Refractive properties of the healthy human eye during acute hyperglycemia

PURPOSE: To measure the refractive properties of the healthy human eye during acute hyperglycemia by means of Scheimpflug imaging and Hartmann-Shack aberrometry. METHODS: Acute hyperglycemia was induced in five healthy subjects (two males, three females, mean age +/-SD 24.8 years +/- 4.6) by means of an oral glucose tolerance test (OGTT) after subcutaneous somatostatin injection. Before and every 30 minutes after the OGTT, measurements with Scheimpflug imaging and Hartmann-Shack aberrometry were performed. The main outcome measures were the thickness and shape of the lens, and the ocular refractive error and higher order aberrations. The equivalent refractive index of the lens was calculated from these parameters. Measurements at baseline and during hyperglycemia were analyzed by means of Wilcoxon signed rank sum tests. RESULTS: During hyperglycemia (mean blood glucose level at baseline: 4.0 mmol/l; mean maximal blood glucose level: 18.4 mmol/l) no changes could be found in the refractive properties within the group. In one subject, a hyperopic shift (0.4 D) was observed, together with a more convex shape of the anterior lens surface and a decrease in the equivalent refractive index of the lens. CONCLUSIONS: This study shows that hyperglycemia generally does not cause changes in the refractive properties of the healthy eye. Nevertheless, in one subject a hyperopic shift accompanied by a change in shape and refractive index of the lens was measured. This finding could provide an explanation for the mechanism underlying the refractive changes that are often observed during hyperglycemia.     

The contribution of the fixational eye movements to the variability of the measured ocular aberration

The purpose of this work is to analyze the contribution of eye movements to the variability of the Zernike coefficients as determined with a Hartmann–Shack aberrometer. In order to isolate this effect we considered static aberrations tied to the eye pupil. We used several eye movements of different magnitude, both synthetic and corresponding to actual series recorded in our laboratory with different subjects. Our results show the relevance of the modal coupling induced by the estimation process and the benefit of correcting eye movements in order to get a better estimate of the ocular aberrations. They also show that eye movements during aberrometric measurements are an important source of apparent wavefront variability.     

单纯性近视屈光不正眼高阶像差的观察

目的 观察年龄18～28岁青年人群眼球高阶像差的分布特点以及近视性屈光不正与高阶像差的关系.方法 对42只正视眼和112只单纯性近视眼使用 Hartmann-Shack原理设计的COAS波前像差仪进行波前像差检查,分别提取不同瞳孔直径时高阶像差的均方根(RMS)值,对比分析不同屈光状态组之间的高阶像差的差异性.结果 正视组和近视各组间在3～6mm 瞳孔直径下球差、慧差、三叶草、总高阶像差以及3rd至6th高阶像差差异有统计学意义.5mm和6mm瞳孔直径下,正视组和近视各组球差、三叶草、总高阶像差以及3rd、4th、6th高阶像差差异有统计学意义.瞳孔直径对高阶像差的影响显著,高阶像差随瞳孔变化的趋势表现出不一致性,随着瞳孔直径增大相应增加,总体以3rd和4th像差变化显著.各屈光度组的全眼高阶像差变异度较大,球差、三叶草分布离散程度分别于5mm和6mm瞳孔直径下差异有统计学意义(F=2.74,P=0.0454;F=3.93,P=0.0102).结论 正常人眼的高阶像差个体差异较大,近视的屈光度对高阶像差有一定的影响.     

KR-1W波前像差仪测量人工晶状体眼像差可重复性研究

目的 通过比较两种不同原理像差仪测量人工晶状体( intraocular lens,IOL)眼高阶像差的一致性与可重复性,评价新型KR-1W波前像差仪的临床应用性.方法 临床选取行白内障超声乳化摘除联合单焦点IOL植入术后的患者98例(98只眼).术后第3个月,对患者行两种像差仪的检查,对所有受试眼高阶像差检查重复3次.测量结果采用完全随机资料的方差分析和Pearson相关分析测量结果的一致性;采用重复系数(coefficient of repetbility,CR)作为评价测量的可重复性.结果 两种仪器大部分测量结果的CR值相近,对于角膜和眼内Trefoil的CR值,两种仪器所测结果均高于平均水平.两组的总高阶像差、高阶像差、彗差、三叶草均方根值比较,差异均无统计学意义(P＞0.05).除全眼及眼内trefoil外(r值分别为0.277,0278;P＞0.05),各数值之间均有线性相关性(P＜0.05).其中两种仪器测量全眼及眼内HOA结果的相关性最强.结论 KR-1W、iTrace两种像差仪测量IOL眼像差结果存在部分差异,但均无统计学意义.KR-1W系统测量IOL眼高阶像差具有很高的重复性,具有较好的临床应用价值.     

