Abstract
Purpose :
To assess whether SP levels in the tear fluid of healthy subjects are associated with clinical measures of ocular pain, inflammation, and corneal sensitivity.
Methods :
Eighteen healthy volunteers (age range: 19-31 ± 2.331) were enrolled in this study. Subjects were then randomly allocated to two groups: group A+ was administered the topical anesthetic (A) oxybuprocaine while group A- did not. Tear samples were collected from groups A+ and A- before and after corneal nerve stimulation using a hypertonic solution. Measures of clinical outcomes were collected before and after nerve stimulation. Specifically, ocular pain and discomfort were assessed using the visual analogue scale (VAS) and ocular surface disease index (OSDI) questionnaires. Corneal sensitivity and inflammation were measured using the Cochet-Bonnet esthesiometer or the Efron scale, respectively. Finally, SP content in tear fluid was quantified using an ELISA test.
Results :
The release of SP in tear fluid was markedly decreased in group A+ (P < 0.01), while it increased not significantly in group A-. Notably, the A+ group showed lower ocular pain (P < 0.001), discomfort (P < 0.05), inflammation (P < 0.01), as well as reduced corneal sensitivity (P < 0.0001). Interestingly, the levels of SP were positively associated with corneal sensitivity (r = 0.6671, P < 0.01) and pain (r = 0.4979, P < 0.05), while borderline significance (P = 0.058) was found with ocular surface inflammation grading.
Conclusions :
Our data show that functional inhibition of corneal nerves not only reduces ocular pain but also inflammation and SP release in the tear fluid. These preliminary findings indicate that SP content in human tears could be used as a marker to quantify the severity of pain and inflammation of the ocular surface.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.