Comparative Ophthalmology Flashcards by Elizabeth Orpwood

How long is a phenol red thread test left in the eye for?

How is it measured?

Normal measurement in rabbits?
Birds?

15-60secs

Colour changes from yellow to red

Rabbits 24mm in 15secs
Birds 22mm in 15secs

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How long is a endodontic absorbent paper point test left in the eye for?

How is it measured?

60secs

Measure bent wetted bit

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What is the STT for rabbits?

Phenol red thread test?

5 +/-3 mm/min

24 +/- 4mm/min in 15secs

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What is the STT for birds?

Phenol red thread test?

5 +/-3 mm/min

22 +/- 4mm in 15secs

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What is a more accurate way of measuring a visual pathway in exotics;
Menace or dazzle reflex?

Dazzle reflex

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Do rabbits with mildly or heavily pigmented irides have a poorer response with atropine/tropicamide?

Heavily pigmented irides

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Which drug is used to dilate reptiles eyes?
Birds eyes?

How much?

Why doesn’t tropicamide/ atropine work?

Rocuronium
Rocuronium

0.2-0.4mg, use 20mu l drop

Pupil controlled by striated muscle under voluntary control (not autonomic)

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What is in focus at dioptre or;
0
+10
+20

0 retina
+10 lens and iris
+20 cornea

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What is normal tonometry in rabbits?

13+/-6

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What is normal tonometry in birds?

Owls

20+/-4

11+/-4

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Should a low or high frequency transducer be used in exotics with small eyes?

High (>10Mhz)

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Do rabbits have one or two puncta on each eye?

One

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Is the cornea in rabbits thicker or thinner than dogs?

What size?

Thinner

355mum

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How do rabbit endothelial cells differ from cats and dogs in regards to repair?

Rabbit endothelial cells can regenerate and divide (in dogs/ cats they enlarge to fill gaps)

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What type of fundus does a Lagomorph/ rabbit have?

Where is the optic disc in comparison to the midline?

Do rabbits have a tapetum?

Merangiotic vascular pattern

Dorsal to the midline

No tapetum

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Do rabbits have a tapetum?

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Do rabbits get optic disc cupping easily or not so easily with glaucoma in comparison to companion animals?

Easily

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Do rabbits have a complete or incomplete orbit

Complete

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What glands to rabbits have in the orbit?

Which gland is known as the Hardarian gland?

Lacrimal gland
Accessory lacrimal gland (3 lobes)
Superficial and deep gland of the TEL

Deep gland of the TEL

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Where are meibomian glands in birds?

Don’t have any

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What muscle in birds pulls the TEL membrane to cover the cornea?

Which nerve innervates this?

Pyramidalis muscle

CN VI

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Does the TEL in birds have a gland?

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Which glands does the eye have in a bird?

Lacrimal gland

Hardarian gland

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How many lacrimal puncta does a bird have, one or two?

Two

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Is the avian orbit complete or incomplete?

Incomplete

Which muscle makes up most of the iris in birds?

Striated muscle

Does the Retina in birds have a tapetum? It is avascular so where does it get its nutrition from?

No tapetum Choroid

What is the pecten in birds?

Heavily pigmented and variably pleated highly vascularised fan like structure that projects from the optic nerve head in to the vitreous

What is the % of decussation at the optic chiasm in birds? What does this mean with the PLR?

100% No consensual PLR

What do snakes have instead of eyelids?

Spectacles

What layer of the spectacle is shed during ecdysis? What does it look like just before shedding? Can the snake see during this? Can topical meds penetrate the spectacle?

Anterior layer Cloudy due to thickening and accumulation of fluid between the new surface layer and the layer that will be shed No No

Which glands (2) in reptiles other than snakes secrete tears?

Lacrimal glands | Harderian glands

Which reptiles don’t have a nasolacrimal duct?

Chelonians

How do reptiles other than snakes accommodate the lens? How do snakes do this?

Ciliary body Increased pressure on the vitreous causing forward movement of the lens

Which enucleation technique should be used for rabbits? | Why?

Subconjunctival Orbital plexus can bleed significantly if damaged

What can cause a dramatic periodic exophthalmos in rabbits?

Mass around the jugular vein (thymoma/ thyroxine carcinoma)

Which bacteria are retrobulbar abscesses in rabbits usually caused by? Cause?

Pasteurella Tooth root abscesses

What is the treatment of orbital gland prolapse in the rabbit? Which glands are prone to prolapse?

Replacement and Pocketing of the gland Harderian gland (superficial and deep glands of the third eyelid)

Which species gets conjunctival overgrowth? Name? What is the treatment? Cause?

Rabbits Pseudopterygium/ conjunctival centripetalisation Radial incisions made, conjunctiva sutured to the sclera (Simple excision results in re growth) Unknown

What are the most common bacterial isolates of conjunctivitis in rabbits (2)?

Staphylococcus | Pasteurella

What does treponema cuniculi in rabbits cause? What is the common name? Transmission? Diagnosis? Treatment?

Blepharitis Rabbit syphilis Infected genitals of mother to neonates Spirochete on conjunctival cytology Parenteral penicillins

What is the most common cause of dacryocystitis in rabbits? Treatment?

Dental disease Flushing nasolacrimal duct Dental tx Long term systemic ABs

How is entropion treated in rabbits? What complicates this?

