Objective To investigate the early changes in tear film after vitreous microsurgery,to compare the postoperative impact of 23-gauge and 25-gauge vitreous microsurgery on tear film.Methods Eighty-six eyes of 86 patients who underwent 23-gauge or 25-gauge vitreous microsurgery monoculady between March 2009 and July 2009 were enrolled in this prospective case series study.The contralateral eyes were regarded as the control group. Among them, 35 eyes each underwent 25- combined 23-gauge surgery (group A), another 35 eyes underwent 25-gauge vitrectomy (group B),and another 16 eyes underwent 23-gauge vitrectomy (group C). Symptoms of discomfort, break-up time (BUT), Schirmer I test (SIT) and corneal fluorescein staining (CFS) were recorded before and after surgery in all patients (86 patients with 172 eyes), and the data from all ophthalmologic examinations were collected. Data were analyzed with a Kruskal-Wallis, a Wilcoxon, an one-way ANOVA and an independent samples t test. Results Nine patients complained of foreign body sensation, burning, or lacrimation with significantly increased SIT (P=0.001) at day 1 and CFS scores (Z=-3.782,P＜0.05) at days 3 postoperatively. Obviously decreased BUT was recorded at day 1 and day 3 postoperatively, BUT recovered significantly 10 days postoperatively (P=0.001). In the subjective scores for symptoms of discomfort and SIT results in the contralateral eyes, no significant changes were found at any follow-up examination, the differences for CFS and BUT were significant 10 days after surgery. Compared to contralateral eyes, all dry eye test values were significantly worse at day 1 and davs 3 postoperatively in the surgical eyes (Z=-5.470, -5.011; t=-4.968, -5.184; t=4.452, 3.963; P＜0.05).CFS values were different at each follow-up examination (Z=-6.229, -5.780, -5.018, -4.379, -2.374,P＜0.05). There were no differences in tear film in both eyes between group A, group B and group C at any follow-up examination. Conclusion The stability of tear film can be affected in the early postop