准分子激光角膜切削术前后的角膜地形图分析

了解准分子激光角膜切削术（ｐｈｏｔｏｒｅｆｒａｃｔｉｖｅｋｅｒａｔｅｃｔｏｍｙ，ＰＲＫ）前、后角膜表面形态变化并对切削区偏中心进行分析。方法应用计算机辅助的角膜地形图仪对８０例（１２２只眼）ＰＲＫ前、后角膜地形图进行检测和分析。结果术前角膜地形图的形态呈对称或非对称性蝴蝶结形者占７５．４％；术后圆形或近似圆形者占６３．９％。切削区偏离瞳孔中心的距离与术前屈光度无关。切削区偏中心距离越大，术后角膜散光增加及术后最佳矫正视力下降越明显。结论ＰＲＫ前、后角膜地形图检查和分析能清楚地显示角膜表面形态变化及定量评估切削区偏中心问题。     

近视患者用准分子激光作角膜切削术后角膜地形图的改变

１７例近视患在准分子激光切割术后第一年中进行了计算机辅助的角膜地形图的分析。角膜中央视区进行了自然过渡到周边角膜的切削。在一些眼出现切割偏中心（３眼小于０．５ｍｍ，１０眼为０．５～１．０ｍｍ，３眼为１～１．５ｍｍ，１眼为２．１ｍｍ），说明瞄准光束是非常重要的。有待改进使切削中心位于瞳孔中心。１７眼中的１２眼在ＰＲＫ术后３～７个月内角膜地形图非常稳定，其余的５眼在６～１２个月的随访时，发现中央屈光     

准分子激光屈光性角膜切削术后角膜地形图的变化

目的探讨准分子激光屈光性角膜切削术（ＰＲＫ）后角膜表面形态和屈光力变化。方法ＴｏｍｅｙＴＭＳ２ＴＭ角膜地形图检查１２４只近视眼ＰＲＫ术前、术后１、６月和１年统计值的变化。结果ＰＲＫ术后眼绝对等级角膜地形图见梯度明显的蓝色低屈光带。ＳＲＩ和ＳＡＩ术后１月时比术前和术后６月、１年时高，ＩＡＩ术前后无变化。近视眼治疗等值球镜屈光度分别与ＳＲＩ、ＳＡＩ和ＩＡＩ的相关系数为０．７６６、０．４６１和－０．１０５。结论ＰＲＫ术后角膜屈光力稳定性较好，对角膜表面规则性和对称性早期有影响，逐渐恢复正常。ＰＲＫ角膜切削区带越多，对角膜表面形态影响越大。     

准分子激光角膜切削中心的角膜地形图分析

目的探讨准分子激光角膜切削术（ｐｈｏｔｏｒｅｆｒａｃｔｉｖｅｋｅｒａｔｅｃｔｏｍｙ，ＰＲＫ）的切削中心对视功能的影响。方法采用Ｅｙｅｓｙｓ角膜形态分析系统对随访６个月以上的９８例（１５８只眼）ＰＲＫ前、后１０天的角膜地形图进行分析，确定激光切削中心相对入射瞳孔中心的方向、距离；比较单区和多区域激光切削的偏中心差异。结果切削区中心相对入射瞳孔中心：０～０．５ｍｍ者１００只眼（６３．３％），０．５～１．０ｍｍ者５５只眼（３４．８％），＞１．０ｍｍ者３只眼（１．９％），平均０．４５ｍｍ。多区域切削３８只眼及单区域切削１２０只眼，其偏心量分别为０．５５ｍｍ和０．４４ｍｍ。差异有显著性（ｔ检验，Ｐ＜０．０５）。偏中心切削致术后最好矫正视力下降１～２行者４只眼，其偏心量＞０．５ｍｍ。结论严重的偏心切削将影响术后视功能恢复，术中眼球跟踪系统（ｐａｓｓｉｖｅｅｙｅ－ｔｒａｃｋｉｎｇ，ＰＥＴ）的应用有利于切削中心的确定，减少偏心量。     

