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A. F. Scheuerle, B. Yang, E. Schmidt, K. Rohrschneider; Intraindividual Variability of Optic Disc Parameters. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5810.
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The intraindividual comparison of the right and left optic disc plays an important role in the detection of pathologic changes. The Heidelberg Retina Tomograph (HRT II) is an approved device to collect precise parameters of the optic disc.We used the HRT II to investigate bilateral stereometric parameters of optic discs in a healthy population.
Over a period of two years 219 volunteers of different age-groups were examined. A full medical history was taken, fast threshold perimetry, air-puff tonometry and laser scanning tomography with the HRT II on both eyes of each subject were performed by the same physician in one setting. The intraindividual variance was tested by comparing the optic disc parameters of the right and the left eye of each volunteer. Besides absolute values a relative deviation from the mean value (cutoff >10%) of the right and the left eye of each individuum was calculated.
The average disc size of 438 healthy eyes was 2.16 ± 0.4 mm2, the mean difference between the right and the left eye was 0.03 ± 0.28 mm2, a relative deviation of >10% was found in 15% of the cases. The average cup area was 0.39 ± 0.29 mm2, a relative deviation of >10% was found in 70% of the cases. The average rim area was 1.77 ± 0.33 mm2, a relative deviation of >10% was found in 13% of the cases. The average cup/disc area ratio was 0.17 ± 0.11, a relative deviation of >10% was found in 68% of the cases. The average rim/disc area ratio was 0.83 ± 0.11, a relative deviation of >10% was found in 7% of the cases.
The HRT II is a reliable tool to evaluate the optic disc in vivo. Despite the large interindividual variability of optic nerve head topography, the intraindividual symmetry of optic disc parameters is very high in a healthy population. While optic disc size, rim area and rim/disc area ratio prooved to be very stable comparing right and left eyes, cup area and cup/disc area ratio showed a higher intraindividual variability. This phenomenon might be explained by the smaller absolute values of cup parameters. In contrast to the high interindividual variability, the intraindividual optic disc parameters of right and left eyes are very similar in the vast majority of healthy subjects.
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