A gastroenterologist is a healthcare professional who has been educated and trained to treat patients who are experiencing health problems or have diseases that affect the gastrointestinal tract and liver. They also diagnose and treat diseases that affect the esophagus, stomach, small intestine, colon, rectum, pancreas, gallbladder, bile ducts, and liver.

An internist or Internal Medicine doctor is someone who specializes in diagnosing and treating illnesses, diseases, and health problems. Most internists are also primary care doctors and treat patients on a regular basis. They can diagnose and treat common illnesses or more serious problems. Most people see an internist regularly. Those with chronic illnesses may do so on a monthly or even weekly basis. Internists are the most common types of doctors.

An ophthalmologist is a healthcare professional who has been trained to treat eye diseases and other conditions that affect the eyes. They diagnose and treat these issues and can even conduct surgery to help repair certain condition. They also conduct eye exams and help patients find the right glasses or other ways to improve their vision.