (which cause most non-specific conjunctivitis in dogs)
-Not suitable for corneal ulcers
-Very good broad-spectrum inc gram -ves (eg pseudomonas)
Describe Ciprofloxacin and Ofloxacin
-Very broad-specturm antibiotics
Which corticosteroids are most commonly used to treat inflammatory eye conditions?
When should steroids not be used?
To treat corneal ulcers (except for rare conditions)
What is Maxitrol?
-Useful for symptomatic treatment of dry eye
What is cyclosporin used for?
-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
When are NSAIDs typically used?
When should they be avoided?
-Mostly pre-cataract surgery
-Don't use on corneal ulcers
What are mydriatics?
-Dilate the pupil
-Indicated for treatment of uveitis and for lens and fundus examination
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
What kind of drug is tropicamide?
-Mydriatic (dilates the pupil)
-Lasts 4-6 hrs
-Aids fundus and lens examination
Which drugs are used to treat glaucoma?
-Dorzolamide and brinzolamide: topical carbonic anhydyrase inhibitors
-Latanoprost and travoprost: topical tx
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
Give some examples of lubricants
-Lubrithal gel (4-6 times daily)
-Lacrilube ointment (longer duration than gel/drops)
-Artelac gel with added lipid
Which muscle encircles the lid margin and acts to close the eye?
What is it innervated by?
-Innervated by facial nerve (CNVII)
Which muscles raise the upper eyelid?
-Levator palpebrae superioris (occulomotor nerve, CNIII)
-Muller's muscle (smooth muscle, sympathetic innervation)
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
What is the tarsal plate?
-A fibrous plate which stiffens and stabilises the lid margins in the terminal 4-5mm
-Tarsal glands found here
Do animals have eyelashes?
Only on upper lid
Do eyelids heal well?
-Yes as they have a very good blood supply
-Also therefore resist infection and necrosis
Which sutures should you use around the eye?
-5/0 (dogs) or 6/0 (cats) vicryl or Polysorb for skin closures
How much hair should you clip for the following procedures:
-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)
How do you prepare the surface of the eye before surgery?
Non-lathering aqueous povidone-iodine at a dilution of 1:50
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
What is distichiasis?
-The growth of hairs from the tarsal gland openings on the lid margin -> can irritate the cornea
How could you determine whether or not distichiasis hairs are irritating the dog?
Look for excess tear production and an increased blink rate
What are the treatment options for distichiasis?
-Plucking (waste of time)
Which dog breed is more prone to irritating distichiasis?
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
Give the clinical signs of conjunctival (ectopic) cilia
-Often severe blepharospasm with refusal to open eye
-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
Conjunctival (ectopic) cilia occur mostly on which lid?
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
Entropion typically affects which dogs?
-Gundogs and larger breeds
-Assumed to be inherited
-Typically young dogs
Give the clinical signs of entropion
-Pain and watering of the eye (typically lateral lower lid)
-Corneal damage and ulceration can occur
When can entropion be secondary?
Can be secondary to pain -> retraction of globe -> entropion
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
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)
Give some negative features of the eyelids of Shar peis
-Downward angle to upper lid lashes
-Entropion from very young age
-360 degree entropion
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
Which dogs are affected by medial entropion?
-Displaces the lower nasolacrimal duct opening -> poor tear drainage
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
How do you treat upper lid trichiasis/entropion?
-Stades procedure: excise skin adjacent to lid margin and leave to granulate
What may occur as a result of ectropion?
-Conjunctivitis (through exposure)
-Poor tear drainage certainly occurs
What do most cases of ectropion result from?
Lid is too long
How can you treat ectropion?
Simple wedge excision to shorten the lid (where necessary or requested which is not often)
What is the most common eyelid tumour in the dog?
-Arises from the tarsal/Meibomian glands and grows as a well-defined mass
-Benign, low metastsic risk
How do you treat a sebaceous epithelioma?
Local excision usually curative as low metastatic risk
What % of the eyelid can be removed before distortion occurs?
When suturing the eyelid, where should you place the sutures?
