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Publications (10 of 26) Show all publications
Kristiansen, M., Linden, C., Qvarlander, S., Wåhlin, A., Ambarki, K., Hallberg, P., . . . Jóhannesson, G. (2018). Blood flow rate of ophthalmic artery in patients with normal tension glaucoma and healthy controls. Paper presented at Annual Meeting of the Association-for-Research-in-Vision-and-Ophthalmology (ARVO), APR 29-MAY 03, 2018, Honolulu, HI. Investigative Ophthalmology and Visual Science, 59(9)
Open this publication in new window or tab >>Blood flow rate of ophthalmic artery in patients with normal tension glaucoma and healthy controls
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2018 (English)In: Investigative Ophthalmology and Visual Science, ISSN 0146-0404, E-ISSN 1552-5783, Vol. 59, no 9Article in journal, Meeting abstract (Other academic) Published
Abstract [en]

Purpose: To determine the blood flow rate of the ophthalmic artery (OA) in patients with Normal Tension Glaucoma (NTG) compared to age-matched healthy controls using phase-contrast magnetic resonance imaging (PCMRI).

Methods: Seventeen patients with treated NTG (11 female; mean age: 70±9 years) and 16 age-matched healthy controls (10 female; mean age: 71±9 years) underwent PCMRI using a 3-Tesla scanner as well as ophthalmological examinations including visual acuity, Goldmann Applanation Tonometry, Humphrey perimetry and fundoscopy. Ophthalmic blood flow was acquired using a 2D PCMRI sequence set to a spatial resolution of 0.35mm/pixel. Mean flow rate and cross-sectional area was calculated using Segment Software. The eye with the most severe glaucomatous damage classified by visual field index (VFI) was chosen for comparison. The primary outcome was blood flow rate of OA.

Results: The mean VFI was 41% ± 26 (mean±SD) for the worse NTG eyes. The intraocular pressure was 13.6±2.6 mmHg for NTG eyes and 13.8±2.1 mmHg for control eyes. The blood flow rate in the NTG group was 9.6±3.7 ml/min compared to 11.8±5.5 ml/min in the control group. The area was 1.7±0.3 mm2 and 2.0±0.6 mm2 respectively. No statistical significance was found between NTG and the control group regarding blood flow rate (p=0.07) or OA area (p=0.12).

Conclusions: Despite OA being an anastomosis between the intracranial and extracranial circulation, possibly generating an eye unrelated variability in blood flow, we found a trend level reduction of approximately 2 ml/min in NTG. The finding warrants blood flow rate analysis of smaller arteries specifically supplying the eye, e.g. the central retinal artery.

Place, publisher, year, edition, pages
The Association for Research in Vision and Ophthalmology, 2018
National Category
Ophthalmology
Identifiers
urn:nbn:se:umu:diva-152420 (URN)000442932805099 ()
Conference
Annual Meeting of the Association-for-Research-in-Vision-and-Ophthalmology (ARVO), APR 29-MAY 03, 2018, Honolulu, HI
Funder
Swedish Society for Medical Research (SSMF)The Swedish Medical Association
Available from: 2018-10-05 Created: 2018-10-05 Last updated: 2018-10-08Bibliographically approved
Schedin, S., Hallberg, P. & Behndig, A. (2017). Analysis of long-term visual quality with numerical 3D ray tracing after corneal crosslinking treatment. Applied Optics, 56(35), 9787-9792
Open this publication in new window or tab >>Analysis of long-term visual quality with numerical 3D ray tracing after corneal crosslinking treatment
2017 (English)In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 56, no 35, p. 9787-9792Article in journal (Refereed) Published
Abstract [en]

