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Intermittent episodes of bright light suppress myopia in the chicken more than continuous bright light.

Lan W, Feldkaemper M, Schaeffel F - PLoS ONE (2014)

Bottom Line: The protective effect of bright light depends on the exposure duration and, to the intermittent form, the frequency cycle.Compared to the saturation effect of continuous bright light, low frequency cycles of bright light (1:1 min) provided the strongest inhibition effect.However, our quantitative results probably might not be directly translated into humans, but rather need further amendments in clinical studies.

View Article: PubMed Central - PubMed

Affiliation: Section of Neurobiology of the Eye, Center for Ophthalmology, University of Tuebingen, Tuebingen, Germany; Zhongshan Ophthalmic Center, State Key Laboratory of Ophthalmology, Sun Yat-sen University, Guangzhou, China; Graduate School of Cellular & Molecular Neuroscience, University of Tuebingen, Tuebingen, Germany.

ABSTRACT

Purpose: Bright light has been shown a powerful inhibitor of myopia development in animal models. We studied which temporal patterns of bright light are the most potent in suppressing deprivation myopia in chickens.

Methods: Eight-day-old chickens wore diffusers over one eye to induce deprivation myopia. A reference group (n = 8) was kept under office-like illuminance (500 lux) at a 10:14 light:dark cycle. Episodes of bright light (15 000 lux) were super-imposed on this background as follows. Paradigm I: exposure to constant bright light for either 1 hour (n = 5), 2 hours (n = 5), 5 hours (n = 4) or 10 hours (n = 4). Paradigm II: exposure to repeated cycles of bright light with 50% duty cycle and either 60 minutes (n = 7), 30 minutes (n = 8), 15 minutes (n = 6), 7 minutes (n = 7) or 1 minute (n = 7) periods, provided for 10 hours. Refraction and axial length were measured prior to and immediately after the 5-day experiment. Relative changes were analyzed by paired t-tests, and differences among groups were tested by one-way ANOVA.

Results: Compared with the reference group, exposure to continuous bright light for 1 or 2 hours every day had no significant protective effect against deprivation myopia. Inhibition of myopia became significant after 5 hours of bright light exposure but extending the duration to 10 hours did not offer an additional benefit. In comparison, repeated cycles of 1:1 or 7:7 minutes of bright light enhanced the protective effect against myopia and could fully suppress its development.

Conclusions: The protective effect of bright light depends on the exposure duration and, to the intermittent form, the frequency cycle. Compared to the saturation effect of continuous bright light, low frequency cycles of bright light (1:1 min) provided the strongest inhibition effect. However, our quantitative results probably might not be directly translated into humans, but rather need further amendments in clinical studies.

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Relative increase in vitreous chamber depth (VCD) in eyes with monocular diffusers (bars grey-scale coded as in Figure 1).Although there was no significant difference among treatment groups for either paradigm (Paradigm I: F = 1.639, P = 0.204 and Paradigm II: F = 2.075, P = 0.109), the increase of VCD in chickens reared under constant bright light for 5 or 10 hours was signifcantly supressed compared with those under standard illuminance (P = 0.029 and 0.037, respectively). In comparison with constant bright light, this effect was further enhanced in chickens exposed to cycles of bright light at a frequency of 7∶7 or 1∶1 minutes (all P<0.05, except for the comparison between the 7∶7 minute cycle and the 5 h constant bright light exposure, P = 0.180 and a borderline significance between the 7∶7 minute cycle and the 1 h constant bright light exposure, P = 0.075).* <0.05, **<0.01. Abbreviations as in Figure 1.
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pone-0110906-g003: Relative increase in vitreous chamber depth (VCD) in eyes with monocular diffusers (bars grey-scale coded as in Figure 1).Although there was no significant difference among treatment groups for either paradigm (Paradigm I: F = 1.639, P = 0.204 and Paradigm II: F = 2.075, P = 0.109), the increase of VCD in chickens reared under constant bright light for 5 or 10 hours was signifcantly supressed compared with those under standard illuminance (P = 0.029 and 0.037, respectively). In comparison with constant bright light, this effect was further enhanced in chickens exposed to cycles of bright light at a frequency of 7∶7 or 1∶1 minutes (all P<0.05, except for the comparison between the 7∶7 minute cycle and the 5 h constant bright light exposure, P = 0.180 and a borderline significance between the 7∶7 minute cycle and the 1 h constant bright light exposure, P = 0.075).* <0.05, **<0.01. Abbreviations as in Figure 1.