-Holds best in the tarsal plate
-Knots must never contact the cornea
Which suture method is best for lid margin closure?
Figure of eight (takes the first knot away from the lid margin)
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)
Do dogs scratch their eyes when they have eye pain/irritation?
No- likely to be a dermatological problem in the peri-ocular skin
Why is the deep surface of the nictitating membrance red and roughened?
Due to presence of numerous lymphoid follicles
What are the functions of the 3rd eyelid?
-Tear film distribution
How can you protrude the 3rd eyelid?
Apply gentle pressure to the globe through the upper lid
How can you examine the deep surface of the 3rd eyelid?
-Local anaesthetic drops, pick up leading edge with forceps
-May need sedation/anaesthetic
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)
-Any condition causing pain and retraction of the globe
-Loss of retrobulbar fat
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
What is 'cherry eye'?
Prolapse of the third eyelid gland (nictitans gland)
Which dog breeds are more prone to 'cherry eye'?
Bulldogs, beagles, some giant breeds
How do you treat 'cherry eye'?
-Gland is buried (but preserved) in a fold of conjunctiva and sub-conjunctival tissue
Excision of gland:
-Lose 30% of tear capacity so is not recommended
Kinking of the 3rd eyelid typically occurs in which dogs?
Young dogs of larger or giant breeds
Give the clinical signs of kinking of the 3rd eyelid
Variable degree of prominence of 3rd eyelid, often with conjunctivitis and ocular discharge
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
Plasma cell infiltration of the 3rd eyelid affects which breed?
-Immune-mediated inflammation of the 3rd eyelid
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
How do you treat plasma cell infiltration of the 3rd eyelid?
-Ciclosporin: lifelong treatment
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)
Horner's syndrome is recognised as idiopathic in which breed?
Older Golden Retrievers
Usually spontaneous improvement over a few months
What is the only reason you'd excise the entire nictitating membrane or leading edge?
Which cells does the conjunctiva contain?
Goblet cells - contribute to the mucus fraction of the tear film
How would you recognise conjunctivitis?
Diffuse redness on all surfaces
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
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
Which pathogen is the most common cause of non-specific conjunctivitis?
How would you treat non-specific conjunctivitis?
-Fusidic acid once daily (antibiotic)
-Or gentamycin/chloramphenicol (broad-spectrum antibiotics)
How would you recognise follicular conjunctivitis?
-Numerous lymphoid follciles appearing as circular raised pink swellings
-Mild/no irritation, no purulent discharge
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)
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
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
-Mucopurulent ocular discharge (green/yellow)
Which dog breeds are more prone to keratoconjunctivitis sicca (dry eye)?
-English cocker spaniel
-Brachycephalics esp bulldogs but including CKCS
How can you diagnose keratoconjunctivitis sicca (dry eye)?
-Schirmer tear test strips (measure tear flow for > 1 min)
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)
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)
How many nasolacrimal puncta are there?
2 on each eye, visible as fine slits situated inside the lids near the medial canthus
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)
Why may a fluorescein flush test be negative in brachycephalics?
Have caudal drainage into the pharynx
Which breeds are more prone to congenital micropuncta and imperforate puncta?
Golden retrievers and cocker spaniels
What are the clinical signs of tear drainage problems?
Tear overflow without pain
What is dacryocystitis?
-Infection and inflammation of the tear duct as a result of a foreign body which may be visible at the punctum
-May be the primary cause of a persistent unilateral conjunctivitis
How can you treat epiphora (tear overflow) due to permanent naso-lacrimal duct obstruction?
-Bypass surgery to the nose or mouth
-Difficult, rarely justified
What are the 4 layers of the cornea?
-Collagenous stroma (fine collagen fibrils arranged in lamellae -> transparent appearance)
-Descemet's membrane (acellular)
-Endothelium (pumps fluid out of cornea into aqueous)
Which cranial nerve innervates the cornea?
Ophthalmic branch of trigeminal
How does the cornea obtain its nutrition?
-From the tear film, perilumbar capillaries and aqueous
Why is the normal cornea transparent?
