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  • 1. Baskaran, Karthikeyan
    et al.
    Rosén, Robert
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Lewis, Peter
    Unsbo, Peter
    Gustafsson, Jörgen
    Benefit of Adaptive Optics Aberration Correction at Preferred Retinal Locus2012In: Optometry and Vision Science, ISSN 1040-5488, E-ISSN 1538-9235, Vol. 89, no 9Article in journal (Refereed)
    Abstract [en]

    Purpose: To investigate the effect of eccentric refractive correction and full aberration correction on both high and low contrast grating resolution at the preferred retinal locus (PRL) of a single low vision subject with a longstanding central scotoma.

    Methods: The subject was a 68 year-old female with bilateral absolute central scotoma due to Stargardt’s disease. She has developed a single PRL located 25° nasally of the damaged macula in her left eye, this being the better of the two eyes. High- (100%) and low contrast (25% & 10%) grating resolution acuity was evaluated using four different correction conditions. The first two corrections were solely refractive error corrections; namely habitual spectacle correction and full sphero-cylindrical correction. The latter two corrections were two versions of adaptive optics corrections of all aberrations; namely full sphero-cylindrical refractive correction with additional aberration correction and habitual spectacle correction with aberration correction.

    Results: The mean high contrast (100%) resolution acuity with her habitual correction was 1.06 logMAR, which improved to 1.00 logMAR with full sphero-cylindrical correction. Under the same conditions, low contrast (25%) acuity improved from 1.30 logMAR to 1.14 logMAR. With adaptive optics aberration correction, the high contrast resolution acuities improved to 0.92/0.89 logMAR and the low contrast acuities, to 1.06/1.04 logMAR under both correction modalities. The low contrast (10%) resolution acuity was 1.34 logMAR with adaptive optics aberration correction; however, with purely refractive error corrections she was unable to identify the orientation of the gratings.

    Conclusion: Correction of all aberrations using adaptive optics improves both high and low contrast resolution acuity at the PRL of a single low vision subject with longstanding absolute central scotoma.

  • 2. Baskaran, Karthikeyan
    et al.
    Unsbo, Peter
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Gustafsson, Jörgen
    Influence of Age on Peripheral Ocular Aberrations2011In: Optometry and Vision Science, ISSN 1040-5488, E-ISSN 1538-9235, Vol. 88, no 9, p. 1088-1098Article in journal (Refereed)
    Abstract [en]

    Purpose. To compare peripheral lower and higher order aberrations across the horizontal (+/- 40 degrees) and inferior (-20 degrees) visual fields in healthy groups of young and old emmetropes. Methods. We have measured off-axis aberrations in the groups of 30 younger (24 +/- 3 years) and 30 older (58 +/- 5 years) emmetropes. The aberrations of OD were measured using the COAS-HD VR Shack-Hartmann aberrometer in 10 degrees steps to +/- 40 degrees horizontally and -20 degrees inferiorly in the visual field. The aberrations were quantified with Zernike polynomials for a 4 mm pupil diameter. The second-order aberration coefficients were converted to their respective refraction components (M, J(45), and J(180)). Mixed between-within subjects, analysis of variance were used to determine whether there were significant differences in the refraction and aberration components for the between-subjects variable age and the within-subjects variable eccentricity. Results. Peripheral refraction components were similar in both age groups. Among the higher order coefficients, horizontal coma (C(3)(1)) and spherical aberration (C(4)(0)) varied mostly between the groups. Coma increased linearly with eccentricity, at a more rapid rate in the older group than in the younger group. Spherical aberration was more positive in the older group compared with the younger group. Higher order root mean square increased more rapidly with eccentricity in the older group. Conclusions. Like the axial higher order aberrations, the peripheral higher order aberrations of emmetropes increase with age, particularly coma and spherical aberration.

  • 3.
    Beckman, Claes
    University of Waterloo.
    The influence of increased interocular lightscatter on the contrast in a confocal scanning laserophthalmoscope image1995In: Vision Science and Its Application, Vol. 1 of 1995 OSA Technical Digest Series (Optical Society of America, 1995) / [ed] Optical Society of America, Washington, 1995, Vol. 1, p. 106-109Conference paper (Refereed)
    Abstract [en]

    the influence of increased intraocular light scatter on image quality in a confocal scanning laserophthalmoscope (CSLO) is quntified through computer simulations and model eye experiments.

  • 4. Beckman, Claes
    et al.
    Jörgen, Thaung
    Göteborgs Universitet.
    Johan, Sjöstrand
    Göteborgs Universitet.
    In vitro Lens Scatter Measurements and Glare Testing1994In: The Association for Research in Vision and Ophthalmology Annual Meeting. Sarasota, Florida, May 1-6, 1994. Abstracts. Investigative Ophthalmology & Visual Science March 1994, Vol.35, 1254-2383., 1994, Vol. 35, p. 1803-Conference paper (Refereed)
  • 5. Björling, Gunilla
    et al.
    Axelsson, Sara
    Johansson, Unn-Britt
    Lysdahl, Michael
    Markström, Agneta
    Schedin, Ulla
    Aune, Ragnhild E.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Frostell, Claes
    Karlsson, Sigbritt
    Clinical use and material wear of polymeric tracheostomy tubes2007In: The Laryngoscope, ISSN 0023-852X, E-ISSN 1531-4995, Vol. 117, no 9, p. 1552-1559Article in journal (Refereed)
    Abstract [en]

    OBJECTIVES: The objectives were to compare the duration of use of polymeric tracheostomy tubes, i.e., silicone (Si), polyvinyl chloride (PVC), and polyurethane (PU), and to determine whether surface changes in the materials could be observed after 30 days of patient use. METHODS: Data were collected from patient and technical records for all tracheostomized patients attending the National Respiratory Center in Sweden. In the surface study, 19 patients with long-term tracheostomy were included: six with Bivona TTS Si tubes, eight with Shiley PVC tubes, and five with Trachoe Twist PU tubes. All tubes were exposed in the trachea for 30 days before being analyzed by scanning electron microscopy (SEM) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). New tubes and tubes exposed in phosphate-buffered saline were used as reference. RESULTS: Si tubes are used for longer periods of time than those made of PVC (P < .0001) and PU (P = .021). In general, all polymeric tubes were used longer than the recommended 30-day period. Eighteen of the 19 tubes exposed in patients demonstrated, in one or more areas of the tube, evident surface changes. The morphologic changes identified by SEM correlate well with the results obtained by ATR-FTIR. CONCLUSIONS: Si tracheostomy tubes are in general used longer than those made of PVC and PU. Most of the tubes exposed in the trachea for 30 days suffered evident surface changes, with degradation of the polymeric chains as a result.

