Focusing on color: How the eye chooses which wavelength to see best

Humans can see in exquisite detail despite the fact that the eyes' optics can only focus light at a single wavelength at a time. It remains an open question what wavelength is brought into best focus by the human eye. Here, we investigate this question. We used a custom optical apparatus to measure the eye's focusing response (accommodation) to a range of stimuli with different wavelength compositions. We then developed a biologically informed model of the measured responses. Conventional wisdom holds that accommodation works to maximize visual acuity, but our findings suggest otherwise. Rather, our results support alternative lines of evidence that accommodation is guided by chromatic mechanisms that maximize signal quality in a color-opponent channel. Our results challenge prevailing views of oculomotor control and can inform therapeutic interventions for slowing the development and progression of myopia.