-Precise arrangement of collagen fibrils in stroma
Which factors can disturb the lamellar arrangement of the collagen fibris in the stroma?
What does this result in?
-Other infiltrates (eg lipid, calcium)
-Results in opacity of cornea
What is a corneal ulcer?
A full-thickness defect in the epithelium
Why should corneal ulcers always be taken seriously?
-Potential for deeper progression and full-thickness perforation
How do you diagnose a corneal ulcer?
-Fluorescein (stains the stroma green)
-The flush with saline
What are the clinical signs of a corneal ulcer?
-May not all appear as a deep crater (if quite superficial)
What does a clear, non-fluorescein-staining area in the centre of a positively staining cornea represent?
-Check for perforation (the anterior chamber collapses to a potential space between the iris and cornea)
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
How do corneal ulcers heal?
From the outside in
Why may a corneal ulcer be fluorescin-negative?
-Down to Descemet's membrane
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)
Why is chloramphenicol not used to treat corneal ulcers?
-Not active against gram -ves (which can infect deeper ulcers -> melting)
Which antibiotics can you use to treat a corneal ulcer?
Why is Isathal (fusidic acid) not used to treat corneal ulcers?
Active against staphs only (gram -ves are what cause deeper infection)
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)
Why should you never use steroids on a corneal ulcer?
-Predispose to infection
-Inhibit epithelial healing
-Potentiate the action of collagenases -> melting
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)
Why should you not use topical NSAIDs on corneal ulcers?
Associated with stromal melting
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
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
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)
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
Which dog breeds are more at risk of indolent ulcers>
How would you identify an indolent ulcer?
-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
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)
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
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
How do you remove a dermoid?
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
Which species are more prone to senile corneal endothelial dystrophy?
English springer spaniels and wire-haired fox terriers
How would you recognise lipid depositions?
Milky or crystalline appearance
What is pannus?
-Inflammatory and vascular tissue advances across the cornea, always from a ventrolateral direction
How do you treat pannus?
Topical ciclosporin (bid) or topical steroids 6x daily for first week, then reduce over several weeks
What does the anterior uvea consist of?
Iris and ciliary body
What is the posterior uvea?
What is special about the uvea?
Is the most vascular, most pigmented, and most immunologically reactive tissue in the eye
What is the function of the iris?
Controls the amount of light entering the eye
Which nerves innervate the dilator and constrictor muscles of the iris?
-Dilator: sympathetic nerves
-Constrictor: parasympathetic portion of occulomotor nerve
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
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
What is anterior uveitis?
Inflammation of the iris and ciliary body
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
Why does aqueous flare occur with uveitis?
-Breakdown of blood-aqueous barrier -> protein release -> aqueous no longer clear
Give some possible causes of anterior uveitis
-Corneal injury and ulceration
-Release of antigenic lens protein
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
What is 'iris bombe'?
Ballooning forward of the iris tissue
Which is the only species to have myelinated nerve fibres in the fundus?
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
Give some differential diagnoses for masses in the anterior uvea
-Ciliary body adenoma
-Others inc lymphoma, metastatic tumour
Where do uveal cysts arise from?
-Posterior surface of iris or from ciliary body
-They break free and move into the anterior chamber
What do uveal cysts look like?
-Transilluminate (let light through)
Which dog breeds are most prone to uveal cysts?
Middle-aged labradors and staffies
Do you treat uveal cysts?
What is the most common intra-ocular neoplasm in all species?
Anterior uveal melanoma
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
How would you treat an anterior uveal melanoma?
Enulceation usually curative
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
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
How do you treat ciliary body adenomas?
What is the most common 'metastatic' tumout of the eye?
What is glaucoma?
An abnormal rise in intra-ocular pressure due to a problem with drainage of aqueous
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
Give the clinical signs of acute glaucoma
-NORMAL globe size
-Severe pain and general lethargy
-Mild 'steamy' corneal oedema
-Unresponsive mid-dilated pupil
-Palpably hard globe
Give the clinical signs of chronic glaucoma
-No response to light
-Tears in Descemets membrane (white lines across cornea)
-Variable corneal opacoty, vascularisation and pigmentation
-Visible retinal degeneration and optic disc cupping
-Variable degree in pain
What is the difference in globe size with acute and chronic glaucoma?
