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Accommodation of the human eye ian extremely complex and dynamiprocess,which iaccomplished by the interaction between the central nervousystem and variouoculastructurethaare relevanto accommodation.Varioumechanismof accommodation have been puforward since the beginning of the 19th century,among which Helmhohz'theory ithe mosfamous.However,iistill challenged by othetheories.So far,the mechanism of accommodation hanobeen fully understood.The mosdirecmethod to study accommodation ito observe changein the biometry of the oculastructureduring accommodation,which ialso the mosobjective interpretation of accommodative mechanisms.The rapid developmenof imaging technologiein regardto ophthalmology makethipossible.Thiarticle aimto describe the use of variouimaging technologiein oculaaccommodative studiein vivo from the perspective of morphology.
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Background Even though the change in wavefront aberrations with correction modality is well documented in the literature,little is known about the underlying mechanism.Complete understanding of the causes responsible for the wavefront change in the combined lens-eye system is important since it provides basic knowledge for further improving the technique to correct refractive error by correcting lenses.Objective The aim of this study was to investigate the influence of refractive correction lens on optical property of the eye by analyzing Zernike aberrations in myopic eyes with contact lens correction.Methods This study was approved by the Ethic Committee of Wenzhou Medical College.Written informed consent was obtained from each subject before entering this study.Zernike aberrations of 52 myopic eyes of 26 subjects with the spherical equivalent-1.75 to-8.50 D were measured using a Hartmann-Shock wavefront sensor.The human eye aberrations were examined at the uncorrected condition,rigid-gas-permeable contact lens (RGP-CL) corrected condition and soft contact lens (Soft-CL) corrected condition.The differences of wavefront aberrations and Zernike coefficients were compared by repeated measurement of single factor variance analysis,and correlation of the aberration changes between uncorrected condition and RGP-CL corrected condition or Sofi-CL corrected condition,between the right eyes and left eyes in different conditions were analyzed by Pearson linear correlation.Results Mean total root-mean-square (tRMS) was (0.71 ± 0.30)μm,(0.54±0.19)μm and (0.74±0.32)μm in the uncorrected condition,RGP-CL corrected condition and Soft-CL corrected condition,with a significant difference (F =8.758,P＜0.001),and tRMS was significant declined under the RGP-CL corrected condition compared with uncorrected condition (t =2.746,P =0.008),and tRMS in RGP-CL corrected condition was significantly lower than that in Soft-CL corrected condition (t =3.428,P =0.001).The high RMS (hRMS) was (0.34±0.12) μm,(0.28 ±0.12) μm,(0.40±0.14) μm in the uncorrected condition,RGP-CL corrected condition and Soft-CL corrected condition,with a significant difference among them (F =10.681,P＜0.001).An insignificant decrease of hRMS was seen in the RGP-CL corrected condition compared with uncorrected condition (t =1.987,P=0.053),but hRMS value was significant higher in the Soft-CL corrected condition than that in the uncorrected condition (t=2.101,P=0.041) and RGP-CL corrected condition (t=4.266,P＜0.001).Compared with uncorrected condition,the axis astigmatism (C5) and spherical aberration (C12) in the RGP-CL corrected condition and spherical aberration (C12) in the Soft-CL corrected condition were significantly reduced (P＜0.05),and the absolute values of trefoil (C6),vertical coma (C7) and tetrafoil (C10) in the RGP-CL corrected condition were lower than those of the uncorrected condition,but vertical coma (C7) absolute value in the Soft-CL corrected condition was increased (P＜0.05).A significantly positive correlation was seen in the spherical aberration (C12) between the RGP-CL corrected condition and uncorrected condition (r =0.763,P＜0.001),and less significant correlation was in the secondary astigmatism (C11) between the Soft-CL corrected condition and uncorrected condition(r=0.469,P＜0.001).Conclusions Different contact lens corrected conditions exert their effects on ocular wavefront structure due to its unique interaction with the eye.RGP-CL wearing has strong modification on wavefront aberrations probably due to its molding effect on corneal surface,which reduces the bilateral symmetry.High order wavefront aberration can be modified by Soft-CL wearing.
