The only difference between Class 1 medical test and Class 2 medical test is their purpose and severity. A Class 1 medical test is necessary when it comes to those who want to become commercial pilots and fly passenger or cargo airliners. This is a more detailed and stringent test as the burden of overseeing the flight of large aircrafts filled with people is big. It is not just an eye sight hearing, to heart and blood pressure, and overall fitness but also stress tests ECG lung performance etc. A Class 1 flying certificate should be renewed periodically (annually or semiannually based on age) in a procedure that manages to keep the pilot fit to the physical and mental challenge of being a professional flyer.
On the other hand Class 2 medical test is less strict and it is commonly the initial test one takes as a student pilot. It is necessary to get a Student Pilot License (SPL) later on to become a Private Pilot License (PPL). Also included in this test are eyesight hearing heart and basic lung functioning and the overall fitness but not as in-depth as Class 1. When a student passes Class 2 and commences training he or she will later have to pass Class 1 to operate a commercial plane. Concisely, Class 2 is an entry level medical examination requirement by any other pilot new in the field, whereas Class 1 involves a professional level medical examination requirement to commercial pilots.