To directly compare the effects of all lighting conditions, we performed a combined analysis of all treatment groups (
Figs. 3,
4,
5). As shown in
Figure 6A, blue and UV lighting had an inhibitory effect on the development of deprivation myopia, since the difference in refraction between deprived and open eyes (Δ = deprived-control eye) was less in blue and UV lighting than in red and white light (ΔUV: −6.10 ± 0.52 D, Δblue: −5.96 ± 0.43 D, Δred: −9.79 ± 0.66 D, Δwhite: −8.87 ± 0.64 D; ΔUV versus Δred and Δwhite,
P < 0.01 in both cases; Δblue versus Δred and Δwhite,
P < 0.02 and
P = 0.07, ANOVA, followed by a Tukey-Kramer HSD test,
Fig. 6A). In previous studies, vitreal DOPAC content was used as an index of retinal DA release. Since it was sometimes difficult to measure the amount of vitreal DOPAC due to technical reasons (an unknown substance coeluted at a similar retention time), we also analyzed HVA and found that the vitreal HVA level was significantly correlated with vitreal DOPAC content (
Fig. 6E). Furthermore, we compared the effect of light with different spectral composition on the ΔDA level in retina and ΔDOPAC and ΔHVA content in vitreous. As shown in
Figure 6B, retinal DA level dropped due to diffuser wear in UV and blue lighting but the drop was lacking in red and white light, although this result was not significant after correction for multiple comparisons (ΔUV: −0.71 ± 0.30 ng/mg protein, Δblue: −0.85 ± 0.32 ng/mg protein, Δred: 0.09 ± 0.35 ng/mg protein, Δwhite: 0.16 ± 0.19 ng/mg protein, ANOVA
P = 0.03, followed by a Tukey-Kramer HSD test, n.s.;
Fig. 6B). On the other hand, the drop in the DA metabolites DOPAC and HVA was more pronounced with diffuser wear in the white light, compared to UV lighting. There was also a trend of higher DOPAC and HVA levels in red light–treated chicks compared to animals reared under UV lighting but it did not achieve statistical significance (ΔDOPAC: UV: −0.64 ± 0.06 ng/0.1 g wet weight, blue: −1.14 ± 0.15 ng/0.1 g wet weight, red: −1.08 ± 0.16 ng/0.1 g wet weight, white: −1.23 ± 0.10 ng/0.1 g wet weight; ΔHVA: UV: −0.55 ± 0.05 ng/0.1 g wet weight, blue: −0.60 ± 0.09 ng/0.1 g wet weight, red: −0.89 ± 0.12 ng/0.1 g wet weight, white: −0.92 ± 0.08 ng/0.1 g wet weight;
Figs. 6C,
6D), suggesting that DA turnover is accelerated in red and white light.