Double-pass System Research Articles

光脉冲压缩器光栅失调的在线监测与调节方法

To solve the misaligned grating problem in the double-pass single-parallel two-grating compressor system, a monitoring system with simple structure is designed. Numerical simulation is investigated based on the system scheme and an original method for online adjusting gratings is proposed. All dimensions of two misaligned gratings are analyzed and then separated to adjust step by step based on the relationship between monitoring variables and misadjustment until the misaligned gratings in the vacuum chamber have been adjusted back to the ideal position. The alignment error and reliability discussion of the method are presented. Based on the existed parameters of the system, the accuracy range from 0.30 murad to 2.78 murad is obtained.

Intra- and Intersession Repeatability of an Optical Quality and Intraocular Scattering Measurement System in Children.

PurposeTo evaluate intra- and intersession repeatability of objective optical quality and intraocular scattering measurements with a double-pass system in children.MethodsForty-two eyes of 42 children were included in the study. An optical quality analysis system (OQAS) was used to measure optical quality parameters, including modulation transfer function cutoff frequency (MTFcutoff), Strehl ratio (SR), OQAS values (OV) at 3 different contrasts and objective scatter index (OSI). Three measurement sessions with 10-min intervals were operated by the same technician, and in each session four consecutive measurements were obtained.ResultsMean values for MTFcutoff, SR and OSI were 46.85 ± 7.45cpd, 0.27 ± 0.06 and 0.34 ± 0.22 respectively. 1) The intraclass correlation coefficients were ranged from 0.89 to 0.97 and coefficients of variation from 0.06 to 0.16 for all the parameters in the first session; the relative repeatability were 11.1% (MTFcutoff), 22.5% (SR), 10.9% (OV100%), 16.6% (OV2%), 22.4% (OV9%) and 56.3% (OSI). Similar results were found in the second and third sessions. 2) Bland-Altman analysis showed that narrow 95% confidence intervals (compared between the first and second sessions) ranged from -5.42 to 5.28 (MTFcutoff), -0.05 to 0.07 (SR), -0.18 to 0.18 (OV100%), -0.26 to 0.29 (OV20%), -0.33 to 0.39 (OV9%) and -0.11 to 0.09 (OSI); the comparison between any two of the three sessions showed similar results.ConclusionMeasurements of optical quality and intraocular scattering in children by the double-pass system showed good intra- and intersession repeatability. Retinal image quality is high and intraocular scattering is low in children.

Reproducibility of optical quality parameters measured at objective and subjective best focuses in a double-pass system.

To evaluate intra-session repeatability and reproducibility of optical quality parameters measured at objective and subjective best focuses in a double-pass system. Thirty Chinese healthy adults (19 to 40 years old) meeting our inclusion criterion were enrolled in the study. After a basic eye examination, two methods of optical quality measurement, based on subjective and objective best focuses were performed using the Optical Quality Analysis System (OQAS) with an artificial pupil diameter of 4.0 mm. With each method, three consecutive measurements of the following parameters: the modulation transfer function cutoff frequency (MTFcutoff), the Strehl(2D) ratio, the OQAS values (OVs) at contrasts of 100%, 20%, 9% and the objective scatter index (OSI) were performed by an experienced examiner. The repeatability of each method was evaluated by the repeatability limit (RL) and the coefficient of repeatability (COR). Reproducibility of the two methods was evaluated by intra-class correlation coefficient (ICC) and the 95% limits of agreement (Bland and Altman analysis). Thirty subjects, seven females and twenty three males, of whom 15 right eyes and 15 left eyes were selected randomly for recruitment in the study. The RLs (percentage) for the six parameters measured at objective focus and subjective focus ranged from 8.44% to 15.13% and 10.85% to 16.26%, respectively. The CORs for the two measurement methods ranged from 8.27% to 14.83% and 10.63% to 15.93%, respectively. With regard to reproducibility, the ICCs for the six parameters of OQAS ranged from 0.024 to 0.276. The 95% limits of agreement obtained for the six parameters (in comparison of the two methods) ranged from -0.57 to 42.18 (MTFcutoff), -0.01 to 0.23 (Strehl(2D) ratio), -0.02 to 1.40 (OV100%), -0.10 to 1.75 (OV20%), -0.14 to 1.80 (OV9%) and -1.46 to 0.18 (OSI). Measurements provided by OQAS with either method showed a good repeatability. However, the results obtained from the two different measurement methods showed a poor reproducibility. These findings suggest that it might be best to evaluate patients' optical quality by OQAS using the best focus as chosen automatically by the instrument.

