Glasser Adrian
College of Optometry, University of Houston, Houston, TX 77204, USA.
Clin Exp Optom. 2008 May;91(3):279-95. doi: 10.1111/j.1444-0938.2008.00260.x.
Accommodation is a dioptric change in the power of the eye to see clearly at near. Ciliary muscle contraction causes a release in zonular tension at the lens equator, which permits the elastic capsule to mould the young lens into an accommodated form. Presbyopia, the gradual age-related loss of accommodation, occurs primarily through a gradual age-related stiffening of the lens. While there are many possible options for relieving the symptoms of presbyopia, only relatively recently has consideration been given to surgical restoration of accommodation to the presbyopic eye. To understand how this might be achieved, it is necessary to understand the accommodative anatomy, the mechanism of accommodation and the causes of presbyopia. A variety of different kinds of surgical procedures has been considered for restoring accommodation to the presbyopic eye, including surgical expansion of the sclera, using femtosecond lasers to treat the lens or with so-called accommodative intraocular lenses (IOLs). Evidence suggests that scleral expansion cannot and does not restore accommodation. Laser treatments of the lens are in their early infancy. Development and testing of accommodative IOLs are proliferating. They are designed to produce a myopic refractive change in the eye in response to ciliary muscle contraction either through a movement of an optic or through a change in surface curvature. Three general design principles are being considered. These are single optic IOLs that rely on a forward shift of the optic, dual optic IOLs that rely on an increased separation between the two optics, or IOLs that permit a change in surface curvature to produce an increase in optical power in response to ciliary muscle contraction. Several of these different IOLs are available and being used clinically, while many are still in research and development.
调节是眼睛屈光力的一种变化，以便能看清近处物体。睫状肌收缩会使晶状体赤道部的悬韧带张力放松，从而使弹性囊膜将年轻的晶状体塑造成调节状态的形状。老花眼是与年龄相关的调节能力逐渐丧失，主要是由于晶状体随年龄增长逐渐变硬。虽然有许多缓解老花眼症状的可能选择，但直到最近才开始考虑通过手术恢复老花眼的调节能力。要了解如何实现这一点，有必要了解调节的解剖结构、调节机制以及老花眼的成因。为恢复老花眼的调节能力，人们考虑了各种不同的外科手术，包括巩膜扩张手术、使用飞秒激光治疗晶状体或使用所谓的可调节人工晶状体（IOL）。有证据表明，巩膜扩张无法也不能恢复调节能力。晶状体的激光治疗尚处于初期阶段。可调节人工晶状体的研发正在蓬勃发展。它们的设计目的是，通过光学部件移动或表面曲率变化，使眼睛在睫状肌收缩时产生近视屈光变化。目前正在考虑三种总体设计原则。这些原则包括：依靠光学部件向前移动的单光学部件人工晶状体、依靠两个光学部件之间距离增加的双光学部件人工晶状体，或允许表面曲率变化以在睫状肌收缩时增加屈光力的人工晶状体。其中几种不同的人工晶状体已经可用并应用于临床，而许多仍在研发中。