-Acute: normal globe size
-Chronic: enlarged globe size
Give the primary causes of glaucoma
-Dysplastic drainage angles, maintain normal pressure for several years -> sudden decompensation -> acute glaucoma
Give some conditions which can lead to secondary glaucoma
-Intumescent and hypermature cataracts
-Trauma and perforated ulcers
-Chronic retinal detachment
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)
How can you medically treat acute glaucoma (non-emergency)?
-Carbonic anhydrase inhibitors eg dorzolamide ('Trusopt') or brinzolamide (Azopt)
How can you surgically treat acute glaucoma?
Laser, cryo etc, to reduce aqueous secretion/improve drainage
How is the lens supported?
By the ciliary body via the zonular fibres which attach at the lens equator
How can you examine the lens?
-Distant direct ophthalmoscopy (light source + magnification)
-Mydriasis often essential (pupil dilation)
How can lens luxation occur?
-Secondary to chronic glaucoma
-Hypermature inflexible cataracts
How does chronic glaucoma lead to lens luxation?
Glaucoma -> rupture of the zonules -> subluxation
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
Give the clinical signs of primary anterior lens luxation
-Sudden onset poor vision
-Some degree of anterior uveitis
-In time: focal sub-central corneal opacity
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)
How would you manage lens luxation?
-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
What is a cataract?
Any opacity of the lens
Does a cataract affect the pupillary light reflex?
Describe the pathogenesis of cataracts
-Disruption of fibre (cell) arrangement
-Accumulation of insoluble proteins
-Oedema due to accumulation of osmotically active substances
What are the classifications of cataracts?
-Seondary to uveitis
-Trauma (blunt or penetrating)
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
What is the most common cause of intumescent cataracts?
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)
Nuclear sclerosis affects dogs of what age?
How would you recognise nuclear sclerosis?
-Blue/grey pearly opalescence of nucleus caused by a condensation of the nucleus
How would you identify a diabetic cataract?
-Wet appearance to cataract, sometimes with clearer zones along the suture lines
-Can get lens-induced uveitis
Lens can rupture
How is pupillary light reflex related to vision?
It's not- a blind animal can still have a positive PLR
How do you manage cataracts?
-Phacoemulsification: delivers high frequency US to fragment the cataract so it can be aspirated, all through a tiny incision
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)
What is the vitreous comprised of?
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
Are persistent hyaloid remnants of clinical significance?
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
How would you recognise asteroid hyalosis?
-Numerous minute opaque spheres in a gel vitreous
Asteroid hyalosis may be seen in the presence of which other conditions?
-May be an otherwise normal eye
How many layers does the retina have?
What are they?
-Neuroretina: light-sensitive (rods and cones) and integrating layer
-Retinal pigment epithelium
How does the inner retina receive its blood supply?
Retinal arteries and veins
How does the outer retina receive its blood supply?
Choriocapillaries across the retinal pigment epithelium
What are the functions of the retinal pigment epithelium?
-Phagocytosis of discarded discs from rods
-Delivery of nutrients to the photoreceptors
What is the choroid?
A very vascular and pigmented layer between the retinal pigment epithelium and sclera
Which cells make up the neuroretina?
-Outermost layer= rods and cones
-Inner retina= ganglion cells (axons comprise the optic nerve)
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
The sclera consists mostly of what?
Where is the tapetum in relation to the optic disc?
How long after birth does it take for the tapetum to gain its adult colour?
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
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
When does vascular attenuation of the retina occur?
Secondary to retinal degeneration as the metabolic demands of the reduced tissue mass decline
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
How would you recognise retinal detachment?
Appears as billowing grey folds with blood vessels on the surface progressively out of focus
What is GPRA?
-Generalised progressive retinal atrophy
Which breeds are most affected by GPRA?
