Analysis of tear inflammatory proteins following Low-Level light therapy in dry eye disease patients

Low-level light therapy (LLLT) in combination with intense pulsed light (IPL) has been shown to improve clinical signs and symptoms of dry eye disease (DED), as well as tear inflammatory protein levels. However, the therapeutic mechanism of LLLT as a stand-alone treatment remains unclear. This single-arm pilot study aimed to determine the impact of LLLT alone on tear protein levels in patients with DED.

Study participants received a 15-minute LLLT session once a week for three weeks using the Eye-light® EPI-C Plus device. Clinical measures of DED were assessed, including first and average non-invasive keratograph tear break-up time (NIKBUT), tear meniscus height (TMH), tear film lipid layer thickness (TFLLT), and Schirmer's test. Tear samples were collected with Schirmer's strips at baseline and after the final treatment. Tear fluid was extracted by eluting the strips in PBS, and the concentrations of ten inflammatory proteins were quantified using a Luminex bead-based multiplex assay.

Thirty participants (mean age ± SD: 31.1 ± 9.5 years; 16 females) with mild to moderate DED completed the study. Compared to baseline, there was a statistically significant fold change in clinical outcome measures after the last LLLT treatment including first and average NIKBUT (mean FC (SD): 1.6 (0.9), 1.4 (0.7)), TMH (1.2 (0.3)), TFLLT (1.3 (0.4)) and Schirmer's test (0.9 (0.5)), (all p < 0.05). There was a significant reduction in MMP-9 levels post-LLLT treatment (mean Log2FC (SD): -0.7 (1.5), p = 0.005). No significant differences were observed in the remaining analytes, and no correlations were observed between the Log2FC of MMP-9 and clinical measures (all p > 0.05).

Findings from this single-arm pilot study suggest that LLLT is associated with improved tear film stability and reduced MMP9 levels in patients with mild to moderate DED.