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Background Intermittent exotropia is a type of strabismus that between latent extropia and manifest extropia.The assessment of fusional convergence/divergence is important for understanding control ability of exodeviation in children with intermittent exotropia.Objective This study was to analyze the correlations between fusional convergence/divergence and control ability of exodeviation in children with intermittent exotropia.Methods Sixty-three children with intermittent exotropia were recruited in Beijing Tongren Eye Centre from July 2013 to February 2014 under the informed consent of children and their parents.Angle of deviation was measured by wearing prism and covering method alternately.The control ability of exodeviation was evaluated and scored by the Revised Newcastle Control Score (RNCS),and fusional convergence and divergence were measured with 1 Δ-40Δ horizonal prisms and regulating targets.The correlations between the measured parameters of fusional convergence/divergence and control scores of exotropia were analyzed by Spearman rank correlation analysis.Results The mean diopter of the right and left eyes was (-1.95 ± 1.63)D and (-2.01 ± 1.73)D,respectively,and the mean deviation angle for distantly and near was (36.67 ± 15.69) Δ and (38.25 ± 14.83) Δ,respectively,without significant differences between them (diopter:t =-0.13,P＞0.05;deviation angle:t =-0.57,P＞0.05).Considerably negative correlations were found between the breakpoints of fusional convergence for distant or near and control scores of exodeviation (rs =-0.41,P=0.03;rs =-0.56,P＜0.01).No significant correlations were found between the breakpoints of fusional divergence for distantly or near and control scores of exodeviation (rs =0.05,P =0.78;rs =0.04,P ＜0.75).In addtion,there was no significant correlation between fusional recovery level and control scores (both at P ＞ 0.05).Conclusions Breakpoints of fusional convergence may be useful in grading the severity of intermittent exotropia in children,and it is probably one of the surgical indications of intermittent exotropia.
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Background Using tablet computer at a short distance is one of the risk factors resulting to pathogenesis and progression of myopia.Studying the effect of such device on accommodative system of human eyes can provide further insights into myopia control.Objective This study was to explore the influences of playing iPAD game for a short duration on accommodative response,accommodative microfluctuation and pupil diameter in adolescent myopia patients.Methods Sixty adolescent myopic patients were included in Peking University People 's Hospital from August 2014 to April 2015,with the mean age (11.6±2.6) years and mean spherical equivalent refraction (SER) (-2.38±1.08)D.The patients were randomly divided into 3 groups according to different playing duration of iPAD game,including 3-minute group,5-minute group and 10-minute group.An open-field infrared refractometer was used to record pupil diameter and accommodation-associated data before and after playing iPAD game.Accommodative response was defined as the difference between the recorded value and theoretical accommodative response,and root mean square (RMS) was used to describe the amplitude of accommodative microfluctuation.One-dimension discrete Fourier transformation was used to analyze spectral characteristic of accommodative response curve.Paired t tests were used to compare these accommodative parameters before and after playing game,while Wilcoxon signed-rank tests were applied for analyzing high frequency component of accommodative microfluctuation.This research conforms to the declaration of Helsinki,and was approved by Peking University People's Hospital Ethics Committee,all the subjects and their guardian signed informed consent.Results The accommodative response values before and after playing iPAD game in 10-minute group were (0.81 ±0.29)D and (0.74 ± 0.27) D,respectively,with significant difference between them (t =2.263,P =0.036),and no significant differences were found in the accommodative response values before and after playing iPAD game in the 3-minute group and 5-minute group (both at P＞0.05).The RMS after playing iPAD game was (0.31 ±0.08) D in the 10-minute group,which was significantly higher than (0.27 ± 0.09) D before playing iPAD game (t =-2.259,P =0.036).The high-frequency spectral power of accommodative response curves in all the three groups were increased after playing iPAD game in comparison with before playing iPAD game,with significant differences in the 5-minute group and 10-minute group (Z =-2.213,-2.016;both at P ＜ 0.05),and the pupil diameters were significantly decreased after playing iPAD game in comparison with before playing iPAD game,with significant differences in the 5-minute group and 10-minute group (t =2.428,P =0.026;t =2.515,P =0.021).Conclusions Short-term exposure to iPAD does not deteriorate accommodative lag in adolescent myopic patients.However,the increase of amplitude and high-frequency spectral power of accommodative microfluctuation,together with accommodation lag will result in blurred images and may bring adverse effects on myopic eyes.
