Health resources include various medical professionals that provide healthcare services. Some key professionals are general practitioners who provide overall medical care, nurses who assist doctors in caring for patients, and dentists who focus on oral health. Other professionals that help maintain health include nutritionists who advise on diets, psychologists and psychiatrists who provide therapy and counseling, and pharmacists who handle medications. Optometrists and ophthalmologists examine eyes and treat certain vision conditions while opticians make eyeglasses. Orthodontic treatment and dentures are procedures to correct teeth, and immunizations help prevent disease through vaccinations.