Corneal Sensitivity, Sub-Basal Corneal Nerve Plexus, and Tear Neuropeptides in Symptomatic Versus Asymptomatic Visual Display Terminal Users.

PURPOSE: The current study evaluated the structure and function of corneal nerves in symptomatic versus asymptomatic visual display terminal (VDT) users, along with tear neuropeptides.

METHODS

A cross-sectional, single-masked study divided VDT users into symptomatic (n = 51; ocular surface disease index (OSDI) > 13, tear osmolarity, noninvasive tear break-up time (NIBUT) < 10 s, and positive corneal staining) and asymptomatic groups (n = 21, OSDI ≤ 13, NIBUT > 10 s). Participants underwent detailed tear film examination (Oculus keratograph 5M), blink rate, corneal sensitivity (Cochet-Bonnet aesthesiometer), and in vivo confocal microscopy (IVCM, HRT II-RCM) testing. ELISA of tear cytokines (IL1a, TNFa, IL6, MMP 9) and neuropeptides (CGRP, NPFF, VIP, Sub P, NGF) were compared between groups.

RESULTS

Symptomatic VDT users had more years of VDT use (P = 0.0002), reduced corneal sensitivity (P = 0.02), lower Schirmer I (P < 0.0001), lower blink rate (P < 0.0001), and more partial glands (P < 0.001) than asymptomatic users. The daily hours of VDT use (6.4 vs. 6.2), tear osmolarity, immature and mature dendritic cell densities, and IVCM parameters were similar across the two groups. A weak negative correlation of corneal sensitivity was noted with OSDI (P = 0.03) and blink rate (P = 0.037). Mature dendritic cell density had a positive correlation (P = 0.009) with corneal sensitivity. Symptomatic users showed reduced NGF and elevated MMP-9 and IL-1α compared to asymptomatic VDT users.

CONCLUSION

Symptomatic VDT users have reduced mechanical corneal sensitivity without morphological changes in the sub-basal corneal nerve structure. Reduced NGF and elevated tear IL1a and MMP-9 in symptomatic VDT users indicate ocular surface inflammation in VDT-associated dry eye disease.