The spherical aberration of aphakic eyes corrected with intra-ocular lenses

The spherical aberration of eyes corrected with intra-ocular lenses is investigated using a model eye with realistic levels of corneal asphericity. The results indicate that the aberration is intermediate between that of paraxial schematic eyes and real eyes. By using standard optical aberration theory, it is shown that for a plano-convex lens with the curved surface facing the cornea, the aberration is similar to that of normal phakic eyes and therefore probably too low to be of any clinical significance. However, for other lens orientations or designs, the level of aberration is usually higher and may lead to a refractive error varying with pupil size and a loss of acuity with large pupil diameters.     

成年近视眼角膜非球面性及其相关因素的分析

目的：探讨成年近视眼角膜非球面参数（Q值）及其相关因素。方法：163例（326眼）近视者按低、中、高度近视程度分为3组,采用i-Trace视觉功能分析仪对Q值进行测量。对Q值与角膜散光和曲率、屈光度、中央角膜厚度及6 mm角膜下、上方平均屈光度差值（I-S值）之间进行相关性分析。结果：所有成年近视眼平均Q值为-0.088±0.095。3组平均Q值分别为-0.083±0.107,-0.085±0.094和-0.099±0.085。Q值与角膜散光呈负相关性（r=-0.27,P〈0.05）。Q值与角膜曲率、屈光度、中央角膜厚度及6 mm区I-S值之间无相关性。结论：近视眼Q值与角膜散光有弱的负相关性,与屈光度及角膜其它参数相对独立。     

近视眼Q值调整对视觉质量的影响

目的 研究角膜前表面非球面形状,观察传统准分子激光原位角膜磨镶术(LASIK)手术组与Q值引导LASIK(Q-LASIK)手术组视觉质量的差异.为个性化屈光手术的改进提供依据.方法 收集2008年10月至2009年4月期间近视眼100眼,均为左眼,分为标准组即无Q值引导LASIK手术组50眼,Q值调整组50眼,对术前、术后3个月6项指标做对照观察(视力和屈光度、对比敏感度,波前像差变化,角膜非球面性和视觉相关生活质量调查表);采用SPSS 12.0统计软件对资料进行分析.结果 LASIK手术前后Q值比较差异有统计学意义(t=31.26,P<0.01);目标Q值引导手术组术后和传统手术组术后3个月视力>5.0相比较, 用χ2检验, 差异无统计学意义(χ2 =0.195,P>0.05);两组术后角膜非球面性Q值均向正值方向发展,但Q值引导手术组低于传统手术组,两组比较差异有统计学意义(t=11.86,P<0.01);球差在两组术后均增高,但Q值引导手术组球差较无Q值引导手术组低,差异有统计学意义(t=21.34,P<0.01);主观评估上像差与对比敏感度上,术后3个月Q值引导手术组暗视下低频和离焦、球差均为负相关;Q值引导手术术后3个月傍晚视力、夜驾驶视力、眩光、夜晚驾驶不适方面优于无Q值引导手术组,差异有统计学意义(P<0.05,P<0.01,P<0.01,P<0.01).结论 传统LASIK手术前后角膜非球面形状的Q值变化明显;Q值引导LASIK术后Q值改变相对较少,能保持角膜相对的长椭圆形,即角膜非球面性,提高视觉质量.提示减少Q值的改变能提高和改善视觉质量. Abstract： Objective To investigate the conformation of cornea asphericity.To observe the difference visual acuity between operation with Q value-guide and traditional LASIK and to provide data for improving individuation refractive surgery. Methods One hundred myopic eyes(all left eyes)were divided into two groups, 50 eyes received operation with Q value-guide LASIK and 50 eyes received traditional LASIK since October 2008 to April 2009. To observe visual acuity,refractive error,contrast sensitivity,wavefront aberration, coraea asphericity and vision quality before and after three months of operation. Using the SPSS 12.0 to analyse the data. Results There were significant difference of Q value before and after no Q value guiding LASIK operation(t=31.26,P<0.01).To compare visual acuit (P>0.05) of after operation for Q value guiding LASIK with no Q value guiding LASIK, There was not statistic difference of visual acuity of two groups(χ2 =0.195,P>0.05);The Q value of two groups was higher after operation, But the Q value guiding operation group was lower than the traditional operation groups,there was statistical difference(t=11.86,P<0.01). The spherical aberration was all increased in two groups,but Q value guiding operation group was lower than the standard group,there was statistical difference(t=21.34,P<0.01). Q value group guiding operation was better than the standard group in halo,in glare,night visual acuity,night driving after operation three months,there was statistical difference(P<0.05, P<0.01,P<0.01,P<0.01). Conclusions There are significant differences in Q value after no Q value guide operation;there are less change of Q values after Q value guide operation, it can maintain long-spherical shape of cornea after Q value guide operation, and then raise the visual quality. It indicate that Q value change reduction can enhance and improve the visual quality.     