Surgery Blepharitis

How Soon should an ulcer in a rabbit heal?

Within 7 days

Which drug can cause KCS in rabbits? What is the treatment for KCS in rabbits?

Trimethoprim sulfamethoxazole Topical Cyclosporine

What is the diagnosis of eosinophilic keratitis in rabbits? Treatment?

Cytology (but rabbit eosinophils look like heterophils, rabbit neutrophils) Topical steroids +/ cyclosporine

What is the cause of early cupping of the optic nerve in rabbits with glaucoma? Cause? Is treatment effective?

Lack of well formed lamina cribosa Goniodysgenesis No

Rabbits can get lens induced uveitis causing white, vascularised, inflammatory lesions in the iris. What is thought to be the cause of these?

E cuniculi

What are the causes of cataracts in rabbits? Treatment?

Congenital/ hereditary E cuniculi - mother to offspring, only causes a cataract when the it causes the lens capsule to rupture causing lens induced uveitis and cataract. Cataract surgery

What ocular signs does Infraorbital and periocular sinusitis cause in birds? Acute v chronic? Treatment?

Acute - exophthalmos/ strabismus Chronic - Enophthalmos Sinus flushing and surgical debridement

What can microphthalmos cause in birds? Cause of this and anophthalmos?

Recurrent conjunctivitis Hereditary?

What is cryptophthalmus in birds? Cause? Is surgery successful?

Constriction of the eyelid aperture Trauma Inflammation Inherited No usually scar up again

What are the ocular signs of hypovitaminosis A in birds? Other signs? Cause?

Periocular and conjunctival swelling Ocular discharge White plaques in and around the mouth Laboured/ open mouth breathing Nasal discharge + sneezing or dry crusted Nares Exclusive high energy seed diet (esp sun flower seeds)

What does poxvirus cause in birds?

Blepharitis Eyelid oedema Epiphora Irritating at eyelids (need to prevent this - soften scabs with shampoo)

What does knemidokoptes cause in birds? Common name? Treatment?

Scaly leg, beak, eye Scaley leg Ivermectin

What are eyelid swellings in birds likely to be?

Cystic/ inflammatory secondary to sinusitis

Which bird gets one eyed cold (conjunctivitis)?

Pigeon

What is the treatment for cockatiel conjunctivitis? Clinical signs?

Topical chlortetracycline, ophthcycline/ exocin Severe conjunctivitis Chemosis Hyperaemia

What is the cause of Amazon parrot keratitis and Mynah bird keratitis? Clinical signs? Treatment?

Stress and trauma of capture and transport Transient ulcerations/ erosions Self limiting with supportive care

What is the treatment of uveitis in birds?

``` Topical steroids/ NSAIDs Curariform drops (mydriasis) ```

What is the treatment of cataracts in birds? What is the main factor that needs to be taken in to consideration before performing the surgery?

Phacoemulsification Needs to be handleable as needs topical tx up to 6x daily

What is the most common cause of retinal disease in birds?

Trauma

What are the clinical signs of horners syndrome in birds? Diagnosis? Most likely cause?

Only ptosis Phenylephrine Trauma

What does hypovitaminosis A cause in chelonians? Treatment?

Eyelid swelling chemotic conjunctiva Resp issues Oral May not be enough, so IM injections

What can septicaemia in reptiles cause to the eyes?

Conjunctivitis

What can be the cause of a retained spectacle in snakes? Treatment?

Husbandry (low humidity) Ill health Mite- ophionyssus natricis Increase humidity Damn cotton wool

What causes Bullous spectaculopathy? What is it?

Blocked nasolacrimal duct causing tear fluid to build up subspectacular Fluid between cornea and spectacle

What is the treatment of subspectacular abscessation?

Excision of a triangle of spectacle and copious flushing

What is the most common cause of uveitis in reptiles? Treatment?

Gram negative infections (eg. Pseudomonas) Systemic ABs Topical anti inflammatories

What can’t you use tonometry in snakes?

They have a spectacle

What is the iris muscle of mammals? Birds and reptiles? What is needed for mydriasis in birds/ reptiles?

Mammals- autonomic innervation of smooth muscle Birds and reptiles - striated muscle under voluntary control Non depolarising muscle relaxant Rocuronium bromide 0.2-0.4mg/eye

What diopters are used in smaller eyes for; Retina Lens and iris Cornea

0 retina +10D lens and iris +20 cornea

What makes enucleating a rabbit more difficult?

Large retrobulbar venous plexus

What is the annular pad in birds used for?

Nutrition and accommodation

In birds is the fundus vascular or avascular?

Avascular

What does the nasolacrimal gland in chelonians do?

Extra site of salt excretion

Generally reptiles extraocular muscles are poorly developed except which one?

Lizards

Generally reptiles have a well developed retrobulbar muscle except?

Snakes

Generally reptiles have limited rotational movement except?

Chameleons

In which of the following do you get scleral ossicles? Lizards Snakes Chelonians

Lizards and Chelonians yes | Snakes no

Reptiles have an equatorial pad other than which? What does this do?

Snakes Accommodation

What is this?

Exophthalmus Compromise to venous return Thymoma Stress Retrobulbar disease

Periocular swellings in reptiles are normally caused by gram positive or negative barriers?

Gram negative

What can Chelonians get post hibernation? Cause?

White corneal lesions Too fat diet

How many times do rabbits blink?

10-12 blinks per hour