A device is presented for scoring peripheral acuity. Values are expressed in percent analagous to what the Snellen scale does for central acuity. Like the recently published scale for the tangent-screen field, it is based on function. The grid consists of 100 units whose unequal size and distribution reflect the unequal functional value of different parts of the field—in effect a weighted or relative-value scale. Because each unit equals 1%, a simple count of units yields the functional score in percent. The grid improves on the American Medical Association method of scoring, although it is based on the same AMA standard isopter for the normal (100%) peripheral field. The device, tested on 1,000 fields by 20 experienced ophthalmologists, yielded a 95.9% correspondence between their estimates and the grid scores. It is simple, quick, inexpensive, consistent, and can, after brief instruction, be delegated by the ophthalmologist to a nonprofessional aide.