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Transverse Chromatic Aberration and Vision: Quantification and Impact across the Visual Field
KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.ORCID iD: 0000-0003-4149-4556
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The eye is our window to the world. Human vision has therefore been extensively studied over the years. However, in-depth studies are often either limited to our central visual field, or, when extended to the periphery, only correct optical errors related to a narrow spectrum of light. This thesis extends the current knowledge by considering the full visible spectrum over a wide visual field. A broad spectrum means that the wavelength dependence of light propagation inside the eye has to be considered; the optics of the eye will therefore not form a retinal image in the same location for all wavelengths, a phenomenon called chromatic aberration.

We present here a new methodology to objectively measure the magnitude of transverse chromatic aberration (TCA) across the visual field of the human eye, and show that the ocular TCA increases linearly with off-axis angle (about 0.21 arcmin per degree for the spectral range from 543 nm to 842 nm). Moreover, we have implemented adaptive psychophysical methods to quantify the impact of TCA on central and peripheral vision. We have found that inducing additional TCA degrades peripheral grating detection acuity more than foveal resolution acuity (more than 0.05 logMAR per arcmin of induced TCA peripherally compared to 0.03 logMAR/arcmin foveally). As stimuli to evaluate peripheral vision, we recommend gratings that are obliquely-oriented relative to the visual field meridian.

The results of this thesis have clinical relevance for improving peripheral vision and are equally important for retinal imaging techniques. To limit the negative impacts of TCA on vision, inducing additional TCA should be avoided when the peripheral refractive errors are to be corrected, such as for people suffering from macular degeneration and central visual field loss. In retinal imaging applications, TCA leads to lateral offsets when imaging is performed in more than one wavelength. Consequently, the measurement of TCA together with careful pupil alignment and subsequent compensation can improve the functionality of these instruments.

Abstract [sv]

Ögat är vårt fönster mot världen, och syn har mätts och studerats i stor utsträckning över åren. Trots detta är forskningen om mänsklig syn oftast begränsad till det centrala synfältet, och i studier av det perifera synfältet korrigeras optiska fel endast över ett smalt våglängdsområde. Denna avhandling vidgar forskningen om vår syn till att inkludera hela det synliga spektrumet över ett stort synfält. Ett brett spektrum innebär att vi måste ta hänsyn till våglängdsberoendet i ljusets brytning i ögat; ögats optik kan därför inte avbilda ett objekt till samma bildläge på näthinnan för alla våglängder, ett fenomen som kallas kromatisk aberration.

Vi presenterar här en ny metod för att mäta mängden transversell kromatisk aberration (TCA) över ögats synfält och visar att ögats TCA ökar linjärt med vinkeln ut i synfältet (ungefär 0,21 bågminuter per grad från 543 nm till 842 nm). Dessutom har vi implementerat adaptiva psykofysiska mätmetoder för att kvantifiera effekten av TCA på central och perifer syn. Våra resultat visar att extra inducerad TCA påverkar den perifera förmågan att upptäcka sinusformade randmönster mer än den centrala förmågan att upplösa motsvarande ränder (mer än 0,05 logMAR per bågminut inducerad TCA i periferin jämfört med 0,03 logMAR/bågminut centralt). Vid utvärdering av perifer syn rekommenderar vi att använda sinusformade randmönster med en sned riktning jämfört med synfältsmeridianen.

Resultaten som presenteras i avhandlingen har klinisk betydelse för att förbättra den perifera synen och är även viktiga för tekniker som avbildar ögats näthinna. För att begränsa den negativa effekt TCA har på synen ska man undvika att inducera extra TCA, t.e.x. när ögats perifera refraktiva fel korrigeras med glasögon för människor med makula degeneration och centralt synfältsbortfall. Vid avbildning av näthinnan ger ögats TCA förskjutningar mellan bilder i olika våglängder. Därför kan mätningar av TCA, tillsammans med välkontrollerad linjering av pupillens position och efterföljande kompensation, förbättra funktionen hos dessa instrument.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. , x, 62 p.
Series
TRITA-FYS, ISSN 0280-316X ; 2016:19
Keyword [en]
transverse chromatic aberration, lateral chromatic aberration, visual optics, peripheral vision, central vision, dispersion, ophthalmic optics and devices, optical effects on vision, retinal imaging, myopia, human eye
National Category
Physical Sciences
Research subject
Physics
Identifiers
URN: urn:nbn:se:kth:diva-186334ISBN: 978-91-7595-980-1 (print)OAI: oai:DiVA.org:kth-186334DiVA: diva2:926994
Public defence
2016-06-03, FD5, AlbaNova Universitetscentrum, Roslagstullsbacken 21, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20160511

Available from: 2016-05-11 Created: 2016-05-10 Last updated: 2016-05-11Bibliographically approved
List of papers
1. Quick contrast sensitivity measurements in the periphery
Open this publication in new window or tab >>Quick contrast sensitivity measurements in the periphery
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2014 (English)In: Journal of Vision, ISSN 1534-7362, E-ISSN 1534-7362, Vol. 14, no 8Article in journal (Refereed) Published
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.

