Comparison of the effects of different chromatic lights on accommodative response and microfluctuation in myopes and emmetropes

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 (F_group=2.626, P=0.113). There was a statistically significant difference under different chromatic light conditions between the two groups (F_light=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 (F_group=12.146, P<0.01; F_light=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.

Myopia; Emmetropia; Accommodation, ocular; Chromatic light; Accommodative response; Accommodative microfluctuation