May 2003
Volume 44, Issue 5
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Erratum  |   May 2003
Erratum
Investigative Ophthalmology & Visual Science May 2003, Vol.44, 1813. doi:
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      Erratum. Invest. Ophthalmol. Vis. Sci. 2003;44(5):1813.

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      © ARVO (1962-2015); The Authors (2016-present)

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Erratum in: In “Using Machine Learning Classifiers to Identify Glaucomatous Change Earlier in Standard Visual Fields” by Sample et al. (Invest Ophthalmol Vis Sci. 2002;43:2660–2665). 
In this paper we reported that machine learning classifiers predicted conversion to abnormal visual fields on average 4 years earlier than traditional Statpac-like methods. When reviewing the data for inclusion in a new study, an error was discovered in the dates of conversion based on the Statpac-like methods. Correction of the error has reduced the reported superiority of the machine classifiers to identify change in visual fields earlier. The support vector machine with a Gaussian kernel (SVMg), the best performing classifier, now predicts visual field conversion a mean ± standard error of 0.40 ± 0.51 years earlier than the Statpac-like techniques. SVMg continued to show the best agreement with the presence of glaucomatous optic neuropathy at 94% (32/34) compared to 74% (25/34) for the Statpac-like methods. 
This error was caused by a fault in Microsoft Excel. Excel stores dates as serial numbers that represent the number of days from the system date. In Excel for Windows, January 1, 1900 is the default system date. In Excel for Macintosh computers, it is January 1, 1904. When dates are copied from a file that uses the 1900 system to a file that uses the 1904 date system, the displayed dates will be 1462 days (4 years 1 day) later. The reverse happens on a Windows computer. Excel does not warn users of this potential error. One must be aware of the problem to seek information in the help file or to change the date system in Excel. 
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