A device is presented for quantitative evaluation of visual fields analagous to what is done for central acuity by the Snellen test. It consists of a grid whose 100 units increase rapidly in area from center to periphery. This produces a relative-value scale, based on function, weighted to assign higher scores to those areas most useful to the patient—higher in center than periphery; higher in lower than in upper field; and higher near horizontal meridian than in the rest of the periphery. Because each of the 100 units equals 1% a direct score, in percentage, of useful field is obtained. The device was given 1,000 tests by a "jury" of 20 ophthalmologists each estimating 50 unknown fields. A satisfactory degree of correspondence was found between their estimates and the grid scores.
Esterman B. Grid for Scoring Visual FieldsI. Tangent Screen. Arch Ophthalmol. 1967;77(6):780-786. doi:10.1001/archopht.1967.00980020782012