准分子激光角膜切削术后屈光回退伴角膜雾浊再次手术疗效

近视眼准分子激光角膜切削术（ｐｈｏｔｏｒｅ－ｆｒａｃｔｌｖｅｋｅｒａｔｅｃｔｏｍｙ，ＰＲＫ）后，部分病例存在远期屈光回退、角膜雾浊（Ｈａｚｅ）影响疗效。我院ＰＲＫ中心于１９９６年８月～１９９７年２月对６例８眼ＰＲＫ术后屈光回退伴角膜Ｈａｚｅ病例行再次ＰＲＫ治疗，效果满意，总结报道如下。１材料与方法１．１临床资料８眼病例为我院ＰＲＫ中心治疗后随访１１．２±１．４ｍｏ出现屈光回退伴角膜Ｈａｚｅ的近视眼患者，男６眼，女２眼，年龄２４．０±４．０６ａ（１９～４０ａ）。首次ＰＲＫ术前平均等值球镜屈光度为一…     

准分子激光角膜切削术前后角膜地形图对比分析

应用角膜地形图仪对比分析了９０例（１７６眼）ＰＲＫ手术前后角膜表面的形态特征及其变化。结果表明,术前角膜地形图以蝴蝶结形为多（７３．３％）;术后７９．０％为圆形或钥匙孔形,半圆形和蝶形为１８．８％中央岛形占２．２％。ＰＲＫ对散光的一次最大矫正量为－１．７５Ｄ,切削中心偏位是最佳矫正视力下降,复视和屈光度回退的重要原因。提示：ＰＲＫ术后角膜地形图的检查可准确显示角膜形态的细微变化,有利于手术设计的不断完善和效果的提高。     

PRK切削中心偏离的临床观察

为研究准分子激光屈光性角膜切削术（ＰｈｏｔｏｒｅｆｒａｃｔｉｖｅＫｅｒａｔｅｃｔｏｍｙ，ＰＲＫ）切削中心偏离对角膜散光与欠矫的影响。对ＰＲＫ术后２１０眼行角膜地形图检查后发现，ＰＲＫ切削偏心小于０５０ｍｍ者为３７２％，０５０～１００ｍｍ者为５３３％，１０ｍｍ以上者为９５％，切削偏心平均为０７６ｍｍ，欠矫平均为１４１Ｄ，散光无明显改变。切削偏心能直接导致欠矫的发生，但对角膜散光无明显影响，减小偏心可以避免欠矫的发生。     

准分子激光原位角膜磨镶术后角膜地形图分析

为分析准分子激光原位角膜磨镶术后角膜地形图的动态变化,随访ＬＡＳＩＫ后１月病人共１３７例（１９６眼）,术后３月４８例（７０眼）。采用随机扫描式消融角膜基质。术后用０．３％氟嗪酸,０．１％ＦＭＬ滴眼１０天。记录术前、术后１个月、３个月的视力,屈光度数,角膜地形图。结果：术后１月角膜表面规则系数、角膜表面非对称系数明显大于术前,术后３月无明显改善。术后１月切削形态中平滑型占８９．８％,其他形态占１０．２％。切削形态随时间延长逐步变规则。术后切削中心平均偏心０．６７±０．４８ｍｍ（０～２．２４ｍｍ）,偏心距离在１ｍｍ以内对最佳矫正视力影响不大,偏心方向以鼻侧居多。结论：ＬＡＳＩＫ手术由于保持了角膜上皮层及前弹力层,术后角膜及切削形态较规则,但仍然存在偏心切削的问题。角膜地形图为临床评估ＬＡＳＩＫ效果提供了客观依据。     

