基于Pentacam HR的角膜屈光指数计算

目的 评估Pentacam HR测量角膜屈光术后眼角膜参数的可重复性并比较用Pentacam HR角膜参数计算未手术眼和角膜屈光术后眼角膜屈光指数的差异。设计 前瞻性研究。研究对象 接受角膜屈光手术术前及术后检查者,分为两组：A组为接受常规术前检查者207例207眼;B组为接受常规术前检查且术后3个月（LASIK）或6个月（PRK）以上复查者67例133眼。方法 A组受试眼行主觉验光和Pentacam HR检查;B组受试眼手术前后分别行主觉验光和Pentacam HR检查。两组中Pentacam HR检查均获得三次有效结果。主要指标  变异系数（CVw）、组内标准差（Sw）和组内相关系数（ICC）评估Pentacam HR获得的未手术眼（A组）和角膜屈光术后眼（B组）的角膜中央前表面3 mm范围内平均曲率半径（Ra）、角膜中央后表面3 mm范围内平均曲率半径（Rp）和中央角膜厚度（CCT）的可重复性。独立样本t检验分别分析A组和B组中计算获得的角膜屈光指数的差异。结果 A组中Pentacam HR获得的Ra、Rp和CCT分别为（7.780±0.235）mm、（6.341±0.225）mm和（541.67±31.79）μm; B组中Pentacam HR获得的Ra、Rp和CCT分别为（8.625±0.412）mm、（6.379±0.237）mm和（461.89±34.70）μm,均具有很好的可重复性（CVw均<1%,ICC均≥0.99）。基于Pentacam HR获得的参数计算角膜屈光指数,A组为（1.3278 ± 0.0008）;B组为（1.3227±0.0019）（t=34.634,P=0.000）。结论 Pentacam HR获得的未手术眼和角膜屈光术后眼角膜中央前、后表面3 mm范围内曲率半径和中央角膜厚度均具有很好的可重复性。基于Pentacam HR获得的角膜屈光术后眼的角膜屈光指数小于未手术眼的角膜屈光指数。（眼科, 2014, 23： 308-312）     

应用旋转Scheimpflug照相系统对角膜参数的研究

目的以旋转Scheimpflug照相技术（Pentacam）研究角膜前表面曲率（Ra）、后表面曲率（Rp）及角膜厚度;根据测量结果,探讨角膜屈光力的计算方法。方法应用Pentacam对302名正常角膜的Ra、Rp、角膜厚度及测量所得K值（Km）进行测量,计算Rp与Ra比值（Rp／Ra）、角膜前表面屈光力（Ka）、后表面屈光力（Kp）,以几何光学公式计算角膜屈光力（Ko）与标定的角膜系数（Nc）,对角膜各参数进行正态分布检验,直线回归分析Rp与Ra的相关性。结果各参数均服从正态分布。Ra为（7．74±0．26）mm,Ka为（48．62±1．61）D,CT为（0．545±0．036）mm,与既往报道的数据相似;角膜后表面参数与既往报道的数据及Gullstrand模型眼不同,Rp为（6．44±0．25）mm,Kp为（-6．22±0．24）D,Rp／Ra为0．832±0．017,低于Gullstrand模型眼的参数;Rp与Ra呈直线相关,回归方程为Rp=0．81×Ra＋0．17（R^2=0．71,P〈0．05）;Nc为1．3288±0．0010,低于标准的角膜系数1．3375。Ko为（42．52±1．42）D,低于Km（43．64±1．44）D,差异有统计学意义（t=151．87,P〈0．01）。K1.3288为（42．52±1．41）D,与Ko比较差异无统计学意义（t=-0．052,P=0．96）。Ko与K1.3288呈直线相关,回归方程为Ko=1．006×K1.3288-0．241（R^2=0．99,P〈0．05）。结论旋转Scheimpflug照相技术与传统角膜地形图仪原理不同,应用该技术发现Rp、Kp、Rp／Ra及Nc与Gullstrand模型眼参数不同,对于标准化角膜光学模型及角膜屈光力的计算具有指导意义。     