A numerical 3D ray tracing model was used to evaluate the long-term visual effects of two regimens of corneal crosslinking (CXL) treatment of 48 patients with the corneal degeneration keratoconus. The 3D ray tracing analyses were based on corneal elevation data measured by Scheimpflug photography. Twenty-two patients were treated with standard CXL applied uniformly across the corneal surface, whereas 26 patients underwent a customized, refined treatment only at local zones on the cornea (photorefractive intrastromal CXL; PiXL). Spot diagrams, spot root-mean-square (RMS) values, and Strehl ratios were evaluated for the patients prior to and 1, 3, 6, and 12 months after treatment. It was found that the group of patients treated with PiXL, on average, tended to attain a long-term improvement of the corneal optical performance, whereas only minor changes of the optical parameters were found for group treated with standard CXL. Our results confirmed that standard CXL treatment stabilizes the corneal optical quality over time, and thus halts the progression of the corneal degeneration. In addition to stabilization, the results showed that a significantly higher proportion of subjects treated with PiXL improved in RMS, 3, 6, and 12 months after treatment, compared to with CXL (p<0.05). This finding indicates that the PiXL treatment might improve optical quality over time.

Place, publisher, year, edition, pages
Optical Society of America, 2017
Keywords
Ophthalmic optics and devices, Geometric optical design, Vision acuity, Visual optics, modeling, Visual optics, refractive anomalies
National Category
Other Physics Topics
Identifiers
urn:nbn:se:umu:diva-142716 (URN)10.1364/AO.56.009787 (DOI)000417553500023 ()29240126 (PubMedID)
Available from: 2017-12-08 Created: 2017-12-08 Last updated: 2018-06-09Bibliographically approved
Wadbro, E., Hallberg, P. & Schedin, S. (2016). Optimization of an intraocular lens for correction of advanced corneal refractive errors. Applied Optics, 55(16), 4378-4382
Open this publication in new window or tab >>Optimization of an intraocular lens for correction of advanced corneal refractive errors
2016 (English)In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 55, no 16, p. 4378-4382Article in journal (Refereed) Published
Abstract [en]

Based on numerical 3D ray tracing, we propose a new procedure to optimize personalized intra-ocular lenses (IOLs). The 3D ray tracing was based on measured corneal elevation data from patients who suffered from advanced keratoconus. A mathematical shape description of the posterior IOL surface, by means of a tensor product cubic Hermite spline, was implemented. The optimized lenses provide significantly reduced aberrations. Our results include a trade-off study that suggests that it is possible to considerably reduce the aberrations with only minor perturbations of an ideal spherical lens. The proposed procedure can be applied for correction of aberrations of any optical system by modifying a single surface.

Place, publisher, year, edition, pages
Optical Society of America, 2016
Keywords
Ophthalmic optics and devices, Geometric optical design, Vision - acuity, Nonspherical lens design, Visual optics, modeling, Visual optics, refractive anomalies
National Category
Ophthalmology
Identifiers
urn:nbn:se:umu:diva-121173 (URN)10.1364/AO.55.004378 (DOI)000377050400017 ()27411190 (PubMedID)
External cooperation:
Available from: 2016-05-27 Created: 2016-05-27 Last updated: 2018-06-07Bibliographically approved
Schedin, S., Hallberg, P. & Behndig, A. (2016). Three-dimensional ray-tracing model for the study of advanced refractive errors in keratoconus. Applied Optics, 55(3), 507-514
Open this publication in new window or tab >>Three-dimensional ray-tracing model for the study of advanced refractive errors in keratoconus
2016 (English)In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 55, no 3, p. 507-514Article in journal (Refereed) Published
Abstract [en]

We propose a numerical three-dimensional (3D) ray-tracing model for the analysis of advanced corneal refractive errors. The 3D modeling was based on measured corneal elevation data by means of Scheimpflug photography. A mathematical description of the measured corneal surfaces from a keratoconus (KC) patient was used for the 3D ray tracing, based on Snell's law of refraction. A model of a commercial intraocular lens (IOL) was included in the analysis. By modifying the posterior IOL surface, it was shown that the imaging quality could be significantly improved. The RMS values were reduced by approximately 50% close to the retina, both for on-and off-axis geometries. The 3D ray-tracing model can constitute a basis for simulation of customized IOLs that are able to correct the advanced, irregular refractive errors in KC.

