| 1. |
- Abrahamsson, Maths, 1953, et al.
(författare)
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[Dim the light! Glare problems in a world with ever increasing demands on visual acuity] : Blända av!
- 1997
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Ingår i: Läkartidningen. - 0023-7205. ; 94:41, s. 3607-11
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Ocular tissue transparency is dependent on the regular lattice configuration of lens and corneal fibres of uniform diameter. Ageing is associated with degeneration of both lens and cornea, which lose some of their structural order and eventually their transparency, though this process is not uniform. The structural changes are local and result in ocular media opacities. When the opacities increase in number and extension, they begin to affect visual acuity. As the loss of acuity becomes clinically significant, we speak of clinically relevant cataract. Retinal exposure to light diffused by intraocular light scattering induces optical glare, one of two forms of glare. The other form is transient glare--i.e., glare due to adaptation problems in an environment with rapidly changing ambient luminance. Contemporary society is characterised by increasing emphasis on visual information in such forms as texts, icons, signs and symbols. The computer revolution has been accompanied by further stress on the importance of the detection and interpretation of written instructions.
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| 2. |
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| 3. |
- Billger, Monica, 1961, et al.
(författare)
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An assessment method for evaluating colour rendering properties of light sources
- 2015
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Ingår i: Proceedings of the 28th Session of the CIE, Manchester, United Kingdom, 28 June – 4 July 2015. - 9783902842558 ; Volume 1:part 2, s. 954-963
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Konferensbidrag (refereegranskat)abstract
- Abstract We present an assessment method to evaluate how the spectral power distribution of light influences the perception of colours and small colour differences. Included in the method are several ways to measure properties of reflected light with a spectroradiometer, visual assessments of perceived colours, and a visual performance test that aims at identifying an individual minimum colour contrast visibility threshold. In a first application of the assessment method, we used a colour contrast test chart printed on paper and studied it under the illumination of three LED light sources, halogen light and daylight. We concluded that the visual performance test was effective for reviling visibility thresholds for colour contrasts and that the method has potential for understanding the influence of spectral power distribution on perceived colour and visual performance. The methodology can be useful for optimizing illumination for individual needs.
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| 4. |
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| 5. |
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| 6. |
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| 7. |
- Jonsson, Kenneth, et al.
(författare)
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Traffic compensated luminance estimation
- 2015
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Active control of street light sources based on sensor data is desired to meet requirements on traffic safety and environmental protection. In this report, we summarise the results of a research study focusing on some of the fundamental problems occurring when performing real-world sensor measurements for lighting control. In particular, we present results on the impact of traffic and the relationship between sensor angle and measured road surface luminance. Moreover, we present a comparison between different approaches to estimating the veiling luminance in tunnel lighting applications.
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| 8. |
- Knutsson, Per, 1978, et al.
(författare)
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Correction of static and non-common path aberrations in an adaptive optics system using inherent calibration data
- 2021
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Ingår i: Optics Express. - : Optica Publishing Group. - 1094-4087. ; 29:3, s. 3406-3414
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Tidskriftsartikel (refereegranskat)abstract
- For low-order adaptive optics systems, a method that is able to correct for system aberrations in the final focal plane is presented. The paper presents a novel figure of merit, corresponding to the integrated non-normalized tip-tilt-free optical transfer function. The inherent singular value decomposition modal content of the interaction matrix is used to optimize this figure of merit. The method has proven to be stable and robust, providing a simple mean to facilitate diffraction limited imaging in an experimental setup for ophthalmic applications. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
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| 9. |
- KNUTSSON, PER, et al.
(författare)
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Correction of static and non-common path aberrations in an adaptive optics system using inherent calibration data
- 2021
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Ingår i: Optics Express. - 1094-4087. ; 29:3, s. 3406-3414
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Tidskriftsartikel (refereegranskat)abstract
- For low-order adaptive optics systems, a method that is able to correct for system aberrations in the final focal plane is presented. The paper presents a novel figure of merit, corresponding to the integrated non-normalized tip-tilt-free optical transfer function. The inherent singular value decomposition modal content of the interaction matrix is used to optimize this figure of merit. The method has proven to be stable and robust, providing a simple mean to facilitate diffraction limited imaging in an experimental setup for ophthalmic applications.
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| 10. |
- Lindgren, Mikael, 1963, et al.
