Unbiased estimation of refractive state of aberrated eyes

We seek unbiased methods for estimating the target vergence required to maximize visual acuity based on wavefront aberration measurements. Experiments were designed to minimize the impact of confounding factors that have hampered previous research. Objective wavefront refractions and subjective acuity refractions were obtained for the same monochromatic wavelength. Accommodation and pupil fluctuations were eliminated by cycloplegia. Unbiased subjective refractions that maximize visual acuity for high contrast letters were performed with a computer controlled forced choice staircase procedure, using 0.125 diopter steps of defocus. All experiments were performed for two pupil diameters (3 mm and 6 mm). As reported in the literature, subjective refractive error does not change appreciably when the pupil dilates. For 3 mm pupils most metrics yielded objective refractions that were about 0.1 D more hyperopic than subjective acuity refractions. When pupil diameter increased to 6 mm, this bias changed in the myopic direction and the variability between metrics also increased. These inaccuracies were small compared to the precision of the measurements, which implies that most metrics provided unbiased estimates of refractive state for medium and large pupils. Thus a variety of image quality metrics may be used to determine ocular refractive state for monochromatic (635 nm) light, thereby achieving accurate results without the need for empirical correction factors.     

Image metrics for predicting subjective image quality.

PURPOSE: Despite the proliferation of wavefront sensors to characterize the optical quality of individual eyes, there is not yet an accurate way to determine from a wave aberration how severely it will impact the patient's vision. Some of the most commonly used metrics, such as RMS wavefront error and the Strehl ratio, predict subjective image quality poorly. Our goal is to establish a better metric to predict subjective image quality from the wave aberration. METHODS: We describe three kinds of experiments designed to compare the effectiveness of different metrics in determining the subjective impact of the wave aberration. Subjects viewed a visual stimulus through a deformable mirror in an adaptive optics system that compensated for the subject's wave aberration. In the first experiment, we show that some Zernike modes such as spherical aberration and defocus interact strongly in determining subjective image quality. In the second experiment, the subject's wave aberration was replaced by the wave aberration corresponding to an individual Zernike mode. The subject then adjusted the coefficient of the Zernike mode to match the blur of a standard stimulus. In the third experiment, the subject viewed the same stimulus through the wave aberration of one of 59 different postoperative patients who had undergone LASIK and matched the blur by adjusting defocus. We then determined which among many image quality metrics best predicted these matching data. RESULTS: RMS wavefront error was a poor predictor of the data, as was the Strehl ratio. CONCLUSIONS: The neural sharpness metric best described the subjective sharpness of images viewed through the wave aberrations of real eyes. This metric can provide a single number that describes the subjective impact of each patient's wave aberration and will also increase the accuracy of refraction estimates from wavefront-based autorefractors and phoropters.     

The precision of wavefront refraction compared to subjective refraction and autorefraction.

