Dataset Information

Development of Experimental Myopia in Chicks in a Natural Environment.

ABSTRACT: The hypothesis that outdoor exposure might protect against myopia has generated much interest, although available data find only modest clinical efficacy. We tested the effect of outdoor rearing on form-deprivation myopia in chicks, a myopia model markedly inhibited by high-intensity indoor laboratory lighting.Unilaterally goggled cohorts of White Leghorn chicks were maintained in a species-appropriate, outdoor rural setting during daylight hours to the extent permitted by weather. Control chicks were reared indoors with incandescent lighting. Besides ocular refraction and ultrasound, we determined dopamine and 3,4-dihydroxyphenylacetic acid (DOPAC) content in retina and vitreous and measured mRNA expression levels of selected clock and circadian rhythm-related genes in the retina/RPE.Myopia developed in the goggled eyes of all cohorts. Whereas outdoor rearing lessened myopia by 44% at 4 days, a protective effect was no longer evident at 11 days. Outdoor rearing had no consistent effect on retinal or vitreous content of dopamine or DOPAC. Conforming to prior data on form-deprivation myopia, retina and vitreous levels of DOPAC were reduced in goggled eyes. Compared with contralateral eyes, the retinal expression of clock and circadian rhythm-related genes was modestly altered in myopic eyes of chicks reared indoors or outdoors.Outdoor rearing of chicks induces only a partial decrease of goggle-induced myopia that is not maintained, without evidence that retinal dopamine metabolism accounts for the partial myopia inhibition under these outdoor conditions. Although modest, alterations in retinal gene expression suggest that studying circadian signals might be informative for understanding refractive mechanisms.

SUBMITTER: Stone RA

PROVIDER: S-EPMC5024671 | biostudies-literature | 2016 Sep

REPOSITORIES: biostudies-literature

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Development of Experimental Myopia in Chicks in a Natural Environment.

Stone Richard A RA Cohen Yuval Y McGlinn Alice M AM Davison Sherrill S Casavant Susan S Shaffer James J Khurana Tejvir S TS Pardue Machelle T MT Iuvone P Michael PM

Investigative ophthalmology & visual science 20160901 11

<h4>Purpose</h4>The hypothesis that outdoor exposure might protect against myopia has generated much interest, although available data find only modest clinical efficacy. We tested the effect of outdoor rearing on form-deprivation myopia in chicks, a myopia model markedly inhibited by high-intensity indoor laboratory lighting.<h4>Methods</h4>Unilaterally goggled cohorts of White Leghorn chicks were maintained in a species-appropriate, outdoor rural setting during daylight hours to the extent per ...[more]

PMID: 27618415

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Project description:Juvenile primates develop myopia when their visual experience is degraded by lid fusion. In response to the abnormal visual input, retinal neural networks cause an excessive growth of the postequatorial segment of the eye, but the mechanism underlying this axial elongation is unknown. By combining analysis of gene expression, injection of the thymidine analog 5-bromo-2'-deoxyuridine and immunocytochemistry, we show that the retinal periphery in both juvenile rhesus macaques and green monkeys harbors a population of mitotically active neuroprogenitor cells that proliferate when the visual experience is altered by lid fusion. Furthermore, the number of dividing cells is highly correlated with the axial elongation of the eye and the resulting myopic refractive error. Thus, the retina undergoes active growth during the postnatal development of the primate eye. This growth is modulated by the visual input and accelerates considerably when the eye develops axial myopia. cDNA subtractions, construction of cDNA libraries and differential screening were performed as previously described (Tkatchenko et al, 2000). Two subtractions were carried out resulting in two cDNA libraries. One library was enriched in clones potentially up-regulated in the retina of the closed eye and the other was enriched in cDNAs potentially down-regulated. One thousand clones from each library were analyzed, and 535 differentially-expressed cDNAs were amplified by PCR and spotted onto glass slides coated with poly-L-lysine (five duplicates for each cDNA). The slides were then processed, hybridized with Cy3- and Cy5-labeled complex cDNA probes and washed in 0.2xSSC as described at http://cmgm.stanford.edu/pbrown/protocols/. Two hybridizations with color swap were carried for each monkey. After hybridization, slides were scanned using a GenePix 4000B microarray scanner (Axon Instruments, Union City, CA). The images were acquired and processed using the GenePix Pro 5.1 software package (Axon Instruments). The data obtained were normalized against GAPDH expression level and mean values (the reported values) and P-values (probability associated with a Student's t-test) were calculated for duplicate experiments (n = 10) with color swap using Microsoft Excel. Genes were defined as differentially regulated if P< 0.05. Cluster analysis was performed using the Genesis software package (provided by Alexander Sturn, Graz University of Technology, Austria).

Project description:ImportanceThe global prevalence of myopia has shown a steady increase over recent decades, with urban areas seemingly experiencing a more significant impact.ObjectiveTo assess the association between urbanization and the prevalence, incidence, progression, and severity of myopia.Design, setting, and participantsThis cohort study included students in grades 1 to 6 in Tianjin, China, who underwent 3 vision examinations conducted over a 2-year period, from March 1, 2021, to March 31, 2023. Participants from grades 1 to 4 completed the 2-year follow-up.ExposuresUrban living environment.Main outcomes and measuresThe association of urbanization with the incidence, progression, prevalence, and severity of myopia. To quantify urbanization, an urban score was constructed using satellite data and an iterative exploratory factor analysis.ResultsOf 177 894 students (51.7% male; mean [SD] age, 10.27 [1.75] years) included in the study, 137 087 students (52.3% male; mean [SD] age, 8.97 [1.21] years) were followed up for 2 years. A positive association was identified between myopia incidence and urbanization. Specifically, each 1-unit increment in the urban score was associated with an increased risk of myopia over a 1-year period (odds ratio [OR], 1.09; 95% CI, 1.01-1.15; P = .02) and a 2-year period (OR, 1.53; 95% CI, 1.50-1.57; P < .001). Conversely, each 1-unit increase in the urban score was associated with a significant decrease in myopia progression at 1 year (OR, 0.84; 95% CI, 0.82-0.86; P < .001) and 2 years (OR, 0.73; 95% CI, 0.70-0.75, P < .001). In a cross-sectional data analysis, the urban score was positively associated with myopia prevalence (OR, 1.62; 95% CI, 1.08-2.42; P = .02) and negatively associated with myopia severity, as indicated by spherical equivalent refraction (OR, 1.46; 95% CI, 1.07-1.99; P = .02).Conclusions and relevanceThis study exploring urban living environments and myopia revealed dual associations of urban living with both the incidence and the progression of myopia. The observed patterns emphasize the urgency of promptly implementing myopia control strategies in less urbanized regions, where myopia progression may be accentuated.

Dataset Information

Development of Experimental Myopia in Chicks in a Natural Environment.

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Development of Experimental Myopia in Chicks in a Natural Environment.

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