The CNP grading of cataracts is a classification of the severity of the cataract, with C usually referring to cortical clouding, N to nucleus pulposus clouding, and P to posterior subcapsular clouding. Each type is graded from 1 to 5 depending on the degree of cloudiness. For mild cataracts, such as early nuclear or cortical cataracts, ultrasound emulsification can be used and usually takes less time. However, if the nucleus is very hard, a small incision may be required.