Place, publisher, year, edition, pages
Optical Society of America, 2016
National Category
Ophthalmology
Identifiers
urn:nbn:se:umu:diva-113596 (URN)10.1364/AO.55.000507 (DOI)000369055100038 ()26835925 (PubMedID)
Available from: 2015-12-21 Created: 2015-12-21 Last updated: 2018-06-07Bibliographically approved
Johannesson, G., Hallberg, P., Ambarki, K., Eklund, A. & Linden, C. (2015). Age-dependency of ocular parameters - a cross sectional study of young and old healthy subjects. Paper presented at Annual Meeting of the Association-for-Research-in-Vision-and-Ophthalmology (ARVO), MAY 03-07, 2015, Denver, CO. Investigative Ophthalmology and Visual Science, 56(7), Article ID Meeting Abstract: 116.
Open this publication in new window or tab >>Age-dependency of ocular parameters - a cross sectional study of young and old healthy subjects
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2015 (English)In: Investigative Ophthalmology and Visual Science, ISSN 0146-0404, E-ISSN 1552-5783, Vol. 56, no 7, article id Meeting Abstract: 116Article in journal, Meeting abstract (Other academic) Published
Abstract [en]

Purpose: To investigate aging effect on ocular parameters inkluding intraocular pressure (IOP) measured with different tonometry methods in healthy young (HY) and elderly (HE) subjects.

Methods: Fifty eyes of 50 HY subjects (28 females, 22-31 years of age) and 43 eyes of 43 HE subjects (22 females, 64-79 years of age) were included. IOP was measured with four tonometry methods in a standardized order: Ocular Response Analyser (ORA), Dynamic Contour Tonometry (DCT), Applanation Resonance Tonometry (ART) and Goldmann Applanation Tonometry (GAT). Other measurements included axial length (AL), central corneal thickness (CCT), corneal curvature (CC), ocular pulse amplitude (OPA) and aqueous humor (aq).

Results: The mean IOP (HY/HE; mmHg ± standard deviation) was 13.9 ± 2.7/16.4 ± 3.4 with ORA, 15.1 ± 2.1/16.3 ± 3.1 with DCT, 12.3 ± 2.0/13.7 ± 2.8 with GAT and 13.1 ± 2.2/12.1 ± 2.5 with ART. IOP was significantly higher (difference ± standard error) in HE compared to HY measured with ORA (+2.5 mmHg ± 0.6), GAT (+1.4 ± 0.5) and DCT (+1.2 ± 0.6). There was a trend towards lower IOP in HE when measured with ART (-1.0 ± 0.5, p=0.05). There was no difference between HE and HY in CCT, CC, AL or OPA.

Conclusions: Tonometry methods are affected differently by age. IOP was measured higher in elderly people with ORA, DCT and GAT in this Scandinavian population. This effect was not seen in measurements with ART. Other ocular parameters did not differ between the age groups indicating that these measured parameters are not influenced by age in this population.

Place, publisher, year, edition, pages
Association for Research in Vision and Ophthalmology, 2015
National Category
Ophthalmology
Identifiers
urn:nbn:se:umu:diva-111516 (URN)000362882200106 ()
Conference
Annual Meeting of the Association-for-Research-in-Vision-and-Ophthalmology (ARVO), MAY 03-07, 2015, Denver, CO
Available from: 2015-12-02 Created: 2015-11-13 Last updated: 2018-06-07Bibliographically approved
Johannesson, G., Hallberg, P., Ambarki, K., Eklund, A. & Linden, C. (2015). Age-dependency of ocular parameters: a cross sectional study of young and elderly healthy subjects. Graefe's Archives for Clinical and Experimental Ophthalmology, 253(11), 1979-1983
Open this publication in new window or tab >>Age-dependency of ocular parameters: a cross sectional study of young and elderly healthy subjects
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2015 (English)In: Graefe's Archives for Clinical and Experimental Ophthalmology, ISSN 0721-832X, E-ISSN 1435-702X, Vol. 253, no 11, p. 1979-1983Article in journal (Refereed) Published
Abstract [en]

