Prospectively, consecutive patients at the University Hospital of Zurich undergoing either trabeculectomy (trab) or phaco-trabeculectomy (phaco-trab) are included in this study between January and December 2017. The study interventions takes place 6 months after surgery and include examination of refraction, biometry and corneal topography in order to assess the patient's astigmatism. The values are compared to the preoperative baseline values, which are available from patient records.