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Background Researches showed that as the non-optical factors,cognitive has certain influence on the regulating system.So accurately experimental design is one of the key steps that evaluates the non-optical factors on regulating system.Objective The present study was to investigate the influence of presenting pattern of target and watching way on the level and amplitude of accommodative fluctuate and to analyze the effect of focus gaze of cognitive on regulating system and the relationship between focus gaze condition under near work and the development of myopia.Methods This study complied with Declaration of Helsinki,and the permission of Ethic Committee and written informed consent was obtained before entering in this trial.Thirty healthy volunteers were included with the mean age (24.80 ± 1.98) years old,equivalent refractive diopter (-1.92 ± 2.02) D and mean cylinder (-0.19±0.58) D.The presenting pattern of the targets was designed as focus gaze and relaxed gaze.The accommodative response and accommodative fluctuation in the complete corrected right eyes for the different targets at the 40 cm under the gazing state was recorded with Grand Seiko WAM 5500 automatic infrared refractor in the experiment.Results The mean accommodative response value was (1.86±0.26) D under the focus gaze and (1.27±0.39) D under the relax gaze,showing a statistically significant difference (t=-8.052,P=0.000).The mean fluctuate value was(0.17±0.06) D under the focus gaze,with a significant lowing in comparison with (0.28±0.17) D under the relax gaze (t =3.600,P =0.001).Conclusions These results demonstrate that the different presenting patterns of sighting target and watching ways of the subjects affect accommodation system.The accommodative response was relatively more accurate with a smaller microwavc moving under the focus gaze condition.
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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.
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Background Both functional and morphological changes in amblyopic development are known to occur at various levels in the central visual pathway.However,whether the retina is involved or not during amblyopic progression remains controversial.Objective This study was designed to compare the thicknesses of the fovea and retinal nerve fiber layer (RNFL) of the normal fellow eye of amblyopic eye using optical coherence tomography (OCT) in children with myopic anisometropia.Methods Twenty-two patients with unilateral myopic anisometropic amblyopia were included as the anisometropia amblyopia group.Ten unilateral myopic anisometropic amblyopia subjects received treatment and recovered were used as the amblyopic cure group,and 11 individuals with simple myopic anisometropia without amblyopia were enrolled as the control group.OCT was performed on both eyes of all the subjects with informed consent.Fovea retinal thickness and RNFL thickness from the superior,inferior,nasal and temporal quadrants in the peripapillary region were evaluated.The measurement parameters were bilaterally compared in all the individuals by paired t test.The multiple regression model was used to analyze the correlation of retinal thickness with amblyopia patients.This study was approved by the Ethic Committee of this hospital.Written informed consent was obtain from each subject prior to the eye examination.Results Fovea retinal thickness increased in the amblyopic eyes compared with the fellow eyes,showing a statistically significant difference between them (P =0.001).However,no significant differences were found in the fovea retinal thickness between both eyes in the amblyopic cure group and simple myopic anisometropia without amblyopia group (P =0.778,0.943).Among the anisometropia amblyopia group,amblyopia cure group and simple myopic anisometropia without amblyopia group,the RNFL thicknesses of the temporal quadrant was significantly thicker in the higher myopic lateral eyes than those of the fellow eyes (P＜0.001,P =0.003,P =0.046).However,the differences in the superior,inferior,nasal and the average RNFL thickness were not statistically significant between the two eyes (P＞0.05).A negative correlation was found between the inferior retinal thickness with age (r=-0.559,P=0.016).Conclusions The fovea may be affected in unilateral myopic anisometropic amblyopia.There is no significant difference in the RNFL thickness between simple myopic eye and unilateral myopic anisometropia amblyopic eye.Improvement in amblyopia is coming along with the reduction of the thickness of the fovea.