PURPOSE: To determine the precision (repeatability) of several methods of calculating refraction from higher-order wavefront aberration data and to compare these wavefront refractions with lower-order (LO) wavefront refraction, subjective refraction, and autorefraction. METHODS: Four clinicians refracted 16 normal participants aged 23.6 +/- 1.2 years, 69% female with an average spherical equivalent refractive error of -3.03 +/- 2.55 D, median sphere -2.50 D (minimum -7.50, maximum +4.75), and median cylinder -0.50 D (minimum -3.00, maximum 0). Participants were cyclopleged and underwent subjective refraction, autorefraction on two machines (Nidek AR-800, Topcon KR-8000), and wavefront sensing using the Wavefront Sciences Complete Ophthalmic Analysis System. Wavefront error was used to calculate: LO refraction, refractions that incorporated higher-order spherical and astigmatism terms from up to the 4th, 6th, and 10th orders (PCM4, PCM6, and PCM10), and a method based on optimizing image quality metrics [wavefront analysis technology (WAT) refraction]. Within and between examiner agreements for total dioptric difference were determined using Bland-Altman limits of agreement (LOA). RESULTS: The interexaminer LOA for individual measurements for M, J0, J45 were: Topcon (+/-0.18, +/-0.10, +/-0.06), Nidek (+/-0.28, +/-0.16, +/-0.09), LO (+/-0.17, +/-0.10, +/-0.06), PCM4 (+/-0.26, +/-0.09, +/-0.06), PCM6 (+/-0.37, +/-0.17, +/-0.34), PCM10 (+/-0.54, +/-0.32, +/-0.40), WAT (+/-0.28, +/-0.20, +/-0.15), and subjective refraction (+/-0.48, +/-0.20, +/-0.13) and averaging across three measures LOA: Topcon (+/-0.15, +/-0.08, +/-0.05), Nidek (+/-0.21, +/-0.13, +/-0.07), LO (+/-0.12, +/-0.06, +/-0.04), PCM4 (+/-0.16, +/-0.05, +/-0.04), PCM6 (+/-0.23, +/-0.09, +/-0.19), PCM10 (+/-0.29, +/-0.19, +/-0.24), and WAT (+/-0.18, +/-0.12, +/-0.10). The within-examiner LOA for M, J0, J45 were: Topcon (+/-0.08, +/-0.04, +/-0.02), Nidek (+/-0.13, +/-0.07, +/-0.05 D), LO (+/-0.11, +/-0.07, +/-0.04), PCM4 (+/-0.17, +/-0.07, +/-0.04 D), PCM6 (+/-0.28, +/-0.12, +/-0.24 D), PCM10 (+/-0.42, +/-0.24, +/-0.32 D), and WAT (+/-0.19, +/-0.14, +/-0.09 D). CONCLUSIONS: All objective refractions except for PCM10 were more repeatable across clinicians than subjective refraction. The precision of all refractions were improved by an expected amount through averaging over multiple measurements. Wavefront refractions were not as precise as standard autorefractions, although not clinically significantly worse.     

In vivo and in vitro repeatability of Hartmann-Shack aberrometry

PURPOSE: To assess the in vivo and in vitro repeatability of objective refraction and higher-order aberrations (HOAs) measured by a commercially available Hartmann-Shack wavefront sensor. SETTING: Department of Ophthalmology, Johann-Wolfgang-Goethe University, Frankfurt am Main, Germany. METHODS: After pupil dilation of 40 myopic or myopic, astigmatic eyes of 20 patients, wavefront measurements were performed 6 times in each eye and in a test object provided by the manufacturer by 2 experienced examiners using a Hartmann-Shack wavefront sensor (Zywave, software version 3.21, Bausch & Lomb). The mean standard deviation (SD) and the coefficient of variation (CV) for sphere, cylinder, and each Zernike polynomial were computed for a 7.0 mm pupil diameter. Vector analysis was performed for the astigmatism. After the data were subdivided into 2 groups with 3 measurements in each, one measurement that best matched the subjective manifest refraction was chosen in each group and the difference between them was calculated. RESULTS: The mean SD (CV) was 0.15 diopter (D) (7%) for the sphere value of the predicted phoropter refraction and 0.16 D (22%) for astigmatism. Thirty-two eyes had an axis deviation of at least 10 degrees. Vector analysis revealed a mean SD of 0.24@109.8. Other results for mean SD and mean CV were as follows: total in vivo higher-order RMS, 0.097 microm, 13.4%; sphere in myopic test device, 0.034 D, 0.65%; sphere in hyperopic test object, 0.035 D, 0.72%. The difference between the 2 best-matched refractions was significantly different from zero (0.11 D, P<.001). The CV was significantly higher for HOAs than for the 2nd-order aberrations (defocus and astigmatism). CONCLUSIONS: Repeatability of Hartmann-Shack aberrometry by the Zywave wavefront sensor was not satisfactory, particularly for small amounts of HOAs. Under these conditions, aberrometry measurements should be repeated several times and outliers should be excluded in calculating the means.     