SMILE与FS-LASIK术后光学区特性比较

目的：比较飞秒激光小切口角膜基质透镜取出术（SMILE）、SCHWIND Amaris1050平台和Wavelight EX500平台的飞秒激光制瓣的准分子激光原位角膜磨镶术（FS-LASIK）单纯近视矫正术后的实际光 学区大小、非球面性和高阶像差。方法：回顾性病例对照研究。选取于2018年1月至2019年1月期 间在广州爱尔眼科医院行近视手术矫正患者，根据手术方式和平台分为SMILE组、Amaris1050组 和EX500组；收集患者术后1、3个月光学区直径、Q值、高阶像差等数据，利用Topolyzer术后切线 曲率图（切线法）和Pentacam术前、术后切线曲率差异图（切线差异法）测量光学区直径。3组间光学 区大小、Q值、高阶像差比较采用ANOVA单因素方差分析，多重比较采用Bonferroni法。2种方法 间比较采用配对样本t检验。结果：共纳入91例（113眼），其中SMILE组42眼，Amaris1050组25眼， EX500组46眼。术后3个月，切线法和切线差异法所测光学区直径SMILE组大于Amaris1050组和 EX500组（均P<0.001），分别为（6.90±0.12）mm和（5.17±0.15）mm，（6.58±0.19）mm和（5.00±0.10） mm，（6.56±0.16）mm和（4.86±0.15）mm；Amaris1050 组切线差异法所测光学区大于EX500 组 （P=0.003）。3组切线法光学区测量值大于切线差异法（t=64.836、34.146、63.927，均P<0.001）；角 膜中央5、6 mm范围Q值，SMILE组小于Amaris1050组和EX500组（5 mm：P=0.017、0.013；6 mm： P=0.004、0.005），Amaris1050组和EX500组差异无统计学意义（P=1.000）；6 mm瞳孔直径下，SMILE 组球差小于Amaris1050组和EX500组（P=0.004、0.017），Amaris1050组和EX500组差异无统计学意 义（P=0.793）。结论：SMILE术后实际光学区大于FS-LASIK，非球面形态优于FS-LASIK，引入球差 更少；再者，SMILE和Amaris1050平台切削深度接近，大于EX500，消耗更多角膜组织。     

Interchangeability of corneal curvature and asphericity measurements provided by three different devices

AIM: To evaluate the interchangeability of keratometric and asphericity measurements provided by three measurement systems based on different optical principles. METHODS: A total of 40 eyes of 40 patients with a mean age of 34.1y were included. In all cases, a corneal curvature analysis was performed with IOL-Master (IOLM), iDesign 2 (ID2), and Sirius systems (SIR). Differences between instruments for flattest (K1) and steepest (K2) keratometric readings, as well as for magnitude and axis of corneal astigmatism were analyzed. Likewise, differences in asphericity (Q) between SIR and ID2 were also evaluated. RESULTS: Mean differences between devices for K1 were 0.20±0.21 (P<0.001), -0.12±0.36 (P=0.046) and -0.32±0.36 D (P<0.001) for the comparisons IOLM-SIR, IOLM-ID2 and SIR-ID2, respectively. The ranges of agreement for these comparisons between instruments were 0.41, 0.70, and 0.70 D. For K2, mean differences were 0.31±0.33 (P<0.001), -0.08±0.43 (P=0.265) and -0.39±0.38 D (P<0.001), with ranges of agreement of 0.65, 0.84, and 0.74 D. Concerning magnitude of astigmatism, ranges of agreement were in the limit of clinical relevance (0.49 D, P=0.011; 0.55 D, P=0.386; 0.43 D, P=0.05). In contrast, ranges of agreement were clinically relevant for astigmatic axis (26.68o, 33.83o and 18.37o, P≥0.121) and for Q between SIR and ID2 (0.16, P<0.001). CONCLUSION: The keratometric corneal power, astigmatic axis and asphericity measurements provide by the three systems evaluated cannot be considered as interchangeable, whereas measurements of corneal astigmatism obtained with SIR and ID2 can be considered as interchangeable for clinical purposes.     

