| Purpose:To investigate the prevalence of non-strabismic binocular vision dysfunctions(NSBVD)in adolescents in northeast Sichuan,China,and to determine the normative data of binocular vision testing in adolescents.In addition,to explore the risk factors of NSBVD in adolescents in China.Methods:A cross-sectional study was implemented in the ophthalmic clinic of Affiliated Hospital of North Sichuan Medical College.Healthy adolescents aged 12 to 35 years who sought routine eye examinations in the clinic were recruited.Subjects who had ocular pathologies that could affect the corrected vision and binocular vision testing were excluded.Primary outcome measurements including visual acuity,subjective refraction,stereopsis,distance and near horizontal heterophoria,distance and near positive fusional vergence(PFV),distance and near negative fusional vergence(NFV),vergence facility(VF),near point of convergence(NPC),monocular accommodative amplitude(MAA),monocular accommodative facility(MAF),monocular estimated method retinoscopy(MEM),and convergence insufficiency symptom survey(CISS)were performed.Based on the findings of binocular vision testing,NSBVD was classed according to the diagnostic criteria.Prevalence of each NSBVD classification was calculated.Normative means and standard deviations of binocular vision testing were calculated for the normal binocular vision(NBV)population.Age,gender,spherical equivalent(SE),and spherical equivalent difference(SED)were compared between the NSBVD population and the NBV population to determine the potential risk factors of NSBVD.Results:A total of 172 subjects(80 male and 92 female)were enrolled in this study,with an average age of(20.72±4.86)years.The prevalence of refractive error was 96.51%,in which myopia was 91.28%,the diopter range was(-0.50~-10.50)D,hyperopia 0.58%and astigmatism 48.26%.The overall prevalence of NSBVD was 36.05%,in which convergence insufficiency(CI)was 12.79%,convergence excess(CE)6.4%,divergence insufficiency(DI)0%,divergence excess(DE)0.58%,fusional vergence dysfunction(FVD)2.9%,basic esophoria(BE)1.16%,basic exophoria(BX)2.9%,accommodative insufficiency(AI)1.16%,accommodative excess(AE)4.65%,and accommodative infacility(AIF)4.65%.In this study,the normative result of NBV adolescents were as follows:stereopsis,(40.32±22.11)?;near and distance horizontal heterophoria,(0.09±2.66)~?and(-0.90±1.64)~?respectively;near PFV break and recovery,(32.23±10.04)~?and(21.50±5.57)~?respectively;near NFV break and recovery,(16.50±7.32)~?and(11.96±4.20)~?respectively;distance PFV break and recovery,(21.35±9.83)~?and(15.21±6.04)~?respectively;distance NFV break and recovery,(8.80±6.78)~?and(5.29±2.69)~?respectively;near VF,(13.54±5.48)cycles per minute(cpm);NPC,(5.18±1.49)cm;MAA,(11.81±2.21)D;MAF,(11.05±4.34)cpm;MEM,(0.63±0.34)D;and CISS scores,(18.77±8.40).No significant linear correlation was found between SED and any binocular vision findings(P>0.05).A significantly negative correlation was found between SE and distant PFV(r=-0.243,P=0.01),distant NFV(r=-0.247,P=0.009)and CISS(r=-0.211,P=0.027),and a significantly positive correlation was found between SE and NPC(r=0.224,P=0.019).There was no significant difference in age,gender,SE and SED between NSBVD and NBV populations(P>0.05),which indicated that none of these was the risk factor of NSBVD.Conclusions:The prevalence of NSBVD in adolescents is high and CI the highest.The prevalence of various types of NSBVD and the normative result of NBV population in this study differed from those in other studies of non-Chinese populations,which would provide a evidence for clinical practice and research for NSBVD in Chinese adolescent population.The degree of myopia may have an impact on fusional vergence and the visual performance of reading or close work.The age,gender,and refractive status of adolescents were not risk factors for NSBVD. |
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