显然验光与不同瞳孔直径下波前像差验光的比较

目的采用波前像差仪进行客观验光,比较分析显然验光与不同瞳孔直径下含有不同高阶成分的波前像差验光的关系。方法横断面研究。选取近视及近视散光患者31例（62眼）,利用基于Hartmann．Shack原理的波前传感系统进行波前像差测量。根据所测数据计算出不同瞳孔直径下仅有离焦的屈光度,包含离焦及球差的屈光度和含有离焦、球差及二级球差的屈光度．并应用Friedman检验分析临床显然验光与这些波前像差验光屈光度的关系。结果2、3、4、5、6mm直径瞳孔下的波前客观屈光度分别与临床显然验光屈光度比较,仅含有离焦时的屈光度差异最小,球镜度差异的中位数分别为－0．540、－0．473、－0．422、－0．407、－0．290D,差异具有统计学意义（Z=99．29,P〈0．01）;柱镜度差异的中位数分别为0．193、0．142、0．119、0．078、0．065D,差异具有统计学意义（Z=30．25,P〈0．01）;平均散光轴差异的中位数分别为-2．41、-2．89、-3．03、-1．94、-2．40°,差异无统计学意义（Z=4．42,P〉0．05）。含有高阶成分的屈光度与临床显然验光差异较大。结论由波前像差计算得到的屈光度与瞳孔直径和高阶像差参与的多少有关。纳入较高阶球差后等效屈光度降低,较大瞳孔直径下无高阶像差参与的波前屈光度与临床显然验光较接近。波前验光散光轴向与主觉验光较接近。     

Effect of pharmacologic pupil dilation with tropicamide and phenylephrine on wavefront measurements

PurposeTo investigate the influence of tropicamide 1% (as a cycloplegic mydriatic) and phenylephrine 10% (as a noncycloplegic mydriatic) on mydriasis, wavefront refraction, and wavefront aberrations.MethodsIn this prospective study, 31 myopic eyes with a large mesopic pupil size were evaluated with an Allegretto Wave analyzer in a natural dilated state, after instillation of tropicamide 1% or phenylephrine 10%. Aberrations expressed as Zernike polynomials up to the sixth order were analyzed. Wavefront refractions were compared with subjective manifest refraction.ResultsBoth tropicamide and phenylephrine cause significant mydriasis (p < 0.001), but phenylephrine induced a larger pupil size than tropicamide under mesopic conditions (p = 0.029). Compared with the natural state, tropicamide induced a significant hyperopic shift in wavefront refraction (by +0.27 ± 0.09 D; p = 0.002). In contrast, wavefront refraction did not significantly change when using phenylephrine as the mydriatic (+0.03 ± 0.10 D; p = 0.75). Compared with the subjective manifest refraction, wavefront refraction before mydriatics and after phenylephrine showed a significant myopic shift (p < 0.0125), whereas the wavefront refraction after tropicamide was not significantly different from subjective refraction. Zernike coefficient C4 showed a less positive defocus after application of tropicamide (p = 0.0017). Other aberration coefficients of Zernike polynomials up to the sixth order did not change significantly from before to after tropicamide application. There was no significant difference in Zernike coefficients up to C27 before and after phenylephrine.ConclusionPhenylephrine preserves accommodation and provides a larger pupil under mesopic conditions, whereas tropicamide relaxes accommodation and provides an objective wavefront refraction that is closer to the subjective manifest refraction. Neither phenylephrine nor tropicamide causes a significant change in high-order aberrations from the natural state.     

Method of determining a patient's subjective refraction based on objective measurement

