Summary of findings 1. No tea tree oil group compared to tea tree oil (intervention) group for Demodex blepharitis.

No tea tree oil group compared to tea tree oil (intervention) group for Demodex blepharitis
Patient or population: Demodex blepharitis Settings: Hospital and University clinical centres Intervention: tea tree oil Comparison: no tea tree oil
Outcomes	Anticipated absolute effects* (95% CI)		Other results	Relative effect (95% CI)	No of participants, no of eyes (studies)	Certainty of the evidence (GRADE)	Comments
	Assumed Risk	Corresponding Risk
Mean change in number of Demodex mites per 8 eyelashes at 4–6 weeks	The mean change in number of Demodex mites per 8 eyelashes in the control group ranged from ‐10.7 to ‐0. 17.	MD 0.7 higher (0.24 higher to 1.16 higher)	—	—	215, 430 eyes (3 RCTs)	⊕⊝⊝⊝ Very lowa,b,c	—
Mean change in participant‐reported change in symptoms at 4–6 weeks	—	—	Three trials reported sufficient data to permit calculation of between‐group difference at short term (MD 3.40, 95% CI –0.70 to 7.50 in Koo 2012; MD ‐2.60, 95% CI ‐11.94 to 6.74 in Murphy 2018; and MD –10.54, 95% CI –24.19 to 3.11 in Zhang 2019), comparing no tea tree oil group versus tea tree oil	—	246, 492 eyes (2 RCTs)	⊕⊕⊝⊝ Lowa,b	The estimates of effect were inconsistent between these two trials, precluding any meta‐analysis. For Murphy 2018, we only considered data from the arms comparing lid scrubbing with and without tea tree oil.
Participants with an improvement in visual acuity at 4–6 weeks	—	—	One multi‐arm study reported data on visual acuity, but it did not provide individual group findings. The authors noted that mean habitual LogMAR visual acuity among all study participants improved post‐treatment (mean LogMAR 1.08, SD 0.26 at baseline; mean LogMAR 1.16, SD 0.26 at 4 weeks)	—	86, 172 eyes (1 RCT)	⊕⊕⊝⊝ Lowa,b	—
Mean change in (or mean) number of cylindrical dandruff at 4–6 weeks	—	—	—	—	0 (0 RCTs)	—	None of the studies addressed this outcome as defined.
Proportion of participants with meibomian gland dysfunction at 4–6 weeks	—	—	—	—	0 (0 RCT)	—	No studies addressed this outcome as defined.
Proportion of participants experiencing conjunctival injection (redness) at 4–6 weeks	—	—	—	—	0 (0 RCTs)	—	None of the studies addressed this outcome as defined.
Adverse events at 4‐6 weeks	—	—	One RCT reported no adverse events; one reported that five participants randomized to treatment with tea tree oil had ocular irritation that was resolved after patient re‐education on eyelid scrubbing methods; and one RCT reported initial discomfort for one participant randomized to treatment with tea tree oil that was self‐resolved on continuing the use of tea tree oil.	—	318, (3 RCTs)	⊕⊝⊝⊝ Very lowa,b,c	Three of the six RCTs provided no information related to adverse events.
CI: confidence interval; LogMAR: logarithm of the minimum angle of resolution; MD: mean difference; RCT: randomized controlled trial; SD: standard deviation.
GRADE Working Group grades of evidence High certainty: we are very confident that the true effect lies close to that of the estimate of the effect. Moderate certainty: we are moderately confident in the effect estimate: the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different. Low certainty: our confidence in the effect estimate is limited: the true effect may be substantially different from the estimate of the effect. Very low certainty: we have very little confidence in the effect estimate: the true effect is likely to be substantially different from the estimate of effect.

^aDowngraded one level due to unclear or high risk of bias in at least one contributing study.
^bDowngraded one level due to inconsistency, substantial statistical and clinical heterogeneity.
^cDowngraded one level due to imprecision around effect estimates.