Muallem Marcus S, Yoo Sonia H, Romano Andre C, Marangon Fabiana B, Schiffman Joyce C, Culbertson William W
Bascom Palmer Eye Institute, Miami, FL 33136, USA.
J Cataract Refract Surg. 2004 Nov;30(11):2295-302. doi: 10.1016/j.jcrs.2004.02.080.
To evaluate whether flap thickness changes after the primary laser in situ keratomileusis (LASIK) procedure and to assess the accuracy of intraoperative pachymetry and ablation depth measurements in predicting stromal bed thickness before enhancement in eyes that have had primary myopic LASIK.
Bascom Palmer Eye Institute, Miami, Florida, USA.
This retrospective noncomparative interventional case series comprised 57 eyes of 42 patients who had LASIK enhancement between June 2001 and September 2002. Exclusion criteria included previous ocular surgery or complications during the first LASIK procedure. Only patients who had had LASIK and enhancement by the same surgeon at our institution and had intraoperative pachymetry readings for both procedures were included. The original flap was relifted in all enhancement procedures. Corneal thickness was routinely measured intraoperatively by ultrasound pachymetry. The age, eye, refraction, date of primary LASIK, central corneal thickness (CCT) and central stromal bed thickness at primary LASIK, depth of ablation, flap thickness (subtraction pachymetry), date of enhancement, CCT and central stromal bed thickness at enhancement, and flap thickness at enhancement were recorded.
Thirty-one eyes of 26 patients were myopic and 26 eyes of 16 patients were hyperopic before primary LASIK. The mean time between LASIK and enhancement was 218 days +/- 115 (SD) (193 +/- 88 days in myopic eyes and 248 +/- 136 days in hyperopic eyes [P = .068]). The flap tended to be thicker at enhancement than in the primary LASIK procedure by 9.3 +/- 25.7 microm in myopic eyes (P = .054) and 10.5 +/- 16.6 microm in hyperopic eyes (P = .004). A strong correlation was found between flap thickness in the first and second procedures in myopic and hyperopic eyes (r = 0.6). In myopic eyes, the mean difference between the estimated stromal bed thickness after the first procedure (central bed thickness- ablation depth) and the stromal bed thickness measured directly at enhancement was not statistically significant (3 +/- 29 microm; P = .54, paired t test). A strong correlation was found between the 2 measurements (r = 0.8, P<.001). Another strong correlation was found in myopic eyes between the estimated corneal thickness after the primary LASIK and the corneal thickness measured at enhancement (r = 0.81, P<.001). No correlation was found between the difference in flap thickness and the time to enhancement (r = 0.09 in myopic eyes and r = 0.01 in hyperopic eyes).
Flap thickness tended to be thicker at enhancement than at primary LASIK. Intraoperative pachymetry and ablation depth measurements proved to be precise tools to predict stromal bed thickness before enhancement in eyes that had had primary myopic LASIK. This information may help in planning LASIK enhancements.
评估初次准分子原位角膜磨镶术（LASIK）后角膜瓣厚度是否发生变化，并评估在初次近视LASIK术后进行增效手术时，术中测厚及消融深度测量在预测基质床厚度方面的准确性。
美国佛罗里达州迈阿密市巴斯科姆·帕尔默眼科研究所。
这是一项回顾性非对照干预性病例系列研究，纳入了2001年6月至2002年9月期间接受LASIK增效手术的42例患者的57只眼。排除标准包括既往眼部手术史或初次LASIK手术期间的并发症。仅纳入在本机构由同一位外科医生进行LASIK及增效手术且两次手术均有术中测厚读数的患者。所有增效手术均重新掀起原角膜瓣。术中常规采用超声测厚仪测量角膜厚度。记录患者年龄、眼别、屈光状态、初次LASIK日期、初次LASIK时的中央角膜厚度（CCT）及中央基质床厚度、消融深度、角膜瓣厚度（相减测厚法）、增效日期、增效时的CCT及中央基质床厚度以及增效时的角膜瓣厚度。
初次LASIK术前，26例患者的31只眼为近视，16例患者的26只眼为远视。LASIK与增效手术之间的平均时间为218天±115（标准差）（近视眼中为193±s88天，远视眼中为248±136天[P = 0.068]）。增效手术时角膜瓣厚度往往比初次LASIK手术时厚，近视眼中厚9.3±25.7微米（P = 0.054），远视眼中厚10.5±16.6微米（P = 0.004）。近视和远视眼中首次与第二次手术时的角膜瓣厚度之间存在强相关性（r = 0.6）。在近视眼中，第一次手术后估计的基质床厚度（中央床厚度 - 消融深度）与增效时直接测量的基质床厚度之间的平均差异无统计学意义（3±29微米；P = 0.54，配对t检验）。两次测量之间存在强相关性（r = 0.8，P<0.001）。在近视眼中，初次LASIK后估计的角膜厚度与增效时测量的角膜厚度之间也存在强相关性（r = 0.81，P<0.001）。角膜瓣厚度差异与增效时间之间无相关性（近视眼中r = 0.09，远视眼中r = 0.01）。
增效手术时角膜瓣厚度往往比初次LASIK时厚。术中测厚及消融深度测量被证明是预测初次近视LASIK术后增效手术前基质床厚度的精确工具。这些信息可能有助于规划LASIK增效手术。