  • 6. Bucht, C.
    et al.
    Söderberg, P.
    Manneberg, Göran
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Fully automated corneal endothelial morphometry of images captured by clinical specular microscopy2009In: Ophthalmic Technologies XIX, SPIE - International Society for Optical Engineering, 2009, p. 716315-Conference paper (Refereed)
    Abstract [en]

    The corneal endothelium serves as the posterior barrier of the cornea. Factors such as clarity and refractive properties of the cornea are in direct relationship to the quality of the endothelium. The endothelial cell density is considered the most important morphological factor. Morphometry of the corneal endothelium is presently done by semi-automated analysis of pictures captured by a Clinical Specular Microscope (CSM). Because of the occasional need of operator involvement, this process can be tedious, having a negative impact on sampling size. This study was dedicated to the development of fully automated analysis of images of the corneal endothelium, captured by CSM, using Fourier analysis. Software was developed in the mathematical programming language Matlab. Pictures of the corneal endothelium, captured by CSM, were read into the analysis software. The software automatically performed digital enhancement of the images. The digitally enhanced images of the corneal endothelium were transformed, using the fast Fourier transform (FFT). Tools were developed and applied for identification and analysis of relevant characteristics of the Fourier transformed images. The data obtained from each Fourier transformed image was used to calculate the mean cell density of its corresponding corneal endothelium. The calculation was based on well known diffraction theory. Results in form of estimated cell density of the corneal endothelium were obtained, using fully automated analysis software on images captured by CSM. The cell density obtained by the fully automated analysis was compared to the cell density obtained from classical, semiautomated analysis and a relatively large correlation was found.

  • 7. Bucht, C.
    et al.
    Söderberg, P.
    Manneberg, Göran
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Fully automated corneal endothelial morphometry of images captured by clinical specular microscopy2010In: Ophthalmic Technologies XX, SPIE - International Society for Optical Engineering, 2010, p. 75501E-Conference paper (Refereed)
    Abstract [en]

    The corneal endothelium serves as the posterior barrier of the cornea. Factors such as clarity and refractive properties of the cornea are in direct relationship to the quality of the endothelium. The endothelial cell density is considered the most important morphological factor of the corneal endothelium. Pathological conditions and physical trauma may threaten the endothelial cell density to such an extent that the optical property of the cornea and thus clear eyesight is threatened. Diagnosis of the corneal endothelium through morphometry is an important part of several clinical applications. Morphometry of the corneal endothelium is presently carried out by semi automated analysis of pictures captured by a Clinical Specular Microscope (CSM). Because of the occasional need of operator involvement, this process can be tedious, having a negative impact on sampling size. This study was dedicated to the development and use of fully automated analysis of a very large range of images of the corneal endothelium, captured by CSM, using Fourier analysis. Software was developed in the mathematical programming language Matlab. Pictures of the corneal endothelium, captured by CSM, were read into the analysis software. The software automatically performed digital enhancement of the images, normalizing lights and contrasts. The digitally enhanced images of the corneal endothelium were Fourier transformed, using the fast Fourier transform (FFT) and stored as new images. Tools were developed and applied for identification and analysis of relevant characteristics of the Fourier transformed images. The data obtained from each Fourier transformed image was used to calculate the mean cell density of its corresponding corneal endothelium. The calculation was based on well known diffraction theory. Results in form of estimated cell density of the corneal endothelium were obtained, using fully automated analysis software on 292 images captured by CSM. The cell density obtained by the fully automated analysis was compared to the cell density obtained from classical, semiautomated analysis and a relatively large correlation was found.

  • 8.
    Bucht, Curry
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Söderberg, P.
    Manneberg, Göran
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    A model for corneal endothelial morphometry by diffraction2006In: Progr. Biomed. Opt. Imaging Proc. SPIE, 2006Conference paper (Refereed)
    Abstract [en]

    As a part of an ongoing project on corneal endothelium morphometry by diffraction, a model for corneal endothelium simulation has been developed. The model has been developed in the mathematical programming language Matlab™. Images of corneal endothelium were simulated and the diffraction pattern of the image was calculated. The diffraction pattern was calculated for a series of endothelial images while varying important variables in the simulated image. This rendered the theoretical relationships between values of variables in the diffraction pattern and values of morphometric variables in the image. At this stage, the analysis focused on the expression of endothelial mean cell size and coefficient of variation in the diffraction pattern, respectively. As expected from diffraction theory, it was found that there is a direct linear relationship between mean cell size and distance between periodic variations in the diffraction pattern. We further found that the ratio between the intensity in the central maximum and the intensity in the first harmonic of the diffraction pattern was functionally depending on the variation in cell size. The current findings demonstrate that it is possible to theoretically determine average cell size and coefficient of variation of cell size in the diffraction pattern.

  • 9.
    Bucht, Curry
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics. Karolinska Institutet, Sweden.
    Söderberg, P.
    Manneberg, Göran
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Recording the diffraction pattern reflected from corneal endothelium2007In: Ophthalmic Technologies XVII, SPIE - International Society for Optical Engineering, 2007, p. 42610-42610Conference paper (Refereed)
    Abstract [en]

    As a part of an ongoing research project on morphometrical diagnosis of the corneal endothelium, an experimental optical setup has been created. The structure of the corneal endothelial cells could be considered a reflecting periodical aperture. Hence, the diffraction pattern reflected from the endothelium contains valuable morphometrical information. In the present work, focus has been on sampling the posterior surface of explanted corneas. Methods: An optical setup was created, using a 632.8 nm He-Ne laser as the light source. The desired diffraction pattern was produced as a collimated reflection. Hence, because the posterior surface of the cornea is concave, lenses were used to attain the right divergence of the light impingent on the corneal endothelium. These lenses also made it possible to adjust the sampling spot size. A beam splitter (BS) was used to provide an optical path for both the impinging laser beam as well as the reflected diffracted beam. The lens acting as a Fourier lens was then placed after the BS. At the back focal plane of the Fourier lens, a CCD detector was used for recording in the Fourier plane. In the process of creating the setup, explanted corneas were emulated using grated contact lenses. Results: The current optical set up allows identification of a diffraction pattern from a concave spherical surface with a radius of curvature of the same order as a human cornea.

