老年性白内障患者中角膜后表面散光对总角膜散光的影响

目的　研究老年性白内障患者模拟角膜曲率计散光和总角膜散光大小及轴位的差异,评价角膜后表面散光对总角膜散光的影响。方法　８０例老年性白内障患者（１０５眼,左４７眼,右５８眼）手术前行Ｐｅｎｔａｃａｍ检查,记录角膜前后表面散光,并对角膜前后表面散光行相关性分析。模拟角膜曲率计散光用屈光指数１．３３７５及角膜前表面曲率半径计算,总角膜散光由前后表面散光在角膜后表面的矢量合计,计算模拟角膜曲率计散光和总角膜散光的矢量差Ｅ→、大小差Ｅ和轴位差Ａ。结果　角膜前表面散光和后表面散光大小间无明显相关性（Ｐ＝０．９８）,后表面散光对前表面散光的平均补偿作用为５．７９％。总角膜散光及模拟角膜曲率计散光大小分别为（１．１２±０．６５）Ｄ和（１．０７±０．６４）Ｄ,差异具有统计学意义（ｔ＝－２．４０,Ｐ＝０．０２）;两者轴位分别为（６７．９３±５６．５０）°和（６８．９０±５９．６８）°,差异无统计学意义（ｔ＝－０．２７,Ｐ＝０．７９）。散光值大小及轴位差异的算术均值分别是（０．０５±０．２３）Ｄ和（－０．５７±１３．０２）°,绝对值是（０．１９±０．１５）Ｄ和（７．００±１０．９７）°。两者散光大小差别大于０．５０Ｄ或轴位差别大于１０°的有３０眼,占２８．５７％。结论　老年性白内障患者忽略角膜后表面测量可能会导致具有临床意义的角膜散光值估计的差异。     

The effect of posterior corneal flat meridian and astigmatism amount on the total corneal astigmatism estimated from anterior corneal measurements

Background

To evaluate the effects of posterior corneal astigmatism and the absolute flat meridian difference between anterior and posterior corneal surfaces (AMD_Ant-Post) on the estimation of total corneal astigmatism using anterior corneal measurements (simulated keratometry [K]).

Methods

Ninety-nine eyes of 99 healthy participants were enrolled. Anterior, posterior, and total mean corneal power, cylinder power, flat meridian, and vector components J₀, and J₄₅ measured by a dual Scheimpflug camera were analyzed. The correlation between the posterior corneal cylinder power, AMD_Ant-Post, and the difference in the cylinder power between simulated K and total cornea (cylinder power difference_SimK-Tot) were evaluated.

Results

The cylinder power difference_SimK-Tot was positively correlated with the posterior corneal cylinder power (rho?=?0.704 and P?Ant-Post (rho?=??0.717 and P?0 was strongly associated with the posterior corneal cylinder power and the AMD_Ant-Post. When corneal J₀ had a positive value, the cylinder power of simulated K tended to be larger than the total corneal cylinder power. In comparison, the opposite trend was presented in eyes with negative anterior corneal J₀. When anterior corneal J₀ was larger than 1.0 or smaller than ?0.9, the errors from estimating the total corneal cylinder power using anterior corneal measurements tended to be larger than 0.25 D.

Conclusion

Posterior corneal astigmatism should be considered for more accurate corneal astigmatism predictions, especially in eyes with anterior corneal astigmatism greater than 2.0 D of with-the-rule astigmatism or greater than 1.8 D of against-the-rule astigmatism.     

