Exotics Flashcards

Question

What congenital conditions of the globe can be present in guinea pigs?

Answer 1

Microphthalmos and anophthalmos Obvious from birth as precocious and born with eyes open Often associated with mucopurulent discharge which builds up in orbit Entropion can occur as globe too small for size of orbit Association between lens and development of globe means often congenital cataracts associated with microphthalmos Clinical management (possibly topical antibiotic if discharge within orbit, entropion - Hotz-celsus)

Answer 2

In turning of eyelid Blepharospasm, epiphora, corneal ulceration May occur secondary to microphthalmos or defect with tarsal plate of lid Can be secondary from irritation of conjunctivitis, KCS, trichiasis Topical anaesthesia to assess if primary or secondary to another cause Hotz celsus can be performed (often only around 1mm needs to be removed as thin delicate lid)

Answer 3

Rex and Texel = thick bristly coats, can get ocular abrasion within 1st hours of life Secondary corneal ulceration/entropion can ensue and further ocular abrasion Petroluem jelly at birth to keep hairs away from eyes Lubrication of eye to relieve discomfort NSAID - keratolac

Answer 4

Similar to dogs - aberrant development of dermal tissue in abnormal place Superficial keratectomy = curative Very little tissue to remove as thin cornea (less than 500um) Magnification essential

Answer 5

Infectious - Chlamydia + Listeria monocytogenes + Salmonella Allergic - poor hay quality/dusty hay Foreign bodies - hay awn Dietary - Vitamin C deficiency - one of the earliest signs

Answer 6

Examine for physical factors/foreign bodies Diet appropriate ?Infectious - topical AB cover treatment trial, sample for bacteriology/PCR

Answer 7

Can normally produce milky white ocular secretion - cell free fluid Differentiate from dacryocystitis - copious white to purulent discharge

Answer 8

Signs of ocular irritation (partial closure of palpebral aperture) Lack of clear sharp reflection of light from ocular surface Potentially mucoid discharge Normal STT 3-12mm/min reported in literature Phenol red test (given small size of eye) - 16-21 = average Unclear if same immune mediated destruction of lacrimal gland as in dogs Topical ciclosporin effective Replacement tears - carbomer based gel

Answer 9

Ocular trauma - hay/grass awn Acute phase - corneal epithelial erosion and sometimes also stromal damage but often little blepharospasm Later changes = scar with inflammatory cell infiltrate and fibrosis Tx = removal of any foreign body, topical AB cover (chloramphenicol) Chronic phase significant scarring - could consider superficial keratectomy (rarely done unless very significant scarring impacting vision)

Answer 10

Fatty eye = deposition of lipid within bulbar conjunctiva - appears as white/pink lesion Flesh eye = pink/red-pink mass in medial canthus (similar to cherry eye) Fatty eye - can be managed by reducing calorific dietary input but reduction in size of lesion will take time

Answer 11

Circular to oval white area in central/paracentral cornea Triglyceride/cholesterol crystals ?Dietary fat plays a role ?Genetic - stromal lipid dystrophy Often no specific treatment - may affect vision being in central axis but often not enough to have significant impact

Answer 12

White lesion at limbus protruding slightly into cornea Often no other ocular changes - IOP often unaffected Ascorbic acid/vitamin C promotes calcium deposition when at high concentrations in tissue Ciliary body secretes vitamin C into the AH potentially to ensure sufficient enough levels in lens to prevent cataract formation. High levels = can lead to calcium build up at limbus causing the heterotrophic bone formation. Most cases = no treatment as often does not impede vision/lead to discomfort ?Tonometry and IOP monitoring

Answer 13

Small nuclear cataracts/posterior subcapsular cortex to full complete mature cataract. Up to 40% have some degree of lens opacity in one study GP require dietary input of ascorbic acid (prevent oxidative changes at heart of many cataracts) - low levels Vitamin C may be associated. Diabetic cataracts also seen in GP ?Phacoemulsification but ?value/ethics

Answer 14

Mydriatics bind to melanin within pigmented irises - less effective in albinos Rodent eyes contain atropinase which degrades mydriatics making less effective - fundoscopy challenging.

