Nuclear sclerosis is an age-relate change in the density of the crystalline lens nucleus that occurs in all older animals. It is caused by compression of older lens fibers in the nucleus by new fiber formation. The more dense construction of the nucleus causes it to scatter light. 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 usually does not affect vision, except for unusually dense cases.