近视屈光度数与角膜屈光力和非球面系数的相关性

目的：对不同近视屈光状态下人眼角膜总屈光力、后表面屈光力、眼轴、角膜非球面参数 Q 值、中央角膜厚度（central cornea thickness, CCT）及眼压进行测量,并探讨近视度数与上述相关参数的关系。 方法：近视患者138例138眼（所有患者选择右眼进行分析）,根据综合验光仪测量的近视度数,患者分为三组：低度近视组（-1.00D～-3.00D）,中度近视组（-3.25D～-6.00D）,高度近视组（〉-6.00D）。各眼使用Pentacam眼前节分析仪（德国,Oculus公司）进行检测,获得角膜总屈光力和后表面屈光力以及Q值,使用非接触式眼压测量仪（日本Canon公司）测量眼压,使用 A 超测量仪（美国Tomey公司AL-3000）测量中央角膜厚度（CCT）和眼轴长度。数据采用Pearson相关性分析、单因素方差分析进行处理。 结果：近视度数与眼轴呈负相关（r=-0.682, P〈0.001）,与角膜屈光力无相关性（r=0.009, P=0.925）,眼轴与角膜屈光力呈负相关（r=-0.554, P〈0.001）。近视度数与Q值呈正相关（r=0.674, P〈0.001）,Q值与眼压成呈负相关（ r=-0.375, P=0.01）。近视度数与CCT及眼压无相关性（ r=-0.138, P=0.141;r=-0.121, P=0.157）。 结论：角膜屈光力在近视发展过程中有正视化作用,Q值与近视度数及眼压的相关关系对指导角膜屈光手术有临床意义。     

近视LASIK术后角膜生物力学参数变化的相关性

目的:观察近视LASIK术后角膜生物力学参数与形态参数变化的相关性。方法:近视患者69例136眼,于LASIK术前及术后1mo行眼反应分析仪(ORA)测量角膜滞后(CH)和角膜阻力因子(CRF),Pentacam眼前节分析仪测量眼前节参数。计算术后角膜生物力学参数变化ΔCH及ΔCRF,Pentacam测量角膜中央厚度变化ΔCCT,中央2,4,6mm平均角膜厚度变化(ΔCCT2mm,ΔCCT4mm和ΔCCT6mm),角膜容积变化ΔCV,角膜前后表面曲率半径变化ΔRa和ΔRp,分析ΔCH和ΔCRF与角膜形态参数的相关性。结果:LASIK术前平均CH及CRF(9.99±1.38和9.96±1.30mmHg)明显高于术后1moCH和CRF(7.90±1.16和6.49±1.28mmHg),差异具有统计学意义(P<0.05)。LASIK术后ΔCH和ΔCRF与ΔRp和ΔCCT6mm无相关性,ΔCH和ΔCRF与ΔCCT,ΔCCT2mm,ΔCCT4mm和ΔCV呈正相关(r:0.513,0.397,0.329和0.314,P<0.05;r:0.616,0.504,0.484和0.466,P<0.01);ΔCRF与ΔRa呈负相关(r:-0.374,P<0.01)。结论:近视LASIK术后角膜CH和CRF变化与角膜厚度及容积有关,CRF评价LASIK术后角膜生物力学变化比CH更有价值。     

应用Orbscan角膜地形测量系统及角膜曲率计测量角膜屈光状况

目的　分别使用 O rbscan角膜地形测量系统及角膜曲率计测量角膜前表面屈光力及角膜总屈光力 ,并比较其差异。方法　选择 50 0只正常人眼使用 O rbscan裂隙光扫描角膜层面照相 /测厚系统测量角膜前、后表面地形图及角膜厚度 ,计算角膜前表面屈光力及总屈光力。再用 N idek KM- 450角膜曲率计测量角膜前曲率 ,计算角膜前表面屈光力 ,据此估算角膜总屈光力。比较 2种方法测量所得结果。结果　使用角膜曲率计及 O rbscan角膜地形测量系统测得的角膜前表面屈光力分别为4 8.3 1D± 1.2 4 D、4 8.12 D± 1.3 6D,两者比较无显著性差异 (P >0 .0 5) ;角膜总屈光力分别为 4 3 .19D± 1.4 5D、4 1.78D±1.3 9D,两者比较有显著性差异 (P<0 .0 1)。结论　角膜总屈光力的测定不应忽视角膜后表面屈光力及角膜厚度这 2个因素 ,Orbscan角膜地形测量系统是一种较好的测量角膜屈光状况的仪器。     

