435 results match your criteria power astigmatic


Agreement and variability of subjective refraction, autorefraction, and wavefront aberrometry in pseudophakic patients.

J Cataract Refract Surg 2021 Aug;47(8):1056-1063

From the VIROS-Vienna Institute for Research in Ocular Surgery, a Karl Landsteiner Institute, Hanusch Hospital, Vienna, Austria.

Purpose: To evaluate the comparability and variability of subjective refraction (SR), autorefraction (AR), and wavefront aberrometry (WA) in pseudophakic patients.

Setting: Hanusch Hospital, Vienna, Austria.

Design: Prospective study. Read More

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Effects of Rebamipide on Differences in Power and Axis of Corneal Astigmatism Between Two Intra-patient Keratometric Measurements in Dry Eyes.

Ophthalmol Ther 2021 Jul 22. Epub 2021 Jul 22.

Department of Ophthalmology, Yokohama City University School of Medicine, 3-9 Fukuura, Kanazawa, Yokohama, 236-0004, Kanagawa, Japan.

Introduction: This study investigated the effect of rebamipide on discrepancies in the power and axis of astigmatism between two intra-patient keratometric measurements in patients with dry eyes.

Methods: Fifty-eight dry eyes (with a short tear breakup time [TBUT] of less than 5 s) were analyzed. Patients with dry eye were treated with 2% rebamipide ophthalmic suspension (group R) or Mytear artificial tear ophthalmic solution (group M) for 4 weeks. Read More

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Agreement and variability of subjective refraction, autorefraction, and wavefront aberrometry in pseudophakic patients.

J Cataract Refract Surg 2021 Aug;47(8):1056-1063

From the VIROS-Vienna Institute for Research in Ocular Surgery, a Karl Landsteiner Institute, Hanusch Hospital, Vienna, Austria.

Purpose: To evaluate the comparability and variability of subjective refraction (SR), autorefraction (AR), and wavefront aberrometry (WA) in pseudophakic patients.

Setting: Hanusch Hospital, Vienna, Austria.

Design: Prospective study. Read More

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Comparison of corneal astigmatism characteristics and prevalence of corneal astigmatism between Turkish individuals and Syrian refugees.

Authors:
Soner Guven

Eur J Ophthalmol 2021 Jul 7:11206721211030779. Epub 2021 Jul 7.

Department of Ophthalmology, Kayseri City Hospital, Kayseri, Turkey.

Purpose: To compare the prevalence, magnitude and type of corneal astigmatism between Turkish individuals and Syrian refugees.

Material And Methods: Data of patients scheduled for cataract surgery between January 2019 and 2020 were reviewed. The patients were randomly stratified according to their ethnicity (Turkish individuals or Syrian refugees). Read More

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Tunable vortex beam generation using an optical parametric oscillator with an antiresonant-ring interferometer.

Opt Lett 2021 Jul;46(13):3235-3238

We report a high-average-power picosecond optical vortex source tunable in the near-infrared, using an antiresonant-ring (ARR) interferometer internal to an optical parametric oscillator (OPO) in combination with an external cylindrical lens for astigmatic mode conversion. The ARR OPO is tunable in the signal across 1457-1647 nm with a vortex intensity profile and up to 1 W of average power at 1602 nm. The corresponding idler is tunable over 3006-3945 nm in a Gaussian intensity profile with as much as 1. Read More

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Artificial accommodating intraocular lens powered by an ion polymer-metal composite actuator.

PLoS One 2021 23;16(6):e0252986. Epub 2021 Jun 23.

Department of Ophthalmology, Faculty of Medicine, University of Tsukuba, Tsukuba-city, Ibaraki, Japan.

The current method of controlling the focus of an accommodating intraocular lens is based on ciliary muscle contraction and cannot be used in older patients with presbyopia. We aimed to develop a dynamically accommodating intraocular lens powered by a membrane-shaped ion polymer metal composite actuator that is thin enough to be inserted in the eye. This study addresses two key problems identified in our previous accommodating intraocular lens prototype: the lack of repeatability due to the use of swine lenses instead of artificial lenses and the occurrence of a sixth order aberration. Read More

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The role of posterior corneal power in 21st century biometry: A review.