Dynamic change of optical quality in patients with dry eye disease.

To evaluate the dynamic changes of optical quality in patients with dry eye disease (DED) by using a double-pass system. Fifty-six patients with DED and 35 control subjects were included in this study. Each patient underwent an evaluation of the ocular surface, using the Ocular Surface Disease Index, tear film breakup time (TBUT), corneal and conjunctival staining (Oxford scale), and Schirmer I test. Using the tear film analysis program of the Optical Quality Analysis System, we recorded the objective scatter index (OSI) every 0.5 seconds within a 20-second period with the subjects asked to blink freely. Several parameters were established to evaluate the dynamic alterations of optical quality and the effects of blinks: OSI standard deviation (SD), ΔOSI, ΔOSI/time, blinking change (BC), blinking frequency (BF), and tolerant limitation (TL). Patients with DED had significant alterations of optical quality compared to control subjects. The ΔOSI, ΔOSI/time, BC, and BF were significantly higher and TL was significantly lower in DED patients than controls. Furthermore, the ΔOSI and ΔOSI/time were also significantly higher in patients with severe DED than patients with mild disease. In univariate analysis, both TBUT and corneal staining were correlated with ΔOSI, ΔOSI/time, and BC. In multivariate analysis, ΔOSI/time was correlated to the corneal staining score. The double-pass system allowed the monitoring of the dynamic changes of optical quality in patients with DED. Optical quality should be evaluated in patients with DED because these alterations cannot be determined from the classical DED clinical tests.

Penanganan Susut Panen dan Pasca Panen Padi Kaitannya dengan Anomali Iklim di Wilayah Daerah Istimewa Yogyakarta

To reduced losses in rice farming requires the application of modern agricultural machinery in harvesting equipment, postharvest and processing. Varying knowledge of farmers and entrepreneur rice milling unit (RMU) in yield loss as well as the impacts of global climate change research should be conducted through a structured survey of farmers and entrepreneurs RMU in Yogyakarta. Results obtained demonstrate the preferred use of new type variety among farmers so that the tool is suitable harvest sickle cutting down system in districts of Bantul and Gunungkidul more popular as straw used for animal feed. More than 70% of farmers do at harvest time by looking at the panicle and leaf color. Utilization of power threshers more developed in Sleman because of such preferred cut up and threshing by stampede way. With the limitations of manpower, the farmer was forced to delay harvest in Gunungkidul. The thickness of the grain is dried in the sun need to be added so as not too thin and can produce more rice intact during milling. Entrepreneur RMU need to complete with seed cleaner to increase the yield, as well as using double-pass system so that quality and yield of rice produced would be better.

Evaluation of double-pass optical quality analysis system between SMILE and femtosecond LASIK for myopia

Evaluation of double-pass optical quality analysis system between SMILE and femtosecond LASIK for myopia

Optimal timing of retinal scanning during dark adaptation, in the presence of fixation on a target: the role of pupil size dynamics.

While validating our newly developed vision screener based on a double-pass retinal scanning system, we noticed that in all patients the signals from the retina were significantly higher when measurements were performed within a certain time interval referenced to the initial moment when the lights were dimmed and the test subject was asked to fixate on a target. This appeared to be most likely attributable to pupil size dynamics and triggered the present study, whose aim was to assess the pupillary “lights-off” response while fixating on a target in the presence of an accommodative effort. We found that pupil size increases in the first 60 to 70 s after turning off the room lights, and then it decreases toward the baseline in an exponential decay. Our results suggest that there is an optimal time window during which pupil size is expected to be maximal, that is during the second minute after dimming the room lights. During this time, window retinal diagnostic instruments based on double-pass measurement technology should deliver an optimal signal-to-noise ratio. We also propose a mathematical model that can be used to approximate the behavior of the normalized pupil size.

Quadruple-pass lateral shearing interferometer for collimation-based applications.

We demonstrate a quadruple-pass lateral shearing interferometer by introducing a single mirror into the conventional double-pass system for collimation-based applications. This interferometer permits the collimation of the double-pass test beam to be evaluated at a self-referencing sensitivity, and at the same time a differential sensitivity in collimation detection can be achieved through the quadruple-pass test beam. The proposed system can be utilized for both refraction-based and reflection-based applications that depend on a test arm with a convergent beam.

Objective optical quality and intraocular scattering in myopic adults.

To evaluate objective optical quality and intraocular scattering in adults with myopia. This was a cross-sectional study. Patients between 18 and 40 years of age were recruited from those undergoing routine preoperative examinations prior to myopic refractive surgery. The spherical equivalent refraction (SE) ranged from -14.25 to -0.63 diopters (D). Right eyes of 274 subjects were included for factor analyses: 25 eyes were super-high myopia (SE < -9 D), 88 eyes were high myopia (-6 D > SE ≥ -9 D),133 eyes were moderate myopia (-3 D > SE ≥ -6 D), and 28 eyes were low myopia (SE ≥ -3 D). A double-pass system was used to measure the modulation transfer function cutoff frequency (MTFcutoff) and objective scatter index (OSI). Mean MTFcutoff was 32.38 ± 9.73 and 27.61 ± 8.11 cycles per degree (cyc/deg) in the high and super-high myopia groups, significantly lower than 39.92 ± 10.53 and 37.39 ± 8.74 cyc/deg in the low and moderate groups (P < 0.01). Mean OSI was 0.89 ± 0.61 and 1.33 ± 0.65 in the high and super-high myopia groups, significantly higher than in the low and moderate groups, 0.50 ± 0.39 and 0.57 ± 0.44 (P < 0.01). No significant difference was found between the low myopia and the moderate myopia group in any of the parameters (P > 0.05). Other factors such as eye side, sex, and age did not significantly affect optical quality parameters or OSI in this study population (P > 0.05). Optical quality and intraocular scattering varied among individuals with myopia. High myopia has more influence on retinal image quality and scattering than moderate and low myopia. Our study also helps to establish MTFcutoff and OSI standards for Chinese refractive surgery candidates.

Light shift manipulation and suppression in a double pass optical-magnetic double resonance system

A double pass optical-magnetic double resonance system is proposed and applied for observing and manipulating the light shift in metastable . By adjusting the degree of overlap in space between the incident and retro-reflected laser beams, the manipulation on light shift is realized and a flat range for light shift insensitive to optical frequency detuning can be formed. A simple hole-burning model based on velocity-selective optical pumping, including the velocity diffusion effect caused by velocity-changing collisions, is adopted to qualitatively clarify the light shift observed in the double pass system.

Objective assessment of nuclear cataract: Comparison of double-pass and Scheimpflug systems

To compare the objective assessment of lens density by 2 systems (double-pass Optical Quality Analysis System and Pentacam Scheimpflug) in eyes with age-related nuclear cataract. Department of Ophthalmology and Visual Science, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, South Korea. Cross-sectional study. In eyes with age-related nuclear cataract, the objective lens density (0 to 100 points) was determined using the Scheimpflug system while subjective grading was achieved using the Lens Opacities Classification System III (LOCS III). The objective scatter index (OSI) (0 to 25) was assessed using the double-pass system. This study enrolled 47 patients (70 eyes). The mean OSI was 4.08 ± 2.22 (SD), and the mean Scheimpflug-measured lens density was 16.44 ± 4.36; the 2 parameters were correlated (r = 0.764, P<.01). There was a positive linear correlation between the OSI and LOCS III grading scores for nuclear opalescence and nuclear color (r = 0.772 and r = 0.752, respectively; P<.01). The cumulated dissipated energy (CDE) was strongly correlated with the OSI (r = 0.768) and Scheimpflug-measured lens density (r = 0.753). The OSI based on the double-pass system was correlated with the Scheimpflug-measured lens density, subjective lens grading, and CDE. The OSI may improve the preoperative evaluation of nuclear cataract and help predict phacodynamics in cataract surgery.

