Comparison of subconjunctival scarring after microincision vitrectomy surgery using 20-, 23-, 25-and 27-gauge systems in rabbits

Purpose: To compare subconjunctival scarring after vitrectomy in rabbit eyes using different gauge systems by analysing anterior segment optical coherence tomography (AS-OCT) images and histological sections. Methods: Vitrectomy using 20-, 23-, 25-and 27-gauge systems was performed for rabbits. Anterior segment optical coherence tomography (AS-OCT) images of the incision sites were obtained before and at day 1, 7 and 1 month after surgery. We measured the thickness of conjunctival epithelium, stroma, Tenon's capsule and total conjunctiva of these three layers, then determined the preservation rates of the borderlines between each layer. Surgical invasion was estimated by histological observation. Results: The thickness of total conjunctiva, or the thickness of both conjunctival stroma and Tenon's capsule in the 20-gauge group was significantly thicker than that in the 27-gauge group at day 1 and day 7 after surgery. Preservation rates of the conjunctival stroma/Tenon's capsule borderline were significantly lower in the 20-gauge group than in the 25-and 27-gauge groups at day 1, day 7 and 1 month. Preservation rates of the Tenon's capsule/sclera borderline were significantly lower in the 20-gauge group than in the 25-and 27-gauge groups at 1 month. In the 27-gauge group, the number of a-smooth muscle actin-positive fibroblasts was significantly smaller than in the 20-gauge group at day 7. Conclusion: Based on the finding of AS-OCT and histology, micro incision vitreous surgery, especially using 27-gauge, contributed to less subconjunctival scarring postoperatively. Therefore, the 27-gauge pars plana vitrectomy (PPV) may be a more effective technique for preserving the structure of conjunctiva.