Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Wavefront Aberrations and Peripheral Vision
KTH, School of Engineering Sciences (SCI), Applied Physics.ORCID iD: 0000-0002-4894-7944
2007 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Failing eyesight causes a dramatic change in life. The aim of this project is to help people with large central visual field loss to better utilize their remaining vision. Central visual field loss means that the person has to rely on peripheral vision since the direct vision is lost, often due to a dysfunctional macula. In these cases, a full restoration of vision would require replacement or repair of the damaged retinal tissue, which is not yet possible. Instead, the present study seeks to improve peripheral vision by enhancing the image quality on the remaining functional part of the retina by optical corrections. The off-axis optics of the human eye often suffers from large optical errors, which together with the lower sampling density of the retina explain the limited visual function in the periphery. The dominating aberrations are field curvature and oblique astigmatism, which induce an effective eccentric refractive error. However, the irregular character of the aberrations and the limited neural function in the periphery will make it difficult to find the optimal refractive correction; the conventional subjective refraction, for example, is not suitable for subjects with large central visual field loss. Within the work of this thesis a Hartmann-Shack wavefront sensor has been constructed for oblique aberration measurements. Wavefront sensing is an objective method to assess detailed information about the optical errors in the human eye. Theory and methods have been developed to allow accurate off-axis measurements of the large aberrations, enable eccentric fixation, and handle the elliptical pupil. The study has mainly concentrated on sphero-cylindrical correction of peripheral vision. Peripheral resolution and detection acuity thresholds have been evaluated for seven subjects with central visual field loss and ten control subjects with normal vision. Five of the subjects with field loss showed improved resolution acuity with eccentric refractive correction compared to their habitual central correction, whereas little change was found for the control subjects. These results demonstrate that correction of peripheral optical errors can be beneficial to people with large central visual field loss in situations where a normal healthy eye does not experience any improvements. In conclusion, it is worthwhile to investigate the peripheral refractive errors in low-vision rehabilitation of central visual field loss and prescribe spectacle correction when those errors are large.

Place, publisher, year, edition, pages
Stockholm: KTH , 2007. , ix, 52 p.
Series
Trita-FYS, ISSN 0280-316X ; 2007:34
Keyword [en]
Optics, Human eye, Aberrations, Peripheral vision, Central visual field loss
National Category
Atom and Molecular Physics and Optics
Identifiers
URN: urn:nbn:se:kth:diva-4385ISBN: 978-91-7178-665-4 (print)OAI: oai:DiVA.org:kth-4385DiVA: diva2:12079
Public defence
2007-06-01, FD5, KTH, AlbaNova, Roslagstullsbacken 21, Stockholm, 13:00
Opponent
Supervisors
Note
QC 20100809Available from: 2007-05-20 Created: 2007-05-20 Last updated: 2010-08-09Bibliographically approved
List of papers
1. Off-axis wave front measurements for optical correction in eccentric viewing
Open this publication in new window or tab >>Off-axis wave front measurements for optical correction in eccentric viewing
2005 (English)In: Journal of Biomedical Optics, ISSN 1083-3668, Vol. 10, no 3, 034002-1-034002-7 p.Article in journal (Refereed) Published
Abstract [en]

In a previous study we have shown that correction of peripheral refractive errors can improve the remaining vision of subjects with large central visual field loss. Measuring peripheral refractive errors with traditional methods is often difficult due to low visual acuity and large aberrations. Therefore a Hartmann-Shack sensor has been designed to measure peripheral wave front aberrations in subjects using eccentric viewing. The sensor incorporates an eye tracker and analyzing software designed to handle large wave front aberrations and elliptic pupils. To ensure that the measurement axis is aligned with the direction of the subject's preferred retinal location, a special fixation target has been developed. It consists of concentric rings surrounding the aperture of the sensor together with a central fixation mark along the measurement axis. Some initial measurements on subjects using eccentric viewing have been performed successfully. As a first step in improving the peripheral optics of the eye, the wave front has been used to calculate the eccentric refraction. This refraction has been compared to the refraction found with the Power-Refractor instrument. Measuring the off-axis wave front is a fast way to assess the optical errors in the subject's eccentric viewing angle and to better understand the problems of eccentric correction.