To investigate the effect of aging on ocular parameters, including intraocular pressure (IOP), measured with different tonometry methods in healthy young (HY) and healthy elderly (HE) subjects and to study the effect of corneal parameters on tonometry methods. In this prospective, cross-sectional study, fifty eyes of 50 HY subjects (28 females, 22-31 years of age) and 43 eyes of 43 HE subjects (22 females, 64-79) were included. IOP was measured with four tonometry methods in a standardized order: ocular response analyser (ORA), dynamic contour tonometry (DCT), applanation resonance tonometry (ART) and Goldmann applanation tonometry (GAT). Other measurements included axial length (AL), central corneal thickness (CCT), corneal curvature (CC), anterior chamber volume (ACV), corneal hysteresis (CH) and corneal resistance factor (CRF). The mean IOP (HY/HE; mmHg +/- standard deviation (SD)) was 12.2 +/- 2.2/14.1 +/- 3.5 with GAT. IOP was significantly higher (difference +/- standard error) in HE compared to HY measured with an ORA (+3.1 mmHg +/- 0.6), GAT (+1.9 +/- 0.6) and DCT (+1.6 +/- 0.6). No significant difference was found in IOP measured with ART. CH and ACV were significantly lower in HE compared to HY. There was no difference between the groups in CCT, CC, AL or CRF. No tonometry method was dependant on CCT or CC. IOP measured with an ORA and via DCT and GAT was higher in HE compared to HY Swedish subjects, while IOP measured with ART did not differ between the groups. In these homogeneous groups, tonometry methods were independent of CCT and CC.

Place, publisher, year, edition, pages
Springer, 2015
Keywords
Intraocular pressure, Age dependency, Central corneal thickness, Corneal curvature, Ocular response analyser, Dynamic contour tonometry, Applanation resonance tonometry
National Category
Ophthalmology
Identifiers
urn:nbn:se:umu:diva-111465 (URN)10.1007/s00417-015-3129-5 (DOI)000363057900020 ()26267751 (PubMedID)
Available from: 2015-12-02 Created: 2015-11-13 Last updated: 2018-06-07Bibliographically approved
Beckman Rehnman, J., Lindén, C., Hallberg, P. & Behndig, A. (2015). Treatment Effect and Corneal Light Scattering With 2 Corneal Cross-linking Protocols: A Randomized Clinical Trial. JAMA ophthalmology, 133(11), 1254-1260
Open this publication in new window or tab >>Treatment Effect and Corneal Light Scattering With 2 Corneal Cross-linking Protocols: A Randomized Clinical Trial
2015 (English)In: JAMA ophthalmology, ISSN 2168-6165, E-ISSN 2168-6173, Vol. 133, no 11, p. 1254-1260Article in journal (Refereed) Published
Abstract [en]

Importance: We describe and evaluate a complementary method to indirectly quantify the treatment effect of corneal cross-linking (CXL). Additional methods to indirectly quantify the treatment effect of CXL are needed.

Objective: To assess the spatial distribution and the time course of the increased corneal densitometry (corneal light backscatter) seen after CXL with riboflavin and UV-A irradiation.

Design, Setting, and Participants: Open-label randomized clinical trial of 43 patients (60 eyes) who were 18 to 28 years of age and had progressive keratoconus and a plan to be treated with CXL at Umeå University Hospital, Umeå, Sweden. The patients were randomized to receive conventional CXL (n = 30) using the Dresden protocol or CXL with mechanical compression of the cornea using a flat rigid contact lens sutured to the cornea during the treatment (CRXL) (n = 30). All participants were followed up during a 6-month period from October 13, 2009, through May 31, 2012.

Interventions: Corneal cross-linking according to the Dresden protocol or CRXL.

Main Outcomes and Measures: Change in corneal densitometry after CXL and CRXL for keratoconus.

Results: Of the original 60 eyes included, 4 had incomplete data. A densitometry increase was seen after both treatments that was deeper and more pronounced in the CXL group (difference between the groups at 1 month in the center layer, zone 0-2 mm, 5.02 grayscale units [GSU], 95% CI, 2.92-7.12 GSU; P < .001). This increase diminished with time but was still noticeable at 6 months (difference between the groups at 6 months in the center layer, zone 0-2 mm, 3.47 GSU; 95% CI, 1.72-5.23 GSU; P < .001) and was proportional to the reduction in corneal steepness (R = -0.45 and -0.56 for CXL and CRXL, respectively).