PURPOSE: To develop a method for predicting the manifest refraction from objective measurement using wavefront sensing. We tested the hypothesis that, when the eye has an optimal refractive correction, the refractive power of the eye is in the most stable state, with the least fluctuation in its total optical aberration and hence least amount of standard deviation in the wavefront error. METHODS: Nine patients were enrolled in this study. All measurements were performed using a grating-based wavefront instrument manufactured by Ophthonix, Inc. The test procedure involved adding defocus power binocularly in the line of sight of the patient. Five added diopter powers were used: plano (no add), +1.00 D, +0.50 D, -0.50 D, and -1.00 D. The eyes were undilated, and the measurement was taken at a single added defocus power each day over 5 days. The patients had a binocular view and were asked to focus on a picture at 20 feet. Manifest refraction was used as the reference point (the +/- added powers are relative to this "plano" power). RESULTS: For each patient, the standard deviation (STDEV) of the total root mean square values of the wavefront measurement were used as a measure of vision fluctuation. Spherical equivalent manifest refraction was tested against the added defocus as a measure of the method's predictability. Graphic plots of standard deviation of the total wavefront error against the added diopter power showed that the minima of the vision fluctuation from the data sets were within -0.10 and +0.30 D (95% limit of agreement). The mean difference between the manifest refraction and the most stable point of vision was 0.14 D. CONCLUSIONS: The preliminary results of 10 eyes show promise that using an objective method of monitoring vision fluctuation may produce good agreement with the manifest refraction. The method should be further validated using a smaller step of added defocus and involving a larger number of test subjects representing a sample of the general population.     

Objective refraction from monochromatic wavefront aberrations via Zernike power polynomials

With the increased popularity of wavefront sensor devices there has been significant interest in relating the subjectively measured sphero-cylindrical refractive error to the objectively measured wavefront aberrations. We investigate the applicability of four different measures for objective refraction assessment that are derived from a set of estimated Zernike wavefront coefficients. Two of the measures are based on the second- and higher-order Zernike polynomials while the other two measures are based on the estimated dioptric power representations. For the latter, closed-form expressions for dioptric powers based on the estimated focal length and the wavefront curvature are derived. We call these two new representations the 'refractive Zernike power polynomials' and 'curvature Zernike power polynomials'. Data from 120 eyes from 60 normal subjects were used to assess the correlation between the subjective and objective refractions. The results indicate that the objective sphero-cylindrical refraction calculated from the estimated refractive power map via the Zernike power polynomials is superior to the other considered representations and achieves best correlation with subjective sphero-cylindrical refraction.     

Intraoperative wavefront monitoring during laser thermal keratoplasty

PURPOSE: Low energy laser thermal keratoplasty (LTK) is being proposed as an alternative to conventional holmium LTK in an effort to minimize corneal tissue necrosis, regression, and induced astigmatism. Real-time wavefront monitoring during surgery is also being proposed as a method for regulating induced aberrations and the treatment end point. We evaluated the feasibility of intraoperative wavefront monitoring during low energy LTK. METHODS: An investigational prototype system combining a Sunrise Hyperion laser with a Shack-Hartmann wavefront sensor (Wavefront Sciences COAS) was used to treat 20 hyperopic eyes with a low energy application of eight spots of 18mJ/shot (144mJ/pulse) at 5 Hz in two rings of 6 mm and 7-mm diameter, while monitoring the treatment with real-time dynamic wavefront sensing up to 10 captures/second of 4th order Zernike data. RESULTS: The integrated wavefront-monitored LTK unit showed good stability in measuring dynamic intraoperative wavefront refractions before, during, and after the low energy LTK treatment. The readings did not interfere with the application of holmium laser pulses, nor did the LTK treatment distort the captured wavefront readings. A steady improvement of the wavefront-derived spherical equivalent refraction followed the laser treatment pattern, with a mean attempted spherical equivalent refractive change of 1.66 D and mean achieved change of 1.71 D. CONCLUSION: Intraoperative wavefront monitoring was feasible during low energy LTK. With future adaptation, it might be possible to dynamically relay the captured wavefront information to the laser during ongoing treatment, to intraoperatively control the surgical endpoint for multiple aberration terms.     

