[Modified threshold Amsler grid testing].

The conventional Amsler grid uses suprathreshold illumination, and hence may fail to detect early scotomas. When the grid is viewed through cross-polarizing filters to reduce luminance to visual threshold, the test becomes far more sensitive. The authors expanded the standard Amsler grid from 400 to 1600 squares and viewed under threshold luminance to examine the visual fields of glaucoma, retinitis, optic neuropathies and brain tumors; the modification was found much more sensitive for the detection of central and paracentral light scotomas.