Background: A ciliary block is the rarer cause of angle block glaucoma. In order to choose the appropriate therapy, however, it is crucial to make the correct diagnosis. We report on a patient who suffered from recurrent increases of intraocular pressure while having renal dialysis. In his case the use of the Orbscan II made the differentiation between a pupillary and a ciliary block easier. Case Report: In addition to basic ophthalmological examinations we performed a topographic analysis using Orbscan II before and after renal dialysis. Since intraocular pressure rise during renal dialysis had been proven, iridotomies on both eyes and an iridectomy on the left one had been performed before the patient was referred to us. In spite of these open shunts we measured an increase of intraocular pressure values of 10 to 12 mmHg directly after renal dialysis had been completed. The anterior chamber became shallower both at its centre and the periphery, thus its volume diminished analogously. Measurements by the Orbscan II showed that the lens swelled up and was displaced anteriorly as well, so that a ciliary block mechanism had to be assumed. Conclusions: Since the Orbscan II is capable of collecting topometric data of the cornea, anterior chamber and also lens, it is helpful in differentiating a pupillary from a ciliary block in angle block glaucoma. Background: A ciliary block is the rarer cause of angle block glaucoma. In order to choose the appropriate therapy, however, it is crucial to make the correct diagnosis. We report on a patient who suffered rec recounts increases of intraocular pressure while having renal dialysis In his case the use of the Orbscan II made the differentiation between a pupillary and a ciliary block easier. Case Report: In addition to basic ophthalmological examinations we performed a topographic analysis using Orbscan II before and after renal dialysis. Since intraocular pressure rise during during renal dialysis had been proven, iridotomies on both eyes and an iridectomy on the left one had been done before the patient was referred to us. dialysis had been completed. The anterior chamber became shallower both at its center and the periphery, so its volume diminished analogously. Measurements by the Orbscan II showed that the lens swelled up and was displaced anteriorly as well, so that a ciliary block mechanism had to be assumed. Conclusions: Since the Orbscan II is capable of collecting topometric data of the cornea, anterior chamber and also lens , it is helpful in differentiating a pupillary from a ciliary block in angle block glaucoma.