The use of crossed polarized filters in the measurement of the relative afferent pupillary defect.

We used crossed polarized neutral density filters to quantitate relative afferent pupillary defects. To prove reproducibility, the relative afferent pupillary defects of 20 patients were measured with this technique by two independent observers. There was no statistically significant difference between the two measurements. Relative afferent pupillary defects as low as 0.03 log unit were easily measured. These filters offer a convenient and reproducible technique that is more sensitive than the use of neutral density filters.