近视眼患者波前像差的分析研究

目的：对近视眼患者存在的波前像差进行相关因素分析。 方法：用波前像差仪对前来我院行LASIK手术的115例218眼进行波前像差的检查,并进行常规角膜屈光手术的各项术前检查,同时用对比敏感度检查表进行对比敏感度的检查,将各项结果分别与波前像差进行相关性分析。 结果：像差成分以低阶像差为主,高阶像差有明显的个体差异,最大值是最小值的62倍;术前像差和瞳孔直径呈正相关关系,即随着瞳孔直径的增加高阶像差增加;高阶像差与中频区对比敏感度存在弱的负相关性;波前像差和患者的屈光度的高低有关系;随着散光度数的增加,波前像差增加。术前像差各成分和性别无显著相关性。 结论：近视眼患者的波前像差受患者具体条件的影响,个性化手术去除波前像差应考虑周全。     

LADARWave wavefront measurement in normal eyes

PURPOSE: We evaluated the correlation of Alcon LADARWave wavefront measurements with clinical refraction and corneal topography. METHODS: In a retrospective, non-comparative case series, 60 eyes (30 patients) of healthy individuals evaluated by preoperative examination for refractive surgery were enrolled (manifest sphere, -11.00 to +4.50 D; manifest cylinder, 0 to -4.75 D; 45 eyes were myopic, 12 eyes were hyperopic, and 3 had mixed astigmatism). Correlation of manifest refraction, cycloplegic refraction, and topographic data with wavefront refraction and higher order aberration was assessed. Match percentage given by the wavefront was analyzed. This number represents how much of the wavefront refraction is due to sphere and cylinder (high percentage match) or is influenced by higher order aberration (low percentage match), in which case aberrometer refraction will not be close to phoropter refraction. Pearson's correlation coefficient was assessed for two continuous variables, adjusting for repeated measurements. RESULTS: The median match percentage was 91%. Mean values for all higher order aberration components in a 7.0-mm pupil were: coma = 0.35 +/- 0.29 microm, spherical aberrations = 0.36 +/- 0.31 microm, and other terms of higher order aberrations = 0.31 +/- 0.14 microm. Wavefront sphere, cylinder, and axis terms were highly correlated to manifest and cycloplegic measurements. The high match subgroup had a higher correlation coefficient than the low match subgroup for refraction. Topographic cylinder and axis were not strongly correlated to wavefront refraction, but manifest axis was significantly correlated to topographic axis. CONCLUSION: In 60 normal eyes, the Alcon LADARWave wavefront measurement was highly correlated with refraction, but less well with corneal topography.     

Optical quality of the eye after lens replacement with a pseudoaccommodating intraocular lens

PURPOSE: To examine the optical quality of healthy presbyopic eyes before and after implantation of the pseudoaccommodating AcrySof ReSTOR Natural intraocular lens (IOL) (Alcon Laboratories) by measuring visual acuity and wavefront aberrations. SETTING: University of Valencia, Fernández-Vega Ophthalmological Institute, Valencia, Spain. METHODS: Monocular refraction and photopic distance (6 m) and near (0.33 m) visual acuities were determined before and after clear lens extraction with bilateral AcrySof ReSTOR Natural IOL implantation in 30 hyperopic eyes (+0.50 to +4.00 diopters [D]) of presbyopic patients with low astigmatism (< or = 1.00 D). Postsurgical binocular visual acuity was measured over a range of effective distances. Wavefront aberrations were measured before and after surgery. Aberrations for 2 pupil diameters (3.0 mm and 5.0 mm) were decomposed using Zernike polynomials; total, defocus, astigmatism spherical, and coma aberration terms were studied separately. Postimplantation results were compared with preoperative values. RESULTS: Safety and efficacy indices for distance vision were 1.01 and 0.96, respectively. At near, they improved to 1.07 and 1.06, respectively. Vision at intermediate distances was noticeably poorer. Total, defocus, and spherical aberrations changed after IOL implantation with both pupil diameters (P<.01). Total and defocus aberrations were significantly reduced postoperatively. Spherical aberration coefficients changed to negative and less positive values for a 3.0 mm and a 5.0 mm pupil, respectively. CONCLUSIONS: Implantation of the pseudoaccommodating IOL in healthy eyes yielded uncorrected levels of high-contrast, distance, and near acuities comparable to preoperative best corrected values. Higher-order aberration levels appeared to be similar to the preoperative values.     

