Quantitative pupillary pathway assessment with automated pupillometry and its correlation with Visual evoked potential latency in multiple sclerosis without a history of optic neuritis

Alteration of visual evoked potential (VEP) latencies during pattern stimulation is considered one of the most characteristic electrophysiological signs in patients with MS. Such alterations are present almost invariably in subjects affected by optic neuritis and also in patients without symptoms and signs of visual system impairment.Aims:The present study was conducted to investigate indicative alterations in features of pupillary light response measured by pupillometry and to assess its potential associations with latency prolongation of the visual evoked response in non-optic neuritis RRMS patients.Methods:We investigated P100 latency and pupillometry parameters including neurological pupil index (NPi), pupil size (PS), minimum size of pupil (MinPS), percentage change of pupil size (CH), Constriction Velocity (CV), Maximum of Constriction Velocity (MCV), Dilation Velocity (DV) and latency (LAT) from 140 subjects(62 non-ON RRMS). Independent-samples t-tests were run, first to determine pupillometry differences between the right eye of cases and controls and then, to determinate differences across age-matched controls and cases while p100 latency was in normal range. To assess P100 latency variation in terms of EDSS and pupillometry variables, right eyes of non-ON cases were quantified through multiple regression.ResultsThe comparison between Case and control subjects showed statistically significant differences of -0.56 (95% CI, -0.9 to -0.2), p=.002; -0.24 (95% CI, -0.4 to -0.05), p=.01; -3.18 (95% CI, -5.7 to -0.6), p=.015; -0.53 (95% CI, -0.94 to -0.12), p=.01 for PS, MinPS, CH, MCV, respectively. And under normal p100 classification it was revealed that there were statistically significant differences of -0.77 (95% CI, -1.3 to -0.2), p = .007; -5.38 (95% CI, -9.1 to -1.6), p = .006; -0.78 (95% CI, -1.4 to -), p = .015 for PS, CH and MCV, respectively. EDSS and CH statistically significantly predicted P100 F (2, 56) =6.26, p<0.005 and R2 for the overall model was 18.3%.Conclusion:Pupillary light response parameters are affected by the pathophysiologic process in MS disease even in the absence of ON and latency prolongation of VEP. Percentage change of pupil size alongside EDSS can predict p100 latency with a medium effect size.