[The Heidelberg Retina Tomograph: reproducibility and measuring errors in different pupillary widths using a model eye].
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.


CONCLUSIONS
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.
Janknecht
P
P
Univ.-Augenklinik Freiburg.
Funk
J
J
D005137:Eye, Artificial; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000295:instrumentation; D008953:Models, Anatomic; D011237:Predictive Value of Tests; D011680:Pupil / Q000502:physiology*; D012025:Reflex, Pupillary / Q000502:physiology*; D015203:Reproducibility of Results; D014054:Tomography / Q000295:instrumentation*
Heidelberg-Retina-Tomograph: Reproduzierbarkeit und Messfehler bei unterschiedlicher Pupillenweite am Modellauge.