Moderately Elevated Fluorescent Light Levels Slow Form Deprivation and Minus Lens-Induced Myopia Development in Tree Shrews
John
T. Siegwart, Jr., Alexander H. Ward1, Thomas T. Norton. Vision Sciences, Genetics and Genomic Sciences,Univ of Alabama at Birmingham, Birmingham, AL.
This abstract is from the ARVO (The Association for Research in Vision and Ophtalmology) website. This study was presented at the May 2012 meeting. Many articles on myopia were presented at that meeting. This study looked at the effect of elevated artificial light levels on young tree shrews with induced myopia and deprivation myopia, and found that the tree shrews exposed to elevated light levels (around 16,000 lux, brighter than a SAD lamp for almost 8 hours) developed induced and deprivation myopia more slowly. Myopia in humans is different, since it generally is not caused by deprivation or induced in a lab, but the studies on time spent outdoors and ocular sun exposure also show that exposure to sunlight is related to lower levels of myopia. This study is interesting because artificial fluorescent light was shown to have an effect too, in animals with induced and deprivation myopia.
From the text:
"Children who spend more time outdoors have a lower prevalence of myopia (Rose
et al., Ophthalmol. 2008) and slower myopic progression (Parssinen and Lyyra,
IOVS, 1993). We examined whether elevated light levels (ELL), produced with
fluorescent bulbs, slow the development of form deprivation myopia (FDM) and
minus lens-induced myopia (LIM) in tree shrews (small diurnal mammals closely
related to primates).
Juvenile tree shrews wore a monocular diffuser to
produce FDM (n=4) or a −5D lens to produce LIM (n=5) starting at 24 days of
visual experience. During treatment, the animals were exposed to ~16,000 lux
for ~7.75 hours per day (~9:15 AM - 5 PM) produced with an array of compact
fluorescent bulbs. The refractive changes in the FDM and LIM animals were
compared to animals from previous studies (FDM, n=6; LIM, n=6) that were
treated in standard light levels of 500 - 1000 lux.
After 11 days of treatment, ELL reduced FDM
(treated-control eye) by 44% (−3.6 ± 0.1 D vs. −6.4 ± 0.7 D) and LIM by 39%
(−2.9 ± 0.4 D vs. −4.8 ± 0.3 D) (figure). Control-eye refractions remained
hyperopic compared with standard lighting control eyes. When ELL stopped and
form deprivation continued, the myopia progression rate increased to parallel
that of standard light-treated animals but did not “rebound”, suggesting a
permanent saving from the reduced rate during ELL. Two LIM animals continued
lens wear and ELL and fully compensated for the −5 D lens after 16 and 23 days.
Moderately elevated light levels, comparable to
those in the shade on a sunny day, slow the development of FDM and LIM in tree
shrews. These findings are consistent with reports that ELL reduces FDM in
chicks and macaque monkeys (Ashby et al., IOVS 2009; Smith et al., ARVO
E-Abstract 3922, 2011) and LIM in chicks (Ashby & Schaeffel, IOVS 2010).
ELL, from fluorescent bulbs that emit minimal UV radiation, may become a useful
tool to slow the progression of environmentally-induced myopia in children. The minimal UV in the ELL is consistent with a previous finding that vitamin D supplementation did not reduce FDM or LIM in tree shrews (Siegwart et al., ARVO E-Abstract 6298, 2011), and suggests that the effect is not due to a light-induced increase in vitamin D levels."
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