角膜屈光手术后的人工晶状体度数计算

角膜屈光手术后用现行的角膜曲率检测方法测量角膜屈光力不精确,导致该类患者白内障手术时人工晶状体度数计算偏低,术后呈较严重的远视状态。随着接受准分子激光角膜屈光手术人数的增加,此问题在未来将日益突出。围绕这一问题,不少学者提出多种修正方案,以期提高角膜屈光手术后人工晶状体度数计算的准确性,本文就此进行综述。     

准分子激光屈光性角膜手术后白内障人工晶状体植入术

目的探讨准分子激光屈光性角膜手术后白内障吸出术中、植入人工晶状体的屈光度计算方法。方法对4例（4眼）准分子激光屈光性角膜手术后的白内障行超声乳化吸出及人工晶状体植入术，术前采用OrbscanⅡ角膜地形图及角膜曲率计测量角膜的K值，分别应用第二代经验公式（SRKⅡ）计算所需人工晶状体的屈光度。术后验光记录术眼屈光状况，与术前结果对比，评价所选择的人工晶状体屈光度的准确性。结果OrbscanⅡ角膜地形图和角膜曲率计分别测量的角膜K值，以及所计算的人工晶状体的屈光度，均有明显的差别。尽管按预留近视状态，选用角膜地形图测量的K值计算人工晶状体的屈光度，术后仍然欠矫，平均产生远视＋1．57D，较术前预留度数仍相差约＋3．44D。结论采用OrbscanⅡ角膜地形图的K值来计算人工晶状体屈光度误差小，在预留的屈光度数基础上加3．50D来选择人工晶状体是较为精确和安全的。     

屈光性角膜手术后人工晶状体度数的计算

屈光性角膜手术后患者行白内障摘除及人工晶状体植入术时 ,用常规方法计算人工晶状体度数往往产生术后远视的误差。对于放射状角膜切开术 (RK)后的患者主要原因是术后角膜中央光学区变平 ,而且仪器测得的角膜曲率值偏高 ,导致计算出的人工晶状体度数偏低 ,从而出现术后远视。对于准分子激光角膜切削术 (PRK)及准分子激光原位角膜磨镶术 (LASIK)患者 ,因去除了中央区的部分角膜组织 ,使角膜前后表面曲率的比值发生改变 ,而目前的各种人工晶状体计算公式均假设角膜前后表面曲率比值恒定 ,故产生了系统误差。因此 ,对于曾行屈光性角膜手术的白内障患者 ,术前应准确测定中央角膜曲率 ,运用适当理论公式推算出实际的角膜曲率值 ,并选择合适的人工晶状体度数计算公式 ,从而减少人工晶状体植入术后的屈光误差     

准分子激光角膜原位磨镶术后应用IOL Master进行白内障术前人工晶状体度数计算相关测量的可靠性

IOL Master(德国Zeiss公司)是一种将眼轴长度(axial length,AL)、角膜曲率、角膜直径、前房深度(anterior chamber depth,ACD)测量集于一体的相干光生物测量仪,并提供多种人工晶状体度数计算公式,可直接计算人工晶状体度数[1-3].IOL Master的测量结果可能会受到屈光性角膜手术的影响,从而影响计算出的人工晶状体度数,本研究应用IOL Master对患者准分子激光原位角膜磨镶术(laser in situ keratomileusis,LASIK)前后各项指标进行测量并比较分析,探讨LASIK后IOL Master测量结果的可靠性.     

屈光性角膜手术后人工晶体状体度数的计算

屈光性角膜手术性后患行白内障除及人工晶状体植入术时，用常规方法计算人工晶体状体度数往往产生术后远视的误差，对于放射状角膜切开术（PK）后的患主要原因是术后角膜中央光学区变平，而且仪器测得的角膜曲率偏高，导致计算出的人工晶状本度数偏低，从而出现术后远视。对于准分子激光角膜切削术（PRK）及准分子原位角膜磨镶术（LASIK）患，因去除了中央区的部分角膜组织，使角膜前后表面曲率的比值发生改变，而目前的各种人工晶状体计算公式均假设角膜前后表面曲率比值恒定，故产生了系统误差。因此，对于曾行屈光性角膜手术的白内障患，术前应准确测定中央角膜曲率，运用适当理论公式推算出实际的角膜曲率值，并选择合适的人工晶状体度数计算公式，从而减少人工晶状体植入术后的屈光误差。     

角膜屈光手术后人工晶状体度数的计算及其影响因素

已行角膜屈光手术的白内障患者,如按常规方法计算人工晶状体度数,会产生较大偏差。本文就角膜屈光术后对角膜曲率测量、术后前房深度预测、眼球长度测量、人工晶状体计算公式选择等影响人工晶状体度数计算的多种因素及其改进方法进行综述,建议根据患者的资料、仪器设备情况的不同而选择不同的计算公式。     

