Abstract
Purpose :
It was previously found that M to L cone ratios were correlated with refraction and ocular length and that chicks develop longer eyes when they have more L-cones. It was also found that less deprivation myopia was induced when chicks were raised in narrow-band blue or UV light, compared to narrow-band red light. Because the spectral composition of ambient lighting can be easily controlled, it may represent a non-invasive and easily applicable intervention of myopia. Therefore, the aim of this study was to find out how light with different spectral compositions interferes with emmetropization and cone ratios.
Methods :
Three lighting conditions were used with different energy contributions in the short wavelength range: (1) laboratory light, (2) blue-enriched white light, and (3) white LEDs, all adjusted to approximately 285 (human) lx. Chickens were monocularly treated with diffusers to induce deprivation myopia and exposed to these conditions for a period of one week. Refraction and ocular biometry were determined at the beginning and the end of the experiment and L, M, and S cone photoreceptors were counted in fresh retinal tissue based on the color of their oil droplets.
Results :
No differences were found in deprivation myopia among the three lighting conditions. Chickens raised under laboratory light displayed significant correlations of M to L (p<0.01) and L to S (p<0.05) cone ratios in both eyes. The key finding of this study was that not only M to L but also L to S (p<0.05) cone ratios were significantly correlated with refractions in eyes with normal vision. Lower L to S cone ratios were linked to more hyperopic refractions. Unexpectedly, these ratios were inverted when deprivation myopia was induced.
Conclusions :
(1) Broadband white light with added energy in the short wavelength range had no effect on deprivation myopia, different from narrow-band short-wavelength light as previously described. (2) Also L to S cone ratios are linked to refractions in eyes with normal vision, in line with the hypothesis that cone photoreceptor densities are linked to refractive development. (3) Inverted correlations of M to L and L to S cone ratios in eyes with deprivation myopia suggest that contrast reduction by the diffusers may affect the mechanism underlying emmetropization. Interesting future questions are why and how.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.