(författare)
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Traffic compensated luminance estimation
- 2015
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Ingår i: 28th CIE Session, 28 jun - 4 jul 2015 Manchester UK.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 11. |
- Löfgren, Stefan, et al.
(författare)
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Laser pointers and Eye injuries. An analysis of reported cases
- 2013
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The safety limits that exist for human exposure of laser radiation are essential to reduce the risk of injuries. These values, however, give very little information on what tissue damages that may be expected at various elevated exposure levels. Similarly, the Swedish Radiation Protection Authority (SSM) has very little information on how such tissue damage is related to the impairment of the vision. This type of relationship between an imaginary exposure and a subsequent disability is very useful in the risk assessments that are made in the authority’s supervision activities. Also, the damage’s evolvement over time is information that the authority can make use of in risk assessments. The purpose of this study was to investigate what dose of laser radiation, in terms of intensity and exposure time, may be associated with eye damages. The study has been limited to unwanted exposures of laser radiation from commercially available laser pointers. Of particular interest has been to search for data that clarify the dose-response relationships for functional disabilities that persist more than 6 months. The study shows that long-term vision loss can occur as a result of involuntary exposure from commercially available (strong) laser pointers at close range. The injury may occur before a normal person is able to respond by closing the eyelid, although there are only a few cases reported. A minor such damage is transient within a few days. It is also likely that such a visible injury to the retina becomes functional, i.e. prevents reading skills. What dosage is required for the disability to become permanent is not clear in the literature. Also, the dynamics of evolvement and repair of tissue damages and disabilities are hardly described at all.
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| 12. |
- Löfving, Björn, 1970, et al.
(författare)
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Visualization of Disability Glare Due to Veiling Luminance
- 2015
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Ingår i: Energy Procedia. - : Elsevier BV. - 1876-6102. ; 78, s. 735-740
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Konferensbidrag (refereegranskat)abstract
- We present a simulation method to evaluate and visualize disability glare problems. Mathematical calculations of visual degradations due to optical imperfections in the eye are performed on luminance photos of scenes and the result is visualized. The method was evaluated in three indoor and outdoor cases where different visual aspects on disability glare were studied. Overall, the simulations predicted problem areas in the scenes to a large extent. The method was also applied in a light rendered 3D-model and gave indications for improvements of the light setting. Aspects on improving environmental planning by better understanding of human vision are discussed.
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| 13. |
- Nylén, Per, et al.
(författare)
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Glare from strong laser pointers pose danger
- 2010
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Ingår i: Nordiska Ergonomisällskapet NES. Stavanger, Norge.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Strong laser pointers have become readily available at low cost during the last years. Predominantly, young men use these pointers for different purposes, from simply playing with it as an advanced torch to disturbing or trying to injure e.g. police men. Apart from the eye injury, pointing a strong hand held laser pointer towards a person can cause intense glare and lost dark adaptation. Such glare is a great, even life threatening danger if the exposed person is driving a vehicle at high speed or maneuvering an aircraft about to land. Not only to the driver or pilot himself but to the passengers and people in the nearby environment.
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| 14. |
- Owner-Petersen, Mette, et al.
(författare)
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Multi-object wavefront sensor with spatial filtering
- 2007
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Patent (övrigt vetenskapligt/konstnärligt)abstract
- The present invention relates to an adaptive optics sensor intended for simultaneous detection of several wavefronts on a common camera target. The sensor is intended for use in connection with multi-conjugate adaptive optics (MCAO), where several wavefront measurements are needed at the same time. The sensor includes a spatial filter taking out signals resulting from parasitic reflections of the reference sources and from unwanted parts of the object.
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| 15. |
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| 16. |
- Popovic, Zoran, 1966, et al.
(författare)
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Dual Conjugate Adaptive Optics Prototype for Wide Field High Resolution Retinal Imaging
- 2012
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Ingår i: Adaptive Optics Progress. - Rijeka : Intech. - 9789535108948 ; , s. 3-21
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Retinal imaging is limited due to optical aberrations caused by imperfections in the optical media of the eye. Consequently, diffraction limited retinal imaging can be achieved if optical aberrations in the eye are measured and corrected. Information about retinal pathology and structure on a cellular level is thus not available in a clinical setting but only from histological studies of excised retinal tissue. In addition to limitations such as tissue shrinkage and distortion, the main limitation of histological preparations is that longitudinal studies of disease progression and/or results of medical treatment are not possible. Adaptive optics (AO) is the science, technology and art of capturing diffraction-limited images in adverse circumstances that would normally lead to strongly degraded image quality and loss of resolution. In non-military applications, it was first proposed and implemented in astronomy. AO technology has since been applied in many disciplines, including vision science, where retinal features down to a few microns can be resolved by correcting the aberrations of ocular optics. As the focus of this chapter is on AO retinal imaging, we will focus our description to this particular field.
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| 17. |
- Popovic, Zoran, 1966, et al.
(författare)
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Noninvasive imaging of human foveal capillary network using dual-conjugate adaptive optics.
- 2011
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Ingår i: Investigative ophthalmology & visual science. - : Association for Research in Vision and Ophthalmology (ARVO). - 1552-5783. ; 52:5, s. 2649-55
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: To demonstrate noninvasive imaging of human foveal capillary networks with a high-resolution, wide-field, dual-conjugate adaptive optics (DCAO) imaging instrument. METHODS: The foveal capillary networks of five healthy subjects with no previous history of ocular or neurologic disease or surgery were imaged with a novel high-resolution, wide-field DCAO instrument. The foveal avascular zone (FAZ) in each image was defined using a manual procedure. An automated algorithm based on publicly available and custom-written software was used to identify vessels and extract morphologic FAZ and vessel parameters. Capillary densities were calculated in two annular regions of interest (ROIs) outside the FAZ (500 μm and 750 μm outer radius from the foveal center) and in the superior, inferior, temporal, and nasal quadrants within the two ROIs. RESULTS: Mean FAZ area was 0.302 ± 0.100 mm(2), and mean capillary density (length/area) in the inner ROI was 38.0 ± 4.0 mm(-1) and 36.4 ± 4.0 mm(-1) in the outer ROI. The difference in ROI capillary density was not significant. There was no significant difference in quadrant capillary density within the two ROIs or between quadrants irrespective of ROI. CONCLUSIONS: The authors have demonstrated a technique for noninvasive imaging and semiautomated detection and analysis of foveal capillaries. In comparison with other studies, their method yielded lower capillary densities than histology but similar results to the current clinical gold standard, fluorescein angiography. The increased field of view of the DCAO instrument opens up new possibilities for high-resolution noninvasive clinical imaging of foveal capillaries.
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| 18. |
- Thaung, Jörgen, 1965, et al.
(författare)
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A New Set-up for Contrast Sensitivity Testing at Very Small Glare Angles
- 2003
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Ingår i: Investigative Ophthalmology & Visual Science. ; 44:13
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Purpose: To investigate whether a small angle glare test in a clinical setting can produce and detect a significant decrease in contrast sensitivity with age in normal young and elderly eyes. Methods: Contrast sensitivity (CS), with and without glare, was measured in 20 subjects. The subjects were all fully corrected. CS was measured using the "Freiburg Visual Acuity & Contrast Test" (FrACT) software running on a Macintosh imac (CRT). In our set-up the software uses a 4AFC-method, and the test distance was 4 meters. Glare was induced by a Fostec DCR® II light source with a randomised fiberoptical bundle mirrored into the centre of a Landolt C test target. Full test symmetry was accomplished by using this glare set-up. The test target and the glare source subtended an angle of about 1.3° and 0.2° respectively, yielding a 0.5° glare angle. The target mean luminance was 61 cd/m2 and the illuminance at the eye was 15 lux with glare. Results: We measured 20 subjects (20 to 59 yrs) with no known eye disease. The results from the measurements were analysed seperately and also calculated as glare scores (CS without glare divided by CS with glare). CS data with and without glare produced low correlation with age, but the data showed large correlation with age when calculated as glare scores. The increase in glare score with age was about 2.5 in the tested group. The data was also compared with measurements of after cataract patients. For these patients the glare scores were about 10 to 20 times higher. Conclusions: The results indicate that this method is useful in studies of glare in normal and elderly eyes. The data also indicate a usefulness in quantifying the impact of cataract and after cataract.
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| 19. |
- Thaung, Jörgen, 1965, et al.
(författare)
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Dual-conjugate adaptive optics for wide-field high-resolution retinal imaging.