近视准分子激光屈光性角膜切削术后白内障手术人工晶状体度数计算的临床和理论结果

目的：阐述近视准分子激光屈光性角膜切削术(PRK)后白内障的屈光结果，并寻求一种更加精确的方法预测这些病例中人工晶状体(IOL)的度数。     

角膜屈光手术后的人工晶状体度数计算方法及其比较

准分子激光角膜屈光手术后人工晶状体度数的计算一直是难题,其主要原因是人工晶状体计算所采用的角膜屈光度并不是有效的角膜屈光度,以及使用了不适当的计算公式.目前临床上已有多种方法如临床资料法、Double-K值法、角膜忽略法、回归公式法等,帮助手术医生减少人工晶状体度数计算误差.本文就人工晶状体度数选择错误的原因及解决方法做一综述讨论,并以病例说明,旨在为手术医生选择合适方法进行精确的人工晶状体度数计算提供参考.     

激光角膜屈光术后人工晶状体度数计算方法的进展

近年来, 既往激光角膜屈光手术史的白内障患者逐年增加。由于激光角膜屈光手术改变了角膜形态, 使得传统的人工晶状体(intraocular lens, IOL)计算公式出现较大的术后屈光误差。误差来源包括角膜前表面曲率半径测量、角膜屈光力计算、眼轴长度测量、有效人工晶状体位置计算等。不需要屈光手术术前数据的IOL度数计算公式, 如Hoffer Q公式、Barrett True-K公式、Shammas-PL公式可应用于激光角膜屈光术后患者的IOL计算。基于光线追踪原理或人工智能的新一代IOL公式, 如Olsen公式、EVO公式、Hill-RBF公式、Kane公式等在常规白内障手术患者IOL度数计算中的准确性和预测性已被证实, 但在激光角膜屈光术后患者中的应用价值仍需进一步研究证实。(国际眼科纵览, 2022, 46:460-464)     

准分子激光屈光性角膜手术后人工晶状体度数的计算

准分子激光屈光性角膜手术后,患者发生白内障需行白内障摘除及人工晶状体植入术时,按常规方法计算人工晶状体屈光度往往会在术后产生远视,而这样的误差主要来源于角膜屈光力的测算误差和计算公式的误差,另外还有眼轴长度测量和有效人工晶状体位置计算的准确性降低这两个方面的原因.因此,对于曾行角膜屈光手术的白内障患者,术前运用适当的方法准确估算角膜屈光力,并选择合适的人工晶状体计算公式,可以减少屈光误差.     

LASIK/PRK术后人工晶状体度数计算的研究进展

随着屈光不正患者数量的增加及角膜屈光手术的盛行,越来越多早期选择角膜屈光手术(LASIK/PRK)矫正高度近视的患者如今面临着白内障手术,然而,用常规方法计算这部分患者的人工晶状体度数往往是不精确的。目前的第三代和第四代公式过高地估计了角膜屈光力,导致人工晶状体度数矫正不足,从而出现术后的远视漂移。而传统的角膜地形图采用2.5～3.2mm范围环上的角膜计算角膜屈光力,忽略了角膜中央的真实曲率,导致角膜屈光术后尤其是偏中心切削患者术后出现严重的屈光误差。本文旨在总结LASIK/PRK术后患者人工晶状体度数计算最新的误差来源以及最新计算方法,为提高屈光术后患者人工晶状体度数计算的准确性提供更多的选择。     

Measuring corneal power for intraocular lens power calculation after refractive surgery. Comparison of methods

PURPOSE: To find a more accurate and predictable method for intraocular lens (IOL) power calculation in eyes after refractive surgery. SETTING: Department of Ophthalmology, Kangnam St. Mary's Hospital, Seoul, Korea. METHODS: The accuracy of the following methods for calculating IOL power in 132 eyes after PRK or LASIK was compared: manual keratometry, hard contact lens, refraction-derived keratometry at the corneal plane, and the refraction-derived keratometry at the spectacle plane. Based on this comparison, the IOL power was calculated in the 2 eyes of a patient using refraction-derived keratometry at the spectacle plane with the SRK II formula. Cataract surgery with IOL implantation was then performed. RESULTS: The largest corneal power values were obtained using a manual keratometer and the smallest using refraction-derived keratometry at the spectacle plane (P <.001). In the patient having cataract surgery with IOL implantation, near target refraction was achieved with minimal error in IOL power. CONCLUSIONS: If the corneal power is known before refractive surgery, the use of the smallest value of those obtained using refraction-derived keratometry and the hard contact lens method is recommended. However, if the corneal power before refractive surgery is unknown, the use of the hard contact lens method is recommended.     

