What is cataract and who does the removal operation at teaching hospital?

Cataract definition. The lens in the eye grows like an onion in layers with age. Starting usually around age 20 tiny white spots can form in the part of the lens under the colored part (the iris). They grow very slowly in most people although sunlight and cigarettes have shown to make them grow faster. Genetics is the most important cause.
Doctors in training. After full learning of the technique the resident in training under full supervision of a professor at the institution may perform the surgery. The training can be done starting with animal eyes, mechanical devises and watching many surgeons do the surgery. Only when the professor thinks there is skill to do it will a resident surgeon operate.