Relationship between corneal topographical changes and subjective myopic reduction in overnight orthokeratology: a retrospective study

Background: To investigate the relationship between the change in the manifest refractive error (ΔM), the change in apical corneal power (ΔACP) and initial corneal asphericity (Q) in overnight orthokeratology (ortho‐K). Methods: One hundred and twenty‐eight clinical records of children undergoing ortho‐K from a university optometry clinic were reviewed. The refractive and topographical data at baseline and at two‐week visit of 58 patients who fulfilled the inclusion criteria were retrieved and analysed. Results: Significant differences (p < 0.001) between the change in manifest refractive error and changes in the apical corneal power or the maximum change in corneal power (ΔMCP) within the treatment zone were found. Linear regression analysis was used to describe the change in manifest refractive error and the change in apical corneal power, and the change in manifest refractive error and the maximum change in corneal power, with the equations: ΔM = 0.91ΔACP + 0.57 (r = 0.78, p < 0.001) and ΔM = 0.93ΔMCP + 0.01 (r = 0.79, p < 0.001) respectively. On average, the change in apical corneal power underestimated the change in manifest refractive error by 0.34 ± 0.57 D; whereas on average, the maximum change in corneal power overestimated the change in manifest refractive error by 0.23 ± 0.57 D (paired‐t‐tests, p < 0.001). A low but significant correlation between initial corneal asphericity and the change in manifest refractive error (Spearman r = ‐0.33, p = 0.01) was observed. Conclusions: The change in apical corneal power underestimates the change in manifest refractive error in ortho‐K, whereas the maximum change in corneal power overestimates this parameter. Compared with retinoscopy and autorefraction, the change in apical corneal power is still useful for estimation of the change in manifest refractive error. Although the maximum change in corneal power appears to give a closer estimation of the change in manifest refractive error than the change in apical corneal power, there is no advantage in the use of maximum corneal power (manually located) instead of apical corneal power (a default given by the topographer) to estimate the change in manifest refractive error, as there is no significant difference in the estimations by either parameter. Initial corneal asphericity measured by the Medmont E300 corneal topographer has limited usage in predicting the change in manifest refractive error in overnight ortho‐K.     

LASIK手术前后近视散光患者角膜前、后表面Q值的变化分析

目的 比较青年近视散光患者在准分子激光原位角膜磨镶术（LASIK）手术前后角膜前、后表面非球面性的分布变化以及可能的影响因素。方法 前瞻性系列病例研究。用ALLEGRO Oculyzer眼前房诊断系统分别在术前和术后1～3个月对北京同仁眼科中心18~39岁的近视散光患者共163例（296眼）进行测量,获得角膜前、后表面20°、25°、30°、35°、40°的Q值（AQ和PQ）及其变化（△AQ和△PQ）,分析其与屈光参数的关系。对手术前后角膜前、后表面不同范围的Q值进行秩和检验,对术后各Q值与患者屈光度、角膜中央厚度、最大切削深度进行直线相关分析。结果 术前角膜各AQ值均与术前柱镜度（CD）呈负相关（r=-0.213、-0.279、-0.332、-0.363、-0.133,P＜0.05）。术后各AQ值与术前差异均有统计学意义（U=38.15、43.94、48.47、44.78、25.97,P＜0.05）,术后各PQ值与术前差异均有统计学意义（U=9.10、10.18、9.77、7.75、3.30,P＜0.05,）。术后△AQ20、△AQ25、△AQ30、△AQ35、△AQ40与术前球镜度（SD)呈正相关（r=0.884、0.870、0.871、0.612、0.370,P＜0.05）,与术前等效球镜度（SE）呈正相关（r=0.834、0.866、0.872、0.625、0.388,P＜0.05）,与最大切削深度（MD）呈正相关（r=0.779、0.823、0.842、0.634、0.403,P＜0.05）,与残留角膜基质厚度（CS）呈负相关（r=-0.332、-0.377、-0.410、-0.352、-0.168,P＜0.05）;△AQ35、△AQ40与术前CD呈正相关（r=0.124、0.120,P＜0.05）。△PQ20、△PQ25、△PQ30与术前SD呈负相关（r=-0.210、-0.185、-0.154,P＜0.05）,与术前SE呈负相关（r=-0.225、-0.196、-0.169,P＜0.05）,与MD呈负相关（r=-0.210、-0.184、-0.164,P＜0.05）。另外△PQ35与术前SD和SE均呈负相关（r=-0.121、-0.124,P＜0.05）,△PQ40与术前SD呈负相关（r=-0.120,P＜0.05）。结论 大多数青年近视散光患者角膜形态前表面为长椭圆形,后表面中央为扁椭圆形,周边为长椭圆形,LASIK术后发生明显改变,均向扁椭圆形方向变化,前表面形态变化更为显著,可能受多种因素的影响。     

