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Carius, Staffan
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Publications (10 of 102) Show all publications
Lewis, P., Rosén, R., Gustafsson, J., Carius, S. & Unsbo, P. (2010). Dynamic Visual Acuity in the Peripheral Visual Field Using Gabor Patches. Paper presented at ARVO.
Open this publication in new window or tab >>Dynamic Visual Acuity in the Peripheral Visual Field Using Gabor Patches
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2010 (English)Conference paper, Published paper (Refereed)
Abstract [en]

Purpose:To evaluate dynamic visual acuity (DVA) in the peripheral visual field. This ability is important within the areas of sports, traffic safety, as well as for people with low vision; specifically those with central visual field loss. In this study we investigated both static- and dynamic visual acuity in the periphery of normally sighted observers using Gabor patches.

Methods:DVA and static visual acuity (SVA) was measured on the right eye of normally sighted emmetropes. Stimuli consisted of high-contrast Gabor patches; sine wave gratings multiplied by a Gaussian hull with a diameter of 2º, with the sine gratings drifting at 1, 2, and 4 degrees per second. Stimuli were presented, using MATLAB and Psychophysics Toolbox, on one of seven CRT monitors at the following retinal eccentricities: 10, 20 and 30 degrees, nasally and temporally as well as in the fovea. Subjects were informed to maintain fixation on a central fixation object during measurements at eccentric locations. An Adaptive Bayesian algorithm was employed to determine resolution thresholds at each eccentricity.

Results:The results show a trend towards both better static- and dynamic visual acuities for the temporal visual field at retinal eccentricities 20° and 30° compared to nasally. There appears to be a more rapid decrease in both static- and dynamic visual acuity with increasing eccentricity for the nasal visual field. In addition, we did not find any difference in DVA and SVA in the peripheral visual field for the velocities used in this study.

Conclusions:Results of these first preliminary measurements suggest that dynamic visual acuity measured with drifting Gabor patches is greater in the temporal visual field for eccentricities 20 degrees or larger. To confirm these results more measurements need to be performed on a lager sample of subjects.

Keywords
Acuity, Eye, Fovea, Periphery, Resolution, Retinal eccentricity, threshold, Vision, Visual Acuity, Visual field
National Category
Ophthalmology
Research subject
Natural Science, Optometry
Identifiers
urn:nbn:se:lnu:diva-10202 (URN)
Conference
ARVO
Available from: 2011-01-18 Created: 2011-01-18 Last updated: 2017-02-17Bibliographically approved
Baskaran, K., Theagarayan, B., Carius, S. & Gustafsson, J. (2010). Influence of age on peripheral aberration. Paper presented at 5th EMVPO 2010, Stockholm, Sweden.
Open this publication in new window or tab >>Influence of age on peripheral aberration
2010 (English)Conference paper, Published paper (Refereed)
Abstract [en]

The purpose of this study is to compare peripheral higher order aberrations in young

and old emmetropic eyes across the horizontal (±40°) and inferior (–20°) visual field.

Introduction

 

 

People with central visual field loss use eccentric fixation for various visual tasks.

Recently studies have shown that the correction of lower order aberrations (defocus &

astigmatism) can improve eccentric vision in subjects with central visual field loss

(CFL)[1]. The CFL subjects mostly correspond to older age groups who use eccentric

fixation angles up to 20°–30°. While there have been studies comparing the off-axis

lower order aberrations in normal young and old subjects[2], there is only one recent

study, which has compared off-axis higher order aberrations in normal young and old

emmetropic eyes up to 20° (horizontal and vertical) eccentricity[3]. In this study we

have measured off-axis aberrations in a group of 10 young (23 ± 3 years) and 10 old

(57 ± 4 years) emmetropes. The aberrations of the right eye were measured using

COAS-HD VR Hartmann-Shack aberrometer in steps 10° out to ± 40° horizontally and

–20° inferiorly in the visual field. Subjects rotated the eyes to view the fixation targets,

which were red light emitting diodes, placed at 3 meter from the eye. The aberrations

were quantified for a pupil area 5 mm in diameter.

Discussion

 

 

Mixed between-within subject’s analysis of variance of the horizontal coma C13

showed that there was a statistically significant difference between age groups

(p<0.05). The coma increased linearly in both groups from nasal to temporal visual

field. The rate of change was greater in the old (slope = –0.027 μm/deg) compared

to the young (slope = –0.012 μm/deg) emmetropes. In the inferior visual field,

vertical coma C-13 changed linearly in both groups with higher values in old (slope =

0.015 μm/deg) compared to young (slope = 0.006 μm/deg). The mean spherical

aberration was positive in older emmetropes (0.053 μm) compared to young

emmetropes (-0.030 μm). The HO RMS showed a quadratic increase in the

periphery for both age groups. The HO RMS was greater in older emmetropes but it

was not statistically significant (p>0.05) when compared to young emmetropes.