Corneal wavefront-guided ablation with the Schwind ESIRIS laser for myopia

PURPOSE: To evaluate the outcome of corneal wavefront-guided LASIK for the treatment of myopia and myopic astigmatism. METHODS: This study included 56 myopic virgin eyes of 28 patients with a mean spherical equivalent refraction of -4.40 +/- 1.83 diopters (D) (range: -1.25 to -9.75 D) and astigmatism < 2.50 D. The corneal wavefront aberrations were analyzed using a corneal topography system. The preoperative corneal wavefront aberration data obtained from the above analyses combined with manifest refraction were used to generate a customized ablation profile. The safety, efficacy, and predictability of the correction, contrast sensitivity, and corneal higher order wavefront aberrations were evaluated. RESULTS: At 1-year follow-up, the mean residual spherical equivalent refractive error was -0.15 +/- 0.3 D (range: 0 to -1.25 D) and mean cylinder was -0.54 +/- 0.34 D (range: 0 to -1.50 D). Ninety-five percent of eyes were in the residual refractive error range of +/- 0.50 D and uncorrected visual acuity improved by 1.00 D or better in 94% of eyes. The safety index and efficacy index were 1.13 and 0.92, respectively. After treatment, corneal higher order wavefront aberrations with a 6-mm pupil diameter increased significantly (paired sample t test, P < .01), and contrast sensitivity with glare had small reductions at high spatial frequencies. Changes in spherical-like aberration (R = 0.708, P < .001) and higher order wavefront aberration (R = 0.449, P = .001), except for coma-like aberration (P = .238), were positively correlated with the amount of achieved correction. CONCLUSIONS: Evaluation of clinical results showed that corneal wavefront-guided LASIK for the correction of myopia and myopic astigmatism was safe and effective. There was an increase in all higher order aberrations postoperatively.     

The effect of phenylephrine and cyclopentolate on objective wavefront measurements

PURPOSE: To investigate the impact of phenylephrine and cyclopentolate on wavefront refraction and fourth order spherical aberration C12. METHODS: This cohort study comprised 151 eyes with sphere up to -10.00 diopters (D) and cylinder -3.75 D. Aberrometry was performed using the ALLEGRO WAVE (WaveLight Laser Technologies AG, Erlangen, Germany) after instillation of phenylephrine 5% yielding objective phenylephrine refraction in accommodated steady-state, as well as after cyclopentolate 0.5% providing objective cyclopentolate refraction in non-accommodated state. Accommodation target fogging was turned off. Wavefront aberrations were expressed by Zernike expansion up to the sixth order, and paraxial curvature matching with Taylor series was used to calculate objective wavefront sphere. RESULTS: Objective wavefront sphere was not influenced by pupil size. Eyes showed substantial accommodation after phenylephrine with a myopic shift of -0.66 D comparing objective to subjective manifest sphere (r=0.942, P<.001). Cycloplegic eyes behaved like a model eye, with a difference of -0.08 D between objective and subjective cycloplegic sphere (r=0.976, P<.001). C12 increased ten-fold from 4.0- to 7.0-mm pupil size, keeping the same sign. Comparing cyclopentolate with phenylephrine, the sign of C12 changed in a positive direction by an average +0.124 +/- 0.109 microm (range: -0.052 to +0.632 microm) at 7.0 mm, whereas the total higher order aberrations changed very little. A good correlation was found between C12 and the change in objective wavefront sphere between cyclopentolate and phenylephrine (r=0.75, P<.001). CONCLUSIONS: Fogging of the accommodation target should be used for wavefront measurements. Weaker cycloplegic agents, such as tropicamide, may be used to ensure relaxed but not completely paralyzed accommodation, which would yield "manifest" aberration values close to the natural resting state.     