Keyword
Central visual field loss; Eccentric refraction; Eccentric viewing; Hartmann-Shack sensor; Peripheral wave front aberrations; PowerRefractor; Preferred retinal location; Strehl ratio; Vision; Aberrations; Optical instrument lenses; Optical instruments; Optical sensors; Optical variables measurement; Optics; Optometers; Refraction; Vision; Wavefronts; Biomedical engineering
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-7151 (URN)10.1117/1.1920587 (DOI)000235127400022 ()2-s2.0-27744563913 (Scopus ID)
Note
QC 20100809Available from: 2007-05-20 Created: 2007-05-20 Last updated: 2010-08-09Bibliographically approved
2. Unwrapping Hartmann-Shack images from highly aberrated eyes using an iterative B-spline based extrapolation method
Open this publication in new window or tab >>Unwrapping Hartmann-Shack images from highly aberrated eyes using an iterative B-spline based extrapolation method
2004 (English)In: Optometry and Vision Science, ISSN 1040-5488, E-ISSN 1538-9235, Vol. 81, no 5, 383-388 p.Article in journal (Refereed) Published
Abstract [en]

Purpose. When the wavefront aberrations of the eye are measured with a Hartmann-Shack (HS) sensor, the resulting spot pattern must be unwrapped, that is, for each lenslet the corresponding spot must be identified. This puts a limitation on the measurable amount of aberrations. To extend the range of an HS sensor, a powerful unwrapping algorithm has been developed. Methods. The unwrapping algorithm starts by connecting the central HS spots to the central lenslets. It then fits a B-spline function through a least squares estimate to the deviations of the central HS spots. This function is then extrapolated to find the expected locations of HS spots for the unconnected lenslets. The extrapolation is performed gradually in an iterative manner; the closest unconnected lenslets are extrapolated and connected, and then the B-spline function is least squares fitted to all connected HS spots and extrapolated again. Results. Wavefront aberrations from eyes with high aberrations can be successfully unwrapped with the developed algorithm. The dynamic range of a typical HS sensor increases 3.5 to 13 times compared with a simple unwrapping algorithm. Conclusions. The implemented algorithm is an efficient unwrapping tool and allows the use of lenslets with a low numerical aperture and thus gives a relatively higher accuracy of measurements of the ocular aberrations.

Keyword
B-spline function; Eye; Hartmann-Shack sensor; Ocular wavefront aberrations; Unwrapping; Aberrations; Algorithms; Estimation; Extrapolation; Image analysis; Iterative methods; Sensors; Wavefronts; Eyes; Least squares estimation; Lenslets; Ocular aberrations; accuracy; algorithm; article; eye disease; measurement; priority journal; sensor; Algorithms; Diagnostic Techniques, Ophthalmological; Humans; Models, Statistical; Refractive Errors; Vision Disorders; Visual Fields
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-7152 (URN)10.1097/01.opx.0000135086.61760.b7 (DOI)000221566900013 ()15181365 (PubMedID)2-s2.0-2542616085 (Scopus ID)
Note

QC 20100809

Available from: 2007-05-20 Created: 2007-05-20 Last updated: 2016-05-09Bibliographically approved
3. Transformation of Zernike coefficients: scaled, translated, and rotated wavefronts with circular and elliptical pupils
Open this publication in new window or tab >>Transformation of Zernike coefficients: scaled, translated, and rotated wavefronts with circular and elliptical pupils
2007 (English)In: Journal of the Optical Society of America A, ISSN 0740-3232, Vol. 24, no 3, 569-577 p.Article in journal (Refereed) Published
Abstract [en]

Zernike polynomials and their associated coefficients are commonly used to quantify the wavefront aberrations of the eye. When the aberrations of different eyes, pupil sizes, or corrections are compared or averaged, it is important that the Zernike coefficients have been calculated for the correct size, position, orientation, and shape of the pupil. We present the first complete theory to transform Zernike coefficients analytically with regard to concentric scaling, translation of pupil center, and rotation. The transformations are described both for circular and elliptical pupils. The algorithm has been implemented in MATLAB, for which the code is given in an appendix.

