ABSTRACT
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.
ABSTRACT
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.
ABSTRACT
To improve the clinical skills of medical students and to train qualified and profes-sional ophthalmologist,the school of optometry and ophthalmology in Wenzhou Medical College car-ried out reforms and innovations in clinical practice and training. In order to strengthen and train clin-ical thinking and clinical skills,and to cultivate the humanistic qualities of medical students,the di-verse-training mode were applied in clinical practice and training. In this paper explored the design goal, objective and actual effect of diverse-training mode for clinical practice and training.