Mentions: Interestingly, the changes in vitreous chamber depth due to exposure to the different light regimens were often not as significant as the refractive errors (Paradigm I: F = 1.639, P = 0.204; Paradigm II: F = 2.075, P = 0.109, significances refer to the differences among groups in Paradigm I and II, respectively). However, consistent with previous studies[13], [16], if the data from chickens exposed to 5 or 10 hours of constant bright light was compared to those of the reference group separately, statistical significance was detected (0.45±0.20 mm vs 0.93±0.09 mm, t = −2.590, P = 0.029; 0.56±0.13 mm vs 0.93±0.09 mm, t = −2.451, P = 0.037, respectively). More importantly, it is clear that repeated cycles of bright light generated generally shorter vitreous chambers than constant bright light. Exposure to 7∶7 or 1∶1 min bright light cycles inhibited axial eye growth more than constant bright light (all P<0.05, except for the comparison between the 7∶7 minute cycle and the 5 h constant bright light exposure, P = 0.180 and a borderline significance between the 7∶7 minute cycle and the 1 h constant bright light exposure, P = 0.075). Similar to refractive error, vitreous chamber elongation was almost completely suppressed in the diffusertreated eyes (Figure 3; Table 1) exposed to a 1∶1 min bright light cycle.


Intermittent episodes of bright light suppress myopia in the chicken more than continuous bright light.

Lan W, Feldkaemper M, Schaeffel F - PLoS ONE (2014)

Relative increase in vitreous chamber depth (VCD) in eyes with monocular diffusers (bars grey-scale coded as in Figure 1).Although there was no significant difference among treatment groups for either paradigm (Paradigm I: F = 1.639, P = 0.204 and Paradigm II: F = 2.075, P = 0.109), the increase of VCD in chickens reared under constant bright light for 5 or 10 hours was signifcantly supressed compared with those under standard illuminance (P = 0.029 and 0.037, respectively). In comparison with constant bright light, this effect was further enhanced in chickens exposed to cycles of bright light at a frequency of 7∶7 or 1∶1 minutes (all P<0.05, except for the comparison between the 7∶7 minute cycle and the 5 h constant bright light exposure, P = 0.180 and a borderline significance between the 7∶7 minute cycle and the 1 h constant bright light exposure, P = 0.075).* <0.05, **<0.01. Abbreviations as in Figure 1.
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Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4216005&req=5