Answer 15

90 dioptre with slit lamp 28D lens or 2.2 panretinal lens with indirect headpiece

Answer 16

Very small volume of tear film and lacrimal lake Even 1 drop will overflow eye and lead to nasolacrimal overflow Potential s/e due to systemic absorption

Answer 17

Phenol red STT test strips too large for rodent eye

Answer 18

Often related to mycoplasmal respiratory disease Young animals often more severely affected OR Environmental irritants - ventilation currents in rodent cages may cause airborne suspensions of fine bedding matter (leading to severe keratoconjunctivitis)

Answer 19

Coronavirus associated with ocular irritation with conjunctivitis, periocular swelling followed by sneezing and cervical swelling Usually self limiting - 1-2 weeks but can take longer to clear secondary effects Present within 45% of rat laboratory colonies in UK

Answer 20

Haderian gland Called chromodacryorrhea - diseases such as mycoplasmosis, sialodacryoadenitis, nutritional deficiencies and other physiological stresses are factors that may cause.

Answer 21

Microphthalmos Corneal opacificaition/dystrophies - elliptical paracentral opacifications (basophilic material in sub epithelial stroma) Exposure keratopathy - post GA/surgery most commonly (especially xylazine/ketamine) Glaucoma - often associated with persistent pupillary membranes causing pupil-block glaucoma Persistent hyaloid artery (can be associate with vitreal haemorrhage) Cataracts - often occur spontaneously or secondary to retinal degeneration due to release of metabolic by products

Answer 22

Inherited retinal dystrophies/degenerations Rd gene = albino mice, retinal degeneration and blindness

Answer 23

High amounts of aldose reductase - secondary cataracts

Answer 24

Temporary tarsorrhaphy but poor prognosis for full eye function subsequently

Answer 25

Eyelids - lower more mobile than upper, meibomian glands absent Lacrimal gland inferior and lateral to globe + Haderian gland acting as secondary lacrimal gland at base of nictitating membrane Dorsal and ventral lacrimal punta drain secretions into nasal cavity Nictitating membrane moves across eye - pyrimidalis muscle, posterior sclera, loops through optic nerve in sling via bursalis muscle (quadratus muscle) Orbit = open and occupied predominately by globe EOM not particularly well developed (torsional movements 2-5 degrees only) Close proximity of globe to infraorbital diverticulum of the infraorbital sinus - sinusitis = periorbital swelling, orbital compression, conjunctivitis, exophthalmos or intraocular inflammation. Owls - tubular posterior segment allowing considerably magnified image to be projected onto retina Passerines/Psittaciformes - anterior-posteriorly flattened globe = oblate spheroid with hemispherical posterior segment Cornea = reduced thickness compared to mammals, anterior stroma acellular Scleral ossicles behind limbus - bony structures, firm origin for muscles which allow accomodation (make enucleations more challenging) Shallower anterior chamber than mammals (except owls - can see iridocorneal angle without gonioscopy in owls) Iris = thin, striated muscle (rather than autonomically innervation constrictors/dilator muscles in mammals) - allows conscious control of pupil dilation/constriction, complicates evaluation of PLR Can be used for communication/sexual attraction/signal sexual dimorphism. Pharmacological dilation of pupil more complicated non depolarising muscle relaxants required rather than parasympatholytic drugs (e.g tropicamide/atropine) Decussation at optic chiasm ABSENT in birds - integration of sensory information from each visual field occurs in midbrain. Direct/consensual PLRs redundant in birds. Lens generally soft with annular pad lying under lens capsule in equatorial region allowing considerable attachment between lens and muscles of accommodation (change in focal length) Accommodation - change in focal length of lens produced in ciliary muscles divided in 2 portions - Crampton's muscle (anterior) - originates on sclera beneath scleral ossicles and its contraction flattens cornea at peripheral margin - central bulging increasing refractive power. Posterior = Brucke's muscle = pulls ciliary body forward, lessening tension applied to annular pad by the tenacular ligament from ciliary body.

Answer 26

Can see in 3 colours (red, green, blue) + UV light Exceptional vision Fundus = no blood vessels or choriocapillaris instead have pecten Pecten = protrudes into posterior vitreous and supplies oxygen and nutrients. Continual torsional movements of globe cause pecten to move backwards and forwards within vitreal fluid to diffuse oxygen and nutrients. No tapetum Distinct fovea - increased density of photoreceptors for increased visual resolution

Answer 27

Close proximity of globe to intraorbital sinus and diverticulum = prone Exophthalmos/strabismus of globe - acute phase, space occupying lesion Enophthalmos - chronic condition where sinus collapses due to fibrotic change Avian abscesses = solid caseous material - due to heterophils rather than neutrophils Surgery to resect and remove caseous material - shell out through infraorbital sinus through skin incision below lower eyelid. Needs careful reconstruction. Irrigation may be possible if softer material AB cover based on C+S

Answer 28

Pox virus Range of variation depending on bird - epiphora, lid swelling, proliferative cutaneous growths, ulcerations of eyelids, eyelid oedema, mucopurulent discharge. Fibrosis/scarring- irregular eyelid margin and chronic corneal damage/blindness Prevention of self trauma to prevent scarring = key (dilute baby shampoo around lids - softens scales and makes less irritating) Antiviral medications not effective.

Answer 29

Vitamin A deficiency = periocular and conjunctival swelling with ocular discharge (Other ddx - poxvirus/blepharitis/sinusitis) Consider contributory factor when above disease seen. White plaques in and around mouth, open mouth/laboured breathing, nasal discharge, sneezing, crusted nares, dermal dyskeratosis, feather abnormalities = systemic disease. Vitamin A = key for normal epithelial growth Seed based diet - especially sunflower seeds - dietary deficiency of fat soluble Vit A Long term - dietary change and management Injectable Vit A short term/oral beta carotene Care of periocular area with lubricant/topical AB cover

Answer 30

1. Foreign bodies 2. Infectious disease (usually systemic and associated with septicaemia) - Chlaymdophila, Mycoplasma, Cryptosporidia, M.avium, Poxvirus 3. Sinusitis 4. Hypovitaminosis A

Answer 31

1.. History - other in contacts? New cagemate etc 2. Ophthalmic exam 3. Full PE - is conjunctiviits purely local or other systemic signs 4. Further testing (STT/phenol red), cytology, bacteriology - PCR

Answer 32

Bacterial infection = most common cause avian conjuncitivitis Tetracycline/fluoroquinolone if high likelihood mycoplasma or chlamydophila Systemic + topical AB cover

Answer 33

Blepharospasm, epiphora, self trauma Majority = trauma More chronic non healing ulcers can be seen in older birds - may have basement membrane dystrophy similar to SCCED's in dogs Normal healing time within 1 week Serum can be used for melting corneal ulcers Temporary tarsorrhaphy can be done with sterile non healing corneal ulcers for additional protection

Answer 34

Often full/mature cataracts by time we see Dull/dark homogenous hue to the iris face = lens induced uveitis Also assess for retinal detachment (ocular ultrasound)

Answer 35

Trauma = most common Other ddx - inherited (canaries), age related, dietary deficiency of anti-oxidants Phacoemulsification can be used in larger eyes Irrigation/aspiration in smaller eyes Lens induced/post traumatic uveitis - steroid drops up to 5x daily to reduce intraocular inflammation

Answer 36

Majority Trauma but can be secondary to increased tension on zonules from mature cataract (often larger birds e.g owls with already very spherical lens) Aphakic crescent often visible (subluxation) Often other ocular abnormalities - mature cataracts, lens induced uveitis If only mild inflammation best to leave in place Other option = intracapsular lendectomy/phaco to remove

Answer 37

Scleral ossicles - make accessibility for enucleations more challenging 2 techniques 1. Enlarge palpebral aperture by joining to aural meatus 2. Evisceration - intraocular contents removed and resultant space filled with sphere/gelfoam mesh is possible Evisceration often preferred in birds as easier approach but does make histopath examination of eye difficult compared to an enucleation approach.