J Fr Ophtalmol 2021 Jun 17. Epub 2021 Jun 17.

Instituto de Cirugía Ocular, San José, Costa Rica.

Purpose: Intraocular lens (IOL) calculation and biometry have evolved significantly in recent decades. However, present outcomes are still suboptimal. Our objective is to summarize the results reported in the literature with regard to a new variable, the value of the relationship between anterior and posterior corneal curvature in the biometric calculation of IOL power. Read More

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Surgically induced astigmatism following single site and twin site phacotrabeculectomy augmented with mitomycin C.

Eye (Lond) 2021 Jun 11. Epub 2021 Jun 11.

Glaucoma Clinic, Aravind Eye Hospital, Tirunelveli, India.

Purpose: To determine difference in surgically induced astigmatism (SIA), post-operative intraocular pressure (IOP) and axial length (AL) between single site and twin-site phacotrabeculectomy augmented with Mitomycin C (MMC).

Design: Prospective interventional randomised controlled study.

Methods: In a prospective interventional comparative study, eligible patients were scheduled for phacotrabeculectomy. Read More

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Ratio of torus and equivalent power to refractive cylinder and spherical equivalent in phakic lenses - a Monte-Carlo simulation study.

Acta Ophthalmol 2021 May 20. Epub 2021 May 20.

Department of Ophthalmology, Semmelweis-University, Budapest, Hungary.

Background: Spherical and astigmatic powers for phakic intraocular lenses are frequently calculated using fixed ratios of phakic lens refractive power to refractive spherical equivalent, and of phakic lens astigmatism to refractive cylinder. In this study, a Monte-Carlo simulation based on biometric data was used to investigate how variations in biometrics affect these ratios, in order to improve the calculation of implantable lens parameters.

Methods: A data set of over sixteen thousand biometric measurements including axial length, phakic anterior chamber depth, and corneal equivalent and astigmatic power was used to construct a multidimensional probability density distribution. Read More

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Are changes in visual acuity and astigmatism after corneal cross-linking (CXL) in keratoconus predictable?

Graefes Arch Clin Exp Ophthalmol 2021 Apr 22. Epub 2021 Apr 22.

Specialty Eye Hospital "Svjetlost", Zagreb, Croatia.

Purpose: To evaluate changes in corrected distance visual acuity (CDVA), ratio of anterior and posterior corneal radii over the thinnest region of the cornea (ARC/PRC), and astigmatism after cross-linking (CXL) in keratoconus.

Methods: Subjective refraction and ARC/PRC (using Pentacam™) were monitored over 1 year in (I) keratoconus treated with routine CXL (n = 53), (II) relatively stable keratoconus (n = 23), and (III) age/gender matched controls (n = 24).

Results: CDVA (median, mode, interquartile range) improved significantly in group I, compared with groups II and III (p < 0. Read More

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Cycloplegic Effects on the Cylindrical Components of the Refraction.

J Ophthalmol 2021 2;2021:8810782. Epub 2021 Apr 2.

Poostchi Ophthalmology Research Center, Department of Ophthalmology, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran.

It is important to predict which astigmatic patients require separate refraction for near vision. This study compared cylindrical components changes by cyclopentolate 1% for the low and high amount of astigmatism. The right eyes of 1014 healthy individuals (307 males and 707 females) with cylindrical refractive power more than -0. Read More

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Progressive-toric IOL design reduces residual astigmatism with increasing pupil size: a ray-tracing simulation based on corneal topography data.

Biomed Opt Express 2021 Mar 23;12(3):1568-1576. Epub 2021 Feb 23.

The David J. Apple Center for Vision Research, Department of Ophthalmology, Heidelberg University Hospital, INF 400, 69120 Heidelberg, Germany.

Population studies indicate that astigmatism decreases from the corneal center toward the periphery. A standard toric intraocular lens (IOL) with a constant cylinder power cannot correct uniformly across this gradient. We built an astigmatic eye model based on corneal topography data. Read More

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Time to Keratometric Stability After Pterygium Excision and the Associated Factors: A Clinical Perspective.