Keyword
Algorithms; Eye movements; MATLAB; Polynomials; Pupils; Zernike coefficients; Vision; algorithm; article; biological model; computer assisted diagnosis; computer simulation; human; image enhancement; iris; keratometry; methodology; physiology; reproducibility; rotation; sensitivity and specificity; vision; Algorithms; Computer Simulation; Corneal Topography; Humans; Image Enhancement; Image Interpretation, Computer-Assisted; Iris; Models, Biological; Reproducibility of Results; Rotation; Sensitivity and Specificity; Visual Perception
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-7153 (URN)10.1364/JOSAA.24.000569 (DOI)000244407300001 ()17301846 (PubMedID)2-s2.0-34047118110 (Scopus ID)
Note
QC 20100809Available from: 2007-05-20 Created: 2007-05-20 Last updated: 2010-08-09Bibliographically approved
4. Assessment of objective and subjective eccentric refraction
Open this publication in new window or tab >>Assessment of objective and subjective eccentric refraction
2005 (English)In: Optometry and Vision Science, ISSN 1040-5488, E-ISSN 1538-9235, Vol. 82, no 4, 298-306 p.Article in journal (Refereed) Published
Abstract [en]

Purpose. When performing perimetry, refracting subjects with central visual field loss, and in emmetropization studies, it is important to accurately measure peripheral refractive errors. Traditional methods for foveal refraction often give uncertain results in eccentric angles as a result of the large aberrations and the reduced retinal function. The aim of this study is therefore to compare and evaluate four methods for eccentric refraction. Methods. Four eccentric methods were tested on 50 healthy subjects: one novel subjective procedure, optimizing the detection contrast sensitivity with different trial lenses, and three objective ones: photorefraction with a PowerRefractor, wavefront measurements with a Hartmann-Shack sensor, and retinoscopy. The peripheral refractive error in the horizontal nasal visual field of the right eye was measured in 20 degrees and 30 degrees. Results. In general, the eccentric refraction methods compared reasonably well. However, the following differences were noted. Retinoscopy showed a significant difference from the other methods in the axis of astigmatism. In 300 eccentric angle, it was not possible to measure 15 of the subjects with the PowerRefractor and the instrument also tended to underestimate high myopia (<-6 D). The Hartmann-Shack sensor showed a myopic shift of approximately 0.5 D in both eccentricities. The subjective method had a relatively larger spread. Conclusions. This study indicates that it is possible to assess the eccentric refraction with all methods. However, the Hartmann-Shack technique was found to be the most useful method. The agreement between the objective methods and the subjective eccentric refraction shows that detection contrast sensitivity in the periphery is affected by relatively small amounts of defocus.

Keyword
Contrast sensitivity; Detection; Eccentric refraction; Peripheral vision; Photorefraction; Refractive errors; Retinoscopy; Wavefront aberrations; Aberrations; Diseases; Error analysis; Image sensors; Light refraction; Optical instrument lenses; Sensitivity analysis; Wavefronts; Eccentric angles; Eccentric refraction; Refractive errors; Visual fields; Vision; adult; article; astigmatism; clinical article; contrast sensitivity; eye refraction; female; high myopia; human; light refraction; male; optical instrumentation; priority journal; refraction error; retinoscopy; sensor; visual field; Adult; Aged; Contrast Sensitivity; Corneal Topography; Diagnostic Techniques, Ophthalmological; Female; Fovea Centralis; Humans; Male; Middle Aged; Reference Values; Refraction, Ocular; Retinoscopy; Visual Fields
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-7154 (URN)10.1097/01.OPX.0000159366.61943.62 (DOI)000228572400012 ()15829857 (PubMedID)2-s2.0-17444369423 (Scopus ID)
Note
QC 20100809Available from: 2007-05-20 Created: 2007-05-20 Last updated: 2012-03-21Bibliographically approved
5. Effect of optical correction and remaining aberrations on peripheral resolution acuity in the human eye
Open this publication in new window or tab >>Effect of optical correction and remaining aberrations on peripheral resolution acuity in the human eye
Show others...
2007 (English)In: Optics Express, ