The most serious unsoundness of the eye is a condition known as Moon Blindness. The correct term for the disease is Equine Recurrent Uveitis or Periodic Opthalmia. Symptoms may include redness, swelling, puss, pupil constriction in the dark, cloudiness, squinting, or sensitivity to light. Moon blindness is considered an unsoundness because it is very difficult to treat. Even when progression of the disease can be halted it is only temporary. Episodes can reoccur due to dust, wind, pollen or stress and the horse's sight is compromised with each incident until he is completely blind. The disease can be caused by bacteria, virus, parasites or trauma. Once the disease settles in the eye, the blood flows to the eye to fight the disease and destroys the eye in the process.
Another serious unsoundness to check for in the head and neck areas is Poll Evil. At the top of the horse's head, at the first vertebra of the neck is the area referred to as the Poll. Poll evil is the lay term for supra-atlantal bursitis, which is an enlarged mass or inflation of the cushion (bursa) that lies over that first vertebra. It is believed to start with a trauma to the area which becomes infected, swells and drains down the neck. It is considered an unsoundness because it frequently defies treatment and invades nearby bone and cartilage. The particular bacterium involved can be transmitted through the draining fluids and also cause chronic infections in humans.
Proper conformation of the nostrils, jowls and throatlatch provide clear and efficient airways for breathing. The nostrils should be large and fluted at the tops with no signs of discharge. A clear discharge is not uncommon and posses little concern, but a white, yellow or green discharge is a sign of illness. The jowls should also be nice and large. The throatlatch is the area where the neck comes into the head under the jowl. The conformational defect known as "thick in the throatlatch" refers to poor definition and fat build up around this area. You should be able to fit a fist between the jowls and the neck and the area should look sleek and muscular. You can easily envision the windpipe that lies beneath the skin in this area.
