Preliminary Results Of A Randomized Double Masked Clinical Trial Investigating The Impact Of Low-Level Light Therapy (Lllt) On The Ocular Microbiome

Photobiomodulation in the form of low-level light therapy (LLLT) is increasingly being used to manage chronic, inflammatory ocular conditions such as dry eye disease and blepharitis. Limited research has been done to compare photobiomodulation utilising different wavelengths. The purpose of this pilot study was to compare the impact of using red and blue LLLT in treating patients with dry eye disease along with meibomian gland dysfunction and demodex blepharitis.

This randomised, double-masked, sham-controlled clinical trial was conducted at the Aston Dry Eye Clinic in Aston University, Birmingham, United Kingdom, where participants with dry eye disease, demodex blepharitis and meibomian gland dysfunction were consecutively enrolled in this study.

Participants (n=24, 8 in each treatment group) were randomised into either the red LLLT only (R), red plus blue LLLT (R+B) and sham red and blue LLLT (Sham) calibrated to emit only 10% of the full fluence energy. Each session involved wearing a mask with blue and/or red light emitting diodes for 30 minutes. Three treatment sessions were involved each 1 to 2 weeks apart, with symptomatology, conventional ocular surface measures and lower lid margin cultured microbiome assessed at baseline and 1 month following the final treatment session. 

Both R and R+B groups showed significant symptoms improvement over time (Ocular Surface Disease Index, OSDI, F=5.97, p=0.007), with reduction from baseline in R (45.8±22.9 to 36.4±24.5, p=0.047) and R+B (47.8±20.3 to 27.0±18.8, p=0.02), but not in the Sham group. While not statistically significant (p>0.05), there was a trend for the number of cultured bacterial colonies to decrease from baseline to the final visit for the R group (aerobic: 76.6±182.4 to 19.9±24.3; anaerobic: 53.4±132.7 to 10.2±22.0) and R+B group (aerobic: 121.6±190.3 to 18.9±22.4; anaerobic: 120.4±195.1 to 15.3±21.2), but not in the Sham group (aerobic: 100.1±117.2 to 133.0±227.1; anaerobic: 101.1±110.6 to 110.1±188.5).  

This study suggested the potential for red plus blue LLLT in modulating the microbiome of the lid margins and reducing symptoms in patients with dry eye disease, meibomian gland dysfunction and demodex blepharitis. Future studies with larger sample sizes investigating its use as an adjunctive therapy in addition to currently established dry eye treatments, and the exact bacterial phenotypes and profile affected by photobiomodulation are warranted.