Abstract:  Objective To study the amount of filtration in primary trabeculectomy and the association of filtration amount with intraoperative and early postoperative intraocular pressure (IOP). Design Prospective observational study. Participants 82 cases of glaucoma patients underwent primary trabeculectomy between December 2009 and August 2010 were included. Methods 1. Add different volume of normal saline on the specified location of sterilized filter papers for Schirmer’s test, then observe the correlation of volume of fluid with the wet length. 2. Prospectively enrolled consecutive patients with primary open-angle or angle-closure glaucoma who underwent primary trabeculectomy. Use Tonopen to measure the intraoperative IOP after closure of the scleral flap. Use sterilized filter papers to measure the amount filtration 60 s after injecting BSS through the paracentesis. Wait for 80 s to get the readings. Analysis the relationship between filtration amount and intraoperative IOP, postoperative IOP at 1 and 7 days after surgery. Observe the height and range of filtering bleb and complications. Main Outcome Measures Wet length of the filter paper, intraoperative IOP, early postoperative IOP and the height, range and complications of filtering bleb. Results The wet length of the filter paper was significantly associated with the liquid volume. The liquid volume can be calculated by the following equation: Volume (μl) = 1.0434 × Length (mm) + 2.4086 (R2 = 0.97). In Eighty-two consecutive eligible patients (82 eyes) who underwent primary trabeculectomy, mean preoperative IOP was 32.3±9.0 mmHg. According to the intraoperative wet length of the filter paper, the patients were divided into three groups: group 1(≤5 mm, n=46), 2 (6~10 mm, n=18), and 3 (≥11 mm, n=18). The intraoperative IOP of the three group was 13.9±8.3 mmHg, 12.1±5.4 mmHg,12.1±6.5 mmHg, respectively (P=0.543). At 1d postoperatively, the IOP was 13.3±7.9 mmHg, 12.7±7.3 mmHg, 15.9±9.0 mmHg, respectively. At 7d postoperatively, the IOP was 12.2±6.9 mmHg, 10.7±5.6 mmHg, 13.1±8.1 mmHg, respectively. The postoperative IOP among these three groups had no significant differences (all P>0.05). There were no shallow anterior chamber postoperatively. Conclusion The wet length of the filter paper is significantly associated with the liquid volume. In trabeculectomy, the filtration amount can be measured by the filter papers for Schirmer’s test. Filtration amount during trabeculectomy can not be independently used to determine the intraoperative IOP and predict the early postoperative IOP. (Ophthalmol CHN, 2014, 23: 94-98)

Key words: glaucoma/surgery, trabeculectomy, filtration amount, intraocular pressure