Spörl E, Genth U, Schmalfuss K, Seiler T
Augenklinik des Universitätsklinikums der Technischen Universität Dresden.
Klin Monbl Augenheilkd. 1996 Feb;208(2):112-6. doi: 10.1055/s-2008-1035180.
Shrinkage of corneal collagen is used during thermokeratoplasty, a method to remodel the corneal curvature. The goals of our investigations were to determine the optimal temperature range for maximal shrinkage of the collagen fibers with minimal damage.
By means of a commercially available stress-strain-measuring device with a paraffin oil bath of temperatures varying from 35 degrees C to 120 degrees C strips of pig cornea 5 mm in width and 9 mm in length were investigated in the physiological stress range from sigma = (0,5-12,5) . 10(4) N/m2 by stress-strain, stress relaxation and creep measurements.
Biomechanical properties of the cornea remain unchanged in the temperature range from 30 to 50 degrees C. Starting at 60 degrees C shrinkage occurs that increases up to 90 degrees C. The maximal rate of shrinkage of (57 +/- 12)% was measured at temperatures of 75 to 80 degrees C. Above 100 degrees C this effect is reduced by the destruction of intermolecular bonds between the collagen fibers. The stress-strain curves of the shrunk corneas are flatter than that of native corneas, which means, the Young's modulus is significantly reduced.
In order to realize optimal shrinkage during thermokeratoplasty temperatures of 65-85 degrees C should be achieved in the coagulated tissue. Higher temperatures cause also a shrinkage effect but also a destruction of tissue.
角膜胶原纤维收缩应用于热角膜成形术，这是一种重塑角膜曲率的方法。我们研究的目的是确定能使胶原纤维最大程度收缩且损伤最小的最佳温度范围。
使用市售的应力应变测量装置，其石蜡油浴温度范围为35℃至120℃，对宽度为5mm、长度为9mm的猪角膜条在生理应力范围σ = (0.5 - 12.5)×10⁴ N/m²内进行应力应变、应力松弛和蠕变测量。
角膜的生物力学特性在30至50℃温度范围内保持不变。从60℃开始出现收缩，收缩程度持续增加直至90℃。在75至80℃温度下测得最大收缩率为(57 ± 12)%。高于100℃时，由于胶原纤维间分子间键的破坏，这种收缩效应减弱。收缩后角膜的应力应变曲线比天然角膜的更平缓，这意味着杨氏模量显著降低。
为在热角膜成形术中实现最佳收缩效果，凝固组织的温度应达到65 - 85℃。更高的温度虽也会产生收缩效应，但同时会导致组织破坏。