Keyword
peripheral vision, contrast sensitivity, adaptive optics, qCSF
National Category
Ophthalmology
Identifiers
urn:nbn:se:kth:diva-156464 (URN)10.1167/14.8.3 (DOI)000343878600003 ()2-s2.0-84904265976 (Scopus ID)
Note

QC 20141128

Available from: 2014-11-28 Created: 2014-11-28 Last updated: 2017-12-05Bibliographically approved
2. Effect of induced transverse chromatic aberration on peripheral vision
Open this publication in new window or tab >>Effect of induced transverse chromatic aberration on peripheral vision
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2015 (English)In: Optical Society of America. Journal A: Optics, Image Science, and Vision, ISSN 1084-7529, E-ISSN 1520-8532, Vol. 32, no 10, 1764-1771 p.Article in journal (Refereed) Published
Abstract [en]

Transverse chromatic aberration (TCA) is one of the largest optical errors affecting the peripheral image quality in the human eye. However, the effect of chromatic aberrations on our peripheral vision is largely unknown. This study investigates the effect of prism-induced horizontal TCA on vision, in the central as well as in the 20 degrees nasal visual field, for four subjects. Additionally, the magnitude of induced TCA (in minutes of arc) was measured subjectively in the fovea with a Vernier alignment method. During all measurements, the monochromatic optical errors of the eye were compensated for by adaptive optics. The average reduction in foveal grating resolution was about 0.032 +/- 0.005 logMAR/arcmin of TCA (mean +/- std). For peripheral grating detection, the reduction was 0.057 +/- 0.012 logMAR/arcmin. This means that the prismatic effect of highly dispersive spectacles may reduce the ability to detect objects in the peripheral visual field.

Place, publisher, year, edition, pages
Optical Society of America, 2015
Keyword
HUMAN-EYE, CONTRAST SENSITIVITY, VISUAL PERFORMANCE, RESOLUTION, ACUITY, LENS, TOPOGRAPHY, QUALITY, RETINA, FOVEAL
National Category
Natural Sciences
Identifiers
urn:nbn:se:kth:diva-180636 (URN)10.1364/JOSAA.32.001764 (DOI)000367201100004 ()26479929 (PubMedID)2-s2.0-84959339275 (Scopus ID)
Note

QC 20160119

Available from: 2016-01-19 Created: 2016-01-19 Last updated: 2017-11-30Bibliographically approved
3. Choice of grating orientation for evaluation of peripheral vision
Open this publication in new window or tab >>Choice of grating orientation for evaluation of peripheral vision
2016 (English)In: Optometry and Vision Science, ISSN 1040-5488, E-ISSN 1538-9235, Vol. 93, no 6, 567-574 p.Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Lippincott Williams & Wilkins, 2016
Keyword
grating orientation, peripheral vision, resolution, detection, meridional effect, psychophysics, forced-choice procedure
National Category
Ophthalmology
Identifiers
urn:nbn:se:kth:diva-186323 (URN)10.1097/OPX.0000000000000832 (DOI)000377852500003 ()26889822 (PubMedID)
Funder
Swedish Research Council, 621-2011-4094
Note

QC 20160511

Available from: 2016-05-10 Created: 2016-05-10 Last updated: 2017-11-30Bibliographically approved
4. Eye-tracking technology for real-time monitoring of transverse chromatic aberration
Open this publication in new window or tab >>Eye-tracking technology for real-time monitoring of transverse chromatic aberration
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2016 (English)In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 41, no 8, 1728-1731 p.Article in journal (Refereed) Published
Abstract [en]

Objective measurements of transverse chromatic aberration (TCA) between two or more wavelengths with an adaptive optics scanning laser ophthalmoscope (AOSLO) are very accurate, but frequent measurements are impractical in many experimental settings. Here, we demonstrate a pupil tracker that can accurately measure relative changes in TCA that are caused by small shifts in the pupil relative to the AOSLO imaging beam. Corrections for TCA caused by these shifts improve the measurement of TCA as a function of eccentricity, revealing a strong linear relationship. We propose that pupil tracking be integrated into AOSLO systems, where robust and unobtrusive control of TCA is required.

Place, publisher, year, edition, pages
Optical Society of America, 2016
Keyword
Adaptive optics, Eye movements, Optical devices, Eye tracking technologies, Linear relationships, Objective measurement, Pupil tracking, Real time monitoring, Scanning laser ophthalmoscope, Transverse chromatic aberration
National Category
Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:kth:diva-186324 (URN)10.1364/OL.41.001728 (DOI)000374391900010 ()27082330 (PubMedID)2-s2.0-84964577638 (Scopus ID)
Funder
EU, European Research Council, PITN-GA-2010-264605Swedish Research Council, 621-2011-4094
Note

QC 20160511

Available from: 2016-05-10 Created: 2016-05-10 Last updated: 2017-11-30Bibliographically approved
5. Transverse chromatic aberration across the visual field of the human eye
Open this publication in new window or tab >>Transverse chromatic aberration across the visual field of the human eye
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2016 (English)In: Journal of Vision, ISSN 1534-7362, E-ISSN 1534-7362, Vol. 16, no 14, 9Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Association for Research in Vision and Ophthalmology Inc., 2016
Keyword
Adaptive optics scanning laser ophthalmoscope, Lateral chromatic aberration, Peripheral vision, Retinal imaging, Transverse chromatic aberration
National Category
Natural Sciences Ophthalmology
Identifiers
urn:nbn:se:kth:diva-186395 (URN)10.1167/16.14.9 (DOI)000392946600009 ()2-s2.0-85004143323 (Scopus ID)
Funder
Swedish Research Council, 621-2011-4094
Note

QC 20170210

Available from: 2016-05-11 Created: 2016-05-11 Last updated: 2017-11-30Bibliographically approved

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