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BackgroundCycloplegia is well accepted for the first refraction estimate in childhood.Yet no good evidence is offered in terms of which cyclopegia is preferable for the different ages and refractive status in children. ObjectiveThis study aimed to compare the effectiveness of cycloplegia between 1％ cyclopentolate and 1％ atropine sulphate before optometry in ametropia children. Methods This was a prospective clinical trail.The self matched-pairs control randomly observation was designed.One hundred and sixty eyes of 80 children of 4-9 years old with refractive error were recruited in this study.1％ cyclopentolate eye drops were topically administered once per 5 minutes for 3 times and 1％optometry was performed 45 minutes after eye dropping.Three days after that,1％ atropine then was used 3 times per day for consecutive 3 days and again the refractive diopter was obtained.The differences of the results in autorefraction,retinoscope and residual accommodation were compared between 1％ cyclopentolate and 1％atropine eye drops.This trail was approved by the Ethic Committee and written informed consent was obtained from each custodian. Results The autorefraction values were ( 0.55 ±3.52 ) D and ( 2.22 ±3.52) D before and after the administration of 1％ atropine with the difference value( 1.66± 1.62) D (t =13.02,P =0.00 ).The autorefraction value was( 1.74±3.46 ) D after dropping of 1％ cyclopentolate and the difference value from that of 1％ atropine was (0.48 ± 0.46) D ( t =13.08,P =0.00 ).The cy(e)lplegic autorefractions of atropine and cyclopentolate have strong correlation ( R2 =0.98,P =0.000 ).The residual accommodation values were ( 0.32± 0.44 )D and(0.05±0.41 ) D after dropping of 1％ cyclopentolate and 1％ atropine with the difference( 0.27±0.55 ) D ( t =4.56,P =0.00 ).The difference value of refractive diopter was (0.31 ± 0.37 )D in myopic group,(0.56±0.48 )D in moderate hypermetropic group and(0.59±0.50)D in high myopic group,and that of myopic group was significantly lower than the moderate hypermetropic group ( t =- 3.14,P =0.00 ).No significant difference was found in the autorefraction difference between 4-6 years group and 7 -9 years group [ ( 0.61 ±0.53 ) D vs ( 0.49 ±0.39 ) D ] ( t =1.21,P=0.23 ).The hidden value because of accommodation had weak correlation with the difference value between atopine and cyclopentolate(r=0.43,P=0.00). ConclusionsBoth 1％ atropine and 1％ cyclopentolate have the cycloplegic effects.This study suggestes that 1％ atropine should be used for the optometry of hypermetropia children.
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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.
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Background The evaluation of visual function after laser in situ keratomileusis(LASIK) mainly focuses on the study of contrast sensitivity funetion (CSF).However,CSF measurement is a subjective method and therefore has a limiting in application.A point spread function (PSF) is becoming a study topic because of its objectivity in assessing visual quality.Objective Present study was to evaluate the change of the modulation transfer function (MTF) of eyes and compare the optical and visual quality of human eyes after LASIK.Methods Thirty-six patients(72 eyes) were included in this study.The patients were divided into low myopia(-2.72±0.52 D),moderate myopia (-4.89+0.80 D) and high myopia (-8.00+0.98 D) groups according to the spherical equivalent (SE)diopter before the sugery.The uncorrected visual acuity (UCVA),best corrected visual acuity (BCVA) were examined before and after operation,and PSF data was obtained with Topoeon PSF-1000 analyzer under the 3.0 mm and 6.0 mm pupil size conditions.The follow-up visits of the patients were scheduled at the 7th days,1 st and 3rd months.Written informed consent was obtained from each patient before this study. ResuIts The MTF values among the three refractive groups were significantly different between 3 mm and 6 mm pupil preoperatively (P＜0.05).Under the condition of 3 mm pupil size,the MTF values in the spatial frequencies of 2.98 cpd and 14.88 cpd were significantly declined in different time points after operation in comparison with preoperative ones (P＜0.05).However,the MTF changes had no statistical significance in the spatial frequencies from 18.85-37.70 cpd among various time points(P＞0.05).Under the condition of the 6 mm pupil size,MTF values in low and moderate myopia groups were reduced after operation in comparison with before operation at the spatial frequencies from 2.98-7.44 cpd(P＜0.05),however,there were no obvious difference was found in the spatial frequencies of 9.42-37.70 cpd(P＞0.05).The MTF values of high myopia group was decreased significantly at all spatial frequencies(P＜0.05).The MTF values improved gradually as the prolong of time after operation but was still lower at the 3rd postoperative month than that of preoperation. Conclusion The postoperative visual quality is associated with refractive power and pupil diameter.PSF is a feasible method in assessing the early visual quality after LASIK.