-English cockers and miniature poodles
-Prone to secondary dense cataracts
What are the clinical signs of GPRA?
-Night-blindness/fear of the dark -> day and total blindness
-Later stages may be accompanied by cataracts
Give the ophthalmoscopic signs of GPRA
-Generalised hyper-reflectivity followed by vascular attenuation as the retina atrophies
-Non-tapetal fundus undergoes a blotchy depigmentation
Collie eye anomaly affects which breeds?
Rough collie, sheltie, border collie, smooth collie
What is collie eye anomaly?
-Hypoplasia/dysplasia and hypopigmentation of the RPE and choroid in the area lateral to the optic disc
How does collie eye anomaly appear ophthalmoscopically?
Pale patch with abnormal choroidal blood vessels against the white of the sclera
When does retino-choroiditis occur?
With distemper and toxoplasmosis
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
Retinal haemorrhage may be seen with which conditions?
•Hyperviscosity syndrome (plasma cell myeloma)
•Sometimes in association with retinitis
•In association with retinal detachment
How does hypertension affect the retina?
Give the clinical signs of SARD (sudden acquired retinal degeneration)
-Sudden onset loss of vision
-Bilaterally dilated fixed pupils
-Ophthalmoscopically normal eye
What is the cause of SARD?
What is the prognosis for SARD?
-Permanent total blindness is inevitable
-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
Give the clinical signs of optic neuritis
-Similar appearance to papilloedema (swollen optic disc)
-Sudden loss of vision
-Fixed dilated pupils
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
When does atrophy of the optic nerve occur?
Usually as a result of advanced retinal degeneration
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)
What is meant by the orbit?
The anatomical region containing the eye, optic nerve, lacrimal gland, extraocular muscles and associated nerves and blood vessels
The bony orbit is complete laterally by what?
Orbital ligament (runs from frontal to zygomatic bone)
How may nasal tumours enter the orbit?
Through the medial wall of the orbit, which is very thin where it overlies the ethmoturbinates
Where is the lacrimal gland situated?
Deep to the orbital ligament
Where is the zygomatic salivary gland situated?
In a recess of the maxilla, rostroventral to the globe
Give some clinical signs of orbital disease
-protrusion of the nictitating membrane
-pain or difficulty in opening the mouth
Give some differential diagnoses of retrobulbar swellings
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
Describe the clinical history of a dog with a retrobulbar neopasia
Gradual onset retrobulbar swelling with slow progression and little pain
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
What does a unilateral retrobulbar swelling suggest?
What about bilateral?
-Unilateral: neoplasia or abscess
What does exophthalmus with a deviation of the globe (squint, strabismus) indicate?
Focal mass eg tumour deviating the eye to the opposite direction
What does exophthalmus without a deviation of the globe indicate?
Abscess or masticatory myositis
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
Give some possible causes of retrobulbar abscess/cellulitis
-Penetration of the skin/oropharynx with/without a foreign body
-Extension from sinus/tooth root infection
How do you treat a retrobulbar abscess/cellulitis?
-Broad spectrum antibiotics for 3-4 weeks
-Lubricant for cornea
Where may retrobulbar tumours arise from?
-Within tissues of the orbit
-Extension from nasal neoplasia
What is the most common retrobulbar neoplasia type?
-Optic nerve meningioma
-Grows as a partly-mineralised mass surrounding the optic nerve
Give the clinical signs of retrobulbar neoplasia
-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
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
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
How do you treat extraocular myositis?
Oral steroids (taper off gradually)
Extraocular myositis affects which kinds of dogs?
Young dogs of larger breeds (about a year old)
Is any treatment required for enophthalmos?
(Abnormally deep globe position)
Give some causes of enophthalmos
-Retraction of a painful eye
-Normal in some nreeds eg rough collie
Give some causes of phthisis bulbi
-Primary or secondary glaucoma
-Severe intraocular inflammation
-Severe penetrating/blunt trauma
How do you treat phthisis bulbi?
How does prolapse of the globe occur?
-Trauma by man
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
How should you respond to a prolapsed globe?
