| BackgroundVirtual reality(VR)refers to computer technologies that use software to generate the realistic images,sounds and other sensations that replicate a real environment.VR has been extensively applied in a variety of civilian areas,such as education,entertainment,medical treatment,industry and business.However,many scholars suggest that inconsistence in accommodation with convergence when watching 3D video may lead to functional eye diseases such as asthenopia,dry eye,transient accommodative strabismus and visual display terminal syndrome.In the meantime,other scholars propose that watching VR stereoscopic video can exercise ciliary muscle function,relieve ciliary muscle spasm,improve asthenopia and control the development of myopia.Effect of the use of VR on visual function remains unclear so far;in addition,to the best of our knowledge,there is no article comprehensively assessing the effect of VR goggles designed based on head-mounted display on visual function so far.Therefore,this research proposed to comprehensively evaluate changes of visual acuity,diopter,accommodative function,convergence function,pupil size,angle of strabismus and asthenopia before and after use of VR goggles,and to probe into the correlation among changes of all indexes,which could provide health examination and evaluation of eyes for the healthy use of VR goggles and certain foundation for diagnosing and treating such symptoms in clinic.Part ?.Effect of Short-term Use of VR Goggles on Human Visual FunctionObjective:To investigate changes of visual function parameters and asthenopia symptom after use of VR goggles for 15min and 30min continuously,and to probe into the cause of changes in parameters.Methods:This research was approved by Ethics Committee of First Affiliated Hospital,Medical College of Zhejiang University.Subjects with no obvious eye diseases consulting in First Affiliated Hospital,Medical College of Zhejiang University as well as International Hospital of Zhejiang University from November 2016 to March 2017 were recruited.Visual acuity(includes:far visual acuity,near visual acuity,corrected visual acuity,low contrast sensitivity visual acuity,glare visual acuity),diopter,range of accommodation,accommodative response,positive/negative relative accommodation,accommodation sensitivity,convergence function,AC/A value,pupil size,angle of strabismus,visual operational capacity and asthenopia questionnaire score before and immediately after VR use as well as 30min of rest after use in all subjects were measured,respectively.Differences in the above parameters between immediately after use as well as 30min of rest after use and before use were analyzed using paired sample t test or paired sample Wilcoxon signed rank sum test.Correlation among changes of all visual parameters before and after use was tested using Pearson or Spearman pairwise correlation test.Results:Altogether 55 subjects were enrolled in the research,including 40 in the 15min group(16 in the youth subgroup with the age ranging from 18 to 24 years,and 12 in the middle and old age group with the age ranging from 45 to 60 years)and 15 in the 30min group.It was discovered through research that:1.Visual acuity:Distant visual acuity(LogMAR)in 15min group had improved by-0.09(95%CI,-0.12?-0.06,P<0.001),near visual acuity(LogMAR)had elevated by-0.05(95%CI,-0.08?-0.03,P<0.001),corrected visual acuity(LogMAR)improved by-0.04(95%CI,-0.06?-0.02,P<0.001),and low contrast sensitivity visual acuity(LogMAR)had increased by-0.06(95%CI,-0.08?-0.03,P<0.001)after use of VR,with differences being of statistical significance.After 30min of rest,near visual acuity(LogMAR)had significantly elevated by-0.02(95%CI,-0.04?-0.01,P=0.005)compared with that before use,but differences in distant visual acuity,corrected visual acuity and low contrast sensitivity visual acuity before and after VR use were not statistically significant(P>0.05).As could be found in correlation analysis,changes in distant visual acuity,low contrast sensitivity visual acuity and corrected visual acuity were negatively correlated with changes in pupil size(P<0.01);but those showed no correlation with changes in diopter,accommodation function,convergence function and asthenopia score(P>0.05).Pupil size reduced by-0.34mm after VR use compared with before VR use(95%CI,-0.46?-0.22,P<0.001).Difference in diopter before and after VR use was not significant(95%CI,-0.04?0.13,P>0.05).Changes in near visual acuity showed positive correlation with range of accommodation(P<0.01);but they showed no correlation with changes in pupil size,diopter,convergence function and asthenopia score(P>0.05).2.Accommodation and convergence function:range of accommodation in 15min group had elevated by 0.41D after VR use(95%CI,0.11?0.71,P=0.008),the maximal focusing dioptre had increased by-0.32D(95%CI,-0.61?