Clin Ophthalmol 2021 25;15:1277-1283. Epub 2021 Mar 25.

Center of Excellence for Cornea and Stem Cell Transplantation, Department of Ophthalmology, Faculty of Medicine, Chulalongkorn University and King Chulalongkorn Memorial Hospital, Thai Red Cross Society, Bangkok, Thailand.

Purpose: To determine the percentage of eyes with corneal astigmatic power stability and mean corneal keratometric power at 6-month post-pterygium excision, and to identify the time, and the associated factors, required to achieve stability.

Methods: This prospective observational study enrolled patients undergoing pterygium excision. Patients were evaluated for baseline characteristics and keratometric data before and every month after pterygium excision for six months using IOL Master 500 (Carl Zeiss, Meditec). Read More

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Toric intraocular lens power calculation in cataract patients with keratoconus.

J Cataract Refract Surg 2021 Mar 9. Epub 2021 Mar 9.

Ein-Tal Eye Center, Tel Aviv, Israel.

Purpose: Intra-ocular lens (IOL) power calculation in eyes with keratoconus typically results in hyperopic postoperative refractive error. We investigated the visual and refractive outcomes in keratoconus patients having cataract surgery with a toric IOL and compared IOL power calculation accuracy of conventional formulae and keratoconus specific formulae.

Setting: Ein-Tal Eye Center, Tel-Aviv, Israel. Read More

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Kerr-lens mode-locked Cr:ZnS oscillator reaches the spectral span of an optical octave.

Opt Express 2021 Jan;29(2):2458-2465

We report, to the best of our knowledge, the first super-octave femtosecond polycrystalline Cr:ZnS laser at the central wavelength 2.4 µm. The laser is based on a non-polarizing astigmatic X-folded resonator with normal incidence mounting of the gain element. Read More

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January 2021

Simulative and Experimental Characterization of an Adaptive Astigmatic Membrane Mirror.

Micromachines (Basel) 2021 Feb 5;12(2). Epub 2021 Feb 5.

Institute for Microsystems Technology (IMST), Department of Mechanical & Medical Engineering, Furtwangen University of Applied Science, D-78120 Furtwangen, Germany.

Adaptive optical (AO) components play an important role in numerous optical applications, from astronomical telescopes to microscope imaging systems. For most of these AO components, the induced wavefront correction, respectively added optical power, is based on a rotationally symmetric or segmented design of the AO component. In this work, we report on the design, fabrication, and characterization of a micro-electronic-mechanical system (MEMS) adaptive membrane mirror in the shape of a parabolic cylinder. Read More

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February 2021

Optical performance of progressive addition lenses (PALs) with astigmatic prescription.

Sci Rep 2021 Feb 4;11(1):2984. Epub 2021 Feb 4.

School of Optometry, Hong Kong Polytechnic University, Hong Kong, China.

The progressive addition lens (PAL) is a spectacle lens design with progressive refractive power changes across the lens surface to provide sharp vision at different viewing distances for patients with reduced accommodative strength. It has gained in popularity not just for presbyopic patients, but also patients with occupational (office, driving, or digital device) and therapeutic (e.g. Read More

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February 2021

Surgical Treatment of Epiblepharon Effectively Alleviates Keratopathy but Not Astigmatism: A Case-Control Study Utilizing Vector Analysis in East Asian Children.

J Ophthalmol 2020 5;2020:5073895. Epub 2020 Dec 5.

Department of Ophthalmology, National Taiwan University Hospital, College of Medicine National Taiwan University, Taipei, Taiwan.

Purpose: To identify an appropriate surgical indication of epiblepharon by comparing keratopathy and astigmatism outcomes after surgical and medical treatments for epiblepharon in Asian children.

Methods: Children diagnosed with epiblepharon ( = 82, age 5.93 ± 2. Read More

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December 2020

Gender and age distribution of refractive errors in an optometric clinical population.

J Optom 2021 Jan 21. Epub 2021 Jan 21.