Double-Pass System (Optical Quality Analysis System) for Analysis of the Multifocal Function of a Diffractive Multifocal Intraocular Lens (Acrysof ReSTOR®) Compared to a Monofocal Intraocular Lens (Acrysof IQ®)

In this study, we objectively determined whether the ReSTOR as a multifocal IOL (intraocular lens) has a multifocal function compared to the IQ as a monofocal IOL in vivo by OQAS (Optical Quality Analysis System). Eighteen patients who had cataract surgery with implantation of ReSTOR (27 eyes) and 15 patients with IQ (21 eyes), were included inthis study. Uncorrected distance visual acuity (UCDVA), corrected distance visual acuity (CDVA), uncorrected near visual acuity (UCNVA)and distance corrected near visual acuity (DCNVA) were measured. After setting the artificial pupil size to 3 mm, we performed 'Optical quality'. We inputted defocus diopters of (objective spherical refraction)(far), (objective spherical refraction-1.25 D)(intermediate),(objective spherical refraction-2.5 D)(near), and (objective spherical refraction-3.5 D)(very near) into 'selected spherical refraction' simulating the optical quality at far, intermediate, and near distance. We changed the pupil size to 5 mm and repeated the same measurements. The UCDVA and CDVA did not show significant differences between the 2 groups. But, the UCNVA and DCNVA of the ReSTOR group were better than those of the IQ group (p=0.000, p=0.000). For 3 mm pupil, at far distance, modulation transfer function (MTF) cut off and point spread function (PSF) width at 50% of ReSTOR were worse than those of IQ (p=0.039, p=0.020). At intermediate distance, MTF cut off, Strehl ratio and PSF width at 50% of ReSTOR were worse than those of IQ (p=0.001, p=0.001, p=0.000). At near distance, MTF cut off of ReSTOR was worse than that of IQ (p=0.033). At very near distance, MTF cut off and Strehl ratio of ReSTOR were worse than those of IQ (p=0.002, p=0.002), but PSF width at 50% of ReSTOR was better than that of IQ. For 5 mm pupil, most parameters at each distance, there was no significant difference between the 2 groups. Only PSF width at 50% of ReSTOR were worse than those of IQ at intermediate distance (p=0.013). It was impossible to show the multifocal function of ReSTOR compared to the IQ byOQAS.

Double-Pass System Assessing the Optical Quality of Pseudophakic Eyes

To compare the optical quality measurements obtained from the double-pass system and ocular aberrations, subjective visual acuity, and contrast sensitivity score in pseudophakic eyes. Three months after cataract surgery, modulation transfer function (MTF) cutoff frequency, Strehl ratio, objective scatter index, and objective pseudoaccommodation obtained from the double-pass system were compared with total aberration, higher-order aberration, and spherical aberration obtained from ray-tracing aberrometer. In addition, parameters of the double-pass system were compared with subjective visual acuity and the contrast sensitivity score. Forty eyes of 40 patients were included. The MTF cutoff frequency and Strehl ratio were negatively correlated with total aberration (r = -0.503, p = 0.003; r = -0.509, p = 0.003, respectively) and subjective visual acuity (r = -0.453, p = 0.007; r = -0.354, p = 0.040, respectively). The objective scatter index was positively correlated with total aberration (r = 0.451, p = 0.024) and subjective visual acuity (r = 0.516, p = 0.008). The MTF cutoff frequency showed a correlation with contrast sensitivity score under photopic and mesopic conditions. Optical quality parameters obtained from the double-pass system were correlated with ocular aberrations, subjective visual acuity, and contrast sensitivity score in pseudophakic eyes.

Optical quality assessment in normal and forme fruste keratoconus eyes with a double-pass system: a comparison and variability study

PurposeTo comparatively evaluate the image quality in normal and forme fruste keratoconus patients using a double-pass system.MethodsFourteen normal eyes and 15 eyes with forme fruste keratoconus were included. Corneal tomographic...

Technical improvements applied to a double-pass setup for performance and cost optimization

We have studied the possibility of improving the performance, simplifying, and reducing the cost of a double-pass system by the use of alternative technologies. The system for correcting the spherical correction has been based on a focusable electro-optical lens, and a recording device based on CMOS technology and a superluminescent diode (SLED) light source have been evaluated separately. The suitability of the CMOS camera has been demonstrated, while the SLED could not break the speckle by itself. The final experimental setup, consisting of a CMOS camera and a laser diode, has been compared with a commercial double-pass system, proving its usefulness for ocular optical quality and scattering measurements.