-0.03,P=0.033),positive relative accommodation elevated by 0.34D(95%CI,0.11?0.56,P=0.004),and accommodation sensitivity increased by 1.29CPM(95%CI,0.84?1.74,P<0.001),with differences being of statistical significance.Accommodative hysteresis had significantly decreased by-0.19D(95%CI,-0.27?-0.10,P<0.001).Difference in aggregation degree,separation degree and AC/A value before and after VR use were not statistically significant(P>0.05).But AC/A value in 30min group had remarkably reduced by-0.98(95%CI,-1.51?-0.45,P<0.001).As was found in correlation test,changes in range of accommodation were negatively correlated with changes in aggregation degree(P<0.05).3.Asthenopia symptom:Difference in asthenopia score in 15min group before and after VR use was not significant(P>0.05).Asthenopia score in middle and old age subgroup had significantly increased compared with that before use(Z=2.37,P=0.018).Asthenopia score in 30min group had markedly increased compared with that before use(Z=3.41,P=0.001),but difference after 30min of rest and before use was not statistically significant(P>0.05).It was found in correlation test that changes in asthenopia score were negatively correlated with number of correct visual operation and changes in accommodation sensitivity(P<0.05);but they were not correlated with changes in visual acuity,range of accommodation,convergence function,pupil size,AC/A value(P>0.05).Conclusion:1.Watching VR video for a short time can improve uncorrected visual acuity,near visual acuity,corrected visual acuity,and low contrast sensitivity visual acuity within a short time.Of them,improvements in uncorrected visual acuity,corrected visual acuity,and low contrast sensitivity visual acuity may be attributed to corestenoma induced by light adaptation.They are not related to diopter,while improvement in near visual acuity is related to increase in range of accommodation.2.Short-term VR use can improve the range of accommodation,accommodative response,positive relative accommodation and accommodation sensitivity in human eyes.However,it may also break the interaction between normal accommodation and convergence function,which manifests as decrease in AC/A value.3.Use of VR for 30min continuously can lead to asthenopia,and the middle-aged and elderly people more likely to develop asthenopia symptom,which can be improved after 30min of rest.In the meantime,it is discovered that accommodation sensitivity and number of correct visual operation in unit time can be served as the objective indexes to evaluate asthenopia after watching VR video;while changes in range of accommodation,accommodative response,aggregation degree,AC/A value,and pupil size are not correlated with objective asthenopia symptom.Part II.Effect of Long-term Use of VR Goggles on Human Visual FunctionObjective:To investigate the effect of use of VR goggles for 1 month continuously on human visual function.Methods:This research was approved by Ethics Committee of First Affiliated Hospital,Medical College of Zhejiang University.Subjects with no obvious eye diseases consulting in First Affiliated Hospital,Medical College of Zhejiang University as well as International Hospital of Zhejiang University from November 2016 to March 2017 were recruited.Visual acuity(includes:far visual acuity,near visual acuity,corrected visual acuity,low contrast sensitivity visual acuity,glare visual acuity),diopter,range of accommodation,accommodative response,positive/negative relative accommodation,accommodation sensitivity,convergence function,AC/A value,pupil size,angle of strabismus,visual operational capacity and asthenopia questionnaire score before and after VR use for 15min each time for 3 to 4 times a day for 1 month continuously in all subjects were measured,respectively.Differences in the above parameters before and after use were analyzed using paired sample t test or paired sample Wilcoxon signed rank sum test.Results:Altogether 20 subjects were enrolled in this research.It was found that near visual acuity(LogMAR)in subjects with continuous use of VR for 1 month had elevated by-0.03(95%CI,-0.06?-0.01;P=0.01),range of accommodation had increased by 0.69D(95%CI,0.26?1.11;P<0.01),and accommodation sensitivity had increased by 0.90CPM(95%CI,0.45?1.35;P<0.01),with all differences being of statistical significance.Differences in distant visual acuity,corrected visual acuity,low contrast sensitivity visual acuity,glare visual acuity,diopter,accommodative response,positive/negative relative accommodation,convergence function,AC/A,pupil size,strabismus status,visual operational capacity and asthenopia questionnaire score before and after use were not significant(P>0.05).Conclusion:It is discovered in this research that using VR for 15min each time for 3 to 4 times a day for 1 month continuously can improve the near visual acuity,range of accommodation and accommodation sensitivity of human eyes.However,diopter,uncorrected visual acuity,convergence function,strabismus status and asthenopia symptom show no change. |
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