  • 10.
    Bucht, Curry
    et al.
    KTH, School of Engineering Sciences (SCI), Physics.
    Söderberg, Per
    Manneberg, Göran
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Simulation of specular microscopy images of corneal endothelium, a tool for control of measurement errors2011In: ACTA OPHTHALMOLOGICA, ISSN 1755-375X, Vol. 89, no 3, p. e242-e250Article in journal (Refereed)
    Abstract [en]

    Purpose: We aimed at developing simulation software capable of producing images of corneal endothelium close to identical to images captured by clinical specular microscopy with defined morphometrical characteristics. It was further planned to demonstrate the usefulness of the simulator by analysing measurement errors associated with a trained operator using a commercially available semi-automatic algorithm for analysis of simulated images. Methods: Software was developed that allows creation of unique images of the corneal endothelium expressing morphology close to identical with that seen in images of corneal specular microscopy. Several hundred unique images of the corneal endothelium were generated with randomization, spanning a physiological range of endothelial cell density. As an example of the usefulness of the simulator for analysis of measurement errors in corneal specular microscopy, a total of 12 of all the images generated were randomly selected such that the endothelial cell density expressed was evenly distributed over the physiological range of endothelial cell density. The images were transferred to a personal computer. The imagenet-640 software was used to analyse endothelial cell size variation, percentage of hexagonal endothelial cells, and endothelial cell density. Results: The simulator developed allows randomized generation of corneal specular microscopy images with a preset expected average and variation of cell structure. Calculated morphometric information of each cell is stored in the simulator. The image quality can secondarily be varied with a toolbox of filters to approximate a large spectrum of clinically captured images. As an example of the use of the simulator, measurement errors associated with one trained operator using the imagenet-640 software, and focusing on endothelial cell density, were examined. The functional dependence between morphometric information estimated with the imagenet-640 software algorithm and real morphometric information as provided by the simulator was analysed with regression. It was demonstrated that that the estimations of endothelial cell size variation was associated with a scaling error and that the random error was strongly dependent on the operator. Conclusion: The newly developed simulator for randomized generation of morphometrically defined corneal specular microscopy images for the first time makes it possible to estimate a spatial scaling error of an available semi-automatic algorithm and to determine the random measurement error of important morphometric estimates in a defined reference sample of images. It is anticipated that the simulator will be a valuable tool for the generation of a large set of morphometrically well-characterized corneal specular microscopy images that can be used for calibration among research centres, for minimization of random errors and for measurement of quality control. Simulated images will be useful for the development of fully automatic analysis of corneal endothelial cell morphometry.

  • 11. Eriksson, Y.
    et al.
    Gärdenfors, Dan
    KTH, School of Industrial Engineering and Management (ITM), Centres, Stockholm International Toy Research Center, SITREC.
    Computer games for children with visual impairments2005In: Journal of Endocrine Genetics, ISSN 1565-012X, Vol. 4, no 3, p. 161-167Article in journal (Refereed)
    Abstract [en]

    The Swedish Library of Talking Books and Braille (TPB) published web-based computer games for children with different kinds of visual impairments. As the target groups have very different needs, when it comes to the use of graphics and sound, TPB have developed two kinds of games. Image-based games aim to encourage children with partial sight to practice recognizing visual objects, whereas sound-based games also intend to be accessible without relying on vision. Based on the results of two pilot studies, this paper discusses central design issues of the graphical and sound-based interfaces for this type of application.

  • 12. Lakshminarayanan, Vasudevan
    et al.
    Varadharajan, L. Srinivasa
    Diaz-Santana, Luis
    Lundström, Linda
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Vision Science and Ophthalmic Optics2011In: Journal of Modern Optics, ISSN 0950-0340, E-ISSN 1362-3044, Vol. 58, no 19-20, p. 1679-1680Article in journal (Other academic)
  • 13. Lewis, Peter
    et al.
    Baskaran, Karthikeyan
    Rosén, Robert
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Lundström, Linda
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Unsbo, Peter
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Gustafsson, Jörgen
    Objectively Determined Refraction Improves Peripheral Vision2014In: Optometry and Vision Science, ISSN 1040-5488, E-ISSN 1538-9235, Vol. 91, no 7, p. 740-746Article in journal (Refereed)
    Abstract [en]

    Purpose. The purpose of this study was twofold: to verify a fast, clinically applicable method for determining off-axis refraction and to assess the impact of objectively obtained off-axis refractive correction on peripheral low-contrast visual acuity. Methods. We measured peripheral low-contrast resolution acuity with Gabor patches both with and without off-axis correction at 20 degrees in the nasal visual field of 10 emmetropic subjects; the correction was obtained using a commercial open-field Hartmann-Shack wavefront sensor, the COAS-HD VR aberrometer. Off-axis refractive errors were calculated for a 5-mm circular pupil inscribed within the elliptical wavefront by COAS using the instruments' inbuilt "Seidel sphere" method. Results. Most of the subjects had simple myopic astigmatism, at 20 degrees in the nasal visual field ranging from -1.00 to -2.00 DC, with axis orientations generally near 90 degrees. The mean uncorrected and corrected low-contrast resolution acuities for all subjects were 0.92 and 0.86 logMAR, respectively (an improvement of 0.06 logMAR). For subjects with a scalar power refractive error of 1.00 diopters or more, the average improvement was 0.1 logMAR. The observed changes in low-contrast resolution acuity were strongly correlated with off-axis astigmatism (Pearson r = 0.95; p < 0.0001), the J(180) cross-cylinder component (Pearson r = 0.82; p = 0.0034), and power scalar (Pearson r = -0.75; p = 0.0126). Conclusions. The results suggest that there are definite benefits in correcting even moderate amounts of off-axis refractive errors; in this study, as little as -1.50 DC of off-axis astigmatism gave improvements of up to a line in visual acuity. It may be even more pertinent for people who rely on optimal peripheral visual function, specifically those with central visual field loss; the use of open-field aberrometers could be clinically useful in rapidly determining off-axis refractive errors specifically for this patient group who are generally more challenging to refract.

  • 14.
    Lewis, Peter
    et al.
    Linnaeus Univ, Dept Med & Optometry, Kalmar, Sweden..
    Venkataraman, Abinaya Priya
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Lundström, Linda
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Contrast Sensitivity in Eyes with Central Scotoma: Effect of Stimulus Drift2018In: Optometry and Vision Science, ISSN 1040-5488, E-ISSN 1538-9235, Vol. 95, no 4, p. 354-361Article in journal (Refereed)
    Abstract [en]

    SIGNIFICANCE: In the field of visual rehabilitation of patients with central visual field loss (CFL), knowledge on how peripheral visual function can be improved is essential. This study presents measurements of peripheral dynamic contrast sensitivity (with optical correction) for off-axis viewing angles in subjects with CFL. PURPOSE: Subjects with CFL rely on a peripheral preferred retinal locus (PRL) for many visual tasks. It is therefore important to ascertain that contrast sensitivity (CS) is maximized in the PRL. This study evaluates the effect of stimulus motion, in combination with optical correction, on CS in subjects with CFL. METHODS: The off-axis refractive errors in the PRL of five young CFL subjects were measured with a COAS open-view Hartmann-Shack aberrometer. Low-contrast (25% and 10%) and high-contrast resolution acuity for stationary gratings was assessed with and without optical correction. High-contrast resolution was also measured for gratings drifting at 7.5 Hz (within a fixed Gaussian window). Furthermore, resolution CS was evaluated for both stationary and moving gratings with optical correction for a total of two to three spatial frequencies per subject. RESULTS: High-contrast resolution acuity was relatively insensitive to stimulus drift motion of 7.5 Hz, whereas CS for gratings of 0.5 cycles per degree improved with drift for all subjects. Furthermore, both high- and low-contrast static resolution improved with optical correction. CONCLUSIONS: Just as for healthy eyes, stimulus motion of 7.5 Hz enhances CS for gratings of low spatial frequency also in the PRL of eyes with CFL. Concurrently, high-contrast resolution is unaffected by the 7.5-Hz drift but improves with off-axis optical correction. This highlights the importance of providing optimal refractive correction for subjects with CFL and that stimulus motion can be used to further enhance CS at low spatial frequencies.

