Design
We prospectively studied patients with relative afferent pupillary defects by using the swinging flashlight test with a standardized illumination time of 3 seconds (pause time) for each eye. Each relative afferent pupillary defect was graded as follows: grade I, a weak initial constriction and greater redilatation; grade II, initial stall and greater redilatation; grade III, immediate pupillary dilatation; grade IV, immediate pupillary dilatation following prolonged illumination of the good eye for 6 seconds; grade V, immediate pupillary dilatation with no secondary constriction. The grades on the individual resident evaluations were compared with those on the group evaluations, and the grading system was compared with the neutral density filter grading system.

Setting
Neuro-ophthalmology service of an urban teaching hospital.

Study Participants
A total of 119 patients.

Results
There was a good correlation in all grades between individual resident and group evaluations, with an overall 78% agreement. The five grades had corresponding values in neutral density filter log units: grade I, 0.4; grade II, 0.7; grade III, 1.1; grade IV, 2.0; and grade V, infinity.

Conclusions
The 3-second pause technique for the swinging flashlight test is a reliable method for the detection and quantitation of relative afferent pupillary defects. The grading system can be compared with the neutral density filter grading system, and each grade has a corresponding value in log units.