准分子激光屈光性角膜切削术后角膜地形图岛状隆起

目的 探讨准分子激不屈光性角膜切削术（ＰＲＫ）后角膜地形图出现岛状隆起与患者各种因素的关系。方法 对连续３３３例（５９２只眼）接受ＰＲＫ治疗病人术后６个月的角膜地形图进行回顾性分析,将地形图中出现中央岛状隆起与半岛,双峰岛的资料进行比较。结果 双眼再现岛状隆起的比例高于单眼。术后１～３月岛状隆起明显且有不断增加的现象,６月时５２．６３％的岛状隆起消失。岛状隆起与角膜雾浊无关;双峰岛的隆起度较高,可     

准分子激光屈光性角膜切削术与激光原位角膜磨镶术治疗中低度近视的对比

目的对准分子激光屈光性角膜切削术（ｐｈｏｔｏｒｅｆｒａｃｔｉｖｅｋｅｒａｔｅｃｔｏｍｙ，ＰＲＫ）和准分子激光原位角膜磨镶术（ｌａｓｅｒａｓｓｉｓｔｅｄｉｎｓｉｔｕｋｅｒａｔｏｍｉｌｌｅｕｓｉｓ，ＬＡＳＩＫ）治疗中、低度近视的疗效进行前瞻性对比研究。材料和方法术前屈光度为－１．２５～－６．００Ｄ的近视５６９只眼，其中１３７只眼接受ＬＡＳＩＫ手术，４３２只眼接受ＰＲＫ手术，随访６－１６个月（平均８．９±２．６个月）。在术后１周、１个月、３个月、６个月和１２个月复查。结果ＬＡＳＩＫ组术后屈光状态较ＰＲＫ稳定，回退幅度较ＰＲＫ小，术后６个月时，ＬＡＳＩＫ组和ＰＲＫ组分别有９４％和８７％屈光度在±１．００Ｄ内（ｐ＜０．０５），分别有８４％和７１％屈光度在±０．５０Ｄ以内（ｐ＜０．０１）。ＬＡＳＩＫ组术后视力恢复较ＰＲＫ快，术后１周的平均裸眼视力超过１．０，术后６个月时，ＬＡＳＩＫ和ＰＲＫ组中裸眼视力０．５或以上者分别占１００％和９４％（ｐ＜０．０１），裸眼视力１．０以上者分别占８６％和７２％（ｐ＜０．０１）。结论ＬＡＳＩＫ不仅适合治疗高度近视，也适合治疗中、低度近视。对于中、低度近视，ＬＡＳＩＫ的疗效优于ＰＲＫ。     

Late natural history of corneal topography after excimer laser photorefractive keratectomy

PURPOSE: To investigate the 3 month to 1 year natural history of corneal topography after excimer laser photorefractive keratectomy (PRK). DESIGN: A prospective, multicenter, nonrandomized comparative study. PARTICIPANTS: A total of 75 eyes of 68 patients with myopia were studied. INTERVENTION: Excimer laser photorefractive keratectomy and computer-assisted videokeratography were performed. MAIN OUTCOME MEASURES: Preoperative and 3, 6, and 12 month postoperative topography patterns were compared and changes assessed by averaging defined sectors of the ablation zone in individual maps to produce composite "average" topography maps. RESULTS: Corneal topography was relatively smooth 3 months after PRK. By 12 months, the corneal contour in general had become even more uniform. No "central island" effect was observed. When looking at right and left eyes independently, there was a tendency toward maximum flattening nasally. CONCLUSIONS: Corneal topography in general continues to smooth from 3 to 12 months after PRK, possibly as a result of epithelial and stromal healing and remodeling. Right and left eyes on average show mirror-image, spatially oriented topography patterns.     