  • 15. Lindskoog Pettersson, Anna
    et al.
    Jarkö, Caroline
    Alvin, Åsa
    Unsbo, Peter
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Brautaset, Rune
    Spherical aberration in contact lens wear2008In: Contact lens & anterior eye, ISSN 1367-0484, E-ISSN 1476-5411, Vol. 31, no 4, p. 189-193Article in journal (Refereed)
    Abstract [en]

    Introduction: The aim of the present studies was to investigate the effect on spherical aberration of different non custom-made contact lenses, both with and without aberration control. Methods: A wavefront analyser (Zywave™, Bausch & Lomb) was used to measure the aberrations in each subject's right eye uncorrected and with the different contact lenses. The first study evaluated residual spherical aberration with a standard lens (Focus Dailies Disposable, Ciba Vision) and with an aberration controlled contact lens (ACCL) (Definition AC, Optical Connection Inc.). The second study evaluated the residual spherical aberrations with a monthly disposable silicone hydrogel lens with aberration reduction (PureVision, Bausch & Lomb). Results: Uncorrected spherical aberration was positive for all pupil sizes in both studies. In the first study, residual spherical aberration was close to zero with the standard lens for all pupil sizes whereas the ACCL over-corrected spherical aberration. The results of the second study showed that the monthly disposable lens also over-corrected the aberration making it negative. The changes in aberration were statistically significant (p < 0.05) with all lenses. Conclusion: Since the amount of aberration varies individually we suggest that aberrations should be measured with lenses on the eye if the aim is to change spherical aberration in a certain direction.

  • 16.
    Lundström, Linda
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Rosen, Robert
    Abbott Med Opt Groningen BV, Appl Res, Groningen, Netherlands..
    Van der Mooren, Marrie
    Abbott Med Opt Groningen BV, Appl Res, Groningen, Netherlands..
    Unsbo, Peter
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Piers, Patricia A.
    Abbott Med Opt Groningen BV, Appl Res, Groningen, Netherlands..
    Low Amounts of Scattering Reduce Central as well as Peripheral Contrast Sensitivity2014In: Investigative Ophthalmology and Visual Science, ISSN 0146-0404, E-ISSN 1552-5783, Vol. 55, no 13Article in journal (Other academic)
  • 17.
    Lundström, Linda
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Rosén, Robert
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Baskaran, K.
    Jaeken, B.
    Gustafsson, J.
    Artal, P.
    Unsbo, Peter
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Symmetries in peripheral ocular aberrations2011In: Journal of Modern Optics, ISSN 0950-0340, E-ISSN 1362-3044, Vol. 58, no 19-20, p. 1690-1695Article in journal (Refereed)
    Abstract [en]

    A mirror symmetry in the aberrations between the left and right eyes has previously been found foveally, but while a similar symmetry for the peripheral visual field is likely, it has not been investigated. Nevertheless, the peripheral optical quality is often evaluated in only one eye, because it is more time efficient than analyzing the whole visual field of both eyes. This study investigates the correctness of such an approach by measuring the peripheral wavefront aberrations in both eyes of 22 subjects out to +/- 40 degrees horizontally. The largest aberrations (defocus, astigmatism, and coma) were found to be significantly correlated between the left and right eyes when comparing the same temporal or nasal angle. The slope of the regression line was close to +/- 1 (within 0.05) for these aberrations, with a negative slope for the horizontally odd aberrations, i.e. the left and right eyes are mirror symmetric. These findings justify that the average result, sampled in one of the two eyes of many subjects, can be generalized to the other eye as well.

  • 18.
    Papadogiannis, Petros
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Romashchenko, Dmitry
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Unsbo, Peter
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Lundström, Linda
    Influence of optical defocus on peripheral vision with and without aberrations2018In: Investigative Ophthalmology and Visual Science, ISSN 0146-0404, E-ISSN 1552-5783, Vol. 59, no 9Article in journal (Refereed)
  • 19. Pettersson, A. Lindskoog
    et al.
    Mårtensson, L.
    Salkic, J.
    Unsbo, Peter
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Brautaset, R.
    Spherical aberration in relation to visual performance in contact lens wear2011In: Contact lens & anterior eye, ISSN 1367-0484, E-ISSN 1476-5411, Vol. 34, no 1, p. 12-16Article in journal (Refereed)
    Abstract [en]

    Introduction: The aim of the present study was to evaluate changes in spherical aberration and their effect on visual quality (visual acuity and contrast sensitivity) in both distance and near with different non-custom-made contact lenses. Methods: A wavefront analyser was used to measure the aberrations in each subject's eyes uncorrected and with the contact lenses: a standard lens and two aspherical contact lenses. High-contrast visual acuity at distance was measured with Test-Chart 2000(100% contrast) and at near with Sloan ETDRS Near Point chart (100% contrast). Low-contrast visual acuity at distance was measured with Test-Chart 2000 (10% contrast) and contrast measurements at near with Mars letter contrast sensitivity chart. Results: Mean spherical aberration was positive for all pupil sizes in the uncorrected eye, residual spherical aberration was close to zero with the standard lens for all pupil sizes, whereas the two aspheric contact lenses over-corrected spherical aberration. The changes in aberration were statistically significant (p < 0.05) with all lenses. No significant difference could be detected between trial frame correction, spherical and aspherical soft contact lens designs with respect to visual quality. This was the case for both distance and near. Conclusion: The results are in line with previous studies and indicate that non-custom-made spherical aberration control contact lenses have little effect on visual quality as defined in this study.