 

Conclusions

 

 

Our results show that there is an increase in coma, spherical aberration, and HO

RMS with age in the periphery.

Keywords
Peripheral aberrations, Age, COAS-HD VR
National Category
Ophthalmology
Research subject
Natural Science, Optometry
Identifiers
urn:nbn:se:lnu:diva-8670 (URN)
Conference
5th EMVPO 2010, Stockholm, Sweden
Available from: 2010-09-27 Created: 2010-09-27 Last updated: 2016-04-27Bibliographically approved
Baskaran, K., Theagarayan, B., Carius, S. & Gustafsson, J. (2010). Measurement of Off-axis Refraction with a Commercial Open Field Aberrometer. Paper presented at EAOO 2010, Copenhagen, Denmark.
Open this publication in new window or tab >>Measurement of Off-axis Refraction with a Commercial Open Field Aberrometer
2010 (English)Conference paper, Published paper (Refereed)
Abstract [en]

Purpose:

People with central visual field loss (CFL) use their remaining peripheral vision in order to see better when performing various visual related tasks. At large off-axis angles, the eccentric vision can be limited both by the low resolution capacity of the peripheral retina and by the optical aberrations caused due to oblique angles. Previous work has shown that eccentric correction of induced off-axis astigmatism can improve vision in a preferred retinal location (PRL) for people with CFL. However, the eccentric refraction is often difficult to determine with traditional refractive methods. This work therefore shows the use of a commercially available wavefront sensor to measure fast and reliable off-axis refraction. Data on off-axis refraction is also of interest in the field of myopia research.

Methods:

We used the new open-field high-definition complete ophthalmic analysis system, COAS HD -VR, to evaluate off-axis refraction. Using the special Vision Research tool in this system stimulus (fixation objects) can be presented in a large part of the visual field. The instrument can measure out to 40 degrees in the horizontal visual field and 20 degrees in the vertical visual field with a range from sphere +7 D to − 17 D. It measures astigmatism up to 10 D. This instrument also allows natural binocular viewing without obstacles. Aberrations of the right eye of 30 emmetropes (24 ± 4 years) were studied. Off-axis refraction and higher order (HO) aberrations were measured in steps of 10° out to ± 30° in the horizontal visual field

Results:

The first data on young emmetropic eyes with this new instrument showed promising results for low (LO) and higher order (HO) aberrations in the peripheral visual field. Of the LO aberrations, astigmatism increased significantly with the off–axis angle, from 0.25 D at 10° Nasal to 1.65 D at 30° Nasal. In the HO aberrations, coma (C13) showed a linear increase across the horizontal visual field (p < 0.05)

Conclusions:

The COAS HD-VR shows promising results and good usability for future research in evaluation of off-axis refraction. In future we believe the aberrometer can be used clinically to measure off-axis refractions in low vision patients.

Keywords
Off-axis refraction, COAS-HD VR Aberrometer, Peripheral aberrations
National Category
Ophthalmology
Research subject
Natural Science, Optometry
Identifiers
urn:nbn:se:lnu:diva-8669 (URN)
Conference
EAOO 2010, Copenhagen, Denmark
Available from: 2010-09-27 Created: 2010-09-27 Last updated: 2016-04-27Bibliographically approved
Baskaran, K., Theagarayan, B., Carius, S. & Gustafsson, J. (2010). Ocular Aberrations in the Peripheral Visual Field With a Commercial Open-View Aberrometer. Paper presented at ARVO 2010 Annual Meeting. Investigative Ophthalmology and Visual Science, 51(5), Article ID 3951.
Open this publication in new window or tab >>Ocular Aberrations in the Peripheral Visual Field With a Commercial Open-View Aberrometer
2010 (English)In: Investigative Ophthalmology and Visual Science, ISSN 0146-0404, E-ISSN 1552-5783, Vol. 51, no 5, article id 3951Article in journal, Meeting abstract (Refereed) Published
Abstract [en]

