BACKGROUND: We measured the reproducibility and relative error of the Heidelberg Retina Tomograph (HRT) in a model eye with various widths of the pupil. METHODS: We put diaphragms of various diameters in front of the lens of a model eye. The volume of an artificial papilla which was inserted into the model eye was measured three times. The coefficient of variation (standard deviation/mean value) was taken as a measure of the reproducibility. The relative error was defined as the absolute value of the quotient of the difference between measured and real value. RESULTS: The relative error for diaphragms of 1.5 to 5 mm was 7% to 18.4%, for a diaphragm of 1 mm 19.8%, and for a diaphragm of 11 mm 21.3%. The coefficient of variation ranged from 0.49% to 1.95% for diaphragms of 1.5 to 11 mm diameter, and was 8.1 for a diaphragm of 1 mm diameter. CONCLUSION: The HRT is capable of measuring volumes with a reasonable accuracy. The accuracy does not depend on the width of the pupil over a wide range of pupil diameters. In cases of very small or very much dilated pupils the accuracy and reproducibility declines.
BACKGROUND: We measured the reproducibility and relative error of the Heidelberg Retina Tomograph (HRT) in a model eye with various widths of the pupil. METHODS: We put diaphragms of various diameters in front of the lens of a model eye. The volume of an artificial papilla which was inserted into the model eye was measured three times. The coefficient of variation (standard deviation/mean value) was taken as a measure of the reproducibility. The relative error was defined as the absolute value of the quotient of the difference between measured and real value. RESULTS: The relative error for diaphragms of 1.5 to 5 mm was 7% to 18.4%, for a diaphragm of 1 mm 19.8%, and for a diaphragm of 11 mm 21.3%. The coefficient of variation ranged from 0.49% to 1.95% for diaphragms of 1.5 to 11 mm diameter, and was 8.1 for a diaphragm of 1 mm diameter. CONCLUSION: The HRT is capable of measuring volumes with a reasonable accuracy. The accuracy does not depend on the width of the pupil over a wide range of pupil diameters. In cases of very small or very much dilated pupils the accuracy and reproducibility declines.