Conclusions and Relevance: The degree of corneal light backscatter relates to the reduction in corneal steepness after cross-linking and may become a relevant complement to other methods in evaluating the cross-linking effect, for example, when comparing different treatment regimens.

Trial Registration: clinicaltrials.gov Identifier: NCT02425150.

National Category
Ophthalmology
Identifiers
urn:nbn:se:umu:diva-110530 (URN)10.1001/jamaophthalmol.2015.2852 (DOI)000365034000008 ()26312777 (PubMedID)
Available from: 2015-10-22 Created: 2015-10-22 Last updated: 2018-06-07Bibliographically approved
Jóhannesson, G., Lindén, C., Eklund, A., Behndig, A. & Hallberg, P. (2014). Can we trust intraocular pressure measurements in eyes with intracameral air?. Graefe's Archives for Clinical and Experimental Ophthalmology, 252(10), 1607-1610
Open this publication in new window or tab >>Can we trust intraocular pressure measurements in eyes with intracameral air?
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2014 (English)In: Graefe's Archives for Clinical and Experimental Ophthalmology, ISSN 0721-832X, E-ISSN 1435-702X, Vol. 252, no 10, p. 1607-1610Article in journal (Refereed) Published
Abstract [en]

PURPOSE: To evaluate the effect of intracameral air on intraocular pressure (IOP) measurements using Goldmann applanation tonometry (GAT) and applanation resonance tonometry (ART) in an in-vitro porcine eye model.

METHODS: IOP was measured on thirteen freshly enucleated eyes at three reference pressures: 20, 30, and 40 mmHg. Six measurements/method were performed in a standardized order with GAT and ART respectively. Air was injected intracamerally in the same manner as during Descemet's stripping endothelial keratoplasty (DSEK) and Descemet's membrane endothelial keratoplasty (DMEK), and the measurements were repeated.

RESULTS: Measured IOP increased significantly for both tonometry methods after air injection: 0.7 ± 2.1 mmHg for GAT and 10.6 ± 4.9 mmHg for ART. This difference was significant at each reference pressure for ART but not for GAT.

CONCLUSIONS: Although slightly affected, this study suggests that we can trust GAT IOP-measurements in eyes with intracameral air, such as after DSEK/DMEK operations. Ultrasound-based methods such as ART should not be used.

Place, publisher, year, edition, pages
Springer, 2014
Keywords
intraocular pressure; intracameral air; Goldmann applanation tonometry; applanation resonance tonometry; DSEK; DMEK
National Category
Ophthalmology
Identifiers
urn:nbn:se:umu:diva-96875 (URN)10.1007/s00417-014-2720-5 (DOI)000344631600012 ()25030238 (PubMedID)
Available from: 2014-12-05 Created: 2014-12-05 Last updated: 2018-06-07Bibliographically approved
Johannesson, G., Hallberg, P., Eklund, A., Behndig, A. & Linden, C. (2014). Effects of topical anaesthetics and repeated tonometry on intraocular pressure. Acta Ophthalmologica, 92(2), 111-115
Open this publication in new window or tab >>Effects of topical anaesthetics and repeated tonometry on intraocular pressure
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2014 (English)In: Acta Ophthalmologica, ISSN 1755-375X, E-ISSN 1755-3768, Vol. 92, no 2, p. 111-115Article in journal (Refereed) Published
Abstract [en]

Purpose:

To investigate the effects of repeated measurements of intraocular pressure (IOP) using Goldmann applanation tonometry (GAT) and applanation resonance tonometry (ART) to identify mechanisms contributing to the expected IOP reduction.

Methods:

A prospective, single-centre study with six healthy volunteers. Consecutive repeated series (six measurements/serie/method) were made alternately on both eyes for 1 hr with oxybuprocaine/fluorescein in the right eye and tetracaine in the left. The left eye was Pentacam((R)) photographed before and repeatedly for 20 min after the IOP measurements. On a separate occasion, the same volunteers received the same amount of anaesthetic drops for 1 hr but without repeated IOP measurements.

