角膜瓣的优化与准分子激光角膜屈光手术

随着准分子激光角膜屈光手术的演变和进化,屈光不正的矫治质量得到了不断提高.角膜瓣的改进和优化是实现这些进步的真正原因.通过这些不同角膜瓣的特点及其所产生的不足,为如何提高角膜屈光手术的安全性与有效性,同时也为如何进一步发展手术提供了思路.     

准分子激光角膜屈光手术的发展趋势

随着飞秒激光定制薄角膜瓣技术、改良表层切削技术、波阵面像差与角膜地形图引导技术、眼球定位及联机跟踪技术,以及老视补偿技术的不断改进和广泛应用,未来5～10年,准分子激光角膜屈光手术仍将是屈光手术的主流.术前筛选出亚临床圆锥角膜,是预防屈光手术后角膜扩张及继发性圆锥角膜的关键.为保持角膜生物力学的完整性和更好的视觉质量,可选择有晶状体眼人工晶状体植入术矫治超高度近视.     

角膜瓣的种类对准分子激光屈光矫正手术的影响

角膜瓣的制作是影响准分子激光屈光手术疗效较关键的一步,角膜瓣包括基质瓣和上皮瓣,普通基质瓣术后视力恢复快,但存在瓣厚薄不匀、厚度预测性差、制瓣后可诱导像差增大.飞秒激光基质瓣厚薄均匀,对像差影响小,术后视觉质量优于普通基质瓣,但设备昂贵,制瓣时间长.乙醇浸泡制作的上皮瓣操作安全,术后视觉质量优于普通基质瓣LASIK术,微型角膜刀法的上皮瓣无乙醇对角膜上皮的毒副作用,较乙醇浸泡法LASEK术刺激症状和角膜上皮下雾状混浊轻.角膜基质瓣的蒂位于上方时,术后角膜知觉下降较蒂位于鼻侧时明显且恢复慢,干眼症状更重.在手术安全性和术后视觉质量方面,制作上皮瓣优于基质瓣,上皮瓣存在的刺激症状较明显与角膜上皮下雾状混浊是进一步需要研究解决的问题.     

准分子激光角膜屈光术后角膜瓣移位皱褶的处理

目的探讨准分子激光角膜屈光手术后角膜瓣移位皱褶形成原因﹑手术方法及预防措施。方法回顾性分析我院2009年8月至2011年8月激光角膜屈光手术后29例(29只眼)角膜瓣移位皱褶患者资料。结果术后角膜瓣移位皱褶形成早期原因与术者操作经验、角膜瓣厚薄及蒂的位置、屈光度数、挤眼等,晚期多为外伤所致。29例患者经角膜瓣复位术后效果良好,视力无下降。结论有效预防措施可以减少角膜瓣移位皱褶的发生,及时正确的治疗可以避免严重的并发症并获得良好的视觉效果。     

准分子激光角膜屈光手术的利与弊

大量临床研究已证明了准分子激光角膜屈光手术的安全性、有效性和可预测性,使屈光不正患者获得良好的裸眼视力和生活质量,整体满意度达95%以上。但部分患者术后仍出现难治性干眼、暗视力差、虚影等不适,且手术后角膜变薄所带来的潜在危险仍需进一步深入探讨。因此,对准分子激光角膜屈光手术要理性看待、慎重实施、个性化设计,客观地认识其利与弊。目前主要关注的焦点包括:(1)个性化设计与适宜人群选择对视觉质量的影响;(2)并发症的控制与严重并发症的管理;(3)角膜生物力学改变与术后远期安全性的问题。     

Epi-LASIK-准分子激光角膜屈光手术发展的新方向

自80年代初Trokel等首先介绍准分子激光角膜切削术（photorefractive keratectomy，PRK）矫治近视以来，准分子激光角膜屈光手术在不长的时间内得到变革与突破，目前准分子激光原位角膜磨镶术（laser in—situ keratomileusis，LASIK）占据主流地位，但其它术式如准分子激光上皮瓣下角膜磨镶术（laser subepithelial keratomileusis，LASEK）、角膜微型刀上皮瓣下准分子激光原位角膜磨镶术（epipolis laser in—situ keratomileusis，Epi-LASIK）、全激光准分子激光原位角膜磨镶术（femotscend laser asisted laser in-situ keratomileusis，Intra-LASIK）等也得到快速发展，这意味着准分子激光屈光手术在不断的丰富、完善，同时也为医师和患者提供更多的选择。诸多的准分子激光角膜屈光手术中，可将之划分为两大类：即深部角膜屈光手术和表面角膜屈光手术，行准分子激光前制作了一个带有部分角膜基质的角膜瓣的手术属于前者；而不制瓣或仅制作上皮瓣的一类手术属于后者。     