- 2009
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Ingår i: Optics express. - 1094-4087. ; 17:6, s. 4454-67
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Tidskriftsartikel (refereegranskat)abstract
- We present analysis and preliminary laboratory testing of a real-time dual-conjugate adaptive optics (DCAO) instrument for ophthalmology that will enable wide-field high resolution imaging of the retina in vivo. The setup comprises five retinal guide stars (GS) and two deformable mirrors (DM), one conjugate to the pupil and one conjugate to a plane close to the retina. The DCAO instrument has a closed-loop wavefront sensing wavelength of 834 nm and an imaging wavelength of 575 nm. It incorporates an array of collimator lenses to spatially filter the light from all guide stars using one adjustable iris, and images the Hartmann patterns of multiple reference sources on a single detector. Zemax simulations were performed at 834 nm and 575 nm with the Navarro 99 and the Liou- Brennan eye models. Two correction alternatives were evaluated; conventional single conjugate AO (SCAO, using one GS and a pupil DM) and DCAO (using multiple GS and two DM). Zemax simulations at 575 nm based on the Navarro 99 eye model show that the diameter of the corrected field of view for diffraction-limited imaging (Strehl >or= 0.8) increases from 1.5 deg with SCAO to 6.5 deg using DCAO. The increase for the less stringent condition of a wavefront error of 1 rad or less (Strehl >or= 0.37) is from 3 deg with SCAO to approximately 7.4 deg using DCAO. Corresponding results for the Liou-Brennan eye model are 3.1 deg (SCAO) and 8.2 deg (DCAO) for Strehl >or= 0.8, and 4.8 deg (SCAO) and 9.6 deg (DCAO) for Strehl >or= 0.37. Potential gain in corrected field of view with DCAO is confirmed both by laboratory experiments on a model eye and by preliminary in vivo imaging of a human eye.
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| 20. |
- Thaung, Jörgen, 1965, et al.
(författare)
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Dual-conjugate adaptive optics instrument for wide-field retinal imaging
- 2008
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Ingår i: Adaptive optics for industry and medicine, Proceedings of the sixth international workshop, National University of Ireland, Ireland 12-15 June 2007. - 1848161107 ; , s. 263-268
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Konferensbidrag (refereegranskat)abstract
- To date only conventional single-conjugate adaptive optics (SCAO) systems are used to correct ocular aberrations. A major shortcoming of SCAO is the severely restricted corrected field of view. This can be solved with multi-conjugate adaptive optics (MCAO), a solution that is costly and gives bulky instruments. Another problem, especially in the study of the human eye, is unwanted light from parasitic source reflections and light from unwanted object regions. We present a dual-conjugate adaptive optics (DCAO) demonstrator that will enable wide field high resolution imaging of the human retina in vivo, implementing five retinal guide stars, two OKO micromachined membrane deformable mirrors; a 15 mm 37 channel pupil conjugate mirror, and a 40 mm 79 channel mirror conjugated to a plane in the vitreous body approximately 3 mm in front of the retina. The AO system runs with a closed-loop measurement wavelength of 835 nm. It incorporates an array of collimator lenses to spatially filter the light from all guide stars using only one adjustable iris, and a single camera to image the Hartmann patterns of multiple reference sources. Optical simulations in Zemax indicate an increase of the retinal isoplanatic patch from a radius of 0.5 degrees using SCAO to approximately 3.5 degrees or more using DCAO. The advantage of this is a clinically useful imaging area that is approximately 50 times the size of an SCAO system. This is corroborated by measurements on a model eye while performing SCAO, ground layer adaptive optics (GLAO), and DCAO correction.
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| 21. |
- Thaung, Jörgen, 1965, et al.
