Effects of Light on the Choroid and Pupil

Monochromatic light creates longitudinal chromatic aberration, with short wavelength blue light forming a focal point in front of the retina and long wavelength red light forming a focal point behind the retina. The investigators hypothesize that such chromatic aberrations, induced by exposure to red or blue LED lights, will cause the choroid behind the retina to respond to bring the image into focus by modulating its thickness, either thickening in the case of blue light or thinning in the case of red light. The magnitude and direction of this response is difficult to predict as previous studies have shown opposite findings in non-human primates and rodents. Furthermore, the investigators hypothesize that exposure to red or blue light will induce changes in how the pupil responds to light, because the cells in the eye that are involved in pupil control are most sensitive to blue light.