准分子激光屈光性角膜切削术的角膜地形图分析

目的 分析准分子激光屈光性角膜切主后角膜地形图的变化和动态。方法 对接受准分子激光屈光性角膜切削术后随诊３个月的６２例（１２２只眼）和随诊６个月的４９例（９６只眼）的角膜地形图变化和动态进行分析。结果 中央岛型切削是导致术事早期最佳戴镜矫正视力下降１行以上的重要因素，随着时间推移，中央岛型切削逐渐演变其它类型，角膜中央曲率减爱，视力逐步提高。角膜地形图分析，拟似回退指数（ＳｉｍＫ）是反映角膜基质变     

PRK切削中心偏离的临床研究

目的评价准分子激光屈光性角膜切削术（PRK）切削中心偏离瞳孔中心的发生率及其对角膜散光、屈光欠矫的影响。方法采用EyeSys角膜地形图仪对210眼PRK术前及术后3个月行角膜地形图分析。结果术后三个月，PRK切削偏心小于0．50mm者为37．20％，0．50～1．00mm者为53．30％，1．00mm以上者为9．50％，切削们心平均为0．76mm，屈光欠矫平均为1．41D，激光无明显改变（P＞0．05）。结论切削中心的偏离是PRK的一项重要的并发症，它可以直接导致屈光欠矫的发生，但对激光无明显影响，减小偏心可以避免欠矫的发生。     

Comparison of two procedures: photorefractive keratectomy versus laser in situ keratomileusis for low to moderate myopia

PURPOSE: A prospective study was conducted to compare the effectiveness, safety, and stability of photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) for correction of low to moderate myopia. METHODS: Forty-five patients with a manifest refraction (PRK, -4.54 +/- 0.80; LASIK, -4.82 +/- 1.10) from -1.50 to -6.00 diopters (D) were treated and followed-up for 6 months. In each case, 1 eye received PRK and the other LASIK. The first eye treated, and the surgical method used in the first eye, were randomized. Uncorrected and corrected visual acuity, manifest refraction, corneal haze, and topographic analysis of ablation decentration were examined. RESULTS: The uncorrected visual acuity was 20/20 or better in 35 PRK eyes (77.8%) and 28 LASIK eyes (62.2%) at 6 months (P =.107). At 6 months, 28 eyes (62.2%) that received PRK showed a spherical equivalent of within +/-0.5 D as compared with 24 eyes (53.4%) that received LASIK (P =.393). The amount of ablation decentration was 0.37 +/- 0.25 mm in PRK eyes and 0.49 +/- 0.38 mm in LASIK eyes at 3 months (P =.36). CONCLUSIONS: In our study, PRK and LASIK were found to be similarly effective and predictive of correction in low to moderate myopia. PRK has the advantage of less ablation decentration and is safer than LASIK, so we recommend PRK for eyes with low to moderate myopia.     

Ablation centration after active eye-tracker-assisted photorefractive keratectomy and laser in situ keratomileusis

PURPOSE: To evaluate the ablation centration after active eye-tracker-assisted photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) and to investigate the effect of surgery, patient, and surgeon on the centration. SETTING: Department of Ophthalmology, China Medical College Hospital, Taichung, Taiwan, Republic of China. METHODS: This retrospective study comprised 177 eyes of 101 patients: 16 eyes had PRK and 161, LASIK. All laser treatments were performed with the aid of an eye tracker. The amount of decentration was analyzed by corneal topography. The factors influencing centration were divided into surgery related (PRK/LASIK), patient related (low/high myopia and effect of learning), and surgeon related (learning curve). RESULTS: The mean decentration was 0.33 mm in PRK eyes and 0.35 mm in LASIK eyes. For the surgery-related factor, there was no significant difference between the PRK and LASIK eyes. For the patient-related factors, centration was better in the second eye (effect of learning) and decentration was more severe in eyes with high myopia (low/high myopia). For the surgeon-related factor, there was no significant difference between eyes that had the first 50 LASIK procedures and those that had the last 50 procedures. CONCLUSIONS: An eye tracker, which makes the laser beam follow the eye's movements, helps to avoid severe decentration. This study showed, however, that an active eye-tracking system alone cannot ensure good centration. Patient cooperation and fixation are important.     