Pentacam Topolyzer与角膜曲率计测量角膜屈光力的比较

目的 比较Scheimpflug原理摄像系统Pentacam与Placido盘成像Topolyzer角膜地形图及Topcon自动式角膜曲率计测量角膜屈光力的差异,分析三者的一致性,为临床使用提供依据.方法 随机选取拟行角膜屈光手术角膜形态正常的患者39例(39只眼).术前分别采用Pentacam、Topolyzer及Topcon自动式角膜曲率计测量角膜屈光力,并对测量结果进行统计分析.结果 Topcon自动式角膜曲率计测量值为(43.35±1.36)D,Topolyzer测量值为(43.41±1.35)D;Pentacam测量所得simK、true net power(TNK)、4.0mm Holladay equivalent K-reading(EKR)、4.5mm EKR分别为(43.40±1.34)D,(42.14±1.25)D,(43.44±1.31)D,(43.50±1.32)D.Pentacam测量所得simK、4.0mm EKR与Topolyzer测量所得simK差异无统计学意义(P＞0.05);其余各组K值之间比较差异均有统计学意义(P＜0.01).三种测量方法所得K值两两之间均存在高度正相关(r＞0.90,P＜0.01).TNK比其余各种K值均明显小(-1.21～-1.36)D,一致性较差;其余各组K值之间一致性较好,95％一致性界限较窄.结论 对于角膜形态正常的患者,Pentacam测量所得simK及4.0 mm EKR与Topcon自动式角膜曲率计测量所得Km及Topolyzer测量所得simK具有良好的一致性,不过在临床中互相替代使用仍需要慎重.true net power比其余各种K值均明显小,不能用于人工晶状体屈光度计算.     

Orbscan-Ⅱ评估LASIK术后角膜后表面曲率变化的研究

目的采用Orbscan-Ⅱ测量方法对LASIK术后患者角膜后表面曲率的变化进行评估。方法Orbscan-Ⅱ测量95例189眼LASIK术眼手术前后角膜后表面的曲率参数,高斯光学公式计算角膜后表面屈光力,对手术前后角膜后表面曲率半径和屈光力的比较采用配对t检验进行统计学分析,Bland—Altman用于其一致性和可重复性的评估。结果手术前后角膜平均曲率半径分别为（6．42±0．23）mm和（6．32±0．24）mm,即LASIK术后角膜曲率半径较术前下降,差异有统计学意义（P〈0．01）,角膜后表面屈光力手术前后分别为（-6．24±0．22）D和（-6．33±0．24）D,差异有统计学意义（P〈0．01）。LASIK手术前后角膜后表面屈光力的差异值与矫正近视量呈正相关（r=0．326,P=0．0004）。Bland—Ahman显示手术前后角膜后表面曲率半径的一致性界限为（-0．118mm,0．31mm）,角膜后表面屈光力的一致性界限为（-0．116D,0．308D）。结论Orbscan-Ⅱ可用于LASIK术后角膜后表面曲率半径的测定,联合高斯光学公式计算角膜后表面屈光力对于LASIK术后人工晶状体计算的评估是可行的。     

OPD-ScanⅢ与Pentacam测量角膜屈光力和散光的一致性

目的：:分析OPD-ScanⅢ与Pentacam测量角膜散光（CA）患者角膜屈光力、CA及散光轴位的相关性和一致性。方法：:系列病例研究。收集2019年6-12月在苏州大学附属理想眼科医院就诊的屈光不正患者876例（1 072眼）,分别用OPD-ScanⅢ与Pentacam测量角膜平坦轴屈光力（K1）、陡峭轴屈光力（K...     

准分子激光原位角膜磨镶术后OrbscanⅡ估算术前角膜屈光力

目的 比较OrbscanⅡ测量准分子激光原位角膜磨镶术(LASIK)前后周边角膜后表面曲率半径改变,初步确立新的角膜前后表面曲率半径比率R,利用术后周边后表面角膜曲率半径和比率R估算术前角膜总屈光力。方法 回顾分析OrbscanⅡ测量151只眼术前及术后3个月角膜7～10 mm区后表面曲率半径值的变化,计算角膜0～～7 mm区前表面曲率半径与角膜7～10 mm区后表面曲率半径比率R,利用比率R推算30只眼术前角膜总屈光力,并验证计算性角膜总屈光值与测量性角膜总屈光值的一致性。LASIK手术前后角膜7～10 mm后表面曲率半径变化和计算性角膜总屈光力与术前OrbscanⅡ测得角膜总屈光力比较采用配对t检验。结果 LASIK术前后角膜7～10 mm区后表面曲率半径差值为（-0.005±0.154）mm(t=0.417,P=0.677),术前角膜0～7 mm区前表面曲率半径与角膜7 ～ 10 mm区后表面曲率半径比率R为1.167±0.030,利用比率R推算的角膜总屈光力均值为(43.49±1.79)D,OrbscanⅡ测得实际角膜总屈光力均值为(43.77±1.53)D,两者差值均值为（-0.28±1.00）D(t=-1.523,P=0.139)。结论 LASIK手术前后周边区域角膜后表面曲率半径改变无实际临床意义,计算所得新角膜前后表面曲率半径比率R可准确的推算LASIK术者术前角膜总屈光力,为LASIK术后丢失术前资料患者双K法计算人工晶状体度数提供重要条件。     

