Ousley Paula J, Terry Mark A
Lions Vision Research Laboratory of Oregon, Portland, Oregon 97210, U.S.A.
Cornea. 2002 Mar;21(2):181-8. doi: 10.1097/00003226-200203000-00011.
Laser refractive surgery presents a growing contamination of the available corneal donor pool. There currently is no objective method for screening donor tissue for previous refractive surgery. We evaluated the usefulness of pachymetry and curvature maps in the screening of donor corneas.
Pachymetry and curvature maps were generated from the Orbscan for 40 normal donor eyes. The average central pachymetry measurement was subtracted from the thinnest average midperipheral pachymetry measurement for each map to generate a normal range of pachymetry measurements. For curvature, the average curvature at the 3-mm zone was subtracted from the average curvature at the 7-mm zone to generate a normal range of corneal curvature. The pachymetry and curvature results from 10 donor eyes that had undergone refractive surgery were then compared with the normal range for each technique.
The average difference in pachymetry measurements between the midperipheral and central cornea for normal eyes was 0.040 +/- 0.026 mm. Four of 10 corneas that had undergone refractive surgery were outside two standard deviations of this normal range. The average difference in corneal curvature between the 7-mm zone and the 3-mm zone for the healthy eyes was -0.2 +/- 1.0 diopters. Four (40%) of 10 corneas that had undergone refractive surgery were identified with this method. When combined, the pachymetry and curvature methods detected seven (70%) of 10 corneas that had undergone refractive surgery.
Regional differences in thickness and curvature in donor eyes may provide methods for screening for refractive surgery for myopia. Refinement in mathematical manipulations may further improve the sensitivity of these techniques.
激光屈光手术导致可用角膜供体库的污染日益增加。目前尚无客观方法来筛查曾接受过屈光手术的供体组织。我们评估了角膜厚度测量和曲率图在供体角膜筛查中的作用。
对40只正常供体眼进行Orbscan角膜地形图检查以获取角膜厚度测量值和曲率图。从每张图的最薄平均周边角膜厚度测量值中减去平均中央角膜厚度测量值，以得出角膜厚度测量的正常范围。对于曲率，从7毫米区域的平均曲率中减去3毫米区域的平均曲率，以得出角膜曲率的正常范围。然后将10只接受过屈光手术的供体眼的角膜厚度测量和曲率结果与每种技术的正常范围进行比较。
正常眼的周边角膜与中央角膜厚度测量的平均差值为0.040±0.026毫米。10只接受过屈光手术的角膜中有4只超出了该正常范围的两个标准差。健康眼7毫米区域与3毫米区域的角膜曲率平均差值为-0.2±1.0屈光度。用这种方法可识别出10只接受过屈光手术的角膜中的4只（40%）。将角膜厚度测量法和曲率法结合使用时，可检测出10只接受过屈光手术的角膜中的7只（70%）。
供体眼角膜厚度和曲率的区域差异可能为近视屈光手术的筛查提供方法。数学处理方法的改进可能会进一步提高这些技术的敏感性。