Changes in corneal topography after excimer laser photorefractive keratectomy for myopia

Computer-assisted analysis of corneal topography was performed in 17 normally sighted human eyes during the first year after excimer laser photorefractive keratectomy (PRK) for myopia. Laser ablation of the central cornea produced an optical zone with a smooth power transition to the peripheral cornea. Decentration of the ablation was noted in some eyes (less than 0.5 mm in 3 eyes, 0.5 to 1.0 mm in 10 eyes, 1 to 1.5 mm in 3 eyes, and 2.1 mm in 1 eye), suggesting that careful alignment of the laser beam is critical. Improved methods to align the ablation within the center of the entrance pupil are needed. In 12 of 17 eyes, the topographic pattern appeared to stabilize between 3 and 7 months after PRK. In the remaining five eyes, central ablation power changed by more than 0.5 diopters (D) between the 6- and 12-month examinations. Regression was more common and more pronounced in eyes with intended corrections more than 5 D, whereas the majority of eyes with intended corrections of 5 D or less showed good correspondence between the final change in central ablation power and the attempted correction. Two eyes had a loss of at least two lines of best spectacle-corrected visual acuity that was attributable to irregular astigmatism, decentration of the ablation, and/or corneal opacification.     

Natural history of corneal topography after excimer laser photorefractive keratectomy

Purpose

To investigate the natural history of corneal topography after excimer laser photorefractive keratectomy (PRK).

Design

A prospective, single center clinical study.

Participants

A total of 40 eyes of 34 patients with myopia were studied.

Intervention

Excimer laser photorefractive keratectomy and computer-assisted videokeratography were performed.

Main outcome measures

Preoperative, 1 week, and 1,2, and 3 months postoperative topography patterns were compared and changes assessed by averaging defined sectors of the ablation zone in individual maps to produce composite “average” topography maps.

Results

Corneal topography was generally not homogeneous at 1 week after PRK. By 3 months, there had been considerable smoothing of corneal contour. A general “central island” effect early in the postoperative period flattened over time. When right and left eyes were evaluated independently, a tendency toward a keyhole-semicircular pattern was seen on average; the maximum flattening was nasal and the least flattening was inferotemporal for both right and left eyes.

Conclusions

A tendency, on average, toward central island and keyhole-semicircular patterns is seen early in the postoperative course after PRK. Central islands tend to evolve into the keyhole-semicircular pattern, and the corneal topography in general after PRK tends to smooth considerably with time.     

Corneal epithelial healing after photorefractive keratectomy: analytical study

PURPOSE: To characterize the velocity of epithelial migration after photorefractive keratectomy (PRK) with 3 different corneal ablation patterns. SETTING: Department of Ophthalmology, Catholic University of Rome, Rome, Italy. METHODS: Fifteen patients (30 eyes) with mild to moderate myopia and with simple to compound myopic astigmatism were enrolled for this study. The surgical procedure consisted of standardized PRK with final smoothing performed using the Technolas Keracor 217C excimer laser. The reepithelialization process was evaluated at 0 hours, 20 hours, 40 hours, and 60 hours after surgery using a digital photo camera and custom software for measurement. Digital analysis of the images was performed. Corneal topographies were taken at 1 month, 3 months, 6 months, and 12 months after PRK. RESULTS: The mean speed of radial migration in the 10 eyes (33%) in the low spherical ablation group was 0.087 mm/h +/- 0.008 (SD). This was significantly higher than that found in the 10 eyes (33%) in the high spherical ablation group (mean speed 0.078 +/- 0.007 mm/h; P<.001) and in the 10 eyes (33%) in the cross-cylinder ablation group (mean speed 0.055 +/- 0.014 mm/h; P<.001). CONCLUSION: Analysis of the data shows that epithelial migration along the photoablated corneal surface depends on the ablation pattern. The epithelial sliding is highly influenced by local variations in the curvature of the stromal surface. The data demonstrate that faster epithelial wound healing after PRK is predictive of optimal visual performance.