To the Editor.
—In their recent article, Breton and Krupin1 state that color vision loss scores and differential light sense do not correlate with each other but are both related to age. They claim an independent mechanism is responsible for early color loss compared with visual field loss in glaucoma.Many of the correlation coefficients shown in Tables 2 through 5 of their article are found not to be statistically significant; however, in many of these tables, the lack of significance can be attributed to the small sample sizes in the corresponding age groups. For instance, the correlation coefficient of -.46 calculated in Table 5 for the age group 40 through 49 years is not significant at the given sample size of 13; however, the same correlation coefficient would have been found to be statistically significant (using Fisher's z transformation) had the sample size been 19 or more. Indeed, while
Drance SM, Schulzer M. Age Covariance and Open Angle Glaucoma. Arch Ophthalmol. 1987;105(11):1477. doi:10.1001/archopht.1987.01060110023007