  • 20. Pettersson, Anna Lindskoog
    et al.
    Ramsay, Marika Wahlberg
    Lundström, Linda
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Rosén, Robert
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Nilsson, Maria
    Unsbo, Peter
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Brautaset, Rune
    Accommodation in young adults wearing aspheric multifocal soft contact lenses2011In: Journal of Modern Optics, ISSN 0950-0340, E-ISSN 1362-3044, Vol. 58, no 19-20, p. 1804-1808Article in journal (Refereed)
    Abstract [en]

    The aim of the present project was to investigate accommodative behavior in young adults and adolescents fitted with an aspheric multifocal (center distance) contact lens with focus on evaluating whether these lenses can be an alternative treatment for subjects in which a reduced level of blur and thereby accommodation in near vision is aimed at. Twenty normal subjects aged between 21 and 35 years participated in the study. Aberrometry was perfomed using a Zywave (TM) aberrometer, first on the uncorrected eyes of all subjects, and again while the subjects wore a multifocal contact lens with a +1.00 add. A Shin-Nippon N Vision-K 5001 Autoref-Keratometer was used to measure accommodative response with two different refractive corrections: (1) habitual spectacle correction only, and (2) habitual correction and a aspheric multifocal (center distance) contact lens. Four hours of adaptation to the lens was allowed. The lag when wearing only the habitual spectacles was compared with the lag while wearing both the habitual spectacles and the aspheric multifocal contact lens. The mean lag of accommodation for the subject group was 0.85 D (+/-0.57 SD) and 0.75 D (+/-0.52 SD) without and with the multifocal lens, respectively. Statistical analyses showed no difference in lag (t = 0.8479, p = 0.407) with and without the lens. In conclusion, young normal subjects do not relax accommodation when fitted with aspheric multifocal center distance lenses when the addition is +1.00. It is therefore unlikely that subjects with accommodative ability, in whom the treatment purpose is to reduce blur and thereby accommodation, can be effectively treated with such lenses.

  • 21.
    Romashchenko, Dmitry
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Rosen, Robert
    Johnson & Johnson Vis, R&D, Groningen, Netherlands..
    Lundström, Linda
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Peripheral refraction and higher order aberrations2019In: Clinical and experimental optometry, ISSN 0816-4622, E-ISSN 1444-0938Article in journal (Refereed)
    Abstract [en]

    Peripheral image quality influences several aspects of human vision. Apart from off-axis visual functions, the manipulation of peripheral optical errors is widely used in myopia control interventions. This, together with recent technological advancements enabling the measurement of peripheral errors, has inspired many studies concerning off-axis optical aberrations. However, direct comparison between these studies is often not straightforward. To enable between-study comparisons and to summarise the current state of knowledge, this review presents population data analysed using a consistent approach from 16 studies on peripheral ocular optical quality (in total over 2,400 eyes). The presented data include refractive errors and higher order monochromatic aberrations expressed as Zernike co-efficients (reported in a subset of the studies) over the horizontal visual field. Additionally, modulation transfer functions, describing the monochromatic image quality, are calculated using individual wavefront data from three studies. The analysed data show that optical errors increase with increasing eccentricity as expected from theoretical modelling. Compared to emmetropes, myopes tend to have more hypermetropic relative peripheral refraction over the horizontal field and worse image quality in the near-periphery of the nasal visual field. The modulation transfer functions depend considerably on pupil shape (for angles larger than 30 degrees) and to some extent, the number of Zernike terms included. Moreover, modulation transfer functions calculated from the average Zernike co-efficients of a cohort are artificially inflated compared to the average of individual modulation transfer functions from the same cohort. The data collated in this review are important for the design of ocular corrections and the development and assessment of optical eye models.

  • 22.
    Rosén, Robert
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Jaeken, B.
    Lindskoog Petterson, A.
    Artal, P.
    Unsbo, Peter
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Lundström, Linda
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Evaluating the peripheral optical effect of multifocal contact lenses2012In: Ophthalmic & physiological optics, ISSN 0275-5408, E-ISSN 1475-1313, Vol. 32, no 6, p. 527-534Article in journal (Refereed)
    Abstract [en]

    Purpose: Multifocal soft contact lenses have been used to decrease the progression of myopia, presumably by inducing relative peripheral myopia at the same time as the central image is focused on the fovea. The aim of this study was to investigate how the peripheral optical effect of commercially available multifocal soft contact lenses can be evaluated from objective wavefront measurements. Methods: Two multifocal lenses with high and low add and one monofocal design were measured over the ±40° horizontal field, using a scanning Hartmann-Shack wavefront sensor on four subjects. The effect on the refractive shift, the peripheral image quality, and the depth of field of the lenses was evaluated using the area under the modulation transfer function as the image quality metric. Results: The multifocal lenses with a centre distance design and 2 dioptres of add induced about 0.50 dioptre of relative peripheral myopia at 30° in the nasal visual field. For larger off-axis angles the border of the optical zone of the lenses severely degraded image quality. Moreover, these multifocal lenses also significantly reduced the image quality and increased the depth of field for angles as small as 10°-15° Conclusions: The proposed methodology showed that the tested multifocal soft contact lenses gave a very small peripheral myopic shift in these four subjects and that they would need a larger optical zone and a more controlled depth of field to explain a possible treatment effect on myopia progression.

  • 23.
    Rosén, Robert
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Lundström, Linda
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Unsbo, Peter
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Sign-Dependent Sensitivity to Peripheral Defocus for Myopes due to Aberrations2012In: Investigative Ophthalmology and Visual Science, ISSN 0146-0404, E-ISSN 1552-5783, Vol. 53, no 11, p. 7176-7182Article in journal (Refereed)
    Abstract [en]

    PURPOSE. Animal studies suggest that the periphery of the eye plays a major role in emmetropization. It is also known that human myopes tend to have relative peripheral hyperopia compared to the foveal refraction. This study investigated peripheral sensitivity to defocus in human subjects, specifically whether myopes are less sensitive to negative than to positive defocus. METHODS. Sensitivity to defocus (logMAR/D) in the 20 degrees nasal visual field was determined in 16 emmetropes (6 males and 10 females, mean spherical equivalent -0.03 +/- 0.13 D, age 30 +/- 6 10 years) and 16 myopes (3 males and 13 females, mean spherical equivalent -3.25 +/- 2 D, age 25 +/- 6 years) using the slope of through-focus low-contrast resolution (10%) acuity measurements. Peripheral wavefront measurements at the same angle were obtained from 13 of the myopes and 9 of the emmetropes, from which the objective depth of field was calculated by assessing the area under the modulation transfer function (MTF) with added defocus. The difference in depth of field between negative and positive defocus was taken as the asymmetry in depth of field. RESULTS. Myopes were significantly less sensitive to negative than to positive defocus (median difference in sensitivity 0.06 logMAR/D, P = 0.023). This was not the case for emmetropes (median difference -0.01 logMAR/D, P = 0.382). The difference in sensitivity between positive and negative defocus was significantly larger for myopes compared to emmetropes (P = 0.031). The correlation between this difference in sensitivity and objective asymmetry in depth of field due to aberrations was significant for the whole group (R-2 = 0.18, P 0.02) and stronger for myopes (R-2 = 0.8, P < 0.01). CONCLUSIONS. We have shown that myopes, in general, are less sensitive to negative than to positive defocus, which can be linked to their aberrations. This finding is consistent with a previously proposed model of eye growth that is driven by the difference between tangential and radial peripheral blur.