Atlas 9000、Orbscan和Pentacam测量近视角膜非球面系数（Q值）的差异和一致性

目的　评价Ａｔｌａｓ９０００、Ｏｒｂｓｃａｎ及Ｐｅｎｔａｃａｍ三种方法测量近视患者角膜非球面系数（Ｑ值）的差异和一致性。方法　横断面比较性研究,随机选取在广西视光中心就诊的成年近视患者４９例（９８眼）,分别应用Ａｔｌａｓ９０００、Ｏｒｂｓｃａｎ及Ｐｅｎｔａｃａｍ测量患者的角膜Ｑ值。采用随机区组设计资料的方差分析（Ｔｗｏ-ｗａｙＡＮＯＶＡ）比较不同仪器测量结果的差异,采用Ｐｅａｒｓｏｎ相关系数分析不同仪器测量结果的相关性,采用Ｂｌａｎｄ-Ａｌｔｍａｎ分析评价不同方法测量结果的一致性。结果　Ａｔｌａｓ９０００、Ｏｒｂｓｃａｎ及Ｐｅｎｔａｃａｍ测得的角膜Ｑ值分别为－０．３４２±０．１３５、－０．３０２±０．１８２和－０．３０５±０．１２０,三种方法测得角膜Ｑ值差异有统计学意义（Ｆ＝５．４６５,Ｐ＝０．００５）,两两比较表明Ａｔｌａｓ９０００与Ｏｒｂｓｃａｎ、Ｐｅｎｔａｃａｍ的检测结果比较差异均有统计学意义（均为Ｐ＜０．０５）,测得负值更大,但Ｏｒｂｓｃａｎ与Ｐｅｎｔａｃａｍ检测结果间比较差异无统计学意义（Ｐ＞０．０５）。Ｐｅａｒｓｏｎ相关分析显示,Ａｔｌａｓ９０００、Ｏｒｂｓｃａｎ与Ｐｅｎｔａｃａｍ测得的角膜Ｑ值之间均有正相关性（均为Ｐ＜０．００１）。Ｂｌａｎｄ-Ａｌｔｍａｎ一致性分析表明Ａｔｌａｓ９０００与Ｐｅｎｔａｃａｍ一致性好。结论　Ａｔｌａｓ９０００、Ｏｒｂｓｃａｎ及Ｐｅｎｔａｃａｍ测量近视患者角膜Ｑ值存在一定差异,但Ａｔｌａｓ９０００与Ｐｅｎｔａｃａｍ的一致性较好,两者可相互参考。     

两种角膜前表面Q值计算方法的实验研究

目的比较正切图公式和弧矢图公式在非球面测试小珠前表面非球面系数（Q值）计算中的差别和准确性。方法自身配对设计。利用莫尔金刚石车削机床加工制作不同前表面形态的非球面测试小珠共24个,用TalySurf粗糙度轮廓仪对其Q值和顶点曲率半径（r0）进行拟合。对24个非球面测试小珠进行Orbscan Ⅱ角膜地形图仪检查。采用配对t检验和Bland-Altman图一致性评价法,比较2种计算方法的准确性和稳定性。结果①用正切曲率半径和弧矢曲率半径计算所得24个非球面测试小珠0°半子午线的r0均值分别为（7.73±0.09）mm、（7.72±0.09）mm,数值上与拟合值[（7.70±0.08）mm]比较接近,但两者与拟合值的差异均有统计学意义（弧矢图：t=2.95,P<0.01;正切图：t=4.45,P<0.01）。②用正切曲率半径和弧矢曲率半径计算所得24个非球面测试小珠0°半子午线的Q值与拟合值的差异均无统计学意义（弧矢图：t=1.61,P＞0.05;正切图：t=-0.87,P＞0.05）。③用正切曲率半径计算所得24个非球面测试小珠的0°半子午线Q值与拟合值之差的均值较弧矢曲率半径更接近0,且95%一致性界限的上下限范围更小。结论用正切曲率半径和弧矢曲率半径计算非球面系数均比较准确,但是用正切曲率半径计算角膜前表面非球面系数较弧矢曲率半径更为稳定。