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Background When focusing on a target,the accommodative system exhibits small variations in power within a range,termed microfluctuations.Exploring the correlation between the characters of microfluctuations and the aberrations of the eyes through a critical period-teenager can deepen the understanding of the onset and development of myopia.Objective This study was to investigate the correlation between accommodative microfluctuations and wavefront aberrations of human eyes,and to explore the role of accommodative microfiuctuations in the development of myopia.Methods A cross-sectional study was designed and performed.Fifty-four teenagers aged from 12 to 15 years were enrolled in this study in Eye Hospital,Wenzhou Medical University from 2010 to 2011,including 19 emmetropic subjects,18 incipient myopic subjects and 17 progressive myopic subjects,who were chosen based on the refractive changes for the last two years.The accommodative response and microfluctuations were measured by WAM-5500 infrared autorefractor with RSVP at 25,33 and 50 cm respectively,each RSVP distance was tested for 5 minutes.The accommodative values were divided into low frequency component (LFC) (0-0.6 Hz),middle frequency component(MFC) (0.6-0.9 Hz) and high frequency component (HFC) (1.0-1.4 Hz) after Fourier spectrum analysis.The wavefront aberrations of the whole eye and corneal were recorded by i-Trace aberrometer and Humphrey corneal topography.The differences of accommodative response,microfluctuations and aberrations were evaluated and compared among the emmetropic group,incipient myopic group and progressive myopic group.The correlations of accommodation and aberrations were analyzed.This study followed Declaration of Helsinki,and informed consent was obtained from each subject.Results Under the 25 cm and 33 cm reading distance,the accommodative response values were (2.78 ± 0.35) D and (2.19 ± 0.27) D in the emmetropic group,which were significantly higher than (2.44±0.33) D and (1.89±0.35)D in the progressive myopic group (P=0.002,0.003).LFC,MFC and HFC were remarkably increased as the reading distance decreased (Fdistance =8.480,14.270,21.400;all at P ＜0.01).A significant difference was seen in LFC among different reading distances (Fgroup =4.115,P＜0.05),and the LFCs in the progressive myopic group were considerably higher than those in the emmetropic group in the 25,33 and 50 cm reading distances (P=0.044,0.038,0.032).No significant differences were found in MFC and HFC among the three groups (Fgroup =0.859,0.682;both at P＞0.05).Under the 25 cm and 33 cm reading distances,significant positive correlations were found between LFC and corneal coma,intraocular coma,whole ocular aberrations or intraocular higher order aberrations (all at P＜0.05),however,no significant correlations were seen between MFC or HFC and wavefront aberrations (all at P＞0.05).Conclusions In teenagers,the accommodative response of emmetropia is much stronger than that of progressive myopia,and the accommodative microfluctuation in emmetropia and incipient myopia is much less than that in progressive myopia.These shifts are possibly associated with the variability,and microfluctuations of accommodation is greater in progressive myopes than emmetropes.There are certain correlations between wavefront aberrations and accommodative microfluctuations.The refractive group differences in the accommodative microfluctuations may be related to differences in the wavefront between myopes and emmetropes.Under near reading distance,LFC is correlated with higher order aberrations.
