An 80-CRI luminaire would normally invite questions on a senior living project. A study published Oct. 13 in Optics Express suggests that, for older eyes, the relevant question may be different. A custom-mixed LED spectrum with an 80 CRI helped people in their 70s and 80s sort colors more accurately than a daylight reference rated 97. The lower score was not the objective; the spectrum was tuned for age-related changes in vision.
The research came from Fudan University in Shanghai, with two Opple Lighting employees among eight authors. It begins with a known problem: the eye's lens yellows with age and filters short-wavelength light. Ra and TM-30, the color metrics specifiers use, are calculated with a fixed standard observer and make no allowance for lens aging, even though the CIE's 2006 physiological model includes an age parameter.
The team modeled the color response of aging eyes and created two metrics. One estimates how much lost color discrimination a spectrum recovers for an older viewer; the other measures color fidelity against a 32-year-old's perception. From a 16-channel LED luminaire, all at 5000 K and Ra of at least 80, they screened 11,541 candidate spectra. Two were tested against a simulated D50 daylight reference with Ra of 97. P1 prioritized discrimination at Ra 80. P2 balanced discrimination and fidelity at Ra 90.
When the authors re-ranked every candidate using the conventional standard observer, P1 lost its top position. The result points to a distinction that matters for specifications: the spectrum favored by a standard metric and the spectrum favored by an aging eye can be different.
Test with older adults
Participants were aged 70 and older, with a mean age of 81.7. They sorted colored caps from the Farnsworth-Munsell 100 Hue test in a viewing booth at 300 lux. Mean error scores fell from 79.2 under the reference to 62.4 under P1 and 65.0 under P2. Both reductions were statistically significant. Color discrimination improved for 26 of 34 participants (76.5%) under P1 and 22 of 34 (64.7%) under P2. The difference between the two optimized spectra was not significant.
Asked whether fruits and vegetables looked natural, 28 participants said yes under P1, compared with 26 under both the reference and P2. A two-person difference proves little, but it suggests the lower Ra did not appear to cost P1 in perceived naturalness.
Caveats and product questions
The sample was small. People with advanced cataracts, glaucoma or macular degeneration were excluded, removing many residents a memory care designer might light for. Chromaticity between the reference and test lights was not perfectly matched. The naturalness question was a simple yes or no. The authors also warned against reading 300 lux as a recommendation.
Opple financially supported the study, according to the paper's disclosures. The paper names no product, but a news release distributed through Optica, the journal's publisher, says Opple is working to translate the findings into lighting products. That makes the work early product development as much as academic research. The underlying data is available only on request, so independent replication matters.
The method requires at least four independently controlled LED channels. Multichannel color-mixing fixtures rarely appear in a care facility bid. Most products sold as tunable in healthcare and senior living adjust color temperature across two channels, which would not reproduce these spectra. The paper does not make that product-gap claim; it is a practical inference from the channel requirement.
For lighting people in senior living and healthcare, the study raises a pointed question. Industry color metrics make no allowance for aging eyes, and a growing share of building occupants are well past middle age. If a tuned spectrum can help residents read a medication label or judge whether food has spoiled, the debate shifts to how quickly that evidence reaches specifications and product lines, and whose products get there first.