Enhancing color discrimination in older adults through age-adaptive spectral optimization of lighting

Age-related yellowing of the crystalline lens in older adults reduces short-wavelength retinal input and impairs color discrimination. However, current lighting metrics and spectral optimization approaches remain largely based on the standard observer, which does not account for age-related lens yellowing. Therefore, they provide limited guidance for color discrimination in older adults. To address this limitation, an observer-aware visual model incorporating age-dependent spectral absorption by the lens was established. Based on this model, two metrics were defined for spectral optimization: the age-related color discrimination index (a-CDI), which quantifies recovery of age-related discrimination loss, and the age-related color fidelity index (a-CFI), which quantifies color fidelity relative to the 32-year-old observer under the reference illuminant. Multi-objective optimization identified two representative 5000 K spectra for comparison with D50: P1 prioritizing the a-CDI value and P2 balancing a-CDI and a-CFI values. A human-factors study with 34 older adults aged 70 years and above further supported this framework, showing that both optimized spectra outperformed the D50 (simulated) condition in the FM100 Hue test, with total error scores reduced in 76.5% of participants under P1 and 64.7% under P2. Participants still rated object colors as highly natural under the optimized spectra, indicating that the improvement in color discrimination does not induce an obvious reduction in perceived naturalness. These findings show that the age-adaptive spectral optimization can improve color discrimination in older adults and support age-friendly interior lighting design.