角膜后表面屈光力理论计算值与Orbscan测量值的比较

目的 比较角膜后表面屈光力理论计算值与角膜地形图(Orbscan)测量值之间的差异,评价Orbscan在角膜屈光手术领域的应用价值。 方法 应用球面折射公式计算64例64眼角膜后表面屈光力;Orbscan测量受试者角膜后表面屈光力。结果 角膜后表面屈光力Orbscan平均测量值为-6.59 D±0.22 D,平均理论计算值为-5.04 D±0.14 D,Orbscan平均测量值与平均理论计算值差异为-1.55 D±0.19 D(P<0.01)。 结论 角膜后表面屈光力Orbscan测量值大于理论计算值-1.55 D。Orbscan测量角膜后表面屈光力的准确性尚需进一步探讨。     

Evaluation of the Keratometric Index by the Pentacam

Objective: To calculate the total corneal power and the keratometric index based on actual measurements of the anterior and posterior corneal surfaces and the central corneal thickness by Pentacam and evaluate the accuracy of this keratometric index in estimating total and posterior corneal powers. Methods: This was a series case study. Four hundred and nineteen patients (a total of 419 eyes) who had undergone preoperative examination and laser in situ keratomileusis (LASIK) surgery or cataract surgery from February to October 2017 at the Xiangtan Central Hospital and Eye Hospital, Wenzhou Medical University were chosen for the study. The radius of the best-fit sphere for the anterior corneal surface (Ra) and posterior corneal surface (Rp), and central corneal thickness (CCT) were obtained. The ratio of Ra to Rp (AP ratio), anterior corneal power, posterior corneal power and keratometric index were calculated, and the total corneal power in each eye was calculated using the Gaussian optics formula. A paired-samples t-test was used to compare the difference in K values. Results: The means for Ra, Rp, Rsimk, CCT and SimK were 7.73±0.27 mm, 6.34±0.24 mm, 7.73±0.27 mm, 537±33 μm, and 43.65±1.52 D, respectively. The mean calculated AP ratio was 1.220±0.026. The mean calculated keratometric index (Ncal) was 1.328±0.001. Conclusions: The Pentacam-derived keratometric index improves the predictive accuracies of total and posterior corneal powers.     

Validity of the keratometric index: evaluation by the Pentacam rotating Scheimpflug camera

PURPOSE: To determine the keratometric index based on actual measurements of the anterior and posterior corneal surfaces using a rotating Scheimpflug camera (Pentacam, Oculus) and evaluate the accuracy of this keratometric index in estimating total and posterior corneal powers. SETTING: Departments of Ophthalmology, Taipei Medical University Hospital and Taipei City Hospital, Taipei, Taiwan. METHODS: The right eye of 221 subjects was measured with the Pentacam system. The radius of the best-fit sphere for the anterior corneal surface (rant) and posterior corneal surface (rpost), mean radius of simulated keratometry (rsimK), and central corneal thickness were obtained. The ratio of rant to rpost (AP ratio) and keratometric index were calculated in each eye. RESULTS: The means for rant, rpost, rsimK, and AP ratio were 7.75 mm +/- 0.28 (SD), 6.34 +/- 0.28 mm, 7.75 +/- 0.27 mm, and 1.223 +/- 0.034 mm, respectively. These parameters were normally distributed. The mean calculated keratometric index (Ncal) was 1.3281 +/- 0.0018. Using the keratometric indices of 1.3281 (Ncal), 1.3315 (Gullstrand schematic eye), and 1.3375 (conventional), the mean arithmetic and absolute estimation errors for the total corneal power were, 0.00 +/- 0.24 diopter (D) and 0.17 +/- 0.17 D, 0.43 +/- 0.23 D and 0.45 +/- 0.21 D, and 1.21 +/- 0.24 D and 1.21 +/- 0.24 D, respectively. The total corneal power was predicted to within +/-0.50 D of the actual value in 95.0%, 60.2%, and 0.9% of eyes, respectively. The mean arithmetic and absolute estimation errors for the posterior corneal power using an AP ratio of 1.223 (this study) or 1.132 (Gullstrand schematic eye) were 0.00 +/- 0.17 D and 0.13 +/- 0.12 D and 0.47 +/- 0.18 D and 0.47 +/- 0.17 D, respectively. The posterior corneal power was estimated to within +/-0.50 D of the actual value in 97.7% and 60.2% of eyes, respectively. CONCLUSION: Using the Pentacam-derived keratometric index improved the prediction accuracies of total and posterior corneal powers.     