预防为主提高准分子激光角膜屈光手术的安全性

准分子激光角膜屈光手术的首要问题是安全,贯穿着准分子激光矫正屈光不正手术流程的每一个环节。本文主要从预防的角度总结准分子激光角膜屈光手术的术前、术中与术后注意事项及经验和方法,从细节做起,提高准分子激光角膜屈光手术的安全性。     

准分子激光角膜屈光手术中的个体化切削

准分子激光角膜屈光性手术，随着激光设备的改进及控制系统的逐步完善，已经得到很大的发展，个体化切削，是根据个体的特性及需要去建立，适应或改变准分子激光屈光手术方式的一仪系列方法，许多新的和发展的技术，通过增加视网膜成像的对比度，达到更高的清晰度，以克服以往手术的某些弊端，更大程度地提高视力，减少并发症，屈光手术的未来十年将会有更加美好的前景。     

亲水性软性角膜接触镜在准分子激光屈光性角膜手术中的应用

目的:了解亲水性软性角膜接触镜作为物理屏障在准分子激光屈光性角膜手术的作用。方法:对临床观察23例(40眼)准分子激光屈光性角膜切削术后配戴角膜接触镜者进行观察,包括各种临床症状;角膜上皮愈合及角膜瓣对位等,平均配戴1～15d,术后随诊1～3mo。结果:术后配戴角膜接触镜,患者角膜上皮愈合不适症状减轻,角膜瓣无1例发生移位,对位好。结论:准分子激光屈光性角膜手术中及术后早期配戴角膜接触镜具有促进角膜上皮愈合,稳定角膜瓣的作用。     

准分子激光屈光性角膜切削术对角膜内皮细胞的影响

目的 探讨分析准分子激光屈光性角膜切削术（ＰＲＫ）治疗近视后对角膜内皮细胞的影响。方法 对１０１只眼ＰＲＫ术后者,用接触型镜面反光角人皮显微镜（Ｋｏｎａｎ ＳＰ－３５００型,日本）检测不同部位角膜内皮细胞,并统计分析其在不同度数范围内的平均细胞密度、细胞面积的变异系数和六角形细胞的百分率。结果 平均细胞密度在Ｃ组上降１０％,Ａ,Ｂ组的下降无统计学意义。细胞面积的变异系数及六角形细胞百分率均下降１０     

Bilateral corneal infiltrates after excimer laser photorefractive keratectomy

A 26-year-old man developed painless inferior subepithelial infiltrates away from the site of ablation in both eyes after excimer laser photorefractive keratectomy (PRK) for myopia. Clinical characteristics of the corneal infiltrates resembled staphylococcal-immune infiltrates. The condition responded to treatment with topical diluted steroids and antibiotics. There was no residual corneal scarring. The infiltrates did not affect the refractive outcome of the surgery. Recognition of this rare entity will help clinicians avoid aggressive investigative and treatment modalities that can affect the results of PRK.     

准分子激光角膜切削术后角膜地形图的分析

目的：准分子激光角膜切削术（ＰＲＫ）后角膜性状和视力质量和研究。方法：对２３例（３８只眼）近视患者于术后１、３、６个月进行角膜地形图随访。结果：ＰＲＫ术后角膜表面的球面性状发生一定改变。随着时间推移，角膜表面规则指数（ＳＲＩ）和表面不规则指数（ＳＡＩ）均逐渐降低，角膜变得中平滑。模拟角计数数表现一定的回退。术后６个月时，角膜地形图主要表现为四种形态；圆形或椭圆形、哑铃形、半环形、中央小岛形、有珞种     

