 Prior to trabeculectomy corneal biomechanics are measured with the Ocular Response Analyzer ORA, Reichert and the Corvis st Oculus. Both instruments work with an air-puff which deforms the cornea. Intraocular pressure is measured like in non-contact air-puff tonometry. The ORA also measures corneal hysteresis CH and the corneal resistance factor CRF which are qualitative measures of corneal biomechanics. The Corvis is a high-speed Scheimpflug-camera 4330 framessec that records the quantitative movements of the cornea. At least 6 month after uncomplicated trabeculectomy the measurements are repeated. 