Answer 38

Lizards - anterior corneal and posterior orbital segments Cornea = thin stroma but thick Bowman's later devoid of cells and covered by thin epithelium Iridocorneal angle poorly developed Overlapping scleral ossicles (10-14 in lizards) found behind limbus overlying ciliary body and equator of lens (form Ringwulst) bringing lens into contact with ciliary body. Ciliary muscle - Cramptons muscle and Brucke's muslce as in birds - radial and circumferential fibres Snake eyes - covered by spectacle formed from fused transparent eyelids Haderian gland - seromucous fluid between spectacle and cornea Do not have scleral ossicles but fibrous sclera with cartilagenous cap posteriorly Cornea - thin with epithelium of only few layers as spectacle = main defence Chelonians - large lacrimal and Haderian glands compared to other reptiles - marine species help with salt excretion. Predominately cone photoreceptors - oil droplets accentuate colour as in birds

Answer 39

Structure homologous with pineal gland in mammals Histologically similar to conventional eye but an axial mid brain structure is overlain by a dorsal foramen in the skull and translucent skin allowing the parietal eye to play a central role in seasonal physiological and behavioural cycles through light detection in hardwired manner.

Answer 40

Eyelid oedema to more severe eyelid swelling, chemosis of conjunctiva (can be severe and blind animal if obscures globe) Globe can be exophthalmic - orbital glands enlarged through epithelial dyskeratosis Particularly obvious in terrapins as lacrimal/haderian glands take up large space in orbit Tx - address diet Topical tear replacement therapy Topical/systemic antibiosis (cytology showing heterophils/bacteria) - usually fluoroquinolone Vitamin A injections - IM (oral dosing unsuccessful as affect GI epithelium and poor absorption))

Answer 41

Hypovitaminosis A Caiman Pox/Herpesvirus - sea turtles (proliferative/ulcerated lesions) Bacterial blepharitis - Aeromonas infection, pseudomonas, chamydophila Physical irritation - e.g substrate

Answer 42

Discharge and bubble formation at medial canthus Tear overflow/purulent ocular discharge Diagnosis similar to in mammals Systemic antibiosis more effective than topical drop NL flushing difficult due to small size of eye

Answer 43

Spectacle = derived from fusion of the eyelids, closed space in which tears form, circulate and are drained via NL duct. Usually shed with rest of skin (shedding = ecdysis) - becomes oedematous and opaque whilst rest of skin becomes dull. Retention = raised plaque of retained tissue, often opaque in ocular area. Often not noticed until occurred several times when retained eyecaps are multiple. DDx = bullous spectaculopathy, opacity from trauma/infection or subspectacular abscess, neoplasia - keratocanthoma Often seen with incomplete skin shedding in other areas. Underlying problem = husbandry = too low humidity or infestation with snake mite Ophinyssus natricius DO NOT REMOVE WITH FORCE - often remove whole spectacle and leads to severe keratitis with poor prognosis for eye TX - increase humidity, may be enough to remove at next shedding, damp cotton paper in vivarium or soaked cotton wool can help remove. If not working - GA, operating microscope to remove but advise referral to specialist.