Effect of the posterior corneal surface on total corneal astigmatism in patients with age-related cataract

AIM: To explore the effect of the posterior astigmatism on total corneal astigmatism and evaluate the error caused by substituting the corneal astigmatism of the simulated keratometriy (simulated K) for the total corneal astigmatism in age-related cataract patients. METHODS: A total of 211 eyes with age-related cataract from 164 patients (mean age: 66.8±9.0y, range: 45-83y) were examined using a multi-colored spot reflection topographer, and the total corneal astigmatism was measured. The power vector components J0 and J45 were analyzed. Correlations between the magnitude difference of the simulated K and total cornea astigmatism (magnitude differenceSimK-Tca), anterior J0, and absolute meridian difference (AMD) between the anterior and posterior astigmatisms were calculated. To compare the astigmatism of the simulated K and total cornea both in magnitude and axial orientation, we drew double-angle plots and calculated the vector difference between the two measures using vector analysis. A corrective regression formula was used to adjust the magnitude of the simulated K astigmatism to approach that of the total cornea. RESULTS: The magnitude differenceSimK-Tca was positively correlated with the anterior corneal J0 (Spearman’s rho= 0.539; P<0.001) and negatively correlated with the AMDR (Spearman’s rho=-0.875, P<0.001). When the anterior J0 value was larger than 1.3 D or smaller than -0.8 D, the errors caused by determining the total corneal astigmatism with the karatometric calculation tended to be greater than 0.25 D. An underestimation by 16% was observed for against the rule (ATR) astigmatism and an overestimation by 9% was observed for with the rule (WTR) astigmatism when ignoring the posterior measurements. CONCLUSION: Posterior corneal astigmatism should be valued for more precise corneal astigmatism management, especially for higher ATR astigmatism of the anterior corneal surface. We suggest a 9% reduction in the magnitude of the simulated K in eyes with WTR astigmatism, and a 16% addition of the magnitude of the simulated K in eyes with ATR astigmatism.     

复性近视散光角膜地形图的临床分析

目的　全面了解复性近视散光患者角膜各区散光改变及对眼球散光的影响。方法　对15 0眼进行角膜地形图测量及视网膜检影检查 ,进行t检验及直线相关分析。结果　复性近视散光患者角膜 3mm区、 5mm区、 7mm区散光轴差异无显著意义 (P >0 0 5 ) ,3mm区与 5mm区散光度差异无显著意义 ,并与眼球散光度呈正相关 :眼球散光度 (D ) =0 64 7D3mm ( 3mm区散光度 ) 0 810D5mm ( 5mm区散光度 ) -0 14 9D7mm ( 7mm区散光度 ) -0 2 3 5。结论　人眼的散光 71 2 %由角膜散光决定 ,而角膜散光值主要由角膜 3mm区、 5mm区散光值决定 ,尤其 5mm区是反映角膜散光最敏感、稳定的区域     

儿童散光眼角膜地形图形态特征

目的　探讨儿童散光眼角膜地形图形态特点。方法　对 96例 1 92眼屈光不正眼儿童行角膜地形图检查 ,平均年龄 9 88岁 (5～ 1 4岁 )。根据曲率假色分布图对角膜前表面形态进行分类 ,并分析曲率数值分布图、SimK、CIM、SF值。结果　发现儿童屈光不正眼呈中央陡峭周边平坦的托力克面 ,角膜散光占 94 2 7% ,且以顺规为主。除了圆形、椭圆形和不规则形之外 ,角膜表面各图形之间角膜散光、眼散光不同具有统计学意义。表面形态以蝴蝶结形为主 ,随着散光度数增加 ,角膜前表面蝴蝶结形增多、表面变陡峭。 82 81 %地形图顶点、角膜顶点与瞳孔中心不重合 ,却不影响视觉质量。结论　利用计算机辅助角膜地形图仪有利于观察儿童角膜前表面形态特点、分析角膜曲率、△SimK值、粗略估计眼散光、区分病理性角膜 ,从而有利于临床工作顺利开展。     

