Abstract: We included three RCTs, one from New Zealand, one from Japan and one from China, published between 2015 and 2019. Together, these trials enrolled 114 adults (228 eyes). Two studies used a paired-eye (inter-eye comparison) design to evaluate the effects of a sham (control) IPL treatment relative to an actual IPL treatment. One study randomised individuals to either an IPL intervention combined with meibomian gland expression (MGX), or MGX alone (standard therapy). The study follow-up periods ranged from 45 days to nine months. None of the trials were at low risk of bias in all seven domains. The first authors of two included studies were in receipt of funding from patents or the manufacturers of IPL devices. The funding sources and declaration of interests were not given in the report of the third included trial. All three trials evaluated the effect of IPL on dry eye symptoms, quantified using the Standard Patient Evaluation of Eye Dryness (SPEED) questionnaire. Pooling data from two trials that used a paired-eye design, the summary estimate for these studies indicated little to no reduction in dry eye symptoms with IPL relative to a sham intervention (mean difference (MD) –0.33 units, 95% confidence interval (CI) –2.56 to 1.89; I² = 0%; 2 studies, 144 eyes). The other study was not pooled as it had a unit-of-analysis error, but reported a reduction in symptoms in favour of IPL (MD –4.60, 95% CI –6.72 to –2.48; 84 eyes). The body of evidence for this outcome was of very low certainty, so we are uncertain about the effect of IPL on dry eye symptoms. There were no relevant combinable data for any of the other secondary outcomes, thus the effect of IPL on clinical parameters relevant to dry eye disease are currently unclear. For sodium fluorescein TBUT, two studies indicated that there may be an improvement in favour of IPL (MD 2.02 seconds, 95% CI 0.87 to 3.17; MD 2.40 seconds, 95% CI 2.27 to 2.53; 172 eyes total; low-certainty evidence). We are uncertain of the effect of IPL on non-invasive tear break-up time (MD 5.51 seconds, 95% CI 0.79 to 10.23; MD 3.20, 95% CI 3.09 to 3.31 seconds; two studies; 140 eyes total; very low-certainty evidence). For tear osmolarity, one study indicated that there may be an improvement in favour of IPL (MD –7.00 mOsmol/L, 95% –12.97 to –1.03; 56 eyes; low-certainty evidence). We are uncertain of the effect of IPL on meibomian gland orifice plugging (MD –1.20 clinical units, 95% CI –1.24 to –1.16; 84 eyes; very low-certainty evidence). We are uncertain of the effect of IPL on corneal sodium fluorescein staining. One study reported no evidence of a difference between the IPL and sham intervention arms at three months of follow-up (P = 0.409), and a second study reported data favouring IPL (MD –1.00 units, 95% CI –1.07 to –0.93 units; 172 eyes in total; very low-certainty evidence). We considered the incidence of adverse events at the study endpoint, as a measure of safety. As most trials did not specifically report adverse events, the safety of IPL as a treatment for MGD could also not be determined with any certainty. Very low-certainty results from individual studies suggest some adverse effects that may be experienced by participants, include mild pain and burning, and the potential for partially losing eyelashes (due to clinician error). This systematic review finds a scarcity of RCT evidence relating to the effectiveness and safety of IPL as a treatment for MGD. Whether IPL is of value for modifying the symptoms or signs of evaporative dry eye disease is currently uncertain. Due to a lack of comprehensive reporting of adverse events, the safety profile of IPL in this patient population is also unclear. The current limitations in the evidence base should be considered by clinicians using this intervention to treat MGD, and outlined to individuals potentially undergoing this procedure with the intent of treating dry eye disease. The results of the 14 RCTs currently in progress will be of major importance for establishing a more definitive answer regarding the effectiveness and safety of IPL for treating MGD. We intend to update this review when results from these trials become available.

Plain-language summary: we searched for studies that had been published up to 1 August 2019. We identified three randomised controlled trials (RCTs; clinical studies where people are randomly put into one of two or more treatment groups) involving 114 adults (228 eyes) from three countries (New Zealand, Japan and China) that had been published between 2015 and 2019. The maximum time that people in the studies were followed up for after the treatment was nine months. because of very low-quality evidence, we are unclear about the effect of IPL on dry eye symptoms. IPL may be helpful to improve some of the clinical signs of MGD (such as tear stability and tear composition - both signs of how healthy the tears produced by the eye are). We are uncertain about the effect of IPL on meibomian gland blockage or corneal sodium fluorescein staining. As most studies did not report side effects, we are uncertain about the safety of IPL as a treatment for MGD. Very low-quality results from individual studies suggest there may be some side effects, including mild eye pain and burning, and partially losing eyelashes (due to mistakes when using the IPL device). the evidence for how effective and safe IPL is for treating MGD was of low or very low quality. due to limited information in the clinical trials, we could not determine with certainty whether IPL treatment for MGD is effective or safe. The review findings indicate that more research is needed. It is important that eye care clinicians, and people considering having IPL as a dry eye treatment, are aware that there is limited high-quality research to understand whether the procedure is effective or safe.