AIM:To investigate the effects of modified Danggui Yinzi decoction combined with diclofenac sodium eye drops on tear film stability and tear protein levels in patients with allergic conjunctivitis.METHODS:Prospective study. Patients with allergic conjunctivitis who attended Suzhou Hospital of Integrated Traditional Chinese and Western Medicine from March 2021 to August 2024 were enrolled as study subjects. They were divided into two groups based on their treatment regimen: a control group(treated with diclofenac sodium eye drops alone)and an observation group(treated with modified Danggui Yinzi decoction combined with diclofenac sodium eye drops). Propensity score matching was used to balance baseline characteristics between the two groups. Log-binomial regression was performed to estimate the risk of adverse reactions. Repeated-measures analysis of variance(ANOVA)was used to assess tear film stability indicators. A difference-in-differences(DID)model was employed to assess the net effect of the combined therapy on changes in tear protein levels.RESULTS:After propensity score matching, a total of 172 patients(344 eyes)were finally enrolled, with 86 patients(172 eyes)in each of the control and observation groups. In the control group, there were 51 males and 35 females, with a mean age of 35.91±10.10 y; in the observation group, there were 49 males and 37 females, with a mean age of 37.87±8.09 y. After treatment, symptom scores decreased in both groups compared with baseline(all P<0.05). At 2 and 4 wk after treatment, symptom scores in the observation group were significantly lower than those in the control group(all P<0.05). The overall response rate was significantly higher in the observation group(89.5%)than in the control group(77.9%)(P<0.05), while the incidence of total adverse reactions was significantly lower in the observation group(7.0%)than in the control group(36.0%)(RR=0.133, P<0.001). Compared with baseline, both groups showed increases in BUT and SⅠt, and a decrease in FL score at 2 and 4 wk after treatment(P<0.017). At 2 and 4 wk after treatment, the BUT and SⅠt levels in the observation group were higher than those in the control group, and the FL score was significantly lower(all P<0.05). The DID model showed that the observation group had greater increases than the control group in lactoferrin(0.411 g/L), total protein(2.792 g/L), secretory immunoglobulin A(14.610 mg/L), and lysozyme(0.419 g/L), respectively(all P<0.05), and these differences remained significant after adjusting for covariates.CONCLUSION:Modified Danggui Yinzi decoction combined with diclofenac sodium eye drops significantly improves tear film stability indicators and tear protein levels in patients with allergic conjunctivitis, and its therapeutic efficacy is superior to that of diclofenac sodium eye drops alone.