(författare)
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Evaluation of the effect of tinted night driving glasses on contrast sensitivity with and without glare
- 2001
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Ingår i: Journal of Vision. ; 1:3, s. 456-456
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Purpose: To evaluate claims of contrast improvement by tinted night driving glasses (TNDG) during mesonic luminance conditions. Methods: Contrast sensitivity functions (CSF) were measured in two trained myopic subjects, aged 20 and 34 years, with no known eye disease and normal foveal fusion. Both were fully corrected and their accommodative abilities were 13D and 8D, respectively. CSF with and without glare, induced by a Fostec DCR® II Light with four fiberoptical branches, was measured with the Morphonome® 4.2.4 image psychophysics software at two spatial frequencies (3 and 23 cod). All measurements were done with the subjects wearing prescribed glasses, TNDG (Zeiss Clarlet 1.5 GOLD ET 015), and ophthalmic test lenses, with TNDG and test lenses beeing of equal dioptric value. Results: TNDG were found to perform better than prescribed glasses, especially subjectively. CSF was improved both with and without the presence of glare sources. However, no significant difference was found between TNDG and test lenses, neither with nor without glare. Conclusion: CSF was not significantly improved by tinted night driving glasses. Subjectively, the TNDG were prefered by both test subjects. Our findings indicate that at the higher spatial frequency the major improvements are due to the correction of night myopia.
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| 22. |
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| 23. |
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| 24. |
- Thaung, Jörgen, 1965, et al.
(författare)
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Integrated angular light scattering measurements of excised eye lenses
- 2002
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Ingår i: Investigative Ophthalmology & Visual Science. ; 43:13
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Purpose: To investigate the angular light scattering properties of excised eye lenses with intact lens capsule. More specifically to study if the angular distribution changes with wavelength and total light scattering in normal and cataractous lenses. Methods: A TIS-method (Total Integrated light Scattering) is used to estimate the light scattering properties. The lens, surrounded by biological salt solution, is positioned in a lens holding (LH) unit. Light from one of five laser-lines (458, 488, 514, 543 and 633 nm) is fed into an optical fiber whose other end is connected to the bottom of the LH unit. The lens, positioned at focal length distance from the fiber-end, collimates the laser light. The light is collected by an integrating sphere, and by using an extra circular port, the directly transmitted light (collimated light) can be separated from the scattered light. The angular distribution is then measured by using a computer controlled adjustable diaphragm to vary the sphere's angle of acceptance. Results: We measured 9 lenses from 7 donors (51 to 85 yrs). The lenses had a total light scattering range of about 19 to 87%, and a transmission range of about 86 to 94% @ 633 nm. The angular intensity distribution is plotted vs angle in a range of about 1° and 10° (half angle). Data is analyzed with power function (a*x^b) curve fitting, and with Half-Width-Half-Max (HWHM) measures. We found no significant dependency between angular distribution and wavelength. However, when compared to the total light scattering a significant shift towards lower values is found in the power function exponent, b, for lenses with pronounced light scattering. Conclusion: The results indicate that this method is useful in studies to determine light scattering properties of excised eye lenses. In a fairly simple way, dependence of wavelength and angular distribution in normal and cataractous lenses can be investigated.
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| 25. |
- Thaung, Jörgen, 1965, et al.
(författare)
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Integrated light scattering as a function of wavelength in donor lenses.
- 2002
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Ingår i: Journal of the Optical Society of America. A, Optics, image science, and vision. - 1084-7529. ; 19:1, s. 152-7
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this work is to investigate the light-scattering properties of excised eye lenses with intact lens capsules--more specifically, to compare light scattering with light transmission at different wavelengths in aging and cataractous lenses. A lens is positioned at its focal-length distance from an optical fiber end and collimates the light from one of five laser lines (458-633 nm). By use of an integrating sphere with an extra circular port, the collimated directly transmitted light can be separated from the scattered light. For lenses with low light-scattering levels, integrated scattering showed a dependence on wavelength, but when light scattering increased the wavelength difference tended to level out. Despite the higher percentage of lens light scattering at lower wavelengths, when calculated as an "effective light scattering" (compensated for light transmission), more scattered light actually falls toward the retina at longer wavelengths.
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| 26. |
- Thaung, Jörgen, 1965
(författare)
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Intraocular light scattering and glare testing
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Aims: To analyze the parameters that are used in psychophysical glare testing and the validity of the light scattering factor (LSF). The purpose is also to investigate the light scattering properties in excised eye lenses, and to compare these properties with light transmission for different wavelengths in aging and cataractous lenses. Finally, the purpose was to investigate whether a small angle glare test in a clinical setting can produce and detect a significant decrease in contrast sensitivity with age in normal young and elderly eyes.Materials & Methods: The importance of glare testing parameters was studied through theoretical analysis and comparison with earlier studies. Stimulus geometry and contrast definition were studied through optical modeling. Adaptation was modeled according to the laws of Weber and DeVries-Rose. The method for the light scattering measurements used an integrating sphere, an adjustable diaphragm, and a lens holding unit. The lens collimated light from one of five laser-lines (458 to 633 nm). By using a sphere with an extra port, the collimated directly transmitted light could be separated from the scattered light. The diaphragm changed the spheres angle of acceptance during angular measurements. In the small angle glare test, low contrast Landolt-C test targets was presented on a computer monitor. Glare was induced using a fiberoptical bundle mirrored into the center of the Landolt-C test target. Results: The choice of contrast definition may corrupt the result by a factor of 2. At background luminance levels above ~10 cd/m2 the Paulsson-Sjöstrand equation agrees well with theory. At lower luminance levels correction factors must be used. The results with our method for light scattering measurements showed a wavelength dependence for excised lenses with low light scattering levels, but when the light scattering increases the wavelength difference tends to level out. Despite the higher light scattering percentage for shorter wavelengths, when calculated as an "effective light scattering" (compensated for light transmission), more scattered light actually falls towards the retina at longer wavelengths. The angular distribution of the scattered light was found to have no relation with wavelength. However, when compared to the total light scattering a significant shift toward lesser angular dependence was found for lenses with pronounced light scattering. Contrast sensitivity data (CS) in the small angle glare test produced low correlation with age. However, the data showed large correlation with age when calculated as glare factors (CS/CSglare). The relative increase in glare factor with age was about 2.7 (max range) in the tested group (20-59 yrs).Conclusions: Glare testing using the LSF was found to be valid at high luminance levels, with targets of low spatiotemporal frequencies and with the use of a properly chosen definition of contrast. The results from the light scattering measurements indicate that our method is useful in studies of excised eye lenses. The method is very sensitive for early lens changes and can monitor the change in light scattering during various phases of cataract formation. Using the effective light scattering we can explain the disagreements whether the intraocularly scattered light has a wavelength dependence or not. A wavelength dependency with opposite sign was found in agreement with psychophysical findings. Correlation between angular distribution and wavelength was found only when compared to total light scattering. The results indicate that our glare method is useful in studies of glare in normal and elderly eyes. Glare factors show much smaller individual variation than data of contrast and glare measurements analysed separately.
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| 27. |
- Thaung, Jörgen, 1965
(författare)
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Light scatter and wavefront aberrations in the human eye
- 2014
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Ingår i: IMPROVE International Symposium - IMPROving the Visual Environment for all, 22-23 May 2014 Lund, Sweden. ; , s. 20-21
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Like all other optical systems, the human eye is limited by diffraction, optical aberrations and light scattering. Diffraction can be described by diffraction theory and is the fundamental limitation of any optical system. At small pupil sizes the retinal image quality is mainly limited by diffraction. Optical aberrations are errors that concern the focusing capability of an optical system. When aberrations are present focus spots will be spread out and the image quality degraded. Optical aberrations can be both chromatic and monochromatic, and both are present in the human eye. Opposite to the effects from diffraction, aberrations usually increase with pupil size. Light scatter in an optical system causes a reduction of image contrast due to a superimposed veil of light. Depending on the size of the scattering particles, the angular distribution of the veil will be different. Small particles will scatter in large angles, and large particles in narrow angles. Angular distribution in the human eye is fairly constant (inverse square of angle) but the number of particles increases with age. ! 20! ! In young normal eyes less than 10% of the light entering the pupil is scattered by the cornea and the lens. The light scattering increases exponentially with age, and in individuals with diagnosed cataract the amount of light scattering can be very high. One problem with diagnosing cataract is that light scattering has small impact on visual acuity. It is instead image contrast that is reduced and consequently it is retinal contrast sensitivity that should be tested. Preferably, tested with and without a glare source in the visual field [1]. Scattering is also one of the most important causes of glare complaints. To demonstrate the problems with degraded vision due to ocular aberrations and scattering our research group is working on a simulation system (VISSLA) that can visualize retinal image quality. Individual ocular aberration data and estimates of light scattering are calculated and applied on pixel-based images from digital cameras or CAD models. Besides the visualization capabilities, the underlying image data can be further explored by using embedded tools to measure the reduction in image contrast, e.g. to demonstrate the effect of inappropriate lighting designs. Our system, with a simplified eye model, has been validated in a feasibility study [2] and we have recently adopted the CIE standard glare observer model for more accurate simulations. Today there are no tools to ensure that lighting meets the requirements for people with visual impairments. Lighting designers must instead rely on their own experience. We are working close with architects and lighting designers to explore if our tool can be successful in creating visual environments better suited for people with normal ageing and ocular diseases (c.f. Fig). [1] Paulsson L-E, Sjostrand J. (1980) Contrast sensitivity in the presence of a glare light. Invest Ophthalmol Vis Sci.. 19:401-406. [2] Thaung J, Billger M, Löfving B and Sperling K. (2012) ”Visualization tool for increased quality of vision”, Proceedings ARCH12, Perspectives on Nordic Healthcare environments, Gothenburg 2012.
