Ji Qiuzhi, Yoo Young-Sik, Alam Hira, Yoon Geunyoung
Flaum Eye Institute, The Institute of Optics, Center for Visual Science, University of Rochester, Rochester, USA.
Department of Convergence Medical Science, College of Medicine, The Catholic University of Korea, Seoul, South Korea.
Ophthalmic Physiol Opt. 2018 May;38(3):326-336. doi: 10.1111/opo.12452.
To characterise the impact of monofocal soft contact lens (SCL) and bifocal SCLs on refractive error, depth of focus (DoF) and orientation of blur in the peripheral visual field.
Monofocal and two bifocal SCLs, Acuvue Bifocal (AVB, Johnson & Johnson) and Misight Dual Focus (DF, CooperVision) with +2.0 D add power were modelled using a ray tracing program (ZEMAX) based on their power maps. These SCLs were placed onto the anterior corneal surface of the simulated Atchison myopic eye model to correct for -3.0 D spherical refractive error at the fovea. To quantify through-focus retinal image quality, defocus from -3.5 D to 1.5 D in 0.5 D steps was induced at each horizontal eccentricity from 0 to 40° in 10° steps. Wavefront aberrations were computed for each visual eccentricity and defocus. The retinal images were simulated using a custom software program developed in Matlab (The MathWorks) by convolving the point spread function calculated from the aberration with a reference image. The convolved images were spatially filtered to match the spatial resolution limit of each peripheral eccentricity. Retinal image quality was then quantified by the 2-D cross-correlation between the filtered convolved retinal images and the reference image. Peripheral defocus, DoF and orientation of blur were also estimated.
In comparison with the monofocal SCL, the bifocal SCLs degraded retinal image quality while DoF was increased at fovea. From 10 to 20°, a relatively small amount of myopic shift (less than 0.3 D) was induced by bifocal SCLs compared with monofocal. DoF was also increased with bifocal SCLs at peripheral vision of 10 and 20°. The trend of myopic shift became less consistent at larger eccentricity, where at 30° DF showed a 0.75 D myopic shift while AVB showed a 0.2 D hyperopic shift and both AVB and DF exhibited large relative hyperopic defocus at 40°. The anisotropy in orientation of blur was found to increase and change its direction through focus beyond central vision. This trend was found to be less dominant with bifocal SCLs compared to monofocal SCL.
Bifocal SCLs have a relatively small impact on myopic shift in peripheral refractive error while DoF is increased significantly. We hypothetically suggest that a mechanism underlying myopia control with these bifocal or multifocal contact lenses is an increase in DoF and a decrease in anisotropy of peripheral optical blur.
表征单焦点软性接触镜（SCL）和双焦点SCL对屈光不正、焦深（DoF）以及周边视野模糊方向的影响。
使用基于其屈光力地图的光线追踪程序（ZEMAX）对单焦点和两种双焦点SCL进行建模，这两种双焦点SCL分别是强生公司的Acuvue双焦点（AVB）和库博光学公司的米适双焦点（DF），附加屈光力为+2.0D。将这些SCL放置在模拟的阿奇森近视眼模型的角膜前表面，以矫正中央凹处-3.0D的球镜屈光不正。为了量化全聚焦视网膜图像质量，在0°至40°的每个水平偏心率处以10°步长、-3.5D至1.5D以0.5D步长诱导离焦。计算每个视觉偏心率和离焦情况下的波前像差。通过在Matlab（MathWorks公司）中开发的自定义软件程序，将根据像差计算得到的点扩散函数与参考图像进行卷积来模拟视网膜图像。对卷积后的图像进行空间滤波，以匹配每个周边偏心率的空间分辨率极限。然后通过滤波后的卷积视网膜图像与参考图像之间的二维互相关来量化视网膜图像质量。还估计了周边离焦、DoF和模糊方向。
与单焦点SCL相比，双焦点SCL降低了视网膜图像质量，同时中央凹处的DoF增加。在10°至20°时，与单焦点SCL相比，双焦点SCL引起的近视偏移量相对较小（小于0.3D）。在10°和20°的周边视野中，双焦点SCL的DoF也增加。在更大的偏心率下，近视偏移趋势变得不太一致，在30°时DF显示出0.75D的近视偏移，而AVB显示出0.2D的远视偏移，并且在40°时AVB和DF均表现出较大的相对远视性离焦。发现模糊方向的各向异性增加，并在中央视野以外通过聚焦改变其方向。与单焦点SCL相比，双焦点SCL的这种趋势不太明显。
双焦点SCL对周边屈光不正的近视偏移影响相对较小，而DoF显著增加。我们推测，这些双焦点或多焦点接触镜控制近视的潜在机制是DoF增加和周边光学模糊各向异性降低。