PurposeThe interest in off-axis aberrations has increased with the discovery of a possible link between myopia development and peripheral optics. The most common technology to measure the off-axis aberrations is a Shack-Hartmann wavefront aberrometer. This is the first study to report peripheral aberrations in a large sample of emmetropic population with a commercial open-view Shack-Hartmann aberrometer. MethodsThe commercial open-view Shack-Hartmann aberrometer COAS-HD VR was used to measure the aberrations in the peripheral vision. Aberrations of the right eye of 30 emmetropes (24 {+/-} 4 years) were studied. Off-axis aberrations were measured in steps of 10{degrees} out to {+/-} 30{degrees} in the horizontal visual field. The subjects turned their eye to view the off-axis fixation target (light emitting diode placed at 3 meters) during the measurement. The resulting wavefront aberrations were parameterized with Zernike coefficients for a 5 mm diameter pupil. All analyzes are reported according to optical society of America (OSA) recommended standards. ResultsAberrations from the 2nd to 6th order and the total higher-order root-mean-square (HO RMS) were analyzed using one-way ANOVA. The defocus C02 was significantly myopic in the nasal visual field (+20{degrees}, +30{degrees}) whereas there was no significant difference in the temporal visual field. Astigmatism C22 increased quadratically from {+/-}10{degrees} in the periphery and coma C13 showed a linear increase across the horizontal visual field (p < 0.05). The spherical aberration C04 and the total HO RMS showed a significant change at {+/-}30o. ConclusionsOur results showed that in young emmetropes there was a significant increase of HO RMS at {+/-}30{degrees}, which is expected. Astigmatism, horizontal coma, and spherical aberration vary systematically across the horizontal visual field in agreement with Seidel theory. The findings of our study with a large sample of emmetropic population agree with the previous studies done with laboratory built aberrometers.

Keywords
aberrations, visual fields
National Category
Ophthalmology
Research subject
Natural Science, Optometry
Identifiers
urn:nbn:se:lnu:diva-6284 (URN)
Conference
ARVO 2010 Annual Meeting
Available from: 2010-06-17 Created: 2010-06-17 Last updated: 2017-12-12Bibliographically approved
Baskaran, K., Theagarayan, B., Carius, S. & Gustafsson, J. (2010). Repeatability of Peripheral Aberrations in Young Emmetropes. Optometry and Vision Science, 87(10), 751-759
Open this publication in new window or tab >>Repeatability of Peripheral Aberrations in Young Emmetropes
2010 (English)In: Optometry and Vision Science, ISSN 1040-5488, E-ISSN 1538-9235, Vol. 87, no 10, p. 751-759Article in journal (Refereed) Published
Abstract [en]

PURPOSE.: The purpose of this study is to assess the intrasession repeatability of ocular aberration measurements in the peripheral visual field with a commercially available Shack-Hartmann aberrometer (complete ophthalmic analysis system-high definition-vision research). The higher-order off-axis aberrations data in young healthy emmetropic eyes are also reported.

METHODS.: The aberrations of the right eye of 18 emmetropes were measured using an aberrometer with an open field of view that allows peripheral measurements. Five repeated measures of ocular aberrations were obtained and assessed in steps of 10 degrees out to +/-40 degrees in the horizontal visual field (nasal + and temporal -) and -20 degrees in the inferior visual field. The coefficient of repeatability, coefficient of variation, and the intraclass correlation coefficient were calculated as a measure of intrasession repeatability.

RESULTS.: In all eccentric angles, the repeatability of the third- and fourth-order aberrations was better than the fifth and sixth order aberrations. The coefficient of variation was <30% and the intraclass correlation coefficient was >0.90 for the third and fourth order but reduced gradually for higher orders. There was no statistical significant difference in variance of total higher-order root mean square between on- and off-axis measurements (p > 0.05). The aberration data in this group of young emmetropes showed that the horizontal coma (C13) was most positive at 40 degrees in the temporal field, decreasing linearly toward negative values with increasing off-axis angle into the nasal field, whereas all other higher-order aberrations showed little or no change.

CONCLUSIONS.: The complete ophthalmic analysis system-high definition-vision research provides fast, repeatable, and valid peripheral aberration measurements and can be used efficiently to measure off-axis aberrations in the peripheral visual field

Keywords
repeatability, off-axis wavefront aberrations, COAS-HD VR aberrometer, peripheral aberrations, visual field
National Category
Ophthalmology
Research subject
Natural Science, Optometry
Identifiers
urn:nbn:se:lnu:diva-8763 (URN)10.1097/OPX.0b013e3181f36336 (DOI)2-s2.0-78049303467 (Scopus ID)
Available from: 2010-10-04 Created: 2010-10-04 Last updated: 2017-12-12Bibliographically approved
Atwood, W. B., Abdo, A. A., Ackermann, M., Althouse, W., Anderson, B., Axelsson, M., . . . Ziegler, M. (2009). THE LARGE AREA TELESCOPE ON THE FERMI GAMMA-RAY SPACE TELESCOPE MISSION. Astrophysical Journal, 697(2), 1071-1102
Open this publication in new window or tab >>THE LARGE AREA TELESCOPE ON THE FERMI GAMMA-RAY SPACE TELESCOPE MISSION
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2009 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 697, no 2, p. 1071-1102Article in journal (Refereed) Published
Abstract [en]

