Myopia currently affects approximately 25% of the adult population of the United States, while in some areas, notably in Asia, the prevalence may approach 80% of the adult population. While there has been much speculation and controversy over the etiology of this condition, prolonged nearwork has long been suspected as being a contributing factor. My research is aimed towards establishing a mechanism whereby sustained nearwork could lead to axial elongation, the structural correlate of almost all myopia. Of particular interest is the defocus theory, which suggests that axial growth is stimulated by prolonged periods of retinal defocus. However, it is unclear whether this defocus occurs before, during or after the period of nearwork. In addition, work in our laboratory is examining the effects of sustained periods of retinal defocus. We have demonstrated that many individuals are able to adapt to the presence of a sustained blurred retinal image, resulting in substantial, significant improvements in visual resolution, which lasts for several days, is independent of pupil size, and is not attenuated by periods of clear vision. The mechanism underlying this adaptation is currently unclear, although it appears to occur in the visual cortex.