Wildlife Ophthalmology D R. H E A T H E R R E I D T O R O N T O W I L D L I F E C E N T R E T O R O N T O, O N C A N A D A

Wildlife Ophthalmology D R. H E A T H E R R E I D T O R O N T O W I L D L I F E C E N T R E T O R O N T O, O N C A N A D A

Why understand eyes? Wildlife need to have excellent vision to survive in the wild Eye related problems are common in wildlife admitted to rehabilitation centers

What we will cover Anatomy of the eye Differences between birds and mammals The eye exam Recognizing common problems Prognosis Treatment options When to see the vet

Anatomy Around the Eye: Muscles & nerves Skin Eye lids Nictitating eyelid Conjunctiva & sclera Tear glands & ducts Ossicles (birds)

Anatomy Front of the Eye: Cornea Iris Pupil Ciliary body Anterior Chamber Aqueous humor

Anatomy Back of the Eye: Lens Retina Optic nerve Choroid Pecten (birds) Posterior Chamber Vitreous humor

Fundus of the Eye Mammal Eye Bird Eye

The Avian Eye - Differences Small eye size in most birds and small pupil size makes it hard to examine Can control the size of their pupil Lower eyelid more developed The nictitating membrane spreads the tears allowing birds to blink less Moves horizontally across eye

The Avian Eye - Differences Eyes are not as protected by skull Less muscles around eye so less eye movement Boney ossicles support the eye Three main eye shapes; flat, globose & tubular

The Avian Eye - Differences Four different color receptors compared to the three in mammals means better color detail Can see in the ultraviolet range Higher flicker rate can detect lights that flicker at more than 100 flashes per second (humans detect at 50)

The Avian Eye - Differences In some species the eye color changes with age Red Eyed Vireo Red Tailed Hawk Great Horned Owl

Mammal Eyes Tapetum lucidum Many animals have a special layer at the back of their eye that helps reflect light Improves night vision, helping them see better in the dark Some animals do not have a tapetum such as squirrels, birds, rabbits and primates

Injuries to the cornea are common Can range from scratches and abrasions to punctures into the eye Can determine the depth of the injury by using fluorescein stain The outer layer (epithelium) repels the stain The middle layer (stroma) absorbs it, appearing green Cornea - Structure

Cornea - Structure Flourescein stain Corneal ulcer detected

Eye Exam and Vision Assessment Observe animal Physical exam; include area around eyes Assess reflexes; PLR, palpebral reflexes, menace response Direct ophthalmoscope to assess structures in the front and back of the eyes

Eye Exam and Vision Assessment Pupillary Light Reflex - PLR A reflex that controls the size of the pupil Allows animal to adapt to different levels of light Pupil gets smaller when bright light shines on the retina In mammals there is a consensual PLR opposite eye also constricts

Eye Exam and Vision Assessment Pupillary Light Reflex - PLR Eyes very sensitive to light one pupil can be different size than other Birds have some control over their pupil size In birds there is no consensual PLR PLR assesses the function of the retina and the brain.

Eye Exam and Vision Assessment Measure tear production Measure intraocular pressure

Eye Exam and Vision Assessment Take sample for culture and sensitivity if needed Then stain eyes with fluorescein stain Flush with sterile saline before assessing Use cobalt blue light to better appreciate any stain uptake

Eye Exam and Vision Assessment Slit lamp biomicroscopy Indirect ophthalmoscopy

Eye Exam and Vision Assessment Assessment or Test Physical Exam, examine area around the eyes Pupillary Light Reflex Other reflexes; e.g. palpepral reflexes, menace Culture or cytology (if required) Schwimmwer Tear Test Intraocular Pressure Fluorescein stain Direct ophthalmoscopy Indirect ophthalmoscopy Slit lamp biomicroscopy X-ray skull and orbital area Ultrasound eyes Electroretinography Vision check e.g. obstacle course, live prey testing Can you do it? Yes Yes Yes Yes Maybe No Yes Yes Maybe No Maybe No No Yes

