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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.
This study was to investigate the correlation between accommodative microfluctuations and wavefront aberrations of human eyes, and to explore the role of accommodative microfluctuations in the development of myopia.
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.
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).
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.