RÉSUMÉ
Objective:To explore the effects of conflicting stimuli generated by different chromatic lights on visual display terminal (VDT) on accommodative response and microfluctuation of myopes and emmetropes, and to investigate the possible relationship between chromatic light, accommodation and the development and progression of myopia.Methods:A non-randomized controlled trial was conducted.Forty-one subjects aged 22 to 30 years old were enrolled, including 19 emmetropes in emmetropic group and 22 myopes in myopic group.The subjects had the normal color vision and no ocular organic diseases.The interventions were screens of different colors.There were 7 chromatic light conditions, including 3 monochromatic lights (red, green, blue), 3 bichromatic lights (red+ green, red+ blue, green+ blue) and 1 polychromatic light (white=red+ green+ blue). Subjects were asked to look at a black E target on a VDT at a distance of 33 cm for more than 20 seconds.The background color of the VDT was changed randomly in the 7 chromatic light conditions.The accommodative responses were recorded with the Grand Seiko WAM-5500 automatic infrared refractor every 0.2 seconds and the accommodative microfluctuation was calculated as the standard deviation of the accommodative response.Accommodative response and accommodative microfluctuation under different chromatic light conditions were compared.This study adhered to the Declaration of Helsinki.The study protocol was approved by the Ethics Committee of the First Affiliated Hospital, Zhejiang University School of Medicine (No.2019-1564). Written informed consent was obtained from each subject.Results:No statistically significant difference was found in the accommodative response between the two groups ( Fgroup=2.626, P=0.113). There was a statistically significant difference under different chromatic light conditions between the two groups ( Flight=39.070, P<0.01). There were similar trends in the effects of various color lights in both groups, with the largest accommodative response under monochromatic red light, followed by the bichromatic light containing red light, and then the smallest accommodative response under monochromatic blue light, and the differences were statistically significant (all at P<0.05). The accommodative microfluctuations under red, green, blue, red+ blue, red+ green, blue+ green and white light conditions were (0.142±0.033), (0.128±0.038), (0.131±0.043), (0.139±0.039), (0.127±0.034), (0.131±0.043) and (0.139±0.042)D in emmetropic group, and (0.178±0.043), (0.164±0.043), (0.159±0.039), (0.174±0.042), (0.166±0.036), (0.159±0.031) and (0.174±0.035)D in myopic group, respectively, showing statistically significant differences between them ( Fgroup=12.146, P<0.01; Flight=2.782, P<0.05). The accommodative microfluctuations under the 7 light conditions were higher in myopic group than in emmetropic group, and the differences were statistically significant (all at P<0.05). In myopes, the accommodative microfluctuation was the largest under red light, which was significantly larger than that under blue light, and was the smallest under blue+ green light (all at P<0.05). There was no significant difference in the accommodative microfluctuation between bichromatic light and its two monochromatic lights, or between the polychromatic light (white light) and its three monochromatic lights (all at P>0.05). There was no significant effect of various chromatic lights on the accommodative microfluctuation in emmetropic group (all at P>0.05). Conclusions:The accommodative microfluctuation is greater in myopes than in emmetropes.The stimuli produced by long-wavelength light cause larger accommodative microfluctuation, while conflicting stimuli generated by different chromatic lights do not increase accommodative microfluctuation.
RÉSUMÉ
Background The incidence of myopia is increase.Some researches documented that formation of myopia is closely related with weakness of the accommodative response,enhancement of accommodative lag and accommodative microfluctuations in short-distance use of eyes.However,there still is controversy.Objective This study sought to compare the accommodative microfluctuations among emmetropic and myopic school-aged children at reading,and to discuss its potential relationship with the onset and development of myopia.Methods A casecontrolled study was designed.Eighty-nine children aged 8-12 years old were recruited in this study,including 47emmetropic children and 42 myopic children.Refractive error were checked by subjective refraction in phoropters and binocular vision and stereopsis were examined in all the subjects.A Grand Seiko WAM5500 auto-refractor was used to measure the accommodative responses and accommodative microfluctuations with different stimulus in 40 cm and 25 cm.The differences in accommodative response and accommodative microfluctuations at 25 cm and 40 cm reading distance were compared between the emmetropic children and myopic children using independent sample t test,and change of accommodative microfluctuations in myopic children at 25 cm and 40 cm reading distance was evaluated by paired t test.Results When the reading distance was 25 cm and 40 cm,the accommodative responses of emmetropes were (2.67 ±0.31) D and (1.70 ±0.23) D,and they were higher than (2.31 ± 0.33) D and (1.49 ±0.24) D of myopes,showing significant differences (t =5.330,P =0.000; t =4.140,P =0.000).Accommodative microfluctuation of myopes was(0.35 ±0.16)D in 25 cm reading distance and that of emmtropes was(0.26±0.08)D,with significant difference between them (t =3.180,P =0.002).However,there was not significant difference in accommodative microfluctuation at 40 cm reading distance between the myopic children and emmtropie children [(0.27±0.10) D vs.(0.24±0.09) D] (P=0.220).In myopic children,the accommodative microfluctuation at 25 cm reading distance was(0.35±0.16) D,showing a much increase than(0.27±0.10) D at 40 cm reading distance(t=3.850,P =0.000),but an insignificant difference in the accommodative mierofluctuations was seen between the 25 cm and 40 cm reading distance in the emmetropic children (P =0.145).Conclusions With the increased accommodative stimulus,myopic children present lower accommodative responses and larger accommodative microfluctuations.
