Wachtlin J, Blasig I E, Schründer S, Langenbeck K, Hoffmann F
Department of Ophthalmology, Free University of Berlin, Germany.
Cornea. 2000 Jan;19(1):75-9. doi: 10.1097/00003226-200001000-00015.
There are insufficient data on the possible cataractogenic side effects of excimer laser corneal surgery. Higher malondialdehyde (MDA) levels could indicate oxidative events related to the cataractogenic process. We therefore examined MDA levels after refractive laser surgery.
Six white Russian rabbits received laser in situ keratomileusis (LASIK) (Schwind keratome) in the right eye and a 250-microm-deep microkeratome cut (Schwind microkeratome) in the left eye. Six others underwent photorefractive keratectomy (PRK) in the right eye; the left eye remained untreated. The 180 mJ/cm2 fluence applied at a rate of 10 Hz with an optical zone diameter of 5 mm in all rabbits (438 pulses) resulted in an estimated central photoablation depth of 116 microm. Two weeks later, lenses and aqueous were taken immediately after death. MDA was detected in aqueous and homogenate of lenses after reacting with thiobarbituric acid (TBA). MDA bound to TBA (MDA-TBA) was specifically analyzed by high-performance liquid chromatography (HPLC) (excitation, 525 nm; emission, 551 nm) using phosphate-buffered methanol as eluent.
No significant laser-induced MDA alteration was found in either the aqueous or the lens. The microkeratome group, however, had two to three times higher MDA levels in the lenses than the control group (p = 0.12) or the PRK (p = 0.03) group.
Elevation of MDA in the lens of the microkeratome group indicates that LASIK, but not PRK, may be a risk factor in cataractogenesis. The increased MDA levels in the LASIK group are probably caused by the microkeratome incision rather than the secondary radiation of the excimer laser. Postoperative inflammation may explain the surprising results.
关于准分子激光角膜手术可能的致白内障副作用的数据不足。较高的丙二醛（MDA）水平可能表明与致白内障过程相关的氧化事件。因此，我们检测了屈光性激光手术后的MDA水平。
6只俄罗斯白兔右眼接受准分子原位角膜磨镶术（LASIK）（Schwind角膜刀），左眼进行250微米深的微型角膜刀切割（Schwind微型角膜刀）。另外6只右眼接受准分子激光角膜切削术（PRK）；左眼未治疗。所有兔子均以10赫兹的频率、5毫米的光学区直径施加180毫焦/平方厘米的能量密度（438个脉冲），估计中央光凝深度为116微米。两周后，兔子死后立即采集晶状体和房水。与硫代巴比妥酸（TBA）反应后，在房水和晶状体匀浆中检测MDA。使用磷酸盐缓冲甲醇作为洗脱剂，通过高效液相色谱（HPLC）（激发波长525纳米；发射波长551纳米）特异性分析与TBA结合的MDA（MDA-TBA）。
在房水或晶状体中均未发现激光诱导的MDA有显著变化。然而，微型角膜刀组晶状体中的MDA水平比对照组（p = 0.12）或PRK组（p = 0.03）高两到三倍。
微型角膜刀组晶状体中MDA升高表明，LASIK而非PRK可能是白内障发生的危险因素。LASIK组MDA水平升高可能是由微型角膜刀切口而非准分子激光的二次辐射引起的。术后炎症可能解释了这一令人惊讶的结果。