Eye Exam and Vision Assessment Your exam should consist of the below tests as a minimum Can make an exam sheet to use during your eye exam Complicated cases will need to be referred to your veterinarian for further testing Assessment or Test Physical Exam, examine area around the eyes Pupillary Light Reflex Other reflexes; e.g. palpepral reflexes, menace Fluorescein stain Direct ophthalmoscopy Culture or cytology (if required) Vision check e.g. obstacle course, live prey testing Can you do it? Yes Yes Yes Yes Yes Yes Yes

Problems with the Eye The painful eye squinting, swollen, tearing The white or cloudy eye whole eye, partial, front of eye, back of eye The red eye entire eye, around eye, part of eye, front of eye, back of eye Other conditions; trauma around the eye, the missing eye, the blind eye

The Painful Eye

The Painful Eye Quick Differentials: Injury to cornea ulcer Injury to structures around the eye Increased pressure within the eye glaucoma Severe uveitis inflammation within the eye

The Painful Eye Corneal Ulcer Superficial erosion damage to the surface layer Partial thickness ulceration variable depth into stroma Descemetocoele deep ulcer, to the level of Descemet s membrane Perforation right through all layers

The Painful Eye Corneal Ulcer Three questions to answer: Timeline for healing: 1) Why is there an ulcer? 2) How deep is the ulcer? 3) Is it healing as expected? Uncomplicated superficial ulcers should heal within 3-5 days with treatment Deeper ulcers should stop taking up stain within 5-7 days although defect may be visible for longer

The Painful Eye Corneal Ulcer Treatment Corneal ulcers are very painful = pain medication e.g. oral meloxicam There is a risk that it will become deeper and rupture = prevent infection with topical antibiotics Drops vs. ointment

The White or Cloudy Eye

The White or Cloudy Eye Quick Differentials Corneal edema from injury to cornea or uveitis Scar tissue on cornea from injury to cornea Hypopyon = pus in the front of the eye Cataracts lenses are not clear Uveitis inflammation in the front of the eye

The White or Cloudy Eye Corneal edema Cornea becomes leaky and water enters Causes include corneal ulcers, trauma, uveitis, glaucoma Treat the underlying cause!

The White or Cloudy Eye Cataracts Four main causes: Congenital Trauma Geriatric Disease

The White or Cloudy Eye - Cataracts Treatment is surgery to remove the lens In wildlife it is very difficult to replace the lens so vision is compromised Solution for animals that don t rely on perfect vision

The White or Cloudy Eye - Cataracts Exceptions: Very young darkeyed owls have naturally bluish lenses that become clear as they age Dehydrated baby squirrels may have cloudy lenses that resolve once rehydrated

The White or Cloudy Eye - Uveitis Inflammation of the front of the eye Symptoms: pain, squinting, redness, aqueous flare, small pupil size, changes to iris color

The White or Cloudy Eye - Uveitis Causes Infection viral, bacterial, fungal Blunt trauma can lead to leaky vessels Other cancer, problem with the immune system, unknown cause, breed related (dogs) Principle of therapy Treat the underlying cause e.g. topical antibiotics Treat the inflammation topical or oral steroids Treat the pain topical or oral pain medication

The White or Cloudy Eye - Uveitis Use steroids with caution! ALWAYS use fluorescein stain to make sure there is no corneal ulcer present Steroids interfere with ulcer healing so DON T USE if an ulcer is present Can use topical NSAIDs instead Many antibiotic & steroid combinations available

The White or Cloudy Eye - Uveitis Open up the pupil Pupil is often very small because the iris muscle is in spasm Painful and interferes with normal fluid movement in the eye affecting the eye pressure Dilate the pupil (in mammals) with atropine, tropicamide or phenylephrine drops. More drastic solution is a subconjuctival injection of these agents (by veterinarian)

The Red Eye

The Red Eye Quick Differentials Hyphema = blood in the front of the eye Retinal hemorrhage blood in the back of the eye Conjunctivitis inflamed conjunctiva around eye Glaucoma / uveitis inflamed tissue in and around the eye