The Large Area Telescope (Fermi/LAT, hereafter LAT), the primary instrument on the Fermi Gamma-ray Space Telescope (Fermi) mission, is an imaging, wide field-of-view (FoV), high-energy gamma-ray telescope, covering the energy range from below 20 MeV to more than 300 GeV. The LAT was built by an international collaboration with contributions from space agencies, high-energy particle physics institutes, and universities in France, Italy, Japan, Sweden, and the United States. This paper describes the LAT, its preflight expected performance, and summarizes the key science objectives that will be addressed. On-orbit performance will be presented in detail in a subsequent paper. The LAT is a pair-conversion telescope with a precision tracker and calorimeter, each consisting of a 4 x 4 array of 16 modules, a segmented anticoincidence detector that covers the tracker array, and a programmable trigger and data acquisition system. Each tracker module has a vertical stack of 18 (x, y) tracking planes, including two layers (x and y) of single-sided silicon strip detectors and high-Z converter material (tungsten) per tray. Every calorimeter module has 96 CsI(Tl) crystals, arranged in an eight-layer hodoscopic configuration with a total depth of 8.6 radiation lengths, giving both longitudinal and transverse information about the energy deposition pattern. The calorimeter's depth and segmentation enable the high-energy reach of the LAT and contribute significantly to background rejection. The aspect ratio of the tracker (height/width) is 0.4, allowing a large FoV (2.4 sr) and ensuring that most pair-conversion showers initiated in the tracker will pass into the calorimeter for energy measurement. Data obtained with the LAT are intended to (1) permit rapid notification of high-energy gamma-ray bursts and transients and facilitate monitoring of variable sources, (2) yield an extensive catalog of several thousand high-energy sources obtained from an all-sky survey, (3) measure spectra from 20 MeV to more than 50 GeV for several hundred sources, (4) localize point sources to 0.3-2 arcmin, (5) map and obtain spectra of extended sources such as SNRs, molecular clouds, and nearby galaxies, (6) measure the diffuse isotropic gamma-ray background up to TeV energies, and (7) explore the discovery space for dark matter.

National Category
Astronomy, Astrophysics and Cosmology
Research subject
Physics, Astroparticle Physics
Identifiers
urn:nbn:se:hik:diva-2836 (URN)10.1088/0004-637X/697/2/1071 (DOI)000266159500012 ()
Available from: 2010-02-23 Created: 2010-02-23 Last updated: 2017-12-12Bibliographically approved
Abdo, A. A., Ackermann, M., Ajello, M., Ampe, J., Anderson, B., Atwood, W. B., . . . Ziegler, M. (2009). The on-orbit calibration of the Fermi Large Area Telescope. Astroparticle physics, 32(3-4), 193-219
Open this publication in new window or tab >>The on-orbit calibration of the Fermi Large Area Telescope
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2009 (English)In: Astroparticle physics, ISSN 0927-6505, E-ISSN 1873-2852, Vol. 32, no 3-4, p. 193-219Article in journal (Refereed) Published
Abstract [en]

The Large Area Telescope (LAT) on-board the Fermi Gamma-ray Space Telescope began its on-orbit operations on June 23, 2008. Calibrations, defined in a generic sense, correspond to synchronization of trigger signals, optimization of delays for latching data, determination of detector thresholds, gains and responses, evaluation of the perimeter of the South Atlantic Anomaly (SAA), measurements of live time, of absolute time, and internal and spacecraft boresight alignments. Here we describe on-orbit calibration results obtained using known astrophysical sources, galactic cosmic rays, and charge injection into the front-end electronics of each detector. Instrument response functions will be described in a separate publication. This paper demonstrates the stability of calibrations and describes minor changes observed since launch. These results have been used to calibrate the LAT datasets to be publicly released in August 2009. (C) 2009 Elsevier B.V. All rights reserved.