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Background Different depthes or distances are prompted with many visual cues on the flat screen.Which kind of depth cues plays a major role in the accommodation of human eyes,in addition,whether this effect exists in the different distance are still below understood.Objective This study was to research the effect of the monocular space depth perception on accommodative response at different distances,and to analyze the effect of linear perspective and size-constancy perceptual depth cues on the level and amplitude of accommodative fluctation.Methods Four groups of visual targets were designed by FLASH software and placed at the front of eyes with the distance of 50 cm or 33.3 cm,representing static change from far to near and dynamic change from far to near,from near to far respectively.Twenty-six healthy volunteers aged 22-26 years were included in this study,with the spherical power of (-4.06± 1.99) D and cylindrical power of (-0.38±0.41) D under the informed consent.The accommodative response and accommodative fluctuations during monocularly watching the targets were recorded at 5 times/second by Grand Seiko WAM 5500 automatic infrared refractor.This study was approved by Ethic Committee of Wenzhou Medical University,and written informed consent was obtained from each subject before entering the study group.Results At the distance of 50 cm,the accommodative response caused by the depth perception of near was (1.52±0.46) D,the one of distance was (1.37±0.46) D,with a significant difference of 0.15 D under the combined effect of linear perspective and size-constancy (P =0.016).The accommodative response caused by the depth perception of big car was (1.43 ± 0.35) D,and the one of small car was (1.43 ± 0.36) D,without statistically significant difference under the effect of size-constancy alone (P =0.467).At the distance of 33.3 cm,the accommodative response caused by the depth perception of near was (2.40±0.53)D,and the one of distance was (2.35 ±0.51) D,without significant difference under the combined effect of linear perspective and size-constancy (P=0.379).The accommodative response caused by the depth perception of big car was (2.38±0.48)D,the one of small car was (2.39±0.52)D,without statistically significant difference under the effect of size-constancy alone (P =0.820).In addition,the total curve of accommodative microfluctuation showed apparent fluctuation periodically caused by the distance perception involving linear perspective only.Conclusions Monocular space depth perception has some impacts on the accommodative response at certain distance.Linear perspective,which is one of the depth cues of space perception,plays a major role in the accommodative response.Compared with the size-constancy,linear perspective can provide depth perception at higher level.The size-constancy has a little or contrast impact to the accommodation,because it depends on the assistance from other depth cues like linear perspective.
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Background How to control progression of myopia is a central issue in clinical optometry.Some clinical trials showed that wearing base-in (BI) prism can slow down progression of myopia to certain degree.However,whether BI prism or base-out (BO) prism should be used is worth discussing.Objective This study was to investigate the influences of different prisms on accommodative response and microfluctuation in emmetropias.Methods This clinical trail was approved by Ethic Committee of Peking University People's Hospital.During July in 2014,twenty-two emmetropias of 22 normal volunteers aged 21-27 years were recruited from Peking University People's Hospital under the written informed consent.An open-field infrared refractometer was used to monitor and record pupil diameter and accommodative response under three conditions including non-prism,3△ BI prism,and 3△ BO prism.The accommodative response value was calculated as the difference between reading value and-3.0 D,and root mean square (RMS) of accommodative response value served as amplitude of accommodative microfluctuation.Spectrum of accommodative response was analyzed by one dimension discrete Fourier transformation.The differences of accommodative response value,amplitude of accommodative microfluctuation and pupil diameter among three conditions were compared using repeated one-way ANOVA.Results The accommodative response values were (+0.31±0.78),(+0.51±0.75) and (+0.18±0.72) D under the non-prism,3△BI prism and 3△BO prismconditions,respectively,with a significant difference among them (F =28.078,P =0.000),and compared with the non-prism condition,the accommodative lag of 3△BI prism condition was increased and that of 3△BO prism condition was reduced (P =0.000,0.012).No significant difference was found in the amplitude of accommodative microfluctuation among the three conditions (F=0.062,P =0.879).The percentages of low frequency signal power (0-0.5 Hz)/total power (0-2.5 Hz) was 97.5％,98.3％ and 91.4％ under the non-prism,3△BI prism and 3△BO prism condition,respectively.The pupil diameter was (5.37-±0.69) mm under the 3 △ BI prism condition,which was larger than (5.07±0.66) mm under the non-prism condition and (5.01 ±0.69) mm under the 3△ BO prism condition (both at P =0.000).Conclusions Compared with wearing 3△ BI prism,wearing 3△ BO prism lessens the accommodative lag,decreases the pupil diameter and reduces the power of low frequency component in accommodative response.