Discipline of Optometry, School of Health Sciences, University of KwaZulu-Natal, Private Bag X54001, Durban 4000, South Africa. Electronic address:

Aim: To determine the patterns of distribution of refractive errors in a clinical sample of patients examined in an optometry practice.

Method: In this retrospective study, the clinic records of 6687 patients aged 6 to 85 years comprising 2168 (32.2%) males and 4519 (67. Read More

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January 2021

Astigmatic Results of a Diffractive Trifocal Toric IOL Following Intraoperative Aberrometry Guidance.

Clin Ophthalmol 2020 14;14:4373-4378. Epub 2020 Dec 14.

Sengi, Penniac, NB, Canada.

Purpose: To determine if intraoperative aberrometry (IA) improves astigmatic outcomes for trifocal toric IOL (TTI) cases.

Patients And Methods: This was a retrospective study examining 137 eyes that underwent cataract extraction and TTI implantation using femtosecond laser, digital registration, and IA. Final cylinder power and axis of placement were determined by IA. Read More

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December 2020

One-Year Results of Arcuate Keratotomy in Patients With Low to Moderate Corneal Astigmatism Using a Low-Pulse-Energy Femtosecond Laser.

Am J Ophthalmol 2021 04 9;224:53-65. Epub 2020 Dec 9.

Department of Ophthalmology, Medical University of Vienna, Vienna, Austria. Electronic address:

Purpose: To investigate corneal astigmatism (CA) reduction and corneal optical quality after surface-penetrating femtosecond laser arcuate keratotomies (Femto AK) considering anterior (CA) and posterior corneal curvature (CA), total corneal refractive power astigmatism (CA), and corneal higher-order aberrations (HOAs) through 1 year.

Design: Prospective interventional case series.

Methods: Setting: Department of Ophthalmology, Medical University of Vienna. Read More

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Clinical evaluation of toric intraocular lens implantation based on iTrace wavefront keratometric astigmatism.

BMC Ophthalmol 2020 Nov 16;20(1):450. Epub 2020 Nov 16.

Shanxi Eye Hospital, No. 100 Fudong Street, Taiyuan, Shanxi, 030001, People's Republic of China.

Background: Currently, there is no standard technique for determining corneal astigmatism. The iTrace wavefront aberrometry of cornea calculated steep power and axis based on the best Zernike mathematical fit from all topo data within 4 mm circle. It was supposed to be more accurate than iTrace simulated keratometry which was calculated based on only 4 points on the circle of 3 mm. Read More

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November 2020

Does Frontalis Sling Surgery for Congenital Ptosis Change the Corneal Topography and Refractive Characteristics Postoperatively?

Clin Ophthalmol 2020 30;14:3667-3673. Epub 2020 Oct 30.

Department of Ophthalmology, H.I.M.S.R & H.A.H. Centenary Hospital, Alaknanda, New Delhi 110062, India.

Purpose: To evaluate the effect of frontalis sling surgery for congenital ptosis on corneal curvature and refractive status.

Methods: Prospective study of 60 eyes of 48 patients with severe simple congenital ptosis who underwent surgical correction by frontalis sling surgery. Assessment was done pre-operatively and at 1 week, 1 month, 3 months post-operatively by computerized topographer (Shipp Nippon, CT 1000), IOL master (Carl Zeiss, 500), autorefractometer (Unicos URK-800) and AS-OCT (Cirrus HD-OCT). Read More

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October 2020

Initial Single-Site Experience Using SMILE for the Treatment of Astigmatism in Myopic Eyes and Comparison of Astigmatic Outcomes with Existing Literature.

Clin Ophthalmol 2020 29;14:3551-3562. Epub 2020 Oct 29.

Hoopes Vision Research Center, Hoopes Vision, Draper, UT, USA.

Purpose: To assess a single site's initial experience with SMILE for the treatment of myopic astigmatism and compare outcomes and vector analysis results with the US Food and Drug Administration (FDA) results and published literature.

