Eye Pressure Lowering Surgery

Who May Qualify: - Subjects diagnosed with perimetric open angle glaucoma or chronic angle closure glaucoma. - Subjects scheduled to undergo trabeculectomy or tube shunt surgery Who Should NOT Join This Trial: - Best-corrected visual acuity less than 20/40 - Age \< 18 or \>85 years - Refractive error of \> +3.00 D or \< -7.00 D - Previous vision correction surgery such as Laser-Assisted in situ Keratomileusis (LASIK) or Photorefractive Keratectomy (PRK) - Previous intraocular surgery except for uncomplicated cataract extraction with posterior chamber intraocular lens implantation - Diabetic retinopathy - History of heart failure, myocardial infarction, transient ischemic attack or stroke - Other diseases that may cause VF loss or optic disc abnormalities - Inability to clinically view or photograph the optic discs due to media opacity or poorly dilating pupil - Inability to perform reliably on automated VF testing - Life-threatening or debilitating illness making it unlikely patient will successfully complete the study. - Refusal of willing to sign a consent form or of commitment to the full length of the study Always talk to your doctor about whether this trial is right for you.