Answer 44

Obstruction of NL duct system in snakes = build up of tear film under spectacle leading to enlargement (swelling of this space rather than epiphora) Appearance = protuberant opaque mass or can be transparent where spectacle remains clear Mechanical swelling of spectacle NL obstruction: 1. Congenital - development atresia of duct 2. Acquired physical obstruction - infection/abscess, shed epithelium obscuring duct Can aspirate fluid but will only give temporary relief (done under sedation/GA) - can be useful for bacteriology/C+S, often viscous fluid Standard tx: done under GA Excise triangle ventrally within spectacle allowing continual drainage of tears until the next shed Perform using operating microscope/specialist Often inflammatory rather than infectious obstruction

Answer 45

Abscess forms between spectacle and cornea - yellow mass in ventral subspectacular space or severe cases occupying whole ocular surface. Optimal tx = same as with bullous spectaculopathy - making window in ventral spectacle to allow drainage + irrigation

Answer 46

Corneal ulceration - often trauma related Opacification - pigmentation, lipid, calcium, proteinaceous deposit (Corneal lipidoisis in chelonia - dietary hyperlipidaemia)

Answer 47

Not very common Usually sign of systemic infection/inflammation Main signs = flare, hazy appearance of iris, hypopyon Majority of reptiles = gram -ve bacteria TX - antibiosis (systemically) - often enrofloxacin Topical steroids/NSAIDs for ocular inflammation Atropine ineffective in reptiles - striated muscle (Glaucoma not really reported in reptiles)

Answer 48

Nutritional deficiencies - particularly antioxidants UV illumination in enclosures in captive reptiles Freeze artifact during hibernation (tortoises) Age related change

Answer 49

Congenital abnormality Can affect feeding as high visually motivated feeders Concurrent orbital infections due to lack of filled orbit space May be associated with incubating eggs at too high temperature

Answer 50

Has to be adapted to both aquatic and terrestrial environments. Eyelids - protect ocular surface Harderian gland - tears to moisten corneal surface Globe spherical with cornea and sclera having same radius and curvature Retractor oculi - pulls eye in and down and forms integral part of roof of buccal cavity when swallowing. Iris = thin and well vascularised, striated iridial muscle also autonomous activity allows pupil to constrict directly on light stimulation with contraction (does this even in enucleated eye so care with PLR intepretation)

Answer 51

Risk of toxicity due to systemic absorption through highly permeable skin Fluoroquinolones/chloramphenicol preferred over aminoglycosides - renal toxicity

Answer 52

Inflammatory keratitis or degenerative white opacity (sparser more crystalline appearance than lipid) Intraocular changes - opacification of lens

Answer 53

Lipid keratopathy White opacity of cornea, often protruding from corneal surface DDX - corneal scarring/UV radiation Raised surface and intense white colouration pathognomonic ? more common in females ready to spawn but unable to find appropriate place in captive environment and elevated blood lipid levels for long periods

Answer 54

Fungal infections Chromomycosis and Phycomycosis = skin ulceration wih/without reddening Saprolegnia = fluffy white deposit on skin Treatment = immersion in Malachite Green for periods of 5 minutes/laying gauze swabs soaked in medication over the area but not touching ocular surface.

Answer 55

Often secondary uveitis - systemic gram -ve septicaemia Systemic disease most likely so should be isolated Blood culture/post mortem of any deceased amphibians vital Tx - enrofloxacin s/c or IM once daily or oxytetracycline Rifampicin baths or baths of methylene blue or malachite green

Answer 56

Glaucoma occurs in amphibians secondary to intraocular inflammation. Carbonic anhydrase in amphibians = acid-base regulation and muscle contraction. Drug can be absorbed across skin - severe s/e and risk death so not advised

Answer 57

Enucleation not recommended in amphibians - eye retracted caudally and ventrally when swallows to form dorsal buccal cavity as amphibians do not have a hard palate. Frogs/toads retropulse eye into buccal cavity to provide intraoral pressure for swallowing. Enucleation = great difficulty swallowing and poor QOL ?evisceration and implantation of prosthesis but not been reported.