角膜地形图引导下准分子激光矫正角膜不规则散光及不对称性散光

目的 探讨角膜地形图引导下准分子激光个性化切削手术矫正角膜不规则散光及不对称性散光的效果和优缺点.方法 应用MEL - 70准分子激光仪及配套TOMEY -Ⅲ角膜地形图引导个性化切削系统进行准分子激光原位角膜磨镶术(LASIK)矫正不对称性或不规则角膜散光复性近视散光58例108眼.其中49例97眼为初次手术;另9例11眼为二次手术,系由不均匀切削、偏心切削或中央岛而形成的不规则散光.术前最佳矫正视力均值0.98±0.32;屈光度:球镜平均(-4.59±1.68)D,柱镜平均(-1.62±0.78)D.结果 108眼手术均顺利完成,无术中或术后并发症.术后角膜地形图显示:角膜中央3 mm切削深度平整、均匀,术后1周平均裸眼视力1.03 ±0.29.屈光度:球镜-0.50～+0.75D,平均(-0.35 ±0.29)D,柱镜0～- 0.75D,平均(-0.38 ±0.24)D.结论 TOMEY -Ⅲ角膜地形图捕捉角膜曲率信息准确,引导准分子激光个性化切削程序设计合理,系统安全可靠.用它来进行个性化LASIK可较为精确地矫正角膜不规则及不对称散光.     

Distribution of the anterior,posterior, and total corneal astigmatism in healthy eyes

Purpose

To evaluate the magnitude and axis orientation of the anterior, posterior, and total corneal astigmatism in normal healthy eyes of an Iranian population.

Methods

In a prospective cross-sectional study, ophthalmic and anterior segment parameters of 153 healthy eyes of 153 subjects were evaluated by Galilei dual Scheimpflug analyzer. The magnitude and axis orientation [with-the-rule (WTR), against-the-rule (ATR), and oblique] of the anterior, posterior, and total corneal astigmatism measurements (ACA, PCA, and TCA) were compared according to the age, sex, and other ophthalmic parameters.

Results

The mean ± SD age of the study population was 30 ± 5.9 years. The mean magnitude was 1.09 ± 0.76 diopters (D) for ACA, 0.30 ± 0.13 D for PCA, and 1.08 ± 0.77 D for TCA. Males had a significantly higher magnitude of PCA than females (p = 0.041). Most eyes had a WTR anterior astigmatism and an ATR posterior astigmatism. The WTR astigmatism had a higher mean magnitude compared to the ATR and oblique astigmatism in all the astigmatism groups, with a significant difference in the ACA and TCA groups (p < 0.05). PCA magnitude exceeded 0.50 D in only 7.8% of the subjects. ACA, PCA, and TCA were significantly correlated with each other and also had a significant correlation with the anterior and posterior maximum corneal elevation measurements (p < 0.001).

Conclusion

The results of this study although are limited due to the small number of participants and confined to our demographics, provided information regarding a population that was not described before and may be helpful in obtaining optimum results in astigmatism correction in refractive surgery or designing new intraocular lenses.

     

Posterior corneal surface toricity and total corneal astigmatism.

The influence of posterior corneal surface toricity upon total corneal astigmatism was investigated in 60 young subjects (mean age 22.04 +/- 3.24 years). Both surfaces were found to be flatter horizontally than vertically. Astigmatism arising from the anterior corneal surface was therefore reduced by astigmatism of the opposite sign arising from the posterior surface. Had the toricity of the posterior corneal surface been purely governed by that of the anterior surface this reduction would have amounted to about 5%. However, the posterior surface was found to exhibit additional toricity bringing about a greater reduction of total corneal astigmatism amounting to approximately 14%.     

角膜后表面散光的测量及临床意义

角膜散光由角膜前表面散光（anterior astigmatism,AA）和角膜后表面散光（posterior astigmatism,PA）组成。据文献统计,PA在-0.01~-1.10 D范围内,85.0%~96.1%为逆规散光。随着年龄的增长,PA总体呈现由逆规向顺规漂移的趋势,AA的趋势则与之相反。因此,对于青年人,PA使总角膜散光（total astigmatism,TA）减小;对于老年人,PA使TA增大。在临床上,忽略PA会错误估计TA,影响屈光性白内障手术后的视觉质量。本文旨在介绍PA的测量方法及临床意义,以供眼科医生在临床工作中参考。     

