Subjects with normal tension glaucoma that is unstable with current medication needing filtration surgery are recruited in the study. All patients meeting the inclusion criteria and giving informed consent will be randomized to whether having deep sclerectomy or trabeculectomy.
The purpose of this study is to assess whether deep sclerectomy is as effective in lowering intraocular pressure (IOP) as trabeculectomy in patients with normal tension glaucoma.