Validity of the keratometric index: large population-based study

PURPOSE: To determine the accuracy of the keratometric index of 1.3315 based on the Gullstrand model eye in predicting the power of the posterior cornea, Gullstrand's model was compared to a calculated keratometric index derived from actual measurements of the cornea. SETTING: Eye Institute, Tan Tock Seng Hospital, Singapore. METHODS: One eye of 2429 subjects with a mean spherical equivalent of -5.32 diopters (D) +/- 2.88 (SD) was measured with the Orbscan II (Bausch & Lomb). The following variables were analyzed: anterior radius of curvature (r(anterior)), posterior radius of curvature (r(posterior)), radius of keratometry (r(simK)), and central pachymetry. RESULTS: The r(anterior), r(posterior), and r(simK) were normally distributed, with a mean of 7.87 +/- 0.25 mm (95% confidence interval [CI], 7.38-8.36), 6.46 +/- 0.26 mm (95% CI, 5.95-6.97), and 7.71 +/- 0.27 mm (95% CI, 7.18-8.24), respectively. The mean ratio between the anterior corneal curvature and posterior corneal curvature was 1.22 +/- 0.03 (95% CI, 1.16-1.28). Based on the measurements of each eye, the mean calculated keratometric index, N(calc), was 1.3273 +/- 0.0013 (95% CI, 1.3248-1.3298). Using N(calc), the posterior corneal power was predicted to within +/-0.50 D of the actual posterior power in 98.3% of eyes. The mean absolute error between the actual and calculated posterior power was 0.157 +/- 0.123 D using N(calc) and 0.326 +/- 0.133 D using the Gullstrand model. CONCLUSION: Modifying the keratometric index increased the accuracy of predicting the posterior corneal power.     

Validation of Orbscan II posterior corneal curvature measurement for intraocular lens power calculation

AIMS: To validate the use of Orbscan II slit-scanning topography for measuring posterior corneal curvature, by comparing corneal power calculations using this value with the standard keratometric method of corneal power calculation. METHOD: Corneal measurements were taken from both eyes of 15 normal subjects using the Javal-Schiotz keratometer and the Orbscan II topographer. Corneal power was calculated using standard keratometric indices of 1.337.5 or 1.331.5 and Javal-Schiotz keratometry. Corneal power was then recalculated using the thick-lens formula, with anterior corneal curvature from the Javal-Schiotz or Orbscan II and posterior measurements from the Orbscan II; in addition, the 3.0 mm 'Mean Power' value from the Orbscan II software was noted. Six comparisons were then made using mean-difference plots. RESULTS: The smallest difference and therefore the most predictable agreement was between Javal-Schiotz keratometry using a refractive index of 1.331.5 and the thick-lens formula using Javal-Schiotz anterior curvature and Orbscan II posterior curvature. The mean difference was 0.27 D with a confidence interval of 0.02-0.52 D. CONCLUSIONS: In normal eyes, data on posterior corneal curvature from the Orbscan II can be used to calculate corneal power in close agreement with the standard keratometric method. This suggests the use of the Orbscan II in eyes that have previously undergone refractive surgery, for calculation of intraocular lens power prior to cataract surgery.     

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.     

基于儿童正视眼的眼光学模型构建

目的根据正视儿童眼部参数,构建正视儿童的眼光学模型。方法实验研究。基于“安阳儿童眼病研究”数据,包括角膜曲率半径、角膜厚度、前房深度、晶状体厚度、屈光度和眼轴长度,取右眼数据,应用ZEMAX光学设计软件构建一个符合我国儿童眼球特点的正视眼光学模型。正态性检验采用单样本K-S分析。结果共纳入正视儿童332名,年龄（7.1±0.4）岁,等效球镜度（SE）为（0.11±0.24）D。构建的正视儿童眼光学模型的光学参数为：角膜前表面曲率半径7.78 mm,非球面系数-0.18;后表面曲率半径6.4 mm,非球面系数-0.60;厚度0.54 mm,折射率1.376。前房深度3.00 mm,房水折射率1.336。晶状体前表面曲率半径12.4 mm,非球面系数-0.94;后表面曲率半径-8.1 mm,非球面系数0.96;厚度3.55 mm,折射率为梯度渐变折射率。玻璃体厚度15.94 mm,折射率1.336。视网膜曲率半径-12.3 mm,眼轴长度23.03 mm,总屈光力62.55 D。结论本研究构建了一个符合儿童正视眼特点的眼光学模型,该模型眼的总屈光力为62.55 D,眼轴长度23.03 mm,该模型可作为儿童眼正视化和近视研究的参考工具。