Cataracts
A cataract is defined as any spot on the lens, regardless of size, that does not allow light to pass through. Cataracts can be confined to a single area within the lens or affect the entire structure. They were identified in dogs as early as 1925. Some cataracts are clearly visible to the naked eye, appearing as white flecks within the eye, or giving a milky-gray or bluish-white cast to the lens behind the pupil. They result in varying degrees of blindness. Aging animals often have a graying of the lens, which should not be mistaken for a cataract.
Cataracts are classified as primary or secondary. Primary cataracts usually result from a (presumed) recessive mode of inheritance and typically appear at an early age. Usually both eyes are affected, though not necessarily with symmetrical development. Primary cataracts do not always advance to cause total blindness and are sometimes associated with other ocular diseases.
Secondary cataracts are generally associated with other hereditary eye diseases where the nutrition of the lens is disturbed as in diabetes. They can also develop secondary to PRA or Lens Luxation.
Cataracts can be also be acquired as a result of trauma.