The purpose of this trial is to study the change in corneal endothelial cell after glaucoma surgery, non-contact specular microscopic examination is performed for the patients who underwent glaucoma surgery; trabeculectomy and Ahmed glaucoma valve implant surgery prospectively. Change in corneal endothelial cell density, hexagonality, and coefficient of variation of cell area will be analyzed and compared to the baseline and between the types of the surgeries.

To study the change in corneal endothelial cell after glaucoma surgery, non-contact specular microscopic examination is performed for the patients who underwent glaucoma surgery; trabeculectomy and Ahmed glaucoma valve implant surgery prospectively. Specular microscopy using non-contact type specular microscope (Noncon Robo SP-8000, Konan Medical Inc., Tokyo, Japan) was performed by one experienced examiner before surgery and 1, 6, 12, 18, and 24 months after surgery. All examinations were done at the center, superior, superonasal, and superotemporal area of the cornea, while the patient maintain fixation at the target in the equipment. The follow-up was stopped if serious complication requiring surgical treatment was developed or additional intraocular pressure lowering surgery is needed, and the data before the second surgery were collected.

Inclusion Criteria:

• Patients who need glaucoma surgery for intraocular pressure control

Exclusion Criteria:

• congenital glaucoma
• Pre-existing corneal abnormality
• lost from follow up without any ocular problem within 6 months from surgery

Patients who underwent glaucoma surgery; trabeculectomy and Ahmed glaucoma valve implant surgery