Low-level light therapy alone versus combination therapy with intense pulsed light in the treatment of dry eye disease with meibomian gland dysfunction: A randomised paired-eye and mechanism of action trial

Purpose:
To investigate ocular surface changes following intense pulsed light therapy (IPL) combined with low level light therapy (LLLT) versus LLLT alone for the treatment of meibomian gland dysfunction (MGD) in patients with dry eye disease (DED).

Methods:
Twenty-four participants with MGD and DED were recruited into a double-masked, paired-eye clinical trial, with one eye randomised to being treated with combined therapy and the other eye with LLLT alone across 4 treatment sessions, each 2 to 3 weeks apart. Follow-up assessments were also conducted at 2 weeks and then 3 months after the final treatment. Outcome measures included change in DED signs, symptomatology and in-vivo confocal microscopy parameters at final follow-up from baseline. Mechanism of action was explored with laser doppler flowmetry and fluorescence measures of the central lower eyelid.

Results:
Symptom frequency rated with the Symptom Assessment Questionnaire in Dry Eye improved from baseline to final follow-up with combined therapy (mean difference − 21.6; 95 % CI − 38.5, −4.8; p = 0.005) and LLLT alone (−20.5; 95 % CI − 37.9, −3.1; p = 0.01), while symptom severity improved only with combined therapy (−18.5; 95 % CI − 34.5, −2.6; p = 0.01). Both modalities improved meibum expressibility following 3 treatment sessions, although improvement remained at final follow-up only with LLLT alone (−0.5, 95 % CI − 0.8, −0.2; p < 0.001). Tissue flavin fluorescence decreased after the fifth visit only with combined therapy (−12.7; 95 % CI − 4.9, 20.6; p = 0.001).

Conclusions:
Combined therapy may have further mechanistic changes in increasing cellular metabolism, in addition to improvements in symptoms and meibum expressibility compared to LLLT alone. LLLT alone could be considered an adjunctive therapy for MGD if IPL is contraindicated.