There has been a great deal of interest in the idea that dark focus (DF) has a potential role in myopia development i.e., the inward shift of DF after a near visual task may have the potential to induce myopia. Before we can evaluate this hypothesis, two important questions must be addressed: "Can we differentiate true adaptive changes of DF from normal DF variability" and, "Are the DF positions different in some subjects who develop myopia?" The purpose of our study was to both characterize DF in a manner that would later allow us to identify adaptive changes in DF after a task, and to compare DF in age-of-onset based refractive error groups. We used an SRI eyetracker to measure DF and dark vergence (DV) 4 times each, in 28 subjects: 9 emmetropes, 9 early onset myopes, and 10 late onset myopes. We found that: (1) DF was better characterized as a "zone" than a "point;" (2) the magnitude of DF was correlated with the variability of DF, i.e., the more myopic the DF, the larger the within-session variability; (3) there was no significant difference in DF or DV between refractive error groups. These results suggest first, that DF is more variable than previously thought and therefore should be thought of as existing within a "zone" of resting focus, and second, that actual adaptation of DF may be a function of DF variability rather than absolute position of DF.