Evaluation of Ocular Irritation Sensitivity: Implications of Clinical Parameters, Pain Sensitivity, and Tear...

Background/Objectives: Sensitivity to ocular irritation varies among individuals, being influenced by clinical, subjective, and biochemical factors. This study aimed to evaluate individual variability in ocular irritation sensitivity, focusing on clinical parameters, pain perception, and tear neuromediator profiles. Methods: Sixty female participants aged 20-40 were classified into high-sensitivity and low-sensitivity groups based on their response to an irritant (Tween20). Clinical assessments included the ocular surface disease index (OSDI), tear break-up time (TBUT), Schirmer test, and corneal touch threshold measured with the Cochet-Bonnet esthesiometer. Pain sensitivity was assessed using the pain sensitivity questionnaire (PSQ), and tear neuromediators were quantified in tear samples before and after stimulation. The concentrations of calcitonin gene-related peptide (CGRP), nerve growth factor, neuropeptide Y, vasoactive intestinal peptide (VIP), and substance P were measured using an enzyme-linked immune sorbent assay (ELISA). Results: The high-sensitivity group exhibited significantly higher OSDI scores (p = 0.038). No significant differences were observed in TBUT, corneal staining scores, or Schirmer's test results. The PSQ results revealed that the high-sensitivity group had lower total and moderate pain scores (p = 0.037 and p = 0.040, respectively). An analysis of the tear neuromediator showed elevated baseline CGRP levels (p = 0.017) and a significant post-stimulation increase in substance P (p = 0.021) in the high-sensitivity group. Conclusions: These findings emphasize the value of combining clinical, subjective, and biochemical measures to understand sensitivity to ocular irritation. This comprehensive approach may guide the development of safer cosmetic formulations and improve safety assessment protocols.