  • 24.
    Rosén, Robert
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Lundström, Linda
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Unsbo, Peter
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Atchison, D. A.
    Have we misinterpreted the study of Hoogerheide et al. (1971)?2012In: Optometry and Vision Science, ISSN 1040-5488, E-ISSN 1538-9235, Vol. 89, no 8, p. 1235-1237Article in journal (Refereed)
    Abstract [en]

    In 1971, Rempt et al. reported peripheral refraction patterns (skiagrams) along the horizontal visual field in 442 people. Later in the same year, Hoogerheide et al. used skiagrams in combination with medical records to relate skiagrams in emmetropes and hyperopes to progression of myopia in young adults. The two articles have spurred interest in peripheral refraction in the past decade. We challenge the understanding that their articles provide evidence that the peripheral refraction pattern along the horizontal visual field is predictive of whether or not a person develops myopia. First, although it has been generally assumed that the skiagrams were measured before the changes in refraction were monitored, Hoogerheide et al. did not state that this was the case. Second, if the skiagrams were obtained at an initial examination and given the likely rates of recruitment and successful completion of training, the study must have taken place during a period of 10 to 15 years; it is much more likely that Hoogerheide et al. measured the skiagrams in a shorter period. Third, despite there being many more emmetropes and hyperopes in the Rempt et al. article than there are in the Hoogerheide et al. article, the number of people in two types of "at risk" skiagrams is greater in the latter; this is consistent with the central refraction status being reported from an earlier time by Hoogerheide et al. than by Rempt et al. In summary, we believe that the skiagrams reported by Hoogerheide et al. were taken at a later examination, after myopia did or did not occur, and that the refraction data from the initial examination were retrieved from the medical archives. Thus, this work does not provide evidence that peripheral refraction pattern is indicative of the likely development of myopia.

  • 25.
    Rosén, Robert
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Lundström, Linda
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Venkataraman, Abinaya Priya
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Winter, Simon
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Unsbo, Peter
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Quick contrast sensitivity measurements in the periphery2014In: Journal of Vision, ISSN 1534-7362, E-ISSN 1534-7362, Vol. 14, no 8Article in journal (Refereed)
    Abstract [en]

    Measuring the contrast sensitivity function (CSF) in the periphery of the eye is complicated. The lengthy measurement time precludes all but the most determined subjects. The aim of this study was to implement and evaluate a faster routine based on the quick CSF method (qCSF) but adapted to work in the periphery. Additionally, normative data is presented on neurally limited peripheral CSFs. A peripheral qCSF measurement using 100 trials can be performed in 3 min. The precision and accuracy were tested for three subjects under different conditions (number of trials, peripheral angles, and optical corrections). The precision for estimates of contrast sensitivity at individual spatial frequencies was 0.07 log units when three qCSF measurements of 100 trials each were averaged. Accuracy was estimated by comparing the qCSF results with a more traditional measure of CSF. Average accuracy was 0.08 log units with no systematic error. In the second part of the study, we collected three CSFs of 100 trials for six persons in the 20 degrees nasal, temporal, inferior, and superior visual fields. The measurements were performed in an adaptive optics system running in a continuous closed loop. The Tukey HSD test showed significant differences (p < 0.05) between all fields except between the nasal and the temporal fields. Contrast sensitivity was higher in the horizontal fields, and the inferior field was better than the superior. This modified qCSF method decreases the measurement time significantly and allows otherwise unfeasible studies of the peripheral CSF.

  • 26.
    Rosén, Robert
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Lundström, Linda
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Venkataraman, Abinaya Priya
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Winter, Simon
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Unsbo, Peter
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Quick measurements of contrast sensitivity in the peripheral visual field2014In: Investigative Ophthalmology and Visual Science, ISSN 0146-0404, E-ISSN 1552-5783, Vol. 55, no 13Article in journal (Other academic)
  • 27. Scott, Rolene
    et al.
    Beckman, Claes
    University of Göteborg, Sweden.
    Garner, Leon F
    A preliminary investigation into the direct measurement of intra-ocular light scatter after radial keratotomy1991In: Clinical and experimental optometry, ISSN 0816-4622, E-ISSN 1444-0938, Vol. 74, no 6, p. 204-209Article in journal (Refereed)
    Abstract [en]

    A glare score based on intra-ocular light scatter and a questionnaire-based subjective assessment of glare were determined for 18 patients who had undergone radial keratotomy (RK) two weeks to 27 months previously. Results were compared to those of 15 control subjects. T-tests showed no significant difference in glare experienced under photopic conditions by RK patients and control subjects. There was no systematic relationship between glare scores and the subjective assessment of glare, nor between glare scores or subjective assessment of glare and the time which had elapsed since surgery. However, a weak relationship (r2=0.36) was found between glare scores and absolute refractive error. It was concluded that RK did not produce significant levels of intra-ocular light scatter under photopic conditions (155 lux).

  • 28. Thaung, Jörgen
    et al.
    Beckman, Claes
    KTH, Superseded Departments (pre-2005), Wireless at KTH.
    Abrahamsson, Maths
    Sjöstrand, Johan
    The importance of optical and psychophysical test parameters for the determination of the light scattering factor1995Conference paper (Other academic)
  • 29.
    Van der Mooren, Marrie
    et al.
    AMO Groningen BV, Res & Dev, Groningen, Netherlands..
    Rosen, Robert
    AMO Groningen BV, Res & Dev, Groningen, Netherlands..
    Franssen, Luuk
    AMO Groningen BV, Res & Dev, Groningen, Netherlands..
    Lundström, Linda
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Piers, Patricia A.
    AMO Groningen BV, Res & Dev, Groningen, Netherlands..
    Prediction of contrast sensitivity in the presence of glare2017In: Investigative Ophthalmology and Visual Science, ISSN 0146-0404, E-ISSN 1552-5783, Vol. 58, no 8Article in journal (Other academic)
  • 30. Van der Mooren, Marrie
    et al.
    Steinert, Roger F.
    Tyson, Farrell
    Rosen, Robert
    Lundström, Linda
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Piers, Patricia A.
    Understanding visual complaints of two intraocular lens explant cases2015In: Investigative Ophthalmology and Visual Science, ISSN 0146-0404, E-ISSN 1552-5783, Vol. 56, no 7Article in journal (Refereed)
    Abstract [en]

     Purpose 

    In two different cases, multifocal intraocular lenses (MFIOLs) were explanted due to visual complications related to the presence of micro-vacuoles in the optic body. These micro-vacuoles cause straylight, which resulted in complaints of hazy and blurry vision. The purpose of this study is to objectively measure and systematically quantify the visual impact of this straylight. The study will thereby give a better understanding of the origin of reported visual complaints when micro-vacuoles are present.

