INAG 120 – Equine Health
Management
December 5, 2011

The Equine Eye

The Equine Eye
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Recognize the normal
Ocular – pertaining to the eye
Periocular – area around the eye
 Examine eye in bright sunlight or shaded area with flashlight

Eye Examination
 Overall appearance of head
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Erectness of ears
Symmetrical eyelids?
 Appearance
 Position
 Eye Sockets
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Assess placement of eyes in sockets
Symmetrical?

Eye Examination…
 Eyelids
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Lightly touch
Symmetrical?
Make note of normal pigmentation of third eyelid
Third eyelid – visible when horse retracts eye into socket

Eye Examination…
 Anterior Chamber
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Space between the cornea and colored portion of the eye (iris)
Filled with transparent fluid
 Symmetrical?
 Conjuctiva
 Mucous membrane lining inner surface of eyelid and outer surface of sclera
 Should be moist and shiny

Eye Examination…
 Iris, Pupil and Lens
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Iris = eye color
Pupil (horizontal hole) should constrict with light
Corpora nigra above and below pupil
Pupil should be dark
 Posterior Chamber / Eye
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“Fundus”
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Requires special instrumentation
Contains “tapetum”

Recognizing the Abnormal
 PAIN
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Blepharospasm
Photophobia
Epiphora
 CHANGE IN COLOR
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Redness
Milky-white color
 SWELLING

Specific Problems of the Eye
 Eyelids:
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Entropion
Lacerations
Pockets of inflammation
Tumors
 Sarcoid
 Squamous cell carcinoma
 Melanoma
Tetanus/Lockjaw

Specific Problems of the Eye
 Conjunctiva:
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Dermoid
Conjunctivitis
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Redness and swelling
Irritating rather than painful
If pain is evident – may be due to another problem
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Dirt/foreign materials
Flush with mild eyewash
Squamous cell carcinoma
Angiosarcoma  highly malignant

Specific Problems of the Eye
 Cornea:
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Congenital dermoid
Trauma = corneal ulcer
Treatment usually requires antibiotic application
 NO STEROIDS
 Be sure antibiotic used is Optic
Puncture
 Eye will appear partially collapsed
 Requires immediate surgical intervention

Specific Problems of the Eye
 Iris and Ciliary Body:
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Uveitis
Iris Cysts
 Cause iris to bulge forward
 Related to Silver Dapple c oat coloration!
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Inflammation of iris

Recurrent Uveitis
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Aka Periodic Opthalmia, Moon Blindness
Clinical signs:
 Acute pain
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Redness to eyes and lids
Darkened iris
Iris appears moth-eaten
Multiple Causes
 Leptospirosis main cause
 Onchocerchiasis
Treatments
Complete recovery unlikely
MICHAEL A. BALL, DVM
Classic appearance of long-standing uveitis. Note the scarring of the iris and the white reflective cataract.

Specific Problems of the Eye
 Lens:
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Flattened, transparent & malleable marble behind the iris (helps focus images
Diseased lens is usually opaque
Cataracts
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Progressive in nature
Congenital in foals  more successfully removed

Specific Problems of the Eye
 Retina/Choroid:
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Usually go undetected until blindness is evident
Appaloosas & Congenital Stationary Night
Blindness
 Autosomal recessive gene
 Malfunction of motion-detecting retinal cells (rods) which function best in low light
 Day vision = normal

When to Call the Vet…
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Increased discharge
Squinting and/or excessive blinking
Cloudy appearance
Vision problems
Blood in the eye
Any foreign object in the eye or eyelids
Any sign of tumor development on the eye or eyelids

Do’s
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Call the vet early – don’t wait
Only remove a foreign object if it’s confined to the eyelid
 Flush dirt, ash, sand or plant material with water or saline
 Treat chemicals in eyes as you would humans
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Flush with lots of water
Call the vet
 Did I mention to call the vet?

Don’ts
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Don’t ignore eye problems
 Be careful using leftover ointment (some ointments can make problems worse)
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 Triple antibiotic probably ok; avoid atropine or steroid until vet advises
Don’t remove foreign object from eyeball itself, let a vet do it.

Head Shaking
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Poorly understood disease
Horse may flick, nod and/or shake head
Causes:
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Behavioral
Ill-fitting tack
Teeth
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Middle Ear disorders
Ear Mites
Eye Disorders
Allergies
Gutteral Pouch Infection

Symptoms of Headshaking
 Behavior/Ill-fitting tack:
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Physical head movements
No disease process (i.e., nasal discharge)
 Dental Disease:
 Nasal discharge
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Foul breath
Pain, swelling over facial bones
Difficulty eating
Abrasions on tongue/cheeks
Weight Loss

Symptoms of Headshaking
 Gutteral Pouch Infection:
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White non-odorous nasal discharge
Swollen lymph nodes
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Painful distension of area behind ears
Noisy breathing
 Ear Disease:
 Rub ears
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Sensitive ears
Can be VIOLENT (dangerous for rider/handler)
Head tilt (due to affected balance)

Symptoms of Headshaking
 Eye Disease:
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Cancerous growth
Difficult to catch
Spook easily
Previous slides…
 Nasal Disease:
 Discharge
 Allergies:
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Sneezing
Snorting, rubbing nose on legs

Photic Headshake
 Caused by exposure to light
 Overstimulation of eye  stimulation of opthalmic branch of trigeminal nerve  impulses to face
 Probably causes sensation in nasal cavity similar to hayfever sufferers!
 Treat by lowering light (fly mask or darkened environment); use of cyproheptidine (0.3 mg/kg BW
2x per day) ± melatonin therapy in summer
 Present in spring/summer, worsens with exercise

Ear Problems – Aural Plaques
 Caused by same virus as warts
 Respond poorly to treatment and do not spontaneously regress
 Once thought to be caused by biting flies
 Can become severely irritated during biting fly season  horses may become defensive about having ears touched!
 Soothing ointment such as mentholatum can be helpful; panalog may also help

Warts and Aural Plaques

Ear Problems – Middle Ear
Infection
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Problem in gutteral pouch can migrate
 Bacterial or fungal
Doesn’t burst eardrum like other species
Causes fusion of stylohyoid bone and temporal bone of the middle ear
 Can lead to stress fractures and neurological problems
 Ear rubbing, head tossing, chomping movements, pain around ear, depression, head-tilt, dizzy, facial paralysis

Ear Problems – parasites
 Most common problem of the equine ear
 Chiggers, ticks, and psoroptes mites
 Ear mites:
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Head rubbing, shaking and irritability
Not always visible
Treat with dewormer and ear drops