PURPOSE: To investigate how the central visual field would be changed after fornix-based trabeculectomy with mitomycin C in Japanese normal-tension glaucoma (NTG) patients monitored for more than 10 years including before surgery. METHODS: This is a retrospective cohort study. We identified twenty-eight eyes of 28 NTG cases regularly monitored for more than 5 years and examined static visual field (VF) tests for more than five times before and after fornix-based trabeculectomy (including combined surgery). Based on preoperative data for 6.3 years, we evaluated postoperative changes for 6.0 years in 10-2 VF and 30-2 VF. RESULTS: Six patients were male and 22 females, the mean age was 57.9 years, and the mean deviation was - 13.7 decibels. After surgery, mean IOP decreased from 13.9 to 9.0 mmHg (P ≤ 0.01), and medication score also did. The rate of 10-2 VF deterioration was significantly suppressed from - 1.0 dB/year preoperatively to - 0.4 dB/year postoperatively (P ≤ 0.01). And when 30-2 VF was divided into six relevant sectors, the rate of deterioration at cecocentral and arcuate areas of the superior hemifield was suppressed postoperatively (P ≤ 0.01 and P = 0.042, respectively). CONCLUSION: Based on long-term preoperative data, a significant positive change in 10-2 VF was observed after fornix-based trabeculectomy with mitomycin C in Japanese NTG patients with a mean IOP of 13.9 mmHg. Central vision could be expected to be maintained for NTG patients even if its preoperative IOP is low after successful trabeculectomy.