-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)
-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
What is the prognosis like for prolapse of the globe?
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
What does buphthalmos imply?
-Severe irreversible damage and a blind eye
How does chronic glaucoma affect sight?
Irreversible retinal and optic nerve damage therefore no communication between eye and brain -> blind
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
Which eyelid tumour is most common in cats?
-Squamous cell carcinoma
-Usually ulcerative/erosive or nodular
(Lid tumours in general are uncommon)
'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
Hpw do you treat 'cat flu'?
-Young cats: also clean the eye, broad-spectrum antibiotics, adequate diet
-Surgery may be required for serios ulcers
How may chlamydophila present?
-As part of a respiratory tract infection or as conjunctivitis alone
-All ages of cats
How do you treat chlamydophila infection?
Oral doxycycline or synulox (amoxycillin)
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
Is symblepharon usually treated?
No as doesn't seem to cause a serious problem
Which kind of cats have poor tear drainage?
Corneal sequestrum is unique to which species?
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
What causes a corneal sequestrum?
Chronc injury eg a non-healing ulcer
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
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
How do you treat eosinophilic keratitis in cats?
Topical steroids (reduce over several weeks)
Where does the herpes virus of cat flu remain dormant?
How may herpes virus affect adult cats?
-Ulcerative keratitis without conjunctivitis or respiratory infection
-Superficial dendritic or serpentine pattern in eye
How do you treat herpatic ulcers in adult cats?
Debridement and lubrication alone are ususally successful
Anterior uveitis in the cat is an indicator of what?
Systemic/viral disease inc FIV, FeLV, FIP, tuberculosis, toxoplasmosis
Retinal vasculitis in the cat is very suggestive of what condition?
What is the most common form of uveitis in the cat>
Which kinds of cats does lymphoplasmacytic uveitis occur in?
Male, older, outdoor or ex-stray, often FIV+ve
What has been implicated as the cause of lymphoplasmacytic uveitis?
Bartonella but cause unproven
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
Give some possible secondary changes that may occur due to lymphoplasmacytic uveitis
How would you treat lymphoplasmacytic uveitis?
-May respond to steroids in the early stages
-Tropicamide BID/TID (pupil dilator)
How does most glaucoma occur in the cat?
Due to obstruction of the drainage angle from acute or chronic anterior uveitis
What is the most common intraocular tumour in the cat?
What are naevi?
-Two-dimensional areas o fpigment on the iris surface without thickening
-No action required
What is the prognosis for intraocular melanoma in the cat?
-Worse than dog
-Metastases more likely
Give a possible consequence of lens luxation in the cat
-Does not usually cause glaucoma
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
Generalised retinal atrophy is hereditary in which cat breeds?
-Siamese and Abyssinian (but not common)
A deficiency in what can cause degenerative retinal atrophy in cats?
-Severe vit E or A deficiency (dogs and cats)
How would you identify generalised retinal atrophy in cats?
-Slow progression to complete blindness
-Extreme hyper-reflectivity (-> retinal thinning)
-Vascular attenuation (loss in intensity)
Retinal detachment in cats may be associated with which systemic diseases?
-Hypertension (eg primary, CRF, hyperthyroidism)
Give some presenting signs of hypertension in the eye in cats
-Retinal exudation, haemorrhage and detachment
Excess doses of which drug can cause sudden irreversible blindness in cats?
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
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
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
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)
How many tear duct openings do rabbits have?
-One per eye
-Situated deep in the fornix between the third eyelid and the lower lid
What is the usual cause of tear duct infections in rabbits?
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
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
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
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
How does Encephalitozoan cuniculi affect the eye of rabbits?
-Severe chronic reaction -> large solid yellowish mass in one quadrant (looks like a tumour), eventually fills anterior chamber
-Eye is red and painful
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
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
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
What focus would you set the ophthalmoscoep to when looking at the:
-Anterior chamber: +12-15
-Ocular surface: +15-20
The 'arms length method' of distant direct ophthalmoscopy is useful for identifying what?
-Opacities in the eye (cast a shadow over tapetum)