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Choice of grating orientation for evaluation of peripheral vision
KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.ORCID iD: 0000-0002-2155-7030
KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.ORCID iD: 0000-0003-4149-4556
KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.ORCID iD: 0000-0002-4894-7944
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. Vol. 93, no 6, 567-574 p.
Keyword [en]
grating orientation, peripheral vision, resolution, detection, meridional effect, psychophysics, forced-choice procedure
National Category
Ophthalmology
Identifiers
URN: urn:nbn:se:kth:diva-186323DOI: 10.1097/OPX.0000000000000832ISI: 000377852500003PubMedID: 26889822OAI: oai:DiVA.org:kth-186323DiVA: diva2:926906
Funder
Swedish Research Council, 621-2011-4094
Note

QC 20160511

Available from: 2016-05-10 Created: 2016-05-10 Last updated: 2016-08-25Bibliographically approved
In thesis
1. Transverse Chromatic Aberration and Vision: Quantification and Impact across the Visual Field
Open this publication in new window or tab >>Transverse Chromatic Aberration and Vision: Quantification and Impact across the Visual Field
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
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:nbn:se:kth:diva-186334 (URN)978-91-7595-980-1 (ISBN)
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
2. Vision Beyond the Fovea: Evaluation and Stimuli Properties
Open this publication in new window or tab >>Vision Beyond the Fovea: Evaluation and Stimuli Properties
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This research is about evaluating vision in the periphery. Peripheral vision is of fundamental importance in the performance of our everyday activities. The aim of this thesis is to develop methods suitable for the evaluation of peripheral vision and to assess how different visual functions vary across the visual field. The results have application both within the field of visual rehabilitation of people with central visual field loss (CFL)and as well as in myopia research.

All methods for assessing peripheral vision were implemented with adaptive psychophysical algorithms based on Bayesian statistics. A routine for time-efficient evaluation of peripheral contrast sensitivity was implemented and verified for measurements out to 30° in the visual field. Peripheral vision was evaluated for different properties of the stimuli: sharpness, motion, orientation, and extent. Optical quality was controlled using adaptive optics and/or corrective spectacles specially adapted for the peripheral viewing angle. We found that many peripheral visual functions improved with optical correction, especially in people with CFL. We also found improvements in peripheral contrast sensitivity for low spatial frequencies when stimuli drifted at 5 to 10 Hz; this applies both for people with normal vision and those with CFL. In the periphery, it is easier to see lines that are oriented parallel with respect to the visual field meridian. We have shown that this directional bias is present for both resolution and detection tasks in the periphery, even when the asymmetric optical errors are minimized. For accurate evaluation of peripheral vision, we therefore recommend using gratings that are oriented oblique to the visual  field meridian. The directional bias may have implications in how peripheral image quality affects myopia progression. Another proof that peripheral vision can influence central visual function is the fact that, when the stimulus extent was increased beyond the fovea, the blur in the stimulus was less noticeable.

Abstract [sv]

Denna forskning handlar om att utvärdera synen i periferin. Vår perifera syn är ovärderlig i det dagliga livet. Målsättningen med denna avhandling är dels att utveckla metoder speciellt lämpade för perifer synutvärdering och dels att mäta hur olika synfunktioner varierar över synfältet. Resultaten har tillämpning både inom synrehabilitering för personer med centraltsynfältsbortfall och inom närsynthetsforskning.

Adaptiv psykofysisk metodologi baserad på Bayesiansk statistik användes vid all utvärdering av det perifera seendet. Vi implementerade en rutin för tidseffektiv mätning av perifer kontrastkänslighet och verifierade den ut till 30° i synfältet. Den perifera synen utvärderades för olika egenskaper hos objektet: skärpa, rörelse, riktning och utbredning. Skärpan kontrollerades med hjälp av adaptiv optik och/eller glasögonkorrektion speciellt anpassad för den perifera synvinkeln. Vi fann att många periferasynfunktioner förbättras av optisk korrektion, särskilt för personer med centralt synfältsbortfall. Vi hittade även förbättringar i periferkontrastkänslighet för låga ortsfrekvenser när objektet modulerades med hastigheter mellan 5 och 10 Hz, vilket gäller både normalseende och personer med centralt synfältsbortfall. I periferin är det lättare att se linjer som är orienterade parallellt med synfältsmeridianen. Vi har visat att denna riktningsbias gäller både för upplösning och detektion i periferin, även när de asymmetriska optiska felen minimeras. För bästa mätnoggrannhet rekommenderar vi därför att använda randmönster som ligger snett relativt synfältsmeridianen. Denna riktningsbias skulle även kunna påverka hur den perifera bildkvalitén inverkar på utvecklingen av närsynthet. Ytterligare ett bevis för att perifer syn kan påverka den centrala synfunktionen är att, när objektets utbredning ökades, uppfattade personen det som mindre suddigt.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. 64 p.
Series
TRITA-FYS, ISSN 0280-316X ; 2016:57
Keyword
Peripheral vision, Visual optics, Optical correction, Orientation, Stimulus extent, Moving stimulus, Contrast sensitivity, Visual acuity, Central vision loss, Myopia
National Category
Physical Sciences
Research subject
Biological Physics
Identifiers
urn:nbn:se:kth:diva-191212 (URN)978-91-7729-071-1 (ISBN)
External cooperation:
Public defence
2016-09-23, FB 42, Albanova University Center, Roslagstullsbacken 21, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

QC 20160826

Available from: 2016-08-26 Created: 2016-08-25 Last updated: 2016-08-29Bibliographically approved

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