     Methods 

    The amount of straylight in the two explanted MFIOLs was measured using an in-vitro setup and quantified using the scattering parameter s. To determine the impact of straylight on vision, photographic filters characterized in the same in-vitro setup were used to induce straylight on five subjects. Four different psychophysical visual tests were used: halo size, luminance detection with a glare source, and contrast sensitivity (CS) with and without the presence of glare. For all tests, the impact was modeled as a linear interpolation of the logarithm of the test score against the logarithm of the scattering parameter, log(s).

     Results 

    The straylight measured by the in-vitro setup was 6 deg2/sr for case 1 and 4 deg2/sr for case 2. Assuming a base straylight level of 1.1 log(s), the induced increase for the two patients was 0.17 log(s) and 0.12 log(s) respectively.<br /> The impact for the visual tests per unit of log(s) was the following: for halo size, 0.55 log(degrees)/log(s); for luminance detection 2.72 log(cd/m2)/log(s); for CS without glare, 0.33 log(CS)/log(s); and for CS with glare, 0.58 log(CS)/log(s). The induced straylight for the two explanted MFIOLs therefore corresponds to an increase of halo size of 24% and 16%, a luminance detection threshold increase of 190% and 112%, a contrast sensitivity decrease of 12% and 9% without a glare source, and a contrast sensitivity decrease of 20% and 9% with a glare source.

     Conclusions 

    In the explanted MFIOLs we could objectively measure straylight. This straylight corresponds psychophysically to increases in halo size, loss of luminance sensitivity and decrease in contrast sensitivity. Among the visual tests, measurement of luminance detection showed the highest sensitivity.

  • 31.
    Venkataraman, Abinaya Priya
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Lundström, Linda
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Winter, Simon
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Unsbo, Peter
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics. Royal Inst Technol, KTH, Biomed & Xray Phys, Stockholm, Sweden..
    Small and Large Field Blur Adaptation: Foveal and Peripheral Contrast Sensitivity Changes2014In: Investigative Ophthalmology and Visual Science, ISSN 0146-0404, E-ISSN 1552-5783, Vol. 55, no 13Article in journal (Other academic)
  • 32.
    Venkataraman, Abinaya Priya
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Winter, Simon
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Rosén, Robert
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Lundström, Linda
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Choice of grating orientation for evaluation of peripheral vision2016In: Optometry and Vision Science, ISSN 1040-5488, E-ISSN 1538-9235, Vol. 93, no 6, p. 567-574Article in journal (Refereed)
    Abstract [en]

    Purpose: Peripheral resolution acuity depends on the orientation of the stimuli. However, it is uncertain if such a meridional effect also exists for peripheral detection tasks because they are affected by optical errors. Knowledge of the quantitative differences in acuity for different grating orientations is crucial for choosing the appropriate stimuli for evaluations of peripheral resolution and detection tasks. We assessed resolution and detection thresholds for different grating orientations in the peripheral visual field.

    Methods: Resolution and detection thresholds were evaluated for gratings of four different orientations in eight different visual field meridians in the 20-deg visual field in white light. Detection measurements in monochromatic light (543 nm; bandwidth, 10 nm) were also performed to evaluate the effects of chromatic aberration on the meridional effect. A combination of trial lenses and adaptive optics system was used to correct the monochromatic lower- and higher-order aberrations.

    Results: For both resolution and detection tasks, gratings parallel to the visual field meridian had better threshold compared with the perpendicular gratings, whereas the two oblique gratings had similar thresholds. The parallel and perpendicular grating acuity differences for resolution and detection tasks were 0.16 logMAR and 0.11 logMAD, respectively. Elimination of chromatic errors did not affect the meridional preference in detection acuity.

    Conclusions: Similar to peripheral resolution, detection also shows a meridional effect that appears to have a neural origin. The threshold difference seen for parallel and perpendicular gratings suggests the use of two oblique gratings as stimuli in alternative forced-choice procedures for peripheral vision evaluation to reduce measurement variation.

  • 33. Wahlberg, M.
    et al.
    Pettersson, A. Lindskoog
    Rosén, Robert
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Nilsson, M.
    Unsbo, Peter
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Brautaset, R.
    Clinical importance of spherical and chromatic aberration on the accommodative response in contact lens wear2011In: Journal of Modern Optics, ISSN 0950-0340, E-ISSN 1362-3044, Vol. 58, no 19-20, p. 1696-1702Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to evaluate the accommodation response under both mono-and polychromatic light while varying the amount of spherical aberration. It is thought that chromatic and spherical aberrations are directional cues for the accommodative system and could affect response time, velocity or lag. Spherical aberration is often eliminated in modern contact lenses in order to enhance image quality in the unaccommodated eye. This study was divided into two parts. The first part was done to evaluate the amount of spherical and other Zernike aberrations in the unaccommodated eye when uncorrected and with two types of correction (trial lens and spherical-aberration controlled contact lens) and the second part evaluated the dynamic accommodation responses obtained when wearing each of the corrections under polychromatic and monochromatic conditions. Measurements of accommodation showed no significant differences in time, velocity and lag of accommodation after decreasing the spherical aberration with a contact lens, neither in monochromatic nor polychromatic light. It is unlikely that small to normal changes of spherical aberration in white light or monochromatic mid-spectral light affect directional cues for the accommodative system, not in white light or mid-spectral monochromatic light, since the accommodative response did not show any change.

  • 34.
    Winter, Simon
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics. Royal Inst Technol, Biomed & Xray Phys, Stockholm, Sweden..
    Lundström, Linda
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Fathi, Mohammad Taghi
    Rodenstock GmbH, Corp Res & Dev, Munich, Germany..
    Venkataraman, Abinaya Priya
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Seidemann, Anne
    Rodenstock GmbH, Corp Res & Dev, Munich, Germany..
    Unsbo, Peter
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Horizontally induced transverse chromatic aberration reduces peripheral acuity2014In: Investigative Ophthalmology and Visual Science, ISSN 0146-0404, E-ISSN 1552-5783, Vol. 55, no 13Article in journal (Other academic)
  • 35.
    Winter, Simon
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Sabesan, Ramkumar
    Tiruveedhula, Pavan N.
    Privitera, Claudio
    Lundström, Linda
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Roorda, Austin
    Objective measurements of transverse chromatic aberration across the visual field of the human eye2015In: Investigative Ophthalmology and Visual Science, ISSN 0146-0404, E-ISSN 1552-5783, Vol. 56, no 7Article in journal (Refereed)
    Abstract [en]

    Purpose: The purpose of this study was to use a new image-based technique to make the first-ever objective measures of TCA at different eccentricities within the human visual field.

