CHAPTER 41: EYE DISEASES
Eye Diseases
The eye functions to capture light and convert it to electrical stimulus which is transmitted to the brain and interpreted into vision.
The eye is made up 3 layers:
Outer fibrous layer –
Vascular layer –
Inner nervous layer –
The lens is suspended by ligaments attached to the ciliary body which sits behind the iris. Light passes through the pupil of the iris. The aqueous humor is a clear water like fluid that bathes the lens & cornea providing oxygen & . Vitreous humor a gel like fluid sits behind the lens to hold the retina in position & act as a shock absorber. The conjunctiva lines the inside of the eyelids and covers the sclera for protection. The eyeball sits within the bony orbit by muscles. Light passes through the clear structures of the eye to reach the retina. It passes through the retina and converted into an electrical impulse sent to the brain via the nerve. A horse’s vision is binocular. The blind spots of the horse include directly behind the head, between the eyes and directly under the body to about 4 feet in front of the legs. monocular & A horse’s night vision is excellent due to a structure called the which acts as a reflective layer. An increase in the number of rod photoreceptors also aid in better night vision. Horses have poor colour vision due to a decrease in cone photoreceptors. It is believed horse can see yellow/green & blue/grey but not . Vision problems in horses is common. Bilateral vision disturbances are easier to diagnose than unilateral. In general horses with vision problems develop behaviour, self- inflicted trauma, resistant to move from place to place, especially if dark, they may spook easily or shy away from things.
Causes of vision problems include:
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