pone-0110906-g003: Relative increase in vitreous chamber depth (VCD) in eyes with monocular diffusers (bars grey-scale coded as in Figure 1).Although there was no significant difference among treatment groups for either paradigm (Paradigm I: F = 1.639, P = 0.204 and Paradigm II: F = 2.075, P = 0.109), the increase of VCD in chickens reared under constant bright light for 5 or 10 hours was signifcantly supressed compared with those under standard illuminance (P = 0.029 and 0.037, respectively). In comparison with constant bright light, this effect was further enhanced in chickens exposed to cycles of bright light at a frequency of 7∶7 or 1∶1 minutes (all P<0.05, except for the comparison between the 7∶7 minute cycle and the 5 h constant bright light exposure, P = 0.180 and a borderline significance between the 7∶7 minute cycle and the 1 h constant bright light exposure, P = 0.075).* <0.05, **<0.01. Abbreviations as in Figure 1.
Mentions: Interestingly, the changes in vitreous chamber depth due to exposure to the different light regimens were often not as significant as the refractive errors (Paradigm I: F = 1.639, P = 0.204; Paradigm II: F = 2.075, P = 0.109, significances refer to the differences among groups in Paradigm I and II, respectively). However, consistent with previous studies[13], [16], if the data from chickens exposed to 5 or 10 hours of constant bright light was compared to those of the reference group separately, statistical significance was detected (0.45±0.20 mm vs 0.93±0.09 mm, t = −2.590, P = 0.029; 0.56±0.13 mm vs 0.93±0.09 mm, t = −2.451, P = 0.037, respectively). More importantly, it is clear that repeated cycles of bright light generated generally shorter vitreous chambers than constant bright light. Exposure to 7∶7 or 1∶1 min bright light cycles inhibited axial eye growth more than constant bright light (all P<0.05, except for the comparison between the 7∶7 minute cycle and the 5 h constant bright light exposure, P = 0.180 and a borderline significance between the 7∶7 minute cycle and the 1 h constant bright light exposure, P = 0.075). Similar to refractive error, vitreous chamber elongation was almost completely suppressed in the diffusertreated eyes (Figure 3; Table 1) exposed to a 1∶1 min bright light cycle.

Bottom Line: The protective effect of bright light depends on the exposure duration and, to the intermittent form, the frequency cycle.Compared to the saturation effect of continuous bright light, low frequency cycles of bright light (1:1 min) provided the strongest inhibition effect.However, our quantitative results probably might not be directly translated into humans, but rather need further amendments in clinical studies.

View Article: PubMed Central - PubMed

Affiliation: Section of Neurobiology of the Eye, Center for Ophthalmology, University of Tuebingen, Tuebingen, Germany; Zhongshan Ophthalmic Center, State Key Laboratory of Ophthalmology, Sun Yat-sen University, Guangzhou, China; Graduate School of Cellular & Molecular Neuroscience, University of Tuebingen, Tuebingen, Germany.

ABSTRACT

Purpose: Bright light has been shown a powerful inhibitor of myopia development in animal models. We studied which temporal patterns of bright light are the most potent in suppressing deprivation myopia in chickens.

Methods: Eight-day-old chickens wore diffusers over one eye to induce deprivation myopia. A reference group (n = 8) was kept under office-like illuminance (500 lux) at a 10:14 light:dark cycle. Episodes of bright light (15 000 lux) were super-imposed on this background as follows. Paradigm I: exposure to constant bright light for either 1 hour (n = 5), 2 hours (n = 5), 5 hours (n = 4) or 10 hours (n = 4). Paradigm II: exposure to repeated cycles of bright light with 50% duty cycle and either 60 minutes (n = 7), 30 minutes (n = 8), 15 minutes (n = 6), 7 minutes (n = 7) or 1 minute (n = 7) periods, provided for 10 hours. Refraction and axial length were measured prior to and immediately after the 5-day experiment. Relative changes were analyzed by paired t-tests, and differences among groups were tested by one-way ANOVA.

Results: Compared with the reference group, exposure to continuous bright light for 1 or 2 hours every day had no significant protective effect against deprivation myopia. Inhibition of myopia became significant after 5 hours of bright light exposure but extending the duration to 10 hours did not offer an additional benefit. In comparison, repeated cycles of 1:1 or 7:7 minutes of bright light enhanced the protective effect against myopia and could fully suppress its development.

Conclusions: The protective effect of bright light depends on the exposure duration and, to the intermittent form, the frequency cycle. Compared to the saturation effect of continuous bright light, low frequency cycles of bright light (1:1 min) provided the strongest inhibition effect. However, our quantitative results probably might not be directly translated into humans, but rather need further amendments in clinical studies.

Show MeSH
Related in: MedlinePlus