Optical quality and intraocular scattering assessed with a double-pass system in eyes with contact lens induced corneal swelling

To evaluate the impact of contact lens (CL)-induced corneal swelling on the optical quality of the eye by means of the double-pass technique. Measurements of 6 healthy subjects were obtained in 5 visits over 1 week, at baseline and after sleeping with 4 different CLs of +0.50 D, +2.00 D, +5.00 D and +8.00 D (Acuvue2), randomly fitted on 4 different days. The control eye wore no CL. Corneal pachymetry and optical quality of the eye (OQAS, Visiometrics) were measured once at baseline and at three interval times in the follow-up visits: immediately after CL removal, and 1 and 2 h after CL removal. Optical quality was evaluated by means of the Strehl ratio and OQAS values at 100%, 20% and 9% contrasts. Intraocular scattering was evaluated with the objective scatter index (OSI). Mean overnight swelling was 5.98 ± 4.29% in CL-eyes versus 0.30 ± 0.78% in control eyes (p < 0.01). Corneal swelling was maximal immediately after CL removal and decreased with time (p < 0.01). A significant worsening in all optical quality parameters and a significant increase of the OSI were found in eyes with corneal swelling (p < 0.05). Two hours after CL removal there were no statistically significant differences (p > 0.05) between CL-eyes and control eyes in any of the measured parameters. Corneal swelling has a significant impact on the optical quality of the eye and on intraocular scattering as assessed with the double-pass technique.

Non-cycloplegic spherical equivalent refraction in adults: comparison of the double-pass system, retinoscopy, subjective refraction and a table-mounted autorefractor.

To evaluate the accuracy of spherical equivalent (SE) estimates of a double-pass system and to compare it with retinoscopy, subjective refraction and a table-mounted autorefractor. Non-cycloplegic refraction was performed on 125 eyes of 65 healthy adults (age 23.5±3.0 years) from October 2010 to January 2011 using retinoscopy, subjective refraction, autorefraction (Auto kerato-refractometer TOPCON KR-8100, Japan) and a double-pass system (Optical Quality Analysis System, OQAS, Visiometrics S.L., Spain). Nine consecutive measurements with the double-pass system were performed on a subgroup of 22 eyes to assess repeatability. To evaluate the trueness of the OQAS instrument, the SE laboratory bias between the double-pass system and the other techniques was calculated. The SE mean coefficient of repeatability obtained was 0.22D. Significant correlations could be established between the OQAS and the SE obtained with retinoscopy (r=0.956, P<0.001), subjective refraction (r=0.955, P<0.001) and autorefraction (r=0.957, P<0.001). The differences in SE between the double-pass system and the other techniques were significant (P<0.001), but lacked clinical relevance except for retinoscopy; Retinoscopy gave more hyperopic values than the double-pass system -0.51±0.50D as well as the subjective refraction -0.23±0.50D; More myopic values were achieved by means of autorefraction 0.24±0.49D. The double-pass system provides accurate and reliable estimates of the SE that can be used for clinical studies. This technique can determine the correct focus position to assess the ocular optical quality. However, it has a relatively small measuring range in comparison with autorefractors (-8.00 to +5.00D), and requires prior information on the refractive state of the patient.

Evaluation of optical quality parameters and ocular aberrations in multifocal intraocular lens implanted eyes.

PurposeWe investigated the correlations between optical quality parameters obtained from the double-pass system and ocular aberrations obtained from the ray-tracing aberrometer in multifocal intraocular lens (IOL) implanted eyes.Materials and MethodsTwenty eyes from 20 patients were enrolled in this study. Modulation transfer function cutoff frequency, The Strehl ratio, objective scatter index, and objective pseudo-accommodation obtained from the double-pass system were compared with root mean square (RMS) total aberration, RMS higher-order aberration, and spherical aberration obtained from the ray-tracing aberrometer. Additionally, parameters of the double-pass system and ray-tracing aberrometer were compared with manifested refraction values and subjective visual acuity, respectively.ResultsThere was no statistically significant correlation between optical quality parameters obtained from the double-pass system and ocular aberrations, except between the Strehl ratio and RMS total aberration (r=-0.566, p=0.018). No significant correlations were found between the parameters of both devices, and manifested refraction values or subjective visual acuity.ConclusionOptical quality parameters, especially the Strehl ratio, in multifocal IOL implanted eyes were affected by RMS total aberration. Further studies based on accurate measurements of ocular aberrations and additional optical quality parameters are needed to delineate relationships between optical quality parameters and ocular aberrations in multifocal IOL implanted eyes.