自适应光学在眼科屈光手术中的应用

自适应光学理论中的哈特曼-夏克(Hartmann-Shack)波前传感技术是实时测量人眼睛波前像差的有效、可靠和准确的方法.而利用所得到的波前像差数据引导进行的"个体化"角膜屈光手术能明显减少手术后眼睛屈光系统的高阶像差,提高眼睛的成像质量和视觉灵敏度.     

Intensity Analysis of Hartmann-Shack Images in Cataractous, Keratoconic, and Normal Eyes to Investigate Light Scattering

Purpose

A clinical investigation of novel methods for evaluating light scattering using a Hartmann-Shack aberrometer.

Methods

Aberrometry was performed on normal eyes (n = 7; patient age, 26.7 ± 2.5 years, mean ± SD), eyes with keratoconus (n = 22; patient age, 26.1 ± 8.1 years), and eyes with cataract (n = 17; patient age, 56.5 ± 16.9 years) using a Hartmann-Shack wavefront aberrometer. We introduced two methods: (1) a contrast method, in which we calculated the inverse of contrast of the local images around 12 spots in a Hartmann-Shack image, and (2) a difference of point spread function (PSF) method, in which we analyzed the difference between the width of the PSF computed with aberration information and the width of the measured PSF, which contains both aberration and light scattering information.

Results

The inverse contrast in cataractous eyes (5.04 ± 3.06 inverse contrast units) was significantly larger than that in normal eyes (1.57 ± 0.56) or keratoconic eyes (1.83 ± 0.79). The difference of PSF in cataractous eyes (81.8 ± 65.2?μm) was also significantly larger than that in normal eyes (9.3 ± 4.3?μm) or keratoconic eyes (30.0 ± 20.1?μm). The inverse contrast and the difference in the PSF were highly correlated (r = 0.89, P < 0.0001).

Conclusions

The two methods introduced here successfully distinguished cataractous eyes from normal and keratoconic eyes. After the results were analyzed by a discriminant analysis, the separation of the three categories proved to be excellent.?Jpn J Ophthalmol 2006;50:323–333 © Japanese Ophthalmological Society 2006     

Comparison of aberrations in different types of progressive power lenses

Recently, computer numerically controlled machines have permitted the manufacture of progressive power lenses (PPLs) with different designs. However, the possible differences in optical performance among lens designs are not yet well established. In this work, the spatially resolved aberrations, at 20 relevant locations, of three PPLs with different designs were measured with a Hartmann-Shack wavefront sensor. The wavefront aberration (WA), its root mean square error (RMS) and the point-spread function were obtained. Spatially resolved plots are shown for all aberrations, astigmatism alone, and for higher order aberrations. The average RMS of all zones is also compared, and the standard deviation is used as a parameter to evaluate the level of hard-soft design. We find differences in the spatial distribution of the aberrations but not in the global RMS, indicating that current PPLs are rather similar to a waterbed, with the aberrations being the water: they can be moved but they cannot be eliminated.     

