The purpose of this study is to determine the effects of the working distance on the accuracy of confocal scanning laser tomography using the Heidelberg Retina Tomograph II. Twenty eyes of normal patients were imaged and the topographies of the retinal surfaces were recorded. Each eye was imaged first at the optimum working distance,
establishing the baseline exam, and then re-imaged at four different working distances (one at a shorter distance than optimum, three more at longer distances than optimum, variation done in 2 mm increments). The recorded data at various working distances was compared to the baseline data. The deviation from the baseline was compared to the
normal standard deviation for the instrument reported in the literature. Data is within the normal standard deviation when staying between -2 mm and +4 mm of optimum working distance. Some stereometric parameters vary greater than the normal standard deviation if working distance is more than +4 mm from optimum. To minimize error in recorded data, the operator of the Heidelberg Retinal Tomograph II should image the patient’s eye between -2 mm and
+4 mm of optimum working distance. Staying in this range should provide results that vary within the normal standard deviation.
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