Patients And Methods: Forty-eight eyes (29 patients) with mean preoperative sphere of -5.11 ± 1. Read More

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October 2020

On obtaining high spectral resolution in extreme ultraviolet/soft X-ray monochromators operating off-plane diffraction in a divergent incident beam.

Authors:
Werner Jark

J Synchrotron Radiat 2020 Nov 14;27(Pt 6):1499-1509. Epub 2020 Oct 14.

Elettra - Sincrotrone Trieste SCpA, SS 14 - km 163.5 in AREA Science Park, Basovizza, Trieste 34149, Italy.

When the trajectory of an incident beam is oriented parallel to the grooves of a periodic grating structure the radiation beam is diffracted off-plane orthogonal to the plane of incidence. The diffraction efficiency in this condition is very high and in a grating with a sawtooth profile it can approach the reflection coefficient for a simple mirror, when the diffraction order of interest follows the direction for specular reflection at the flat part of the steps. When this concept is used in a plane grating in a monochromator for synchrotron radiation sources, the incident beam is almost always collimated in order to minimize any deterioration of the beam properties due to aberrations, which will be introduced in the diffraction process when an uncollimated beam is used. Read More

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November 2020

Sources of Error in Toric Intraocular Lens Power Calculation.

J Refract Surg 2020 Oct;36(10):646-652

Purpose: To evaluate the influencing factors on remaining astigmatism after implanting a toric intraocular lens (IOL) during cataract surgery.

Methods: This retrospective study included parameters that were considered to have an influence on toric IOL power calculation. Therefore, data from the literature and the authors' own data were used. Read More

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October 2020

Presbyopia Correction in Astigmatic Eyes Using a Toric Trifocal Intraocular Lens With Quadrifocal Technology.

J Refract Surg 2020 Oct;36(10):638-644

Purpose: To evaluate the visual performance after bilateral implantation of a toric diffractive aspheric multifocal intraocular lens (IOL) with a +2.17 diopters (D) (60 cm) intermediate and a +3.25 D (40 cm) addition (add) power. Read More

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October 2020

Long-term Vector Outcomes of SMILE in Correcting Moderate to High With-the-Rule Astigmatism Under Astigmatism Axis Marked Condition.

J Refract Surg 2020 Sep;36(9):585-591

Purpose: To evaluate the vector outcomes of small incision lenticule extraction (SMILE) in correcting moderate to high myopic astigmatism under astigmatic axis marked condition.

Methods: In a prospective, longitudinal, interventional study, 71 eyes (71 patients) that had with-the-rule preoperative cylinder refraction exceeding 1.50 diopters (D) were corrected with the VisuMax femtosecond laser (Carl Zeiss Meditec AG) at Zhongshan Ophthalmic Center. Read More

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September 2020

High-power structured laser modes: manifestation of quantum Green's function.

Opt Lett 2020 Aug;45(16):4579-4582

The distributions of resonant frequencies in an astigmatic cavity are theoretically confirmed to be analogously equivalent to the quantum energy structures of two-dimensional commensurate harmonic oscillators. In the first part [Opt. Lett. Read More

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The Impact of Changes in Corneal Back Surface Astigmatism on the Residual Astigmatic Refractive Error following Routine Uncomplicated Phacoemulsification.

J Ophthalmol 2020 22;2020:7395081. Epub 2020 Jul 22.

Kyiv City Clinical Ophthalmological Hospital "Eye Microsurgical Center", Kyiv, Ukraine.

Purpose: To determine the significance of any association between intersessional changes in ocular residual astigmatism (RA) and astigmatism at corneal front (FSA) and back (BSA) surfaces following uneventful routine phacoemulsification.

Methods: Astigmatism was evaluated by autorefractometry and subjective refraction and at both the corneal surfaces with Orbscan II™ (Bausch & Lomb) over central 3 mm and 5 mm optical zones at 1, 2, and 3 months after routine phacoemulsification in 103 patients implanted with monofocal nontoric intraocular lenses (IOLs, one eye/patient). Data were subjected to vector analysis to determine the actual change (Δ) in astigmatism (power and axis) for the refractive and Orbscan II findings. Read More

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