不同原理波前像差仪测量人工晶状体眼像差的比较

目的 比较激光光束追踪（laser ray tracing,LRT）、Hartmann-Shack（H-S）感受器以及空间分辨折射仪 （spatially resolved refractometer,SRR）三种不同像差仪测量人工晶状体（intraocular lens,IOL）眼像差的差异。方法 临床选取行白内障超声乳化摘除联合IOL植入术后的患者24例（34眼）。年龄为50～80岁,最佳矫正视力≥4.9。暗室条件下瞳孔直径均为5 mm。术后第3个月,对患者行三种像差仪的检查,顺序不定,测量结果采用完全随机资料的方差分析和秩和检验进行统计学方法。结果 三组的总像差、高阶像差、彗差、三叶草以及2～6阶像差的均方根值比较,差异均无统计学意义（P〉0.05）;LRT组与SRR组球差的均方根值差异有统计学意义（t=2.29,P〈0.05）。Zernike系数的比较：Z3项LRT组与H-S组,H-S组与SRR组间差异有统计学意义（P〈0.05）;Z4项三组间差异均有统计学意义（P〈0.05）;Z6项和Z12项H-S组与SRR组间差异有统计学意义（P〈0.05）;Z11项和Z20项LRT组与SRR组间差异有统计学意义（P〈0.05）;其余Zernike系数比较,差异均无统计学意义（P〉0.05）。结论 LRT、H-S和SRR三种像差仪测量IOL眼像差结果存在部分差异。每种仪器都有各自的优缺点,使用时应根据不同的目的选用适合的波前像差仪。     

基于模型眼的球面人工晶状体单色像差分析

目的运用基于Hartmann-Shack原理的模型眼来评价球面人工晶状体（IOL）单色像差。方法前瞻性研究。本研究分为2个部分。①选取SA60AT（美国Alcon公司）系列IOL 5片,屈光度分别为+10、+15、+20、+25、+30 D;②选取IOL 3片,屈光度均为+20 D,分别为SA60AT、Akreos Adapt（美国博士伦公司）、AR40e（美国AMO公司）。搭建模型眼光路,将待测IOL置于光路中,以电子耦合设备（CCD）图像传感器接受像点,测出在436、486、525、546、589、660、710 nm不同波长下的像点图,经Matlab软件进行处理,采用双因素Pearson相关分析及单因素方差分析评价IOL的单色像差。结果第一部分：SA60AT系列IOL的球差（Z12,r=0.599,P<0.05）、垂直彗差（Z7,r=0.817,P<0.05）、水平彗差（Z8,r=0.488,P<0.05）与屈光度呈正相关,总高阶像差均方根值（RMSh）与屈光度不相关（r=0.007,P>0.05）;波长与球差（r=-0.213,P>0.05）、垂直彗差（r=-0.074,P>0.05）、水平彗差（r=0.021,P>0.05）及RMSh（r=-0.322,P>0.05）均不相关。第二部分：3种IOL的球差（F=74.637,P<0.05）、水平彗差（F=6.719,P<0.05）及RMSh（F=11.768,P<0.05）差异有统计学意义,垂直彗差差异无统计学意义（F=1.295,P>0.05）,AR40e的球差、水平彗差及RMSh相对最小;波长与各IOL的球差（r=0.007,P>0.05）、垂直彗差（r=-0.312,P>0.05）、水平彗差（r=-0.238,P>0.05）及RMSh（r=0.246,P>0.05）均不相关。结论利用Hartmann-Shack原理设计的模型眼可以便捷地检测IOL的单色像差,为临床上IOL的选择及其光学设计的改进提供了参考依据。     

Tear Film Break-up Time Evaluated by Real-Time Hartmann-Shack Wavefront Sensing

Purpose

To develop a novel method for measuring tear break-up time (BUT) by continuously measuring higher order wavefront aberrations using a Hartmann-Shack (H-S) aberrometer.

Methods

Wavefront aberrations up to the sixth order for a 4-mm pupil were measured in six eyes of six normal subjects using an H-S aberrometer. The aberrometry was performed once every second for up to 50?s under topical anesthesia. The sequence of the points was divided into two stages, and the BUT was defined as the wavefront border of the stages (WFBUT). The WFBUT was compared with the BUT by the conventional fluorescein method (FLBUT) or by the disruption of placid-ring images (PLBUT).

Results

In three eyes, the WFBUT (average, 10.9 ± 1.1?s) was shorter than the PLBUT (average, 17.5 ± 2.5?s), while in the other three eyes the WFBUT (average, 21.5 ± 2.2?s) was longer than PLBUT (average, 8.1 ± 2.2?s). The FLBUT was shorter than WFBUT or PLBUT in most cases.

Conclusions

The tear break-up time measured by H-S aberrometer may be used as a practical measure of tear break-up.?Jpn J Ophthalmol 2006;50:85–89 © Japanese Ophthalmological Society 2006