Clinical Results and Optical Quality of Diffractive Multifocal IOL Implantation after Myopic Refractive Surgery

Purpose: To evaluate the visual outcome and optical quality in eyes with diffractive multifocal intraocular lens (DMIOL) implantation after myopic refractive surgery. Methods: Nineteen eyes (15 patients) were implanted with AcriSof ReSTOR SN6AD1, the aspheric DMIOL after myopic refractive surgery (laser-assisted in situ keratomileusis [LASIK] 14 eyes, photorefractive keratectomy [PRK] 4 eyes, laser-assisted subepithelial keratomileusis [LASEK] 1 eye). Preoperative and postoperative visual acuities and manifest refraction were measured. Preoperative corneal higher-order aberrations (HOAs) were measured using Hartmann-Shack (H-S) aberrometer in dilated pupils, and optical qualities were measured 1 month postoperatively using H-S aberrometer and a double-pass system under mesopic conditions. Patient satisfaction was investigated using a questionnaire at 2 months postoperatively. Results: Uncorrected distant and near visual acuities at postoperative 2 months were 0.11 ± 0.19, and 0.19 ± 0.12 (log MAR), respectively. Postoperative spherical equivalent (SE) of 16 eyes (84.2%) was within ±0.50 diopters (D) and all eyes were within ±1.00 D from emmetropia. Preoperative corneal and postoperative ocular spherical aberrations in a 4.0 mm pupil diameter were 0.08 ± 0.08 and 0.07 ± 0.07 (μm), respectively. Objective scatter index was 3.42 ± 1.71 and modulation transfer function (MTF) cut-off value was 21.03 ± 12.37 cpd. General satisfaction score was 3.52 ± 0.96 points out of 5, and 8 patients (11 eyes) were not satisfied with DMIOL implantation. Conclusions: After DMIOL implantation in the eyes with previous myopic refractive surgery, postoperative SE was close to the target D, but optical qualities and patient satisfaction were poor. J Korean Ophthalmol Soc 2014;55(12):1779-1786

Effect of refractive correction on ocular optical quality measurement using double-pass system

Background Optical Quality Analysis System II (OQAS, Visiometrics, Terrassa, Spain) that uses double-pass (DP) technique is the only commercially available device that allows objective measurement of ocular retinal image quality. This study aimed to evaluate the impact of spectacle lenses on the ocular optical quality parameters and the validity of the optometer within OQAS. Methods Seventy eyes of healthy volunteers were enrolled. Optical quality measurements were performed using OQAS with an artificial pupil diameter of 4.0 mm. Three consecutive measurements were obtained from spectacle correction corresponding to subjective refraction and from the OQAS built-in optometer separately. The modulation transfer function cutoff frequency, the Strehl ratio, the width of the point spread function (PSF) at 10% of its maximal height (PSF10), and the width of the PSF at 50% of its maximal height (PSF50) were analyzed. Results There was no significant difference in any of the parameters between the spectacle correction and the optometer correction (all P &gt;0.05, paired t-test). A good agreement was found between both the methods and a good intraobserver repeatability in both the correction methods. Difference in best focus between two methods was the only parameter associated significantly with optical quality parameter differences. Best focus difference, built-in optometer correction with or without external cylindrical lens, and age were associated significantly with PSF10 difference. No linear correlation between refractive status and optical quality measurement difference was observed. A hyperopic bias (best focus difference of (0.50±0.44) D) and a relatively better optical quality using spectacle correction in high myopia group were found. Conclusions OQAS based on DP system is a clinically reliable instrument. In patients with high myopia, measurements using built-in optometer correction should be considered and interpreted with caution.