光路追迹法计算角膜屈光手术后人工晶状体的屈光力

目的建立光路追迹法计算人工晶状体屈光力的方法,探讨其对角膜屈光手术后人工晶状体屈光力计算的准确性。方法根据眼屈光间质的特点以专业光学设计软件Zemax建立人工晶状体眼模型。对25例角膜屈光手术后白内障患者进行回顾性研究,以OrbscanⅡz或C-Scan测量角膜地形图,获得角膜前表面曲率,以IOL-Master测量眼轴长度。将所得参数及人工晶状体的参数输入光学设计软件Zemax,建立人工晶状体眼的光学模型,计算白内障手术后眼的屈光状态。以手术实际屈光状态为标准,计算二者间的差异为预测误差及预测误差的绝对值为绝对预测误差。统计学分析预测误差与绝对预测误差的平均值、标准差及分布。结果光路追迹法的预测误差为-1.09～1.91 D,平均预测误差为（0.28±0.73）D;绝对预测误差为0.01～1.91 D,平均绝对预测误差为（0.63±0.45）D。绝对预测误差≤0.5 D者9例（36%）,0.5 D〈绝对预测误差≤1.0 D者12例（48%）,1.0 D〈绝对预测误差≤1.5 D者3例（12%）,1.5 D〈绝对预测误差≤2.0 D者1例（4%）,绝对预测误差≤1.0 D者21例（84%）。结论光路追迹法是以人工晶状体眼为光学模型计算人工晶状体的屈光力,可对计算角膜屈光手术后人工晶状体屈光力进行较为准确的计算。     

翼状胬肉手术后角膜曲率变化及对人工晶状体度数测算的影响

目的　探讨翼状胬肉手术后角膜曲率变化及对人工晶状体度数测算的影响。方法　收集2016年7月至2017年4月于广州医科大学附属第二医院行手术治疗的原发性鼻侧翼状胬肉患者,共32例42眼,设为胬肉组;对照组为胬肉组中单眼翼状胬肉患者的对侧眼,共22例22眼。术前测量胬肉组患者翼状胬肉长度、宽度和面积,同时计算对照组理论人工晶状体度数。在术前及术后1个月、3个月使用IOL Master测量胬肉组患者眼轴长度、前房深度、角膜曲率、理论人工晶状体度数等。结果　胬肉组术前角膜水平曲率为（43.32±1.69）D,术后1个月为（44.30±1.40）D,术后3个月为（44.32±1.43）D。术前角膜平均曲率（44.32±1.32）D,术后1个月为（44.78±1.40）D,术后3个月为（44.73±1.38）D,术后角膜水平曲率和角膜平均曲率均较术前升高（均为P<0.05）,但术后1个月与术后3个月差异均无统计学意义（均为P>0.05）。胬肉组患者术前术后眼轴长度、前房深度、角膜垂直曲率均无明显变化（均为P>0.05）。胬肉组患者术前理论人工晶状体度数为（21.46±1.57）D,术后1个月为（20.84±1.65）D,术后3个月为（20.86±1.64）D。术后理论人工晶状体度数较术前下降,差异均有统计学意义（均为 P<0.01）。根据ROC曲线计算得出,翼状胬肉长度2.15 mm、宽度4.20 mm、面积5.18 mm²为判断翼状胬肉及其手术对人工晶状体度数测算是否有较大影响的最佳诊断界值。结论　翼状胬肉术后角膜水平曲率和角膜平均曲率增加。角膜曲率的改变导致测算的人工晶状体度数下降。当翼状胬肉较大时会对人工晶状体度数测算产生有临床意义的影响。     

角膜屈光手术后人工晶状体度数的测算

角膜屈光手术后人工晶状体（IOL）度数的测算很复杂。按常规的测算方法,术后常会出现较大偏差。本文分析了角膜屈光手术后IOL度数测算的误差原因,并列出了多种解决策略,希望为该类患者IOL度数测算提供依据。（中华眼科杂志,2008,44：82-85）     

Topography-based intraocular lens power selection

PURPOSE: To provide mathematical tools for selecting intraocular lens (IOL) power for normal eyes and for "odd" eyes, particularly after corneal refractive surgery. SETTING: Universitats-Augenklinik, Mainz, Germany. METHODS: First, IOL power is selected based on the radii and numerical eccentricity of the cornea, extracted from corneal topography in a consistent numerical model of the cornea. To fine-tune the result, the visual impression is simulated by blurred Landolt rings superimposed on the retinal receptor grid. The calculation uses numerical ray tracing of the whole pseudophakic eye comprising all monochromatic errors. The error contributions of the influencing parameters, such as anterior and posterior corneal shape and corneal thickness, are quantified in detail. The method is verified in IOL power selection for normal eyes and for eyes after corneal refractive surgery. RESULTS: The main difference between normal corneas and corneas after refractive surgery results from different asphericities. Normal corneas are prolate, with typical numerical eccentricities of 0.5, whereas corneas after laser surgery for myopia are oblate. This causes the main difference (hyperopic shift up to 2.0 diopters) in IOL power selection. Shifts in the posterior corneal radius and corneal thickness are of minor importance. CONCLUSION: Intraocular power selection after corneal refractive surgery should be based on all the information corneal topography provides.     

