Final answer:
The Snellen chart is the tool used to check visual acuity in the medical office. It assesses the clarity of vision at a distance of 20 feet by comparing to the normal benchmark of visual acuity.
Step-by-step explanation:
Of the following options, the Snellen chart is used to check visual acuity in the medical office. It is a standardized tool for assessing how well a person can see. The Snellen chart presents a series of letters in decreasing size which a person is asked to read from a standard distance of 20 feet. This chart helps in determining a person's visual acuity by comparing it to what is considered normal vision; a common reference is being able to identify letters that subtend 5 minutes of an arc from that distance. A finding of 20/60 vision, for example, indicates that what a person can see at 20 feet, a person with normal vision could see at 60 feet.
The opthalmometer, also known as a keratometer, is a different instrument used to measure the curvature of the cornea, particularly in the context of fitting contact lenses or diagnosing conditions like astigmatism. The ophthalmoscope is an instrument used to inspect the retina and other internal structures of the eye, and it is not directly used for testing visual acuity. An ergometer, on the other hand, is a type of exercise equipment that measures the work output of muscles during physical exercise and is not related to eye examinations.