主觉波前像差仪引导准分子激光角膜原位磨镶术

目的前瞻研究主觉式像差仪引导的准分子激光角膜原位磨镶术的临床效果。方法对主觉像差仪检查与术前验光结果一致的患者随机分成2组,实验组以主觉波前像差仪引导LASIK手术,对照组进行传统LASIK手术。前瞻分析2组术后1周、3月屈光状况、裸眼视力,以及3月高阶波前像差总的均方根RMS。结果符合研究标准的共有86例,实验组为43例85眼,男∶女为22∶21;对照组共43例84眼。术后1周和3月2组视力和屈光状况无差异(P>0.05)。但实验组RMS增加较对照组明显小(P<0.05)。结论波前像差引导的个体化切削可以减少LASIK术后像差增加,改善视觉质量。     

基于矢量分解的验光法与常规主觉验光法应用于不同程度散光的比较研究

目的 比较矢量分解验光法和常规主觉验光法在不同程度散光下的应用.方法 共纳入143名被检者的143只右眼,根据散光度数0～1.50 D和散光度数＞1.50～3.00 D分为低散光组和高散光组,被检者先后接受两名视光医师的使用矢量分解验光法和常规主觉验光法获取验光数据,比较等效球镜M分量、J0分量、J45分量以及验光时长的差异.结果 高、低散光组间的年龄、性别、M分量、J45分量和常规主觉验光耗时差异均没有统计学意义(均为P＞0.05),两组间的常规主觉J0和矢量验光J0差异均有统计学意义(均为P=0.00).低散光组中,分别使用常规主觉验光和矢量验光法所测得的M、J0和J45一致性较好,差值绝对值的平均值分别为0.04D、0.02D和0.02D,一致性界限范围内,常规主觉验光和矢量验光的差值绝对值最大分别为0.37 D、0.13D和0.17 D,且验光时长差异无统计学意义(P=0.72).高散光组中,分别使用常规主觉验光和矢量验光法所测得的M、J0和j45一致性较差,差值绝对值的平均值分别为0.43 D、0.21 D和0.00D,一致性界限范围内,常规主觉和矢量验光的差值绝对值最大分别为0.75 D、0.50 D和0.30 D,且验光时长差异有统计学意义(P=0.00),矢量验光法耗时较长.结论 目前的矢量分解验光法只在针对较低的散光时有较好的表现,需要对其进一步完善,使其能较好地应用于临床.     

Assessment of objective and subjective eccentric refraction.

PURPOSE: When performing perimetry, refracting subjects with central visual field loss, and in emmetropization studies, it is important to accurately measure peripheral refractive errors. Traditional methods for foveal refraction often give uncertain results in eccentric angles as a result of the large aberrations and the reduced retinal function. The aim of this study is therefore to compare and evaluate four methods for eccentric refraction. METHODS: Four eccentric methods were tested on 50 healthy subjects: one novel subjective procedure, optimizing the detection contrast sensitivity with different trial lenses, and three objective ones: photorefraction with a PowerRefractor, wavefront measurements with a Hartmann-Shack sensor, and retinoscopy. The peripheral refractive error in the horizontal nasal visual field of the right eye was measured in 20 degrees and 30 degrees. RESULTS: In general, the eccentric refraction methods compared reasonably well. However, the following differences were noted. Retinoscopy showed a significant difference from the other methods in the axis of astigmatism. In 30 degree eccentric angle, it was not possible to measure 15 of the subjects with the PowerRefractor and the instrument also tended to underestimate high myopia (<-6 D). The Hartmann-Shack sensor showed a myopic shift of approximately 0.5 D in both eccentricities. The subjective method had a relatively larger spread. CONCLUSIONS: This study indicates that it is possible to assess the eccentric refraction with all methods. However, the Hartmann-Shack technique was found to be the most useful method. The agreement between the objective methods and the subjective eccentric refraction shows that detection contrast sensitivity in the periphery is affected by relatively small amounts of defocus.     

A method to predict refractive errors from wave aberration data.

