Rowsey J J, Balyeat H D, Monlux R, Holladay J, Waring G O, Lynn M J
University of Oklahoma, McGee Eye Institute, Oklahoma City.
Ophthalmology. 1988 Mar;95(3):322-34. doi: 10.1016/s0161-6420(88)33179-9.
Preoperative and postoperative corneascope photographs of 368 myopic patients undergoing radial keratotomy in the Prospective Evaluation of Radial Keratotomy (PERK) study were optically scanned and digitized. A high-resolution scanning system was developed in order to quantify the preoperative and postoperative corneal shape accurately. Careful analysis of the 72 data points in the nine representative rings demonstrated that corneal topography is best represented by radius of curvature from the center to the periphery. The normal myopic cornea flattens approximately +0.28 mm from the center to the periphery, demonstrating the cornea's aspheric nature. More highly myopic patients in the PERK population (-4.50 to -8.00 diopters [D]) demonstrated corneas that are 0.08 to 0.10 mm steeper than the less myopic population (-2.00 to -3.12 D). Optical zone, patient age, and gender are all correlated to changes in corneal topography after radial keratotomy. In more myopic populations, men have corneas which are flatter than those of women by 0.09 to 0.11 mm in all rings represented on corneoscopy. Highly myopic males also experience more corneal flattening after 3.0-mm optical zone radial keratotomy. Regardless of the optical zone used in radial keratotomy, the resulting corneal topography flattens in all rings. However, the ratio of millimeters of radius of curvature change to diopters of correction is consistent for each ring. The dioptric change observed after radial keratotomy corresponds closely with the millimeters of flattening at the respective rings being examined. The central rings flatten 0.166-mm radius of curvature per diopter of refractive alteration obtained. The largest degree of corneal flattening occurs centrally, 0.72 mm, in the more highly myopic patients who underwent 3-mm optical zone radial keratotomy. The use of smaller optical zones in radial keratotomy produces larger changes in the radius of curvature and, consequently, in the amount of refraction than when larger optical zones are used. When compared with younger patients, older patients with 3.0, 3.5, and 4.0 optical zone radial keratotomies experience more central and peripheral corneal flattening. This study of the corneal topography of the myopic population demonstrates that the refractive change resulting from radial keratotomy is related to alterations in corneal topography. The use of similar modifications of the corneal surface may be effective for newer refractive surgical procedures.
在“放射状角膜切开术前瞻性评估（PERK）”研究中，对368例行放射状角膜切开术的近视患者的术前和术后角膜镜照片进行了光学扫描和数字化处理。为了准确量化术前和术后的角膜形状，开发了一种高分辨率扫描系统。对九个代表性环中的72个数据点进行仔细分析后发现，角膜地形图最好用从中心到周边的曲率半径来表示。正常近视角膜从中心到周边大约变平+0.28毫米，这表明角膜的非球面性质。PERK研究人群中近视程度更高的患者（-4.50至-8.00屈光度[D]）的角膜比近视程度较低的人群（-2.00至-3.12 D）的角膜陡峭0.08至0.10毫米。光学区、患者年龄和性别均与放射状角膜切开术后角膜地形图的变化相关。在近视程度更高的人群中，在角膜镜检查所显示的所有环中，男性的角膜比女性的角膜平0.09至0.11毫米。高度近视男性在3.0毫米光学区放射状角膜切开术后也会经历更多的角膜变平。无论放射状角膜切开术中使用何种光学区，所产生的角膜地形图在所有环中都会变平。然而，每个环的曲率半径变化毫米数与矫正屈光度的比率是一致的。放射状角膜切开术后观察到的屈光度变化与所检查的各个环处的变平毫米数密切相关。每获得1屈光度的屈光改变，中心环的曲率半径变平0.166毫米。在接受3毫米光学区放射状角膜切开术的高度近视患者中，角膜变平程度最大的发生在中心，为0.72毫米。与使用较大光学区相比，在放射状角膜切开术中使用较小的光学区会使曲率半径产生更大的变化，从而使屈光度变化更大。与年轻患者相比，接受3.0、3.5和4.0光学区放射状角膜切开术的老年患者在中央和周边角膜变平方面更为明显。这项对近视人群角膜地形图的研究表明，放射状角膜切开术引起的屈光变化与角膜地形图的改变有关。对角膜表面进行类似的改变可能对更新的屈光手术有效。
