Bryant M R, Szerenyi K, Schmotzer H, McDonnell P J
Doheny Eye Institute, Los Angeles, CA 90033.
Invest Ophthalmol Vis Sci. 1994 Jun;35(7):3022-31.
To investigate the susceptibility to rupture of a human donor cornea with fully healed radial keratotomy (RK) incisions using biomechanical measurement methods and finite element analysis.
A human cornea 8 years after RK was cut into four strips and subjected to tensile testing until rupture occurred. The fellow cornea was pressurized on an artificial anterior chamber beyond the initiation of wound gape. The tensile strengths of nine strips from unincised corneas were measured as controls. To investigate the effect of epithelial plugs on the RK strip test results, a finite element model of a strip containing an epithelial plug was analyzed.
Rupture occurred along the wound site with wide variability in the measured tensile strengths. There was no significant difference in tensile strength between the RK corneal strips (16.6 +/- 4.43 N/mm2) and the control strips (19.1 +/- 3.50 N/mm2). Four of the eight incisions of the fellow RK cornea gaped, but the cornea did not rupture up to a pressure of 2740 mm Hg. An epithelial plug of 10% of the corneal thickness was found in one of the incisions. The finite element results demonstrated higher stresses at the wound site that increased with the size of the epithelial plug.
The presence of an epithelial plug in a fully healed radial keratotomy incision will create a stress concentration at the incision site that may predispose the cornea to rupture. The variability in the strength measurements indicates that the increase in rupture susceptibility due to RK may be hard to predict and may depend on factors such as the size of the plug and the strength of the wound collagen.
使用生物力学测量方法和有限元分析，研究具有完全愈合的放射状角膜切开术（RK）切口的人类供体角膜的破裂易感性。
将RK术后8年的人类角膜切成四条，并进行拉伸测试直至破裂。对另一只角膜在人工前房上加压，直至伤口张开开始。测量未切开角膜的九条角膜条的拉伸强度作为对照。为了研究上皮栓对RK角膜条测试结果的影响，分析了包含上皮栓的角膜条的有限元模型。
破裂沿伤口部位发生，测量的拉伸强度变化很大。RK角膜条（16.6±4.43 N/mm²）和对照角膜条（19.1±3.50 N/mm²）的拉伸强度没有显著差异。另一只RK角膜的八个切口中有四个出现了伤口张开，但在高达2740 mmHg的压力下角膜未破裂。在其中一个切口中发现了占角膜厚度10%的上皮栓。有限元结果表明，伤口部位的应力较高，且随着上皮栓大小的增加而增加。
在完全愈合的放射状角膜切开术切口中存在上皮栓会在切口部位产生应力集中，这可能使角膜易于破裂。强度测量的变异性表明，RK导致的破裂易感性增加可能难以预测，并且可能取决于诸如栓子大小和伤口胶原强度等因素。