RÉSUMÉ
Background Epidemiologic studies found that the incidence of myopia is higher in Hong Kong and Taiwan regions of China than that of the mainland.So whether the general reading words with traditional Chinese characters and simplified characters is associated with myopia deserves attention.Objective This study was to test the accommodative responses and the regression levels of nearwork-induced transient myopia (NITM) induced by traditional complex Chinese characters and modern simplified ones in the same size,and to explore the differences and inherent relationship of the accommodative regulations based on the structures of the two types of Chinese character in causing reading triggered myopia.Methods Twenty two volunteers aged 24-29 years were included in this study with informed consent.The corrected vision of both eyes from each subject was ≥ 1.0 with a mean spherical equivalence of (-1.86±2.34)D.Accommodative response was tested with 4 different reading texts using the rapid sequence visual presenting model with the GRAND SEIKO-WV5500 infrared autorefractor,and this procedure was performed after full correction of refractive error.An initial test of looking at a certain distance was performed (as baseline),and then the subjects read intensively at the targets for 10 minutes at 33 cm to calculate the accommodative responses.After a 10 second pause,the ocular refractive status was obtained exactly at 15 seconds,20 seconds.The one-way ANOVA method was used to determine the effects of the different font types and sizes on the adjustive responses and the causation of NITM.Results Accommodative response induced by simplified and traditional Chinese characters showed an accommodative lag of (1.11 ±0.38),(0.95 ±0.43),(1.18 ±0.33) and (1.06±0.28) D,showing a significant difference among the 9 pt and 12 pt simplified and traditional Chinese characters (F =1.62,P =0.19),and significantly different accommodative lag values between 12 pt simplified characters and 9 pt traditional characters was found (t =5.56,P =0.02).NITM induced by the four different targets were (-0.45 ±0.45),(-0.47 ±0.46),(0.45 ±0.82) and (-0.46±0.78) D in the 4 types of characters,without a significant difference among them (F=0.01,P =0.99).Conclusions Near-distance reading causes accommodative lag regardless of the type of reading texts.The target demonstrated stimuli spatial frequency and font size play an impact on accommodative responses.NITM appears when one reads simplified or traditional Chinese for 10 minutes.The accommodative lag and NITM trend might be responsible for the onset or regression of myopia,yet it is not supportive for the hypothesis that reading traditional Chinese causes more strain since there is no difference between the two.
RÉSUMÉ
Background Image clarity during near work is influenced by several factors,such as accommodative lag,pupil size and monochromatic aberrations.Since image clarity during extended reading at near distance has been cited as a possible inducement of myopia in childhood and a possible difference between myopic and emmetropic people throughout life,it is important to examine these factors in myopic and emmetropic myopic juvenile during reading at near distance. Objective The aim of this study was to investigate the relationships among wavefront aberrations,accommodative response and pupil size in early onset and progressive myopes eyes under the different reading status and explore the possible mechanism of the development of myopia as well. Methods Fiflyseven subjects aged from 12 to 16 years were enrolled and grouped as emmetropes,the onset of myopes and progressive myopes.Reading material were Chinese novels presented by rapid serial visual presentation at a distance of 25 cm. Accommodative response and pupil size were recorded by a Grand Seiko WV-500 autorefractor.The Image J software was used to calculate the pupil diameter.Wavefront aberrations were then measured with a WASCA wavefront analyzer. Results Aberrations and accommodative response showed large inter-subjeet variability.With accommodative stimulus of 4 diopter,the accommodative lag in the early-onset of myopes group and progressive myopes group were ( 1.72 ±0. 53) D and ( 1.74 ±0. 44) D, showing larger value in comparison with ( 0. 96 ±0. 55) D of emmetropes group( t＝4.25 ,t=4.47 ,P0. 05). The mean value of pupil diameter, total RMS value, high-order RMS value, spherical aberration and coma were all significantly reduced with the stimulus varied from 0 D to 4 D( P0. 05). Conclusion The early-onset of myopes and progressive myopes had larger accommodative lag. The lower sensitivity to defocus at near reading distance,inducing the larger accommodative lag and hyperopic defocus may be linked to the developing myopia.