Abstract
Ambient light exposure is one environmental factor thought to play a role in the regulation of eye growth and refractive error development, and choroidal thickness changes have also been linked to longer term changes in eye growth. Therefore in this study we aimed to examine the influence of a 1-week period of morning light therapy upon choroidal thickness. Twenty two healthy young adult subjects had a series of macular choroidal thickness measurements collected with spectral domain optical coherence tomography before, and then following a 7-day period of increased daily light exposure. Increased light exposure was delivered through the use of commercially available light therapy glasses, worn for 30 minutes in the morning each day. A significant increase in subfoveal choroidal thickness (mean increase of +5.4 ± 10.3 µm) was found following 7-days of increased daily light exposure (p = 0.02). An increase in choroidal thickness was also observed associated with light therapy across the central 5 mm macular region. This study provides the first evidence in the human eye that daily morning light therapy results in small magnitude but statistically significant increases in choroidal thickness. These changes may have implications for our understanding of the impact of environmental factors upon eye growth.
Highlights
Evidence from both human and animal studies suggest that the choroidal tissue that lines the posterior eye, plays an important role in the regulation of eye growth and the development of refractive errors
These findings from both animal and human research suggest that choroidal thickness changes are one of the earliest observable ocular changes during the development of refractive errors, and that these changes may represent a biomarker for the signaling cascade that results in longer term changes in ocular growth and the development of refractive errors in response to environmental stimuli
A number of epidemiological studies have demonstrated an association between increased outdoor activity and a lower risk of myopia development in children, which, given the high ambient light levels typically experienced outdoors compared to indoors, suggests that increased ambient light exposure may help to protect against myopia
Summary
Evidence from both human and animal studies suggest that the choroidal tissue that lines the posterior eye (situated between the retina and the sclera), plays an important role in the regulation of eye growth and the development of refractive errors. An interventional study of indoor lighting in Chinese schools has demonstrated that increasing indoor illumination (by on average ~400 lux) in classrooms resulted in significantly lower myopia incidence and axial eye growth (and a significantly smaller change in refractive error in non-myopic, but not myopic children) compared to children attending control schools where lighting levels in classrooms were not increased[23] This further supports a role for light exposure in the control of human eye growth, and suggests that relatively modest changes in ambient light levels have the potential to impact upon ocular growth. Consistent with ambient light levels influencing myopia development, bright light exposure has been shown to protect against the development of form deprivation myopia in a range of animal species[20,24,25]
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