*An Introduction To The Horse Ocular (Eye) System And Diseases

The eyes are an essential sensory organ.  Fish, birds, insects and reptiles have them as well as just about every mammal.  Finding food, defense, offense, mating or just having fun requires the brain to see what is around us.  

It is interesting to see the embryonic development of eyes.  They start as stalks of neural tissue sprouting from the front part of the brain.  Reach straight out in front of you with both hands and pretend you are holding a ball.  The arms are these stalks called the optic nerves and the cupped hands are the back of the eyeball called the retina.  Your body represents the brain.  In essence, the eyes are a direct extension of the brain visible to all who look at them.

Half of each eye’s nerves from the brain cross over to the other side to the opposite eyeball.  The stalk develops forward into the eye socket of the skull and then forms a unique layer of light receptors called the retina.  Unique to the horse is the shape of this and is called a ramped retina.  This allows for a different focal point depending if the head is lowered for grazing (the flat of the face looking towards the horizon for predators) or raised to look down the nose at something close (you).  

Following the retina forward is a lens to form uniform light rays.  It is suspended in fluids and covered by a diaphragm (the uvea which contains the iris giving the color of the eye) to control the amount of light coming into the eye (the pupil).  Unlike most animals, the horse adds a glob of tissue to this diaphragm to help shade the sun called the corpora nigra.  

Finally the front of the eye is covered with a transparent membrane called the cornea.  This membrane seals the inside of the eye from the outside and is fully transparent unless damaged.  For further protection the eyeball is protected with upper and lower eyelids and a special 3rd eyelid called the nictitating membrane.  The outside of the eyeball is bathed in fluid (tears) to lubricate, preserve corneal transparency, initiates the bending of the light rays for focusing and distribution of nutrition and immunoglobulins to maintain the health of the cornea.  The tears are drained through small holes on the inside corner of the eye connected to a tunnel in the skull that empties the tears at the nostrils (the nasolacrimal ducts).

With so many parts to the eye, there are several areas where problems can occur.  Trauma is the leading problem but infections, immune inflammation and neoplasia can also affect these structures.  Loss of clear vision (corneal ulcer), loss of all vision (cataracts, blind), loss of the eyeball (enucleation) and tear overproduction or poor draining all can occur.  Most of these can be seen with our own eyes especially if we are looking for them.

Base Modifiers – The Silver Gene

SummaryArticleVideosRelated Material The silver gene (Z) is a dilution of the black base coat with or without the Agouti gene (bay). It has no effect on the red base coat. Horses with one or both Z genes will have a dilution to their coat color and therefore it is an...

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Hyperkalemic Periodic Paralysis (HYPP)

SummaryArticleVideosRelated Material Welcome to this topic page.  Right now I have not written an article and summary but be sure to check for images in the gallery. As time moves on I am adding summaries and articles, videos and podcasts so eventually there will be...

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Polysaccharide Storage Myopathy (PSSM)

SummaryArticleVideosRelated Material Welcome to this topic page.  Right now I have not written an article and summary but be sure to check for images in the gallery. As time moves on I am adding summaries and articles, videos and podcasts so eventually there will be...

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Sinus Infections

[x_alert type=“info” close=”false” heading=”Overview”]The epiglottis is a tissue that separates the esophagus from the trachea and it’s primary purpose is to keep food and other solid material from entering the lungs.[/x_alert]

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Pharyngitis

[x_alert type=“info” close=”false” heading=”Overview”]The epiglottis is a tissue that separates the esophagus from the trachea and it’s primary purpose is to keep food and other solid material from entering the lungs.[/x_alert]

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*An Introduction To The Horse Urinary System

Blood circulates throughout the body delivering all the materials needed to stay alive but it also acts as a system to recycle materials, return gasses and eliminate waste. In this sense it acts like the post office, the package delivery service, the messenger service...

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Unknown Neoplastic Lesions

Equine Sarcoid is a benign tumor of the skin of the horse that is very common, usually limiting itself to above the knee and forward of the girth.

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Fibrotic Myopathy

SummaryArticleVideosRelated Material Welcome to this topic page.  Right now I have not written an article and summary but be sure to check for images in the gallery. As time moves on I am adding summaries and articles, videos and podcasts so eventually there will be...

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Caudal Heel Pain Videos

These are videos about caudal heel pain which includes navicular disease, sole bruising, long toe-low heel conformation and others. Return to caudal heel pain Navicular disease (caudal heel pain) – Part 1 Navicular disease (caudal heel pain) – Part 2...