National Category
Physical Sciences
Research subject
Natural Science, Physics
Identifiers
urn:nbn:se:hik:diva-2805 (URN)10.1016/j.astropartphys.2009.08.002 (DOI)000272276400005 ()
Available from: 2010-02-23 Created: 2010-02-23 Last updated: 2017-12-12Bibliographically approved
Gavler, S. B., Carius, S., Carlson, P., Johansson, G., Klamra, W. & Pearce, M. (2005). Radiation tests of CsI(Tl) crystals for the GLAST satellite mission. Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment, 545 (3), 842-851
Open this publication in new window or tab >>Radiation tests of CsI(Tl) crystals for the GLAST satellite mission
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2005 (English)In: Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment, ISSN 0168-9002, Vol. 545 (3), p. 842-851Article in journal (Refereed) Published
Abstract [en]

The electromagnetic calorimeter of the Gamma-ray Large Area Space Telescope (GLAST) consists of 16 towers of CsI(Tl) crystals. Each tower contains 8 layers of crystals (each 326.0×26.7×19.9mm3) arranged in a hodoscopic fashion. The crystals are read out at both ends with PIN diodes. Crystals produced by Amcrys-H are used. As a part of the quality control procedure during crystal production, samples from the uncut boules were systematically irradiated with gamma-rays from a 60Co source. The decrease in light yield due to radiation damage was measured, determining the radiation hardness of the boule. All boule samples passed the radiation hardness requirements, showing an average decrease in light yield of (14±4)% after having received a dose of 200 Gy. Studies have also been carried out to verify the correspondence between the post-irradiation properties of the boule samples and the full-size crystals which are subsequently cut from the boule. A crystal log was irradiated with gamma-rays from a 60Co source and showed a decrease in light yield of (24±4)% after a dose of 180 Gy. A full-size crystal was also irradiated with a 180 MeV proton beam and the radiation induced attenuation and induced radioactivity was studied. The light yield was found to have decreased with (22±5)% after 175 Gy, and the dominant radioactive isotopes were identified. © 2005 Elsevier B.V. All rights reserved.

Place, publisher, year, edition, pages
Elsevier, 2005
Keywords
Calorimeter, Crystal scintillators, CsI(Tl), Gamma-rays, GLAST, Radiation damage
National Category
Physical Sciences
Research subject
Natural Science, Physics
Identifiers
urn:nbn:se:lnu:diva-695 (URN)10.1016/j.nima.2005.02.032 (DOI)
Available from: 2010-04-01 Created: 2010-04-01 Last updated: 2013-08-27Bibliographically approved
Steffen, P., Carius, S. & AMANDA Collaboration, . (2005). Results from the AMANDA neutrino telescope. Nuclear physics B, Proceedings supplements, 138(1-3), 167-170
Open this publication in new window or tab >>Results from the AMANDA neutrino telescope
2005 (English)In: Nuclear physics B, Proceedings supplements, ISSN 0920-5632, E-ISSN 1873-3832, Vol. 138, no 1-3, p. 167-170Article in journal (Refereed) Published
Abstract [en]

The AMANDA neutrino telescope at the South Pole has been taking data since 1996. It has been upgraded in steps and reached its final stage in January 2000. Results are presented from the search for extraterrestrial neutrinos and neutrinos from dark matter annihilation.

National Category
Physical Sciences
Research subject
Physics, Astroparticle Physics
Identifiers
urn:nbn:se:lnu:diva-29186 (URN)10.1016/j.nuclphysbps.2004.11.039 (DOI)
Available from: 2013-10-03 Created: 2013-10-03 Last updated: 2017-12-06Bibliographically approved
Ahrens, J., Bai, X., Barwick, S. W., Bay, R. C., Becka, T., Becker, K.-H. -., . . . Young, S. (2004). Calibration and survey of AMANDA with the SPASE detectors. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 522(3), 347-359
Open this publication in new window or tab >>Calibration and survey of AMANDA with the SPASE detectors
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2004 (English)In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 522, no 3, p. 347-359Article in journal (Refereed) Published
Abstract [en]

We report on the analysis of air showers observed in coincidence by the Antarctic Muon and Neutrino detector array (AMANDA-B10) and the South Pole Air Shower Experiment (SPASE-1 and SPASE-2). We discuss the use of coincident events for calibration and survey of the deep AMANDA detector as well as the response of AMANDA to muon bundles. This analysis uses data taken during 1997 when both SPASE-1 and SPASE-2 were in operation to provide a stereo view of AMANDA. © 2003 Elsevier B.V. All rights reserved.

Place, publisher, year, edition, pages
Elsevier, 2004
Keywords
Cosmic rays, Neutrino telescopes
National Category
Physical Sciences
Identifiers
urn:nbn:se:lnu:diva-28446 (URN)10.1016/j.nima.2003.12.007 (DOI)
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Source: Scopus

Available from: 2013-08-27 Created: 2013-08-26 Last updated: 2017-12-06Bibliographically approved
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