Dear Editor,Recently, Abraham et al., investigated the correlations between ocular parameters and amplitude of accommodation (AA).[1] The authors measured the axial lengths (AL), central anterior chamber depths (CACD) and lens thicknesses (LT) of a group of participants and correlated them to the AA in order to explore their relation to the onset of presbyopia. Presbyopia as a public health problem concerns all individuals above 40 years of age. We congratulate the authors, because they used a very basic and simple methodology in the study, but the potential importance of the study goes beyond the methodology used.The authors divided the participants into three categories as emmetropes, myopes and hypermetropes. They investigated the correlations between ocular parameters and AA within each group. We think that investigating the correlation within each group does not reflect the actual correlation between each ocular parameter and AA. For example, Table 1 shows three groups with two variables. Groups 1, 2, 3 include 7, 8, 7 values for each variable. Total number of the values is 22. The Spearman correlation coefficients between the two variables are -0.115 (P=0.805), 0.346 (P=0.402) and -0.487 (P=0.268) for Groups 1 to 3, respectively. Each correlation is statistically insignificant. However, if we include all of the values together in the statistical analysis, the Spearman coefficient shows a significant correlation, 0.676 (P=0.001)[Table 1].
Table 1
Two variables for three groups
Two variables for three groupsFor this reason, we suggest to the authors to perform the correlations between AL, CACD, LT and AA including all the participants. Performing the correlations in each refraction group means holding the numerals into a narrow interval. For us, this may have a major effect on the results of the study.