The aim of this study was to evaluate the concordance of intraocular pressure (IOP) measurements in the supine glaucoma patient using a Perkins applanation tonometer (PAT) compared to the iCare® rebound tonometer (RT), a hand-held device requiring no local anaesthesia.73 left eyes of 73 glaucoma patients were included in this consecutive case study and measured both by supine Perkins applanation tonometry and by right lateral posture rebound tonometry in the supine position (RLP). The patients were divided into three subgroups dependent on IOP (SG-1: 0 - 15 mmHg, SG-2: 16 - 22 mmHg, SG-3: more than 23 mmHg).The mean deviation between RT and PAT was 2.6 ± 4.0 mmHg, the 95 % confidence interval was -5.3 to 10.4 mmHg. 69 % of the measurements showed deviations within 3 mmHg between the two devices. Deviation was smallest in SG-2, and largest in SG-3.Rebound tonometry is comfortable to use even in supine patients. RT measurement agreed overall significantly with those of Perkins applanation tonometry, generally overestimating PAT measurement. In high IOP values, RT did not correlate as well with PAT as in moderate IOP levels.