Intraocular lens power calculation after keratorefractive surgery

The number of keratorefractive procedures designed to correct refractive errors has dramatically increased over the last few years. The techniques for cataract extraction and intraocular lens implantation have evolved into a refractive surgical procedure as well as an operation to improve best corrected visual acuity and/or spectacle independence. The calculation of intraocular lens power for a desired refractive target can be challenging in post-refractive surgically treated eyes, given the frequent case reports of "refractive surprises" after cataract surgery. After corneal refractive surgery, the direct use of the measured topographic or keratometric values, with no correction, results in less accurate calculation of intraocular lens (IOL) power required for cataract surgery than calculation in virgin eyes. After laser refractive surgery for myopia, this could result in an overestimation of the corneal power and subsequent underestimation of the IOL power, therefore leading to a hyperopic outcome after phacoemulsification. Conversely, after laser refractive surgery for hyperopia, inaccuracy in the keratometric power estimation could result in a myopic outcome after phacoemulsification. Despite current progress in this subject, awareness of the shortcomings of classical methods and suggested strategies to improve accuracy can be valuable to clinicians. This article provides an overview of the possible sources of error in intraocular lens power calculation in post-keratorefractive patients, and reviews the methods to minimize intraocular lens power errors.     

后曲率实测法计算准分子激光角膜原位磨镶术后角膜屈光力的准确性

目的 探讨后曲率实测法计算准分子激光原位角膜磨镶术(LASIK)后角膜屈光力的准确性.方法 多种测量角膜屈光力方法的比较性研究.回顾性分析按后曲率实测法计算人工晶状体度数的LASIK术后人工晶状体植入眼8例(11只眼,10只为超声乳化白内障吸除及人工晶状体植入术,1只为人工晶状体置换术),计算术后稳定屈光状态与目标屈光度的差异,并据此推导实际角膜屈光力.分析其他角膜曲率法(自动曲率计、角膜地形图、球镜当量法、前曲率法、Pentacam提供的EKR曲率)计算人工晶状体度数可能造成的届光偏差.对LASIK术后6个月随访眼23例行详细屈光检查,根据术前角膜屈光力及手术前后眼屈光度改变推导术后理论角膜屈光力.分析后曲率实测法计算所得角膜屈光力与理论角膜屈光力的差异,并与其他角膜曲率法作比较.结果 采用后曲率实测法计算的人工晶状体植入眼术后平均裸眼视力0.8±0.2,与目标屈光度绝对偏差平均为(0.36±0.36)D(-0.63～+0.85 D),绝对偏差≤0.25 D、≤0.50 D、≤1.00 D的眼比例数分别为55%、73%和91%.其屈光偏差显著低于自动曲率计[(2.50±1.08)D]、角膜地形图[(1.90±0.88)D]、球镜当量法[(2.09±1.62)D](P<0.01)及前曲率法[(1.45±1.10)D](P<0.05)的预期结果;与EKR曲率法比较差异无统计学意义,但其偏差范围(-1.13～0.85 D)小于后者(-1.10～1.80 D).23例单纯LASIK术后眼的角膜屈光力测算同样显示后曲率实测法计算所得角膜屈光力与理论角膜屈光力偏离程度最小,绝对偏差为(0.67±0.45)D.结论 后曲率实测法计算LASIK术后角膜屈光力,可行性准确性俱佳.     

Corneal topography in cataract surgery

Keratometry and videokeratography are the most important means of evaluating induced corneal changes after surgery and have comparable sensitivities in the paracentral region of the cornea. When cataract surgery is planned, corneal topography can be used preoperatively in the calculation of IOL power, particularly in difficult cases, such as in patients who have undergone corneal refractive surgery or penetrating keratoplasty. A study published in the past year suggests that the mean power in ring 3 of the Tomey TMS-1 videokeratoscope (Cambridge, MA) appears to give the most accurate estimate of corneal power for the calculation of IOL power after radial keratotomy. In the case of PRK, traditional methods of determining the corneal power can lead to great amounts of anisometropia. Further research is needed to develop more accurate methods of calculating IOL power after PRK. Videokeratography can also be used before cataract surgery in planning the location and size of the incision. In general, smaller temporal incisions result in less astigmatism than do larger superior incisions. Postoperatively, videokeratography can be used to detect tight sutures, torsion of the wound, internal wound gape, and irregular astigmatism, as well as to guide suture removal or in cases where best-corrected visual acuity is not adequate and there are no other obvious causes for poor vision to determine if corneal irregularities are present.