Tear film stability after trabeculectomy and its relationship with bleb morphology

Objective To investigate the tear film stability after trabeculectomy and its relationship with bleb morphology using Optical Quality Analysis System Ⅱ (OQAS Ⅱ). Methods A cross-sectional study. Glaucoma patients undergoing trabeculectomy in the Eye Hospital of Wenzhou Medical University from November 2011 to November 2016 were invited by telephone to perform optical quality, bleb photography, and break-up time examinations, and history of surgeries and medications was collected. Bleb morphology was graded according to the Indiana bleb appearance grading scale. The tear film stability was the average objective scatter index value measured using OQAS Ⅱ for 10 seconds after blinking minus the baseline objective scatter index. The higher the tear film stability value, the worse the stability. The difference in the tear film stability between the surgical eyes and non-surgical eyes was compared by the Mann-Whitney U test, and the relationships between the optical quality, bleb height, extent and vascularity were compared by the Kruskal-Wallis H test. Results Sixty-three patients (76 eyes) were enrolled in the study, including 55 surgical eyes and 21 non-surgical eyes. The mean follow-up time was (39.6±26.2) months.In the surgical and non-surgical eyes, the M(QR) of tear film stability was 0.46 (0.86) and 0.23 (0.41), respectively. The tear film stability in the surgical eyes was reduced compared to the non-surgical eyes (P=0.044). The trabeculectomy group was divided into three subgroups according to the height of the filtering bleb: H0 (17 eyes), H1 (24 eyes) and H2-3 (14 eyes). The M(QR) of tear film stability in the three subgroups was 0.40(0.68), 0.70(1.02) and 0.40(1.24), respectively, with no statistically significant difference detected (P=0.481). According to the bleb extent, the surgical group was divided into two subgroups: E0-1 (36 eyes) and E2-3 (19 eyes). The M(QR) of optical quality in the two subgroups was 0.63 (0.78) and 0.26(1.17), respectively, with no significant difference detected (P=0.261). According to the degree of bleb vascularity, the surgical group was divided into three subgroups: V0 (25 eyes), V1 (14 eyes), and V2-3 (16 eyes). The M(QR) of optical quality in the three subgroups was 0.39 (0.69), 0.55 (1.18) and 0.63 (1.24), respectively, with no significant difference (P=0.401). Conclusion Although tear film stability decrease after trabeculectomy, the decrease is not associated with the bleb morphology. (Chin J Ophthalmol, 2019, 55:214-219) Key words: Glaucoma; Trabeculectomy; Tear film stability; Bleb morphology; Objective scatter index