Results:

A significant IOP reduction occurred with both ART and GAT in the oxybuprocaine-treated eye, -4.4 mmHg and -3.8 mmHg, respectively and with ART in the tetracaine eye, -2.1 mmHg. There was a significant difference in IOP reduction between the oxybuprocaine and tetracaine eyes with ART. There was a significant drop in anterior chamber volume (ACV) immediately after the IOP measurements, -12.6 mu l that returned to pretrial level after 2 min. After 1 hr of receiving anaesthetic eye drops (without IOP measurements), the IOP decreased significantly in the oxybuprocaine eye for both ART and GAT, -3.1 and -1.7 mmHg, respectively, but not in the tetracaine eye (p = 0.72).

Conclusion:

The IOP reduction cannot be explained solely by aqueous humor being pressed out of the anterior chamber. While significant IOP reduction occurred with both tetracaine and oxybuprocaine after repeated mechanical applanation, the IOP reduction was significantly greater with oxybuprocaine.

Keywords
aqueous humor, repeated tonometry, applanation resonance tonometry, intraocular pressure, Goldmann applanation tonometry
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:umu:diva-88289 (URN)10.1111/aos.12058 (DOI)000331720200007 ()23387522 (PubMedID)
Available from: 2014-05-02 Created: 2014-04-29 Last updated: 2018-06-07Bibliographically approved
Beckman Rehnman, J., Behndig, A., Hallberg, P. & Lindén, C. (2014). Increased corneal hysteresis after corneal collagen crosslinking: a study based on applanation resonance technology. JAMA ophthalmology, 132(12), 1426-1432
Open this publication in new window or tab >>Increased corneal hysteresis after corneal collagen crosslinking: a study based on applanation resonance technology
2014 (English)In: JAMA ophthalmology, ISSN 2168-6165, E-ISSN 2168-6173, Vol. 132, no 12, p. 1426-1432Article in journal (Refereed) Published
Abstract [en]

Importance: A reliable tool for quantification of the biomechanical status of the cornea in conjunction with corneal collagen crosslinking (CXL) treatment is needed.

Objective: To quantify the biomechanical effects of CXL in vivo.

Design, Setting, and Participants: A prospective, open, case-control study was conducted at the Department of Ophthalmology, Umeå University, Umeå, Sweden. Participants included 28 patients (29 eyes) aged 18 to 28 years with progressive keratoconus and corresponding age- and sex-matched healthy individuals serving as controls. All participants were monitored during a 6-month period between October 13, 2009, and November 5, 2012.

Main Outcomes and Measures: Corneal hysteresis after CXL for keratoconus.

Results: A difference in corneal hysteresis between the control group and the patients with keratoconus was found at baseline, both with an applanation resonance tonometer (ART) and an ocular response analyzer (ORA), at mean (SD) values of -1.09 (1.92) mm Hg (99% CI, -2.26 to 0.07; P = .01) and -2.67 (2.55) mm Hg (99% CI, -4.05 to -1.32; P < .001), respectively. Increased corneal hysteresis was demonstrated with an ART 1 and 6 months after CXL, at 1.2 (2.4) mm Hg (99% CI,-0.1 to 2.5; P = .02) and 1.1 (2.7) mm Hg (99% CI, -0.3 to 2.6; P = .04), respectively, but not with ORA. A decrease in corneal thickness was seen 1 and 6 months after treatment (-24 [26] µm, P < .001; and -11 [21] µm, P = .01, respectively), and a corneal flattening of -0.6 (0.7) diopters was seen at 6 months (P < .001). No significant change in intraocular pressure was identified in patients with keratoconus with any method, except for an increase at 1 month with Goldmann applanation tonometry (P = .005).

Conclusions and Relevance: To our knowledge ART is the first in vivo method able to assess the increased corneal hysteresis after CXL treatment. Given the large-scale use of CXL in modern keratoconus treatment, a tool with this capacity has a great potential value. Refinement of the ART method of measuring and quantifying corneal biomechanical properties will be a subject of further studies.

Place, publisher, year, edition, pages
American Medical Association, 2014
National Category
Ophthalmology
Identifiers
urn:nbn:se:umu:diva-97009 (URN)10.1001/jamaophthalmol.2014.3029 (DOI)000346176400008 ()25171564 (PubMedID)
Available from: 2014-12-08 Created: 2014-12-08 Last updated: 2018-06-07Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-2055-576X

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