What visual acuity reading would indicate that a patient can see at 20 feet what a normal eye sees at 40 feet?

A visual acuity reading is expressed in terms of a fraction, where the numerator indicates the distance at which the test is conducted (typically 20 feet), and the denominator indicates the distance at which a person with normal vision can see the same detail. In this case, a reading of 20/40 means that the patient can see at 20 feet what a person with normal vision can see at 40 feet.

This indicates that the patient's vision is worse than that of someone with standard visual acuity. A person with 20/40 vision may have difficulty seeing details at a distance that a person with normal vision could easily recognize. Hence, the correct answer clearly reflects that the patient's visual performance is at a level where they require the typical viewing distance of a person with normal vision to be doubled in order to see the same details clearly.