We explored the impact of the eye's higher-order aberrations on subjective refraction comparing two classes of methods for estimating refractive state, one based directly on the wave aberration defined in the pupil plane and another based on the retinal image plane. The method defined in the pupil plane chose the sphere and cylinder that either minimized the wave aberration root mean square or minimized the sum of all the spherical and cylindrical components in the wave aberration. The method defined in the image plane chose the sphere and cylinder that optimized an image-quality metric such as the Strehl intensity ratio, the entropy and the intensity variance of the point-spread function, the volume under the modulation transfer function, or the volume under the contrast-sensitivity function. All these methods were compared in a population of six eyes for which we measured both the wave aberration with a Shack-Hartmann wavefront sensor and the subjective refraction under identical conditions. Pupil plane methods predicted subjective refraction poorly. The mean absolute error of the prediction, in spherical equivalent, was about 0.5 D (range, 0.1 to 0.8 D) and increased with increases in higher-order aberrations. However, for all the retinal image plane methods, the mean error between predicted and subjective refraction was about 0.1 D (range, 0 to 0.25 D). The reliability of the method based on the image-quality optimization was further confirmed in a large population of 146 eyes. In conclusion, higher-order aberrations influence the amount of sphere and cylinder required to correct vision. The results indicate that subjective refraction can be predicted from the eye's optics alone by optimizing computed retinal image quality.     

Comparison of objective and subjective refraction before and after laser in situ keratomileusis.

PURPOSE: To compare the accuracy and reliability of objective and subjective refractions before and after laser in situ keratomileusis (LASIK) for myopia, hyperopia, and astigmatism. SETTING: Augenchirurgie und Laserzentrum Hochrum, Innsbruck, Austria. METHODS: In this prospective study, the objective refraction obtained with the Nidek AR-K 900 autorefractor was compared with the subjective refraction in 159 eyes (125 with myopia and 34 with hyperopia) operated on with 2 different lasers. Refractions were done before and 6 months after LASIK. RESULTS: Preoperatively, the objective and subjective refractions correlated better in eyes with low myopia than in those with high myopia (P < .01). Postoperatively, objective refraction was less accurate and reliable than preoperatively. The difference between the objective and subjective spherical refractions was statistically significant (P < .0001) after LASIK in eyes with hyperopia. The correlation between the objective and subjective cylindrical refractions was stronger preoperatively. Especially after LASIK for hyperopia, the objective refraction did not reliably assess the magnitude and axis of the cylinder. The preoperative refractive error did not significantly affect the preoperative and postoperative difference between the objective and subjective refractions or the change between the preoperative and postoperative mean differences. The type of excimer laser used significantly affected the difference between the objective and subjective refractions. CONCLUSIONS: Especially after LASIK for hyperopia, the objective refraction determined with the Nidek AR-K 900 autorefractor delivered erroneous results, which have implications for postoperative care and preoperative measurements for ocular surgery such as enhancement procedures or cataract surgery.     

水平斜视手术对眼波前像差的影响

目的观察并分析水平斜视矫正术前、后眼波前像差的动态变化。方法选择水平斜视患者26例30眼,年龄16～40岁(平均22岁),内斜10例,外斜16例。角膜无病变,均为首次手术患者,无弱视患者,均行单眼水平肌后徙加缩短术。术后随访观察60天。分别于手术前1天和手术后1,7,30,60天。用主观单色波前像差测量仪(苏州亮睛医疗器械有限公司WFA1000B波前像差仪)测量波前总像差及各分阶像差的改变。将所得数据进行统计学处理。结果1.二阶像差和二阶第5项X轴方向散光术后30天内均较术前增高,差别有统计学意义,术后60天恢复。二阶第3项Y轴散光和第4项离焦手术前后无差别。2.总的波前像差和高阶像差术后1天较术前明显增高,差别有统计学意义,但术后7天,即恢复至术前水平。结论1.水平肌退缩术会引起眼低阶像差的增加,术后增大的像差是二阶第五项像差(X轴方向的散光),说明水平斜视手术影响低阶像差中在水平方向的屈光力,而对垂直方向的屈光力和离焦(球镜)无影响。2.水平斜视手术可引起眼高阶像差的显著增加,但这种变化是一过性的,术后7天即可消失。3.斜视手术引起的眼高阶和低阶像差改变分别在术后7-60天内可逐渐恢复至术前水平,不会对视功能造成远期影响。