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The Curly Hair Coat

The breed Bashkir Curly has a hair that maintains a curl throughout the year. The curl can range from no curl to minimal to full curl but it is unique to this breed.

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Anhidrosis (Non-sweating horses)

No one has determined why some horses in the same environment stop sweating while others do sweat but we know that every horse is different with different responses to triggers. And no one (to my knowledge) has determined the mechanism behind anhydrosis.
Accidentally we have found a cure that seems to work in every horse we try it with and we need your help to give us more examples of this treatment’s success.

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Vesicular Stomatitis

SummaryArticleVideosRelated Material Welcome to this topic page.  Right now I have not written an article and summary but be sure to check for images in the gallery. As time moves on I am adding summaries and articles, videos and podcasts so eventually there will be...

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Tetanus

SummaryArticleVideosRelated Material Welcome to this topic page.  Right now I have not written an article and summary but be sure to check for images in the gallery. As time moves on I am adding summaries and articles, videos and podcasts so eventually there will be...

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Aging By Teeth – View Open Mouth

These images include all the ages from 2 years to 30+ years showing just the view from the opened mouth onto the occlusal surface of the incisors. This helps to compare and to observe the changes over time on one individual view.

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Aging By Teeth – View Straight On

These images include all the ages from 2 years to 30+ years showing just the view from straight on the closed incisors. This helps to compare and to observe the changes over time on one individual view.

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Aging By Teeth – View Right Side

These images include all the ages from 2 years to 30+ years showing just the right side. This helps to compare and to observe the changes over time on one individual view.

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Aging By Teeth – View Left Side

These images include all the ages from 2 years to 30+ years showing just the left side. This helps to compare and to observe the changes over time on one individual view.

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Aging By Teeth – 02 – 5 years (Young Horses)

Young horses range in age from birth to 5 years. These images are by year 2 through 5. Each show the left side, the right side, the straight on and the open mouth / occlusal surface of the lower incisors. Comparison can be made for individual variations within each age group.

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Aging By Teeth – 06 – 12 years (Young Adult Horses)

Young adult horses range in age from 6 to 12 years. These images are by year 6 through 12. Each show the left side, the right side, the straight on and the open mouth / occlusal surface of the lower incisors. Comparison can be made for individual variations within each age group.

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Aging By Teeth – 13 – 18 years (Adult Horses)

Young adult horses range in age from 13 to 18 years. These images are by year 13 through 18. Each show the left side, the right side, the straight on and the open mouth / occlusal surface of the lower incisors. Comparison can be made for individual variations within each age group.

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Aging By Teeth – 19 – 24 years (Early Senior Horses)

Young adult horses range in age from 19 to 24 years. These images are by year 19 through 24. Each show the left side, the right side, the straight on and the open mouth / occlusal surface of the lower incisors. Comparison can be made for individual variations within each age group.

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Aging By Teeth – 25 – 30 plus years (Senior Horses)

Young adult horses range in age from 25 years and older. These images are by year 25 through 30+. Each show the left side, the right side, the straight on and the open mouth / occlusal surface of the lower incisors. Comparison can be made for individual variations within each age group.

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Dental Care

Horse’s teeth erupt throughout their lives with constant wear occurring from teeth grinding against opposing teeth and continual stropping by the tongue. This wear is uneven and creates razor sharp edges that cause discomfort as those edges ulcerate the cheek and their tongue. So if eruption and wear is continuous throughout the life of the horse and the result is pain within the mouth, AND the removal of the sharp points (floating) is easily done, WHY DO SO MANY HORSE OWNERS AVOID THIS IMPORTANT ASPECT OF HORSEMANSHIP?

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Asses, Mules And Zebras

SummaryArticleVideosRelated Material Welcome to this topic page.  Right now I have not written an article and summary but be sure to check for images in the gallery. As time moves on I am adding summaries and articles, videos and podcasts so eventually there will be...

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Guttural Pouches

SummaryArticleVideosRelated Material Welcome to this topic page.  Right now I have not written an article and summary but be sure to check for images in the gallery. As time moves on I am adding summaries and articles, videos and podcasts so eventually there will be...

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Mustaches

SummaryArticleVideosRelated Material Some horses have a natural mustache as seen here.  I have seen a bunch in my years with horses but I have never heard any meaning attached to their presence other than most people think they are “cute.” Related material...

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