There are many varied causes of blindness in the equine with disease, old age, and accident being the most common.
But the loss of vision has greater implications for the rest of the animal's body. As an example, you might observe that the head or neck carriage is different to what would normally be considered to be optimal biomechanically - this will be part of the animal’s response to its changed peripheral field of vision.
These biomechanical changes need to be considered when training, trimming or treating an animal with vision impairment.