Palczewska, G. et al. Nat. Med. 20, 785–789 (2014).

The transparency of the vertebrate eye to infrared light makes it possible to image the retina at the back of the eye with two-photon microscopy. To counteract aberrations introduced by the anterior part of the eye, Palczewska et al. increased imaging quality and efficiency with the help of adaptive optics, a short-pulsed laser and highly sensitive detectors. With these improvements, the researchers could visualize and spectrally characterize intrinsically fluorescent products of the visual chromophore regeneration pathway, even in living mice. Depending on the excitation wavelength, different fluorophores can be detected. This technique will be helpful for analyzing the impact of drug therapies, disorders affecting the retina and environmental stress on the biochemical processes in the eye.