    Methods: TCA was measured at visual field angles of 0.5, 2.5, 5, 7.5, 10, 12.5, and 15 degrees from foveal fixation in the right eye of 4 subjects. Interleaved retinal images were taken at wavelengths 543 nm and 842 nm in an adaptive optics scanning laser ophthalmoscope (AOSLO) and were cross-correlated according to methods described in Harmening et al., Biomed Opt Express, 2012. Pupil alignment was controlled with a pupil-camera. To obtain true measures of human eye TCA, the contributions of the AOSLO system TCA were measured using an on-axis aligned model eye and subtracted from the human eye data.

    Results: The system TCA was stable at around 3 arcmin. On all subjects, it was possible to measure TCA out to 12.5 degrees in the nasal, 10 degrees in the temporal, 12.5 degrees in the inferior, and 15 degrees in the superior visual field. The absolute amount of TCA between green and IR varied somewhat between subjects, but was approximately 4 arcmin at 10 degrees out in the nasal visual field. However, the increase in TCA was found to be linear with a slope close to 0.2 arcmin / degree of visual field angle for all subjects. Translating these results to the visual spectrum would yield a slightly higher slope and larger image shifts, which agree with the theoretical calculations by Thibos, J. Opt. Soc. Am. A, 1987.

    Conclusions: We have performed the first objective measurement of the TCA of the human eye across the central 30 degrees visual field. The 4 arcmin of TCA at 10 degrees off-axis is very similar to the resolution acuity of 0.5 to 0.7 logMAR at 10 degrees out in the nasal visual field (about 3 to 5 arcmin). Additionally, the measured cone-size at 10 degrees in the subjects of this study was about 1.4 - 1.7 arcmin, which means that the TCA blur covers around 2-3 cones. Therefore, the peripheral TCA can be visually significant.

  • 36.
    Winter, Simon
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Sabesan, Ramkumar
    Tiruveedhula, Pavan
    Privitera, Claudio
    Unsbo, Peter
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Lundström, Linda
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Roorda, Austin
    Transverse chromatic aberration across the visual field of the human eye2016In: Journal of Vision, ISSN 1534-7362, E-ISSN 1534-7362, Vol. 16, no 14, article id 9Article in journal (Refereed)
    Abstract [en]

    The purpose of this study was to measure the transverse chromatic aberration (TCA) across the visual field of the human eye objectively. TCA wasmeasured at horizontal and vertical field angles out to ±15° from foveal fixation in the right eye of four subjects. Interleaved retinal images were taken at wavelengths 543 nm and 842 nm in an adaptive optics scanning laser ophthalmoscope (AOSLO). To obtain true measures of the human eye's TCA, the contributions of the AOSLO system's TCA were measured using an on-axis aligned model eye and subtracted from the ocular data. The increase in TCA was found to be linear with eccentricity, with an average slope of 0.21 arcmin/degree of visual field angle (corresponding to 0.41 arcmin/degree for 430 nm to 770 nm). The absolute magnitude of ocular TCA varied between subjects, but was similar to the resolution acuity at 10° in the nasal visual field, encompassing three to four cones. Therefore, TCA can be visually significant. Furthermore, for high-resolution imaging applications, whether visualizing or stimulating cellular features in the retina, it is important to consider the lateral displacements between wavelengths and the variation in blur over the visual field.

  • 37.
    Wolffsohn, James S.
    et al.
    Aston Univ, Ophthalm Res Grp, Birmingham, W Midlands, England..
    Kollbaum, Pete S.
    Indiana Univ, Sch Optometry, Bloomington, IN USA..
    Berntsen, David A.
    Univ Houston, Coll Optometry, Ocular Surface Inst, Houston, TX USA..
    Atchison, David A.
    Queensland Univ Technol, Sch Optometry & Vis Sci, Inst Hlth & Biomed Innovat, Brisbane, Qld, Australia..
    Benavente, Alexandra
    SUNY Coll Optometry, New York, NY 10036 USA..
    Bradley, Arthur
    Indiana Univ, Sch Optometry, Bloomington, IN USA..
    Buckhurst, Hetal
    Plymouth Univ, Sch Hlth Profess, Peninsula Allied Hlth Ctr, Plymouth, Devon, England..
    Collins, Michael
    Queensland Univ Technol, Sch Optometry & Vis Sci, Inst Hlth & Biomed Innovat, Brisbane, Qld, Australia..
    Fujikado, Takashi
    Osaka Univ, Grad Sch Med, Dept Appl Visual Sci, Osaka, Japan..
    Hiraoka, Takahiro
    Univ Tsukuba, Dept Ophthalmol, Fac Med, Ibaraki, Japan..
    Hirota, Masakazu
    Osaka Univ, Grad Sch Med, Dept Appl Visual Sci, Osaka, Japan..
    Jones, Debbie
    Univ Waterloo, Sch Optometry & Vis Sci, Waterloo, ON, Canada..
    Logan, Nicola S.
    Aston Univ, Ophthalm Res Grp, Birmingham, W Midlands, England..
    Lundström, Linda
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Torii, Hidemasa
    Keio Univ, Sch Med, Dept Ophthalmol, Tokyo, Japan..
    Read, Scott A.
    Queensland Univ Technol, Sch Optometry & Vis Sci, Inst Hlth & Biomed Innovat, Brisbane, Qld, Australia..
    Naidoo, Kovin
    Univ KwaZulu Natal, African Vis Res Inst, Durban, South Africa..
    IMI - Clinical Myopia Control Trials and Instrumentation Report2019In: Investigative Ophthalmology and Visual Science, ISSN 0146-0404, E-ISSN 1552-5783, Vol. 60, no 3, p. M132-M160Article in journal (Refereed)
    Abstract [en]

    The evidence-basis based on existing myopia control trials along with the supporting academic literature were reviewed; this informed recommendations on the outcomes suggested from clinical trials aimed at slowing myopia progression to show the effectiveness of treatments and the impact on patients. These outcomes were classified as primary (refractive error and/or axial length), secondary (patient reported outcomes and treatment compliance), and exploratory (peripheral refraction, accommodative changes, ocular alignment, pupil size, outdoor activity/lighting levels, anterior and posterior segment imaging, and tissue biomechanics). The currently available instrumentation, which the literature has shown to best achieve the primary and secondary outcomes, was reviewed and critiqued. Issues relating to study design and patient selection were also identified. These findings and consensus from the International Myopia Institute members led to final recommendations to inform future instrumentation development and to guide clinical trial protocols.

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