Figure 6.

Raman analysis of the human retina. Experiments with a 488 nm laser. (a) Photo of a preparation. (b) Raman image based on the integration of the ν₁ band (1500–1550 cm^–1). (c) Raman spectra in the ν₂ region, recorded from the neighboring parts of the macula: dark-adapted (dark) and exposed for 5 min to white light (light). Spectra represent the arithmetic mean from 20 spectra recorded at different positions. The spectra are normalized in the maximum of the ν₁ band. (d) Distribution of the molecular configuration forms of Lut in the central retina exposed to light. Note different scales in the images representing the all-trans and 13-cis and 13′-cis isomers. In the case of Lut all-trans, the intensity is overestimated owing to the contribution of Zea and m-Zea to the resonance Raman spectra. The retina samples from a healthy 79-year-old female donor (a), a healthy 34-year-old female donor (b), and a healthy 18-year-old female donor (c, d).