准分子手术不同制瓣方法瓣厚度的临床观察

目的:通过测量术眼角膜瓣厚度,观察准分子手术制瓣方式的安全性及可预测性。为临床工作提供帮助。方法:将手术眼按照制瓣方式分为四组:飞秒制瓣组(A组)、Moria-Ⅱ90刀制瓣组(B组)、Moria-Ⅱ110刀制瓣组(C组)、EK制瓣组(D组)。用A超测量角膜及基质床厚度,计算得出实际瓣厚度。所得数据进行统计学分析。结果:制瓣平均厚度A组90.95±10.82μm,B组133.61±11.97μm,C组147.70±16.16μm,D组66.35±11.95μm,各组瓣厚统计学差异明显。制瓣厚度影响因素中,A组与等效球镜低度相关。B组与等效球镜中度相关,与术中档位、术前眼压、平均曲率低度相关。D组与制瓣方法中度相关,与等效球镜低度相关。A组锥镜两次使用;B,C组旋转刀两次使用;D组左右眼制瓣厚度无显著差异。结论:几组制瓣均很稳定,但在制瓣厚度上有明显差异。屈光度数可能是影响制瓣厚度的因素之一。飞秒激光制瓣比常规板层角膜刀在预测性和灵活性方面更有优势。EK手术因其制瓣最薄而手术最安全     

Correlation between refractive and measured corneal power changes after myopic excimer laser photorefractive surgery

Purpose: To determine the correlation between the refractive and measured corneal power changes after myopic photorefractive surgery.Setting: Department of Ophthalmology, National Taiwan University Hospital, Taipei, Taiwan.Methods: Eighty-six eyes that had myopic photorefractive surgery were analyzed. The data included preoperative and 1-year postoperative subjective refraction, standard automated keratometry, and computerized videokeratography. Statistical analysis was performed to determine the relationship between the changes in subjective refraction in the corneal plane (Delta SEQco) and in 4 corneal power measurements including the power measured by automated keratometry (Delta Auto K), topographic-simulated keratometric power (Delta Sim K), the power of the first photokeratoscopic ring on videokeratography (Delta Central K), and the average videokeratographic power on the pupil margin (Delta Pupil K).Results: The measured corneal power always underestimated the Delta SEQco, with Delta SEQco > Delta Central K > Delta Sim K > Delta Pupil K > Delta Auto K. All the changes in measured corneal power could predict the Delta SEQco with more than 90.00% (90.19% to 92.31%) reliability at 1 year as calculated by the regression formulas (P <.001). The underestimation of measured corneal power changes was correlated with the amount of myopic correction, especially the Auto K (all P <.001).Conclusions: Direct corneal power measurements using automatic keratometry underestimated the actual corneal flattening after photorefractive surgery, which could be adjusted by a linear regression formula. Measuring the power of the first photokeratoscopic ring on videokeratography might provide a better estimation of actual corneal flattening after photorefractive surgery.     

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.     

PRK术后角膜上皮下雾状混浊的相关因素分析

为探讨准分子激光角膜切削术（ｐｈｏｔｏｒｅｆｒａｃｔｉｖｅｋｅｒａｔｅｃｔｏｍｙ，ＰＲＫ）后角膜上皮下雾状混浊（ｈａｚｅ）的原因及影响因素，对ＰＲＫ后６个月时屈光度在－１．００～－１８．５０Ｄ的３１６例（６１５只眼）近视眼的ｈａｚｅ相关因素进行观察和比较。结果：ＰＲＫ后６个月时ｈａｚｅ发生率为４４．７％，１级或以上ｈａｚｅ为１３．３％。ｈａｚｅ的发生率及密度随屈光度增高而增加（Ｐ＜０．０００１），也随切削深度的增加而增加（Ｐ＜０．０００１），术前非接触眼压超过１８ｍｍＨｇ者，ｈａｚｅ的发生率和密度增加（Ｐ＜０．００５），男性较易发生ｈａｚｅ（Ｐ＝０．０００１），与年龄呈负相关（Ｐ＜０．０５）。而角膜厚度、术前戴用接触镜及散光对ｈａｚｅ的影响不显著。结论：高度近视（＞－６．０Ｄ）和过深的切削（＞８０μｍ）是引起ｈａｚｅ的主要原因。术前眼压偏高、年龄偏低对ｈａｚｅ也有明显影响。对ＰＲＫ治疗高度近视应持审     

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.     

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.