Forbes M
Trans Am Ophthalmol Soc. 1978;76:316-28.
The unopened eye maintains a relatively stable spherical contour due to the expansile influence of the intraocular pressure. When the eye is opened this expansile pressure is lost and some degree of collapse of the scleral shell ensues. In eyes with a relatively flaccid sclera an anterior segment incision may induce significant reduction in the volume of the posterior segment of the globe. During intracapsular cataract extraction on such eyes, scleral collapse can cause anterior displacement of the lens and iris when the eye is opened and vitreous loss as soon as the lens is extracted. Scleral collapse tends to occur during intraocular surgery on previously aphakic eyes. In this situation it may become difficult to achieve a vitreous-free anterior sement by open sky vitrectomy. Metallic scleral supporters prevent inward collapse of that portion of the sclera to which they are attached. They do not prevent downward collapse of the posterior sclera shell. Upward traction is required to prevent the downward component of scleral collapse. A system for controlled suspension of the globe during intraocular surgery has been devised and used in a variety of surgical procedures. The apparatus is simple and it does help to minimize downward scleral collapse. It does not prevent scleral identation or distortion by external forces and cannot substitute for inadequate anesthesia and akinesia or faulty surgical technique.
由于眼内压的扩张作用,未睁开的眼睛保持相对稳定的球形轮廓。当眼睛睁开时,这种扩张压力消失,巩膜壳会出现一定程度的塌陷。在巩膜相对松弛的眼睛中,前段切口可能会导致眼球后段体积显著减小。在这类眼睛上进行囊内白内障摘除术时,眼睛睁开时巩膜塌陷会导致晶状体和虹膜向前移位,晶状体摘除后随即出现玻璃体脱出。巩膜塌陷往往发生在既往无晶状体眼的眼内手术过程中。在这种情况下,通过开放式玻璃体切除术实现无前段玻璃体可能会变得困难。金属巩膜支撑物可防止其附着部位的巩膜向内塌陷。但它们不能防止巩膜后壳向下塌陷。需要向上牵引以防止巩膜塌陷的向下分量。一种用于眼内手术期间控制眼球悬吊的系统已被设计出来并用于各种手术操作中。该装置很简单,确实有助于将巩膜向下塌陷降至最低。它不能防止外力引起的巩膜压痕或变形,也不能替代不足的麻醉、眼球运动麻痹或错误的手术技术。