Comparison between Threshold Pupil Perimetry and Suprathreshold Pupil Perimetry

Purpose: Pupil perimetry has so far been performed by the two following methods: suprathreshold perimetry during which the amplitude or ratio of pupil constriction is determined, and threshold perimetry during which the threshold of pupil reaction is determined. The authors compared the values obtained with these two methods using the modified Octopus 1-2-3. Subjects and methods: Pupil perimetry was performed in ten normal subjects in the upper nasal field on the 135° meridian within the central 30° visual field, using a background luminance of 3 asb, a stimulus size 5, and a stimulus duration of 200 msec. On suprathreshold perimetry, the ratio of pupil constriction was measured using a stimulus intensity of 6dB (1005 asb). On threshold perimetry, the lowest stimulus intensity that caused pupil reaction was determined when the stimulus intensity was gradually increased in 1dB steps. Results: The ratio of pupil constriction in suprathreshold perimetry and the pupillary sensitivity in threshold perimetry were well correlated (Spearman’s rank correlation coefficient: 0.67; n=80; p<0.001). Interindividual and intraindividual variations on suprathreshold perimetry were larger than those on threshold perimetry. The examination time with suprathreshold perimetry was much shorter than that with threshold perimetry. Conclusion: Suprathreshold pupil perimetry was clinically more practical than threshold pupil perimetry.