The Effect Of Ocular Accommodation On Refractive Components In Children

Objective: To study the correlation between ocular accommodation and ametropia by analyzing the effect of accommodation on refractive components in children.Methods: The anterior chamber depth (AD), lens thickness (LT), vitreous chamber length (VL) and ocular axial length (AL) were measured for 270 eyes before and after cycloplegia. The corneal shapes of 136 eyes selected randomly from the 270 eyes were studied before and after cycloplegia by a computerized video keratoscope. Results: The test of normality showed that the distribution of all variables were normal in each refractive state. Paired Samples T test revealed that both the LT and VL decreased (P<0.01), the AD increased (P<0.01) after cycloplegia regardless of their refractive state. The AL increased for hyperopic eyes (P<0.05) and decreased for myopic eyes (P<0.01) after cycloplegia. For hyperopic eyes, the major keratometer K1 increased (P<0.05) while for myopic eyes, the major keratometer K1(P<0.05) and minor keratometer K2 (P<0.01) decreased after cycloplegia. The mean corneal power of zones 5 mm (MD5) and 7 mm (MD7) decreased with myopic eyes decreased dramatically (P<0.01). The mean refractive power of the lower half vertical meridian (LMD) is greater than that of upper half (UMD); and the mean refractive power of the lateral half of the horizontal (LaMD) is greater than that of the medial half (MMD). Conclusion: The ocular accommodation has a great influence on refractive components. It is not only the process by which the refractive power of the lens is increased. But the lens itself moved forward relatively. The accumulation effects of accommodation induced by near-work is the main cause of myopia developed in children. The asymmetry of corneal surface was not only related to keratometer K1 and K2 , even the curvature within the same horizontal or vertical meridian was asymmetry.