I think we may have the same problem check out this thread.
It seems that there are three types of human cataracts; nuclear sclerosis, cortical, and posterior subcapsular.
Other source says a cataract is not a nuclear sclerosis:
"Nuclear sclerosis is an age-related change in the density of the lens nucleus that occurs in all older animals. The nucleus takes on a gray, cloudy appearance but this has no appreciable effect on vision. It is not uncommon for nuclear sclerosis to be confused with cataract. "
"Although nuclear sclerosis may describe a type of early cataract in human medicine, in veterinary medicine the term is also known as lenticular sclerosis and describes a bluish-grey haziness at the nucleus that may not affect vision."