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Discussion | Using a pair of sunglasses modified to include an affixed ruler, we were able to accurately obtain anthropometric measurements for facial analysis and operative planning. The differences in measurements between ruled sunglasses and the calibration standard for both three-quarters views is most likely accounted for by user error. A small change in the angle of the calibration standard away from the midsagittal plane of the head would lead to a distortion in measurement of the ruler proportional to cos. Deviations in other planes away from the imaging plane would yield similar distortions. Because the ruled sunglasses are fixed in motion with the head, measurements obtained using the sunglasses method are more reliable than previous standards such as the handheld ruler. Further limitations include access to 3-dimensional surface imaging, lens distortion, and sample size.
Mittermiller et al. (Wed,) studied this question.