DeVore D P, Scott J B, Nordquist R E, Hoffman R S, Nguyen H, Eiferman R A
Autogenesis Technologies, Inc., Acton, MA 01720, USA.
J Refract Surg. 1995 Jan-Feb;11(1):50-5. doi: 10.3928/1081-597X-19950101-13.
Excimer laser photoablation effectively and precisely removes corneal tissue but may not smooth irregularities on the anterior corneal surface. An even surface might be obtained by applying a smoothing substance that fills in irregularities and ablates at the same rate as corneal tissue. Evaluation of collagen gel as a smoothing agent is reported.
Pure, type I collagen solutions were prepared to remain soluble at physiological pH and to spontaneously gel when exposed to cationic buffers. Collagen gels were formed on the surface of enucleated porcine corneas and on human donor corneas and exposed to varying pulses of 193-nanometer excimer laser energy. Effects of collagen gel on ablation depth, corneal surface smoothness, and smoothing of roughened cornea were evaluated by examining scanning electron micrographs of control and treated specimens.
Collagen gels formed from 5 mg/ml collagen solutions dramatically altered the depth of photoablation. Photoablation of roughened cornea with collagen gels produced smooth corneal surfaces, whereas control eyes remained roughened and irregular. The smoothness of photoablated cornea surfaces improved when collagen gels were applied prior to photoablation.
The rapidly gelling collagen solution appears to exhibit the functional properties required for an effective smoothing agent for excimer laser photoablation. The substance has low viscosity when applied to the corneal surface and forms a rigid gel when exposed to cationic buffer solution. In addition, the concentration of the collagen gel can be adjusted to provide different ablation rates.
准分子激光光消融能有效且精确地去除角膜组织，但可能无法使角膜前表面的不规则处变得平滑。通过应用一种能填充不规则处并以与角膜组织相同速率消融的平滑物质，或许可以获得一个平整的表面。本文报道了对胶原凝胶作为一种平滑剂的评估。
制备纯I型胶原溶液，使其在生理pH值下保持可溶，并在暴露于阳离子缓冲液时自发凝胶化。在摘除的猪角膜表面和人类供体角膜上形成胶原凝胶，并使其暴露于不同脉冲的193纳米准分子激光能量下。通过检查对照和处理样本的扫描电子显微镜图像，评估胶原凝胶对消融深度、角膜表面平滑度以及粗糙角膜平滑效果的影响。
由5毫克/毫升胶原溶液形成的胶原凝胶显著改变了光消融的深度。用胶原凝胶对粗糙角膜进行光消融可产生平滑的角膜表面，而对照眼仍保持粗糙和不规则。在光消融前应用胶原凝胶时，光消融后的角膜表面平滑度得到改善。
快速凝胶化的胶原溶液似乎展现出了作为准分子激光光消融有效平滑剂所需的功能特性。该物质应用于角膜表面时粘度低，暴露于阳离子缓冲溶液时形成刚性凝胶。此外，胶原凝胶的浓度可进行调整以提供不同的消融速率。