The Red Eye Hyphema Blood in the Front Eye Blood in the anterior chamber Most common cause is trauma May be difficult to see all structures in eye May need to wait for clot to form and resolve Ultrasound is an option

The Red Eye Retinal Hemorrhage Blood in the Back Eye Blood in back of eye in the posterior chamber Causes include trauma, clotting disorders, infection, tumor Often see bleeding around pecten in birds after trauma Danger of retinal detachment

The Red Eye Blood in the Eye - Treatment Topical steroids if corneal ulcer not present (stain eye!) Topical NSAIDs if ulcer is present Topical atropine (mammals) if uveitis present and normal eye pressure Poor prognosis if bleeding continues or recurs, in cases of glaucoma, or if retina detaches

The Red Eye Conjunctivis Conjunctiva is the tissue that lines the inside of the eyelids and the white part of the eye Conjunctivitis is an inflammation of these tissues Swelling is also present Irritating but not painful

The Red Eye Conjunctivis - Bacterial Purulent discharge from eyes, can crust shut if extreme Treatment: topical antibiotic NO steroids can make infection worse Culture if not responding to treatment

The Red Eye Finch Conjunctivis Common infectious disease of finches Caused by Mycoplasma gallisepticum Primarily a respiratory problem Treatment is topical antibiotics - ciprofloxacin and oral tylosin in the drinking water Concern about carriers

The Red Eye Conjunctivis Distemper Virus Infectious viral disease of canids, mustelids, skunks and raccoons Caused by Canine Distemper Virus No treatment once infected Prevent with vaccination Poor prognosis

The Red Eye - Glaucoma Increased intra-ocular pressure - EMERGENCY Symptoms extremely painful condition, red eye, blindness Causes secondary to intra-ocular inflammation, tumor, inherited disease (dogs) Affects the flow of fluid within the eye.

The Red Eye - Normal!

Other Conditions Pox Infections Viral infection that causes nodular lesions If nodules are close to the eye can cause irritation to the eye including corneal ulcers In extreme cases lose vision in eye Can recover with supportive care

Other Conditions Wounds Wounds to structures around eyes lids, conjunctiva Concern if the wound affects the function of the eye - e.g. can no longer close eye Surgery has the best outcome

Other Conditions Mange Parasitic infection with Sarcoptes mange mites Skin becomes thickened and crusty Skin around the eye is often affected Can cause corneal irritation or ulceration Treat for secondary bacterial infection

Other Conditions Species specific Overweight Virginia opossums have fat deposits that build up around their eyes so they look crosseyed Aquatic animals, like beavers, muskrats, and water birds can develop crusty eyes when kept out of water. Owls that are blind in one eye have been noted to have tuft down on that side

Other Conditions Missing Eye Irreparably Damaged Eye

Conditions you can treat Treatment by the Wildlife Rehabilitator Simple corneal ulcers Hyphema from trauma Retinal hemorrhage from trauma Trauma around eye that doesn t affect lids, glands, etc. Conjunctivitis

Conditions for your Veterinarian Deep corneal ulcers Non-healing ulcers Complicated eyes Uveitis Suspected glaucoma Lacerations & punctures Hypopyon Anything you aren t sure about!

Equipment and Medications to have: Bright pen light Direct ophthalmoscope Fluorescein strips or drops + saline flush Culture swabs Exam sheet +/- Tonopen +/- STT strips Topical antibiotics Topical steroids Topical NSAIDs Topical antibiotic + steroid combinations Atropine Topical anesthetic Oral pain medication Oral antibiotics

Assess Visual Function Evaluate behavior from a distance Food intake can it find food? Can it hunt? Movement in enclosure - reluctant to climb, jump, swim, fly? Head posture is there one eye used more than the other? Startle reaction is there an exaggerated response?

Dr. Heather Reid Toronto Wildlife Centre 60 Carl Hall Road, Unit 4 Toronto, ON M3K 2C1 (416) 631-0662 x 3206 Veterinary@torontowildlifecentre.com