Threshold Amsler grid testing. Cross-polarizing lenses enhance yield
M. Wall and A. A. Sadun
The Amsler grid is a commonly used test for evaluation of the 10 degrees of
visual field surrounding fixation. The Amsler grid is a suprathreshold
stimulus and thus may not detect relative scotomas. Therefore, we had ten
patients with optic neuropathies view the grid through cross-polarizing
filters that created low luminance conditions in which the grid was barely
perceptible. The patients were also surveyed with a 2-m tangent screen
protocol and threshold automated perimetry. The threshold Amsler grid
technique increased both the number of defects found and the total area of
these defects by approximately a factor of 5. Two thirds of the defects
found were confirmed by one of the other screening techniques. Threshold
Amsler grid testing is a rapid, inexpensive, and sensitive technique for
the evaluation of the central 10 degrees of the visual field.