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| 28. |
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| 29. |
- Thaung, Jörgen, 1965, et al.
(författare)
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Reliability of a standardized test in Swedish for evaluation of reading performance in healthy eyes. Interchart and test-retest analyses
- 2014
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Ingår i: Acta Ophthalmologica. - : Wiley. - 1755-375X. ; 92:6, s. 557-562
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: The purpose of our study was to establish a practical and quick test for assessing reading performance and to statistically analyse interchart and test retest reliability of a new standardized Swedish reading chart system consisting of three charts constructed according to the principles available in the literature. Methods: Twenty-four subjects with healthy eyes, mean age 65 +/- 10 years, were tested binocularly and the reading performance evaluated as reading acuity, critical print size and maximum reading speed. The test charts all consist of 12 short text sentences with a print size ranging from 0.9 to 0.2 logNIAR in approximate steps of 0.1 logMAR. Two testing sessions, in two different groups (C1 and C2), were under strict control of luminance and lighting environment. Reading performance tests with chart Ti, '12 and T3 were used for evaluation of interchart reliability and test data from a second session 1 month or more apart for the test retest analysis. Results: The testing of reading performance in adult observers with short sentences of continuous text was quick and practical. The agreement between the tests obtained with the three different test charts was high both within the same test session and at retest. Conclusion: This new Swedish variant of a standardized reading system based on short sentences and logarithmic progression of print size provides reliable measurements of reading performance and preliminary norms in an age group around 65 years. The reading test with three independent reading charts can be useful for clinical studies of reading ability before and after treatment.
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| 30. |
- Thaung, Jörgen, 1965, et al.
(författare)
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Retinal injuries from handheld lasers: An updated report.
- 2015
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Background Handheld lasers, or powerful laser pointers, continue to cause eye injuries around the world. In 2013 the Swedish Radiation Safety Authority (SSM) published a report on eye injuries from handheld lasers (Löfgren et al. 2013). Objectives The purpose of this study was to update the previous report by examining the medical case histories of retinal injuries during the recent 2-3 years. The main focus was misuse of continuous wave handheld lasers leading to eye injuries. Inclusion criteria were primarily laser exposures using visible and near-infrared radiation (400-1400 nm) and short durations (0.05-1 s). Comparisons of the newly described laser exposures with exposure limits and eye injuries need to be re-examined. Also a timeline overview of the identifiable organic damages needed to be developed. Results A total of 47 new cases were found in the scientific literature. Unfortunately, many of them were described with insufficient data regarding the laser exposure. Analysis of estimated laser exposure were performed in eight cases and compared to international laser exposure limits. In four of the eight cases the exposures were estimated to be more than 100 times higher than the limits, and in one case the exposure was estimated to be 300+ times the safety limit. We found an increase in the number of reported cases with severe retinal injury. Need for further research We have previously identified topics for future research. For example, a national database of laser incidents, studies of photochemical effects, how visual aids can influence retinal exposure, treatments of laser retinal damages, secondary injuries (e.g. by glare), and long term or permanent functional deficits. In this report we have, in addition to the above topics, proposed a study to investigate the increased risk of retinal damage in cases when green handheld laser pointers are leaking infrared radiation.
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| 31. |
- Thaung, Jörgen, 1965, et al.