闭眼和睡眠对人角膜地形和散光的影响研究

目的：观察不同时间长度闭眼和睡眠后角膜地形图、角膜散光等的变化,研究闭眼以及睡眠造成的生理性缺氧对人眼角膜形态的影响。
　　方法：选取年龄22~33(26.19±3.95)岁的自愿者,排除屈光介质疾病及眼部其他疾病、无角膜接触镜配戴史等,共16例32眼,其中男10眼,女22眼。主要参数采用了Zeiss角膜地形图仪获取角膜模拟K值、角膜散光值、角膜表面不规则指数( CIM )和形状因子( SF ),测量时间点分别为：日间闭眼前、闭眼后10,20,30,60,120 min;夜间临睡前、超过6h 的睡眠结束后,开眼立即检测、开眼后10,20,60,120 min。
　　结果：闭眼过程中,人角膜地形图、角膜散光、CIM、SF等的变化差异无统计学意义。在超过6h的睡眠结束,开眼后过程中,人角膜地形图、角膜散光、CIM、SF等的变化差异无统计学意义。
　　结论：闭眼和睡眠没有构成对角膜实质性损伤,所以角膜地形和散光基本不变。     

不同年龄段前角膜散光和后角膜散光相关性的横断面研究

目的：以不同年龄段分组评估前角膜散光(ACA)和后角膜散光(PCA)。同时分析各年龄段ACA、PCA之间散光程度、散光轴的相关性。

方法：横断面研究,包括381眼。将临床测得的散光数值转换为向量记法,以分析ACA和PCA。在整体人群和四个不同年龄段(5～19, 20～39, 40～59, 和≥60)中评估ACA和PCA之间散光程度、散光轴的关系。使用随机效应线性回归模型评估ACA、PCA散光程度之间的关系。

结果：在5～9岁儿童中,ACA平均散光度最高为3.59D,PCA为0.50D。总体上来说,ACA在1～10.0D,PCA在0～3.5D。在较年轻的分组中(5～19岁),ACA和PCA显著相关(r=0.85, P<0.001)。在60岁以上组中,ACA每增加1D,PCA增加0.04D(95%CI： 0.005, 0.07; P=0.03),增加程度相比其余组最少。

结论：在60岁以上人群中,相比仅仅依靠经验公式,通过ACA数据计算IOL度数,更为谨慎的方法是同时测定后角膜散光度和散光轴。     

Vector summation of anterior and posterior corneal topographical astigmatism

PURPOSE: To determine whether vector addition of posterior corneal astigmatism improves the correlation between topographical and refractive astigmatism. SETTING: Massachusetts Eye and Ear Infirmary and Harvard Medical School, Boston, Massachusetts, USA. METHODS: Orbscan topographical maps of 40 eyes (31 patients) showing 1.0 to 6.0 diopters (D) of astigmatism were analyzed. Topographical anterior and posterior corneal surface astigmatism was determined. Refractive astigmatism was compared to topographical astigmatism using 3 methods: anterior topographical astigmatism, overall topographical astigmatism obtained by vector summation of anterior and posterior topographical astigmatism, and simulated keratometry (SimK). RESULTS: Refractive astigmatism ranged from 0.25 to 5.00 D. The mean error in magnitude between topographical and refractive astigmatism was significantly smaller with the overall topographical method (1.06 D +/- 0.92 [SD]) than the anterior topographical method (1.37 +/- 1.04 D) (P <.0001). The mean error in axis between topographical and refractive astigmatism was smaller with the overall topographical method (10.4 +/- 13 degrees) than with the anterior topographical method (15.5 +/- 30.6 degrees) and with SimK (13.3 +/- 15.1 degrees), but these differences were not statistically significant. CONCLUSION: Consideration of the Orbscan measurement of posterior corneal surface toricity may improve the prediction of the magnitude of refractive astigmatism.     

近视眼全眼散光及角膜散光对LASIK术矫正近视散光的影响

目的:探讨全眼散光和角膜散光对LASIK手术矫正散光的影响。方法:回顾性分析84例162眼行LASIK手术矫正的近视散光患者,根据全眼散光与角膜散光轴向相差<15°,全眼散光度数<2倍角膜散光度数和全眼散光与角膜散光轴向相差≥15°,全眼散光度数≥2倍角膜散光度数分为A(112眼)、B(50眼)两组,分析术后视力、散光矫正效果。结果:患者中69%的全眼散光轴与角膜散光轴向相关,差异在15°以内,术后两组眼散光度数分别为-0.39±0.43,-0.73±0.21D,差异有统计学意义(P<0.05)。B组有4例患者主诉夜晚有眩光,近视力差、疲劳。结论:近视眼全眼散光与角膜散光有高度相关性。LASIK矫正散光术前应根据验光和角膜地形图结果分析,合理设计散光的切削量和轴位,选择个性化治疗方案。     

儿童圆锥角膜与高度近视性散光的角膜地形图比较

目的:评价计算机辅助的角膜地形图分析系统在儿童圆锥角膜与儿童高度近视性散光的鉴别诊断中的作用。方法:用TMS-4角膜地形图仪测量圆锥角膜组20例及高度近视性散光组20例的角膜参数并进行分析。结果:圆锥角膜组的角膜中央的屈光力、角膜平均表面对称指数、表面不规则指数、同一患者两眼角膜中央屈光力的差值、I-S值等均明显高于高度近视性散光眼组的各对应值(P<0.01),模拟散光度数与高散光组也有明显差异(P<0.05),特别是同一患者两眼角膜中央屈光力的差值、I-S值对于两者的鉴别最为敏感。结论:用角膜地形图对儿童圆锥角膜及儿童高度近视性散光的角膜参数进行分析,有助于圆锥角膜的鉴别诊断,避免误诊为弱视并进行不必要的弱视训练。     

小儿静态总合散光与角膜散光的关系

目的用强度矢量法研究小儿静态屈光不正,比较视网膜检影测出的总合散光与角膜曲率计测出的角膜散光的关系。方法分别用视网膜检影与角膜曲率计对152只眼(76人)行静态屈光检查。将屈光不正结果表达成三维直角屈光度坐标上的点。直角屈光度坐标上的每一点坐标(x,y,z)对应于屈光处方的三个分解成分:等效球镜成分、Jackson交叉柱镜J0成分在90°和180°轴位上、和Jackson交叉柱镜J45成分在45°和135°轴位上。结果总合散光的绝对值(TA)与角膜散光的绝对值(CA)呈线形关系。相关系数为0.876,相关系数的统计意义检验(t检验)P值<0.001。直线回归方程为(TA)=0.9759(CA)-0.3743。总合散光交叉柱镜J0成分(RJ0)与角膜散光的交叉柱镜J0成分(CJ0)呈线形关系。相关系数为0.878,相关系数的统计意义检验(t检验)P值<0.001。直线回归方程为RJ0=1.0091CJ0-0.2461。总合散光交叉柱镜J45成分(RJ45)与角膜散光的交叉柱镜J45成分(CJ45)呈线形关系。相关系数为0.570,相关系数的统计意义检验(t检验)P值<0.001。直线回归方程为RJ45=0.559CJ45 0.0024。视网膜检影与角膜曲率计在配对t检验中,总合散光的绝对值[TA]与角膜散光的绝对值的差值均值和标准差为(-0.4290±0.6572,P<0.001),Jackson交叉柱镜J0成分的差值均值和标准差为(-0.2362±0.3318,P<0.001),Jackson交叉柱镜J45成分的差值均值和标准差为(-2.3E-0.3±0.2695,P=0.917)。剩余散光为预测的总合散光与实际的总合散光之差值。61.8%的剩余散光在0.25至0.5D,34.2%的剩余散光在0.5至0.75D,2.6%的剩余散光在0.75至1.0D。结论临床上,角膜曲率计测出的角膜散光可以预测总合散光。95%剩余散光小于0.75D,因此,有一定的实用价值。