and prepare laboratory specimens or perform basic laboratory tests on the premises, dispose of contaminated supplies and sterilize medical instruments. They instruct patients about medications and special diets, prepare and administer medications as directed by a physician, authorize drug refills as directed, telephone prescriptions to a pharmacy, draw blood, prepare patients for x-rays, take electrocardiograms, remove sutures, and change dressings. Medical assistants also may arrange examining room instruments and equipment, purchase and maintain supplies and equipment, and keep waiting and examining rooms neat and clean. Ophthalmic medical assistants and podiatric medical assistants are examples of specialized assistants who have additional duties. Ophthalmic medical assistants help ophthalmologists provide eye care. They conduct diagnostic tests, measure and record vision, and test eye muscle function. They also show patients how to insert, remove, and care for contact lenses, and they apply eye dressings. Under the direction of the physician, ophthalmic medical assistants may administer eye medications. They also maintain optical and surgical instruments and may assist the ophthalmologist in surgery. Podiatric medical assistants make castings of feet, expose and develop x rays, and assist podiatrists in surgery. ]