Garner L F, Yap M K
Department of Optometry, University of Auckland, New Zealand.
Ophthalmic Physiol Opt. 1997 Jan;17(1):12-7.
The purpose of this study was to measure the changes in ocular dimensions with accommodation, with particular reference to the radius of curvature of the posterior surface of the crystalline lens. The increase in power of the eye with accommodation is considered to arise primarily from a decrease in the radius of curvature of the anterior surface of the lens, with the role of the posterior surface somewhat unclear. We measured the axial dimensions (A-Scan ultrasonography), corneal radius of curvature (keratometry), refractive error (auto-refractor) and radii of curvature of the lenticular surfaces (video phakometry) for 11 subjects, mean age 21.2 +/- 2.6 years, for five levels of ocular accommodation up to 8.00 D. At maximum accommodation the mean changes were a decrease in anterior chamber depth of 0.24 mm, an increase in lens thickness of 0.28 mm, a decrease in radius of curvature of the anterior surface of the lens of 4.95 mm and 1.34 mm for the posterior surface. The corresponding increase in power of the lenticular surfaces for an equivalent refractive index of 1.422 for the lens was 5.53 D and 3.10 D for the anterior and posterior surfaces respectively. No significant changes were recorded in axial length or vitreous chamber depth. We conclude that when crystalline lens power is calculated on the basis of an equivalent refractive index, changes in the posterior surface of the lens contribute around one third of the increase in lens power associated with 8.00 D of ocular accommodation.
本研究的目的是测量眼睛在调节时眼尺寸的变化，尤其关注晶状体后表面的曲率半径。眼睛调节时屈光力的增加主要被认为是由于晶状体前表面曲率半径的减小，而后表面的作用尚不完全清楚。我们对11名平均年龄为21.2±2.6岁的受试者进行了测量，测量内容包括轴向尺寸（A超超声检查）、角膜曲率半径（角膜曲率计）、屈光不正（自动验光仪）以及晶状体表面的曲率半径（视频晶状体测量法），测量了高达8.00 D的五个眼调节水平。在最大调节时，平均变化为前房深度减少0.24 mm，晶状体厚度增加0.28 mm，晶状体前表面曲率半径减少4.95 mm，后表面减少1.34 mm。对于晶状体等效折射率为1.422的情况，晶状体前、后表面相应的屈光力增加分别为5.53 D和3.10 D。轴向长度和玻璃体腔深度未记录到显著变化。我们得出结论，当基于等效折射率计算晶状体屈光力时，晶状体后表面的变化约占与8.00 D眼调节相关的晶状体屈光力增加的三分之一。
