Heidelberg retina flowmeter parameters at the papilla in healthy subjects

PURPOSE: To assess the Heidelberg Retina Flowmeter (HRF) parameters "volume", "flow", and "velocity", at the papilla in healthy subjects. METHODS: HRF measurements were taken at the papilla (5 degrees x 20 degrees), superficially at level of the retina and at the bottom of the excavation. The effect of increasing frame size (1 x 1 to 50 x 50 pixels) on HRF values was assessed in ten subjects. HRF parameters were calculated (50 x 50 pixels) for 150 eyes of 150 subjects. To assess short-term reliability, measurements were repeated five times in ten subjects. RESULTS: With 50 x 50 pixels the location of the frame had no influence on HRF values. Reliability was > 90%. Values were significantly higher (p < 0.001) in the superficial than in the deeper papillary layers. The correlation between HRF parameters was good (r2 > 0.85). CONCLUSIONS: A low magnification (5 degrees x 20 degrees) and a 50 x 50 frame allows a global assessment of HRF parameters at the papilla with high reliability. In healthy eyes, the HRF values are influenced by the level where measurements are made at the papilla. This might be of importance in glaucoma patients with excavated papilla.