Ophthalmology, Boston Children's Hospital, Boston, Massachusetts, USA.
Ophthalmology, Harvard Medical School, Boston, Massachusetts, USA.
Ophthalmic Physiol Opt. 2023 Jul;43(4):815-826. doi: 10.1111/opo.13133. Epub 2023 Mar 31.
To create a simplified model of the eye by which we can specify a key optical characteristic of the crystalline lens, namely its power.
Cycloplegic refraction and axial length were obtained in 60 eyes of 30 healthy subjects at eccentricities spanning 40° nasal to 40° temporal and were fitted with a three-dimensional parabolic model. Keratometric values and geometric distances to the cornea, lens and retina from 45 eyes supplied a numerical ray tracing model. Posterior lens curvature (PLC) was found by optimising the refractive data using a fixed lens equivalent refractive index ( ). Then, was found using a fixed PLC.
Eccentric refractive errors were relatively hyperopic in eyes with central refractions ≤-1.44 D but relatively myopic in emmetropes and hyperopes. Posterior lens power, which cannot be measured directly, was derived from the optimised model lens. There was a weak, negative association between derived PLC and central spherical equivalent refraction. Regardless of refractive error, the posterior retinal curvature remained fixed.
By combining both on- and off-axis refractions and eye length measurements, this simplified model enabled the specification of posterior lens power and captured off-axis lenticular characteristics. The broad distribution in off-axis lens power represents a notable contrast to the relative stability of retinal curvature.
建立简化的眼球模型，用以确定晶状体的一个关键光学特性，即其屈光度。
对 30 名健康受试者的 60 只眼进行睫状肌麻痹验光和眼轴长度测量，这些眼的偏心距范围从鼻侧 40°到颞侧 40°。采用三维抛物线模型对这些数据进行拟合。6 只眼的角膜曲率计值和距角膜、晶状体和视网膜的几何距离提供了一个数值光线追踪模型。通过使用固定的晶状体等效折射率（ ）优化屈光数据，找到后晶状体曲率（PLC）。然后，使用固定的 PLC 找到 。
中央屈光度≤-1.44 D 的眼的偏心折射误差相对远视，但在正视眼和远视眼中相对近视。无法直接测量的后晶状体屈光度是从优化模型晶状体中得出的。优化后的 PLC 与中央球镜等效屈光度之间存在微弱的负相关。无论屈光不正如何，后视网膜曲率保持不变。
通过结合眼内和眼外的折射和眼轴长度测量，该简化模型能够确定后晶状体的屈光度，并捕获眼外晶状体的特性。眼外晶状体屈光度的广泛分布与视网膜曲率的相对稳定性形成鲜明对比。