(författare)
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Rätt utformad LED‐belysning för bättre synkvalité
- 2015
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- LED‐tekniken är under hastig utveckling och ljusverkningsgraden för dioder kommer sannolikt att vara minst fördubblad inom några år. Tekniken att generera ett brett våglängdsspektrum kommer också troligen att förändras. Det unika med LED‐tekniken är att ljuskällorna är små, avger lite värme och kan byggas in i byggelement på ett sätt som inte tidigare varit möjligt med andra ljuskällor. Det finns nu alltså stora möjligheter att skapa bättre ljusdistribution i alla typer av rum, genom väl placerade och avskärmade ljuskällor som ger hög synkvalitet till rimlig kostnad och arbetsinsats. LED‐tekniken är långt utvecklad och driftsäkerhet, verkningsgrad och materialegenskaper förbättras kontinuerligt, men än så länge saknas en samsyn kring hur våglängdsspektrumen bör designas. Den stora drivkraften är att optimera verkningsgraden lumen/Watt och en annan strävan är att skapa våglängdsspektrum som liknar det från en halogenglödlampa. Det är dock förhållandevis lite forskningsaktivitet kring eventuella fördelar med ett sant dagsljuslikt våglängdsspektrum, med lika effektfördelning över det synliga våglängdsintervallet. Med detta projekt har vi haft ambitionen att öka kompetensen kring synprestation och belysning. Syftet har varit att undersöka hur LED‐belysning bättre kan utnyttjas för att stödja det mänskliga ögats egenskaper och begränsningar. Detta kan leda till att vi bättre kan utnyttja LED‐belysningens speciella fördelar för att åstadkomma optimal synkvalité för alla och för personer med sämre syn än normalt i synnerhet. I projektet har vi påbörjat en kartläggning av LED‐ljuskällors egenskaper med hjälp av olika utvärderingsmetoder som kan bidra till ökad förståelse av hur ljuskällors spektralfördelning påverkar synprestation och uppfattad färg. Vi har gjort en kort sammanfattning av forskningen inom området synprestation och belysning genom att beskriva några viktiga aspekter kring seende såsom färgseende, ögats optik och näthinna, bländning samt teorier rörande uppfattad ljushet. I en experimentell studie har vi kunnat visa hur olika spektralfördelning hos ljuskällor påverkar läsförmåga, reaktionstid och uppfattning av färgkontraster. Vidare forskning med fler observatörer och förfinade metoder behövs för att kunna dra generella slutsatser och tydligare kunna identifiera mönster.
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| 32. |
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| 33. |
- Thaung, Jörgen, 1965, et al.
(författare)
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The 'light scattering factor'. Importance of stimulus geometry, contrast definition, and adaptation.
- 1995
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Ingår i: Investigative ophthalmology & visual science. - 0146-0404 .- 1552-5783. ; 36:11, s. 2313-7
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE. Paulsson and Sjöstrand have suggested that the light scattering factor (LSF) can be estimated by using the equation: LSF = L/E (M2/M1-1). Here L is the space average luminance of the target, E is the illuminance of the glare source, and M2 and M1 are modulation contrast thresholds in the presence and absence of the glare source. To compensate for change of adaptation. Abrahamsson and Sjöstrand later modified the above equation by introducing a correction factor (CF): LSF = L/E ((CF) (M2/M1-1). The purpose of this study is to analyze the validity of the above equations. METHODS. The importance of stimulus geometry, contrast definition, background luminance, and glare illumination is studied through theoretical analysis and comparison with earlier studies. Stimulus geometry and contrast definition are studied through optical modeling. Adaptation is modeled according to the laws of Weber and DeVries-Rose. RESULTS. The choice of contrast definition may corrupt the result by a factor of 2. At background luminance levels above approximately 10 cd/m2, the Paulsson-Sjöstrand equation agrees well with theory. At lower background levels, the Abrahamsson-Sjöstrand equation is used with correction factors derived from adaptation measurements. Using this equation and earlier published data from glare testing performed at 2 cd/m2, the results are found to be in fair agreement with the light scattering theory. CONCLUSIONS. Glare testing using the Paulsson-Sjöstrand equation is found to be valid as long as the measurements are performed at high luminance levels (above 10 cd/m2), with targets of low spatiotemporal frequencies (e.g., 2 cpd and 1 Hz) and with the use of a properly chosen definition of contrast. At lower luminance levels, the Abrahamsson-Sjöstrand equation may be used with well-derived correction factors.
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| 34. |
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| 35. |
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