This is an Allergan study, and they’re the manufacturer, so make what you will of this. But I think there really is plenty of evidence this is helping take the edge of symptoms for many of the severely dry.

Symptom improvement in dry eye subjects following intranasal tear neurostimulation: Results of two studies utilizing a controlled adverse environment. Pattar GR, Jerkins G, Evans DG, Torkildsen GL, Ousle GW, Hollander DA, Holdbrook M, Senchyna M. Ocul Surf. 2019 Sep 19. pii: S1542-0124(19)30196-X

PURPOSE:
To evaluate the safety and effectiveness of the intranasal tear neurostimulator (ITN) in improving dry eye symptoms assessed in a controlled adverse environment (CAE®).
METHODS:
Study 1: Multicenter, subject-masked, randomized-sequence, crossover design. Single intranasal (active) and extranasal (control) ITN administration during CAE exposure. Study 2: Single-arm, open-label design. Intranasal ITN administration ≥2 times/day for 45 days, CAE assessment at days 0 and 45. In both studies, upon CAE entry, and every 5 min thereafter, subjects assessed eye dryness score (visual analog scale, 0-100 mm; EDS-VAS), and ocular discomfort score (ODS; Ora Calibra™, 0-4), for ≈2 h. Study 1: when ODS was ≥3 at 2 consecutive timepoints, subjects applied ITN intranasally or extranasally for ≈3 min, and again when achieving the same ODS criteria in randomized sequence. Study 2: days 0 and 45, ITN was applied for ≈3 min employing the same ODS criteria as Study 1.
RESULTS:
Study 1: Significantly greater pre-to post-application reductions in mean [SEM] EDS (-16.5 [1.7] vs -3.1 [1.7], P < 0.0001) and ODS (-0.93 [0.08] vs -0.34 [0.08], P < 0.0001; n = 143) with intranasal vs extranasal stimulation. Study 2: On day 0 (n = 52) and day 45 (n = 48), significant pre-to post-application reductions in mean [SEM] EDS (-15.9 [2.7] and -15.2 [2.4]; P < 0.0001), and ODS (-1.3 [0.2] and -1.3 [0.1]; P < 0.0001). Few device-related adverse events were reported, none serious.
CONCLUSIONS:
Acute symptom relief is significant with the ITN and remains undiminished after daily use.