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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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Related in: MedlinePlus

Correlation between vitreous chamber depth and the amount of myopia in chickens under different light regimens.Equations for the linear regression, and R2 values are provided for each light regimen. Long dash line represents the data for intermittent bright light, dotted line for constant bright light and short dash line for standard illuminance, respectively. Note that one diopter of myopia was equivalent to about 0.1 mm of axial elongation across groups (data from one single animal were excluded from the plot because of apparent measurement error, data: −13.9D vs 0.25 mm).
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pone-0110906-g002: Correlation between vitreous chamber depth and the amount of myopia in chickens under different light regimens.Equations for the linear regression, and R2 values are provided for each light regimen. Long dash line represents the data for intermittent bright light, dotted line for constant bright light and short dash line for standard illuminance, respectively. Note that one diopter of myopia was equivalent to about 0.1 mm of axial elongation across groups (data from one single animal were excluded from the plot because of apparent measurement error, data: −13.9D vs 0.25 mm).

Mentions: In the two reference groups, vitreous chamber depth (VCD) increased about linearly with the amount of myopia with about 0.1 mm per diopter of myopia (R2 = 0.811, P = 0.005, Figure 2). There was no significant difference between both groups (t = −0.750, P = 0.487). The ratio of vitreous chamber elongation to increase of myopia was similar among the different groups raised in continuous bright light (R2 = 0.716, P<0.001) or in intermittent bright light (R2 = 0.759, P<0.001).


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

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

Correlation between vitreous chamber depth and the amount of myopia in chickens under different light regimens.Equations for the linear regression, and R2 values are provided for each light regimen. Long dash line represents the data for intermittent bright light, dotted line for constant bright light and short dash line for standard illuminance, respectively. Note that one diopter of myopia was equivalent to about 0.1 mm of axial elongation across groups (data from one single animal were excluded from the plot because of apparent measurement error, data: −13.9D vs 0.25 mm).
© Copyright Policy
Related In: Results  -  Collection

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

pone-0110906-g002: Correlation between vitreous chamber depth and the amount of myopia in chickens under different light regimens.Equations for the linear regression, and R2 values are provided for each light regimen. Long dash line represents the data for intermittent bright light, dotted line for constant bright light and short dash line for standard illuminance, respectively. Note that one diopter of myopia was equivalent to about 0.1 mm of axial elongation across groups (data from one single animal were excluded from the plot because of apparent measurement error, data: −13.9D vs 0.25 mm).
Mentions: In the two reference groups, vitreous chamber depth (VCD) increased about linearly with the amount of myopia with about 0.1 mm per diopter of myopia (R2 = 0.811, P = 0.005, Figure 2). There was no significant difference between both groups (t = −0.750, P = 0.487). The ratio of vitreous chamber elongation to increase of myopia was similar among the different groups raised in continuous bright light (R2 = 0.716, P<0.001) or in intermittent bright light (R2 = 0.759, P<0.001).

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