Pupillographic evaluation of relative afferent pupillary defect in glaucoma patients

Aim: To evaluate the association between the magnitude of relative afferent pupillary defect (RAPD) and the laterality of visual fields in glaucoma patients using pupillography. Methods: Evaluations were made with an RAPDx (Konan Medical USA, Irvine, California, USA), which is designed to analyse pupil responses to multiple colour stimuli (white, red, green, blue, and yellow) at multiple controlled stimulus intensities. Humphrey automated perimetry (SITA standard 30-2) was performed to determine mean deviations (MDs), which were used to evaluate associations between MD differences (better eye MD - worse eye MD) and RAPDx amplitude and latency measurements in pupil response to multiple colour stimuli. Results: 58 glaucoma patients (35 men, 23 women; mean age: 62.6±12.8 years; range 28-88 years) were enrolled. The MD values were -2.00±3.1 (range -9.64 to 2.33) dB in the better eyes and -8.17±7.1 (range -26.33 to 1.07) dB in the worse eyes. The differences in MD values (better eye MD - worse eye MD) were 6.17±6.1 (range 0.05-26.41) dB. The results of linear regression analysis between the log-scaled RAPD amplitudes and differences in MD values were as follows: white: R2=0.45 (p<0.001), red: R2=0.18 (p=0.002), green: R2=0.30 (p<0.001), blue: R2=0.29 (p<0.001), and yellow: R2=0.32 (p<0.001). The log-scaled RAPD latencies and the differences in MD values were: white: R2=0.17 (p=0.001), red: R2=0.03 (p=0.22), green: R2 =0.01 (p=0.52), blue: R2=0.1 (p=0.02), and yellow: R2=0.05 (p=0.11). Conclusions: The log-scaled RAPD amplitudes correlated moderately with the differences in MD values, but the log-scaled RAPD latencies showed a weaker correlation. Stimulation with white light produced the strongest correlation with differences in MD values.