Quantitative Pupillometry of Relative Afferent Defects in Glaucoma

To the Editor. —A relative afferent pupillary defect usually indicates a disorder in the anterior visual pathway anterior to the optic chiasm. Its detection is helpful in the diagnosis of optic nerve diseases. It has generally been evaluated using Kestenbaum's number¹or the swinging flashlight test and neutral-density filters that were calibrated in logarithmic units of light attenuation and percentage of light transmittance.² We measured the relative afferent pupillary defect employing the infrared video camera of the OCTOPUS perimeter 201 (Interzeag AG, Switzerland). The study included 10 healthy subjects (mean ± SD age, 41.6 ± 16.7 years; refractive error, +0.27 ± 1.81 diopters [spherical equivalent]) and 17 patients suffering from primary open angle glaucoma (mean age, 53.0 ± 11.9 years; refractive error, −0.15 ± 2.22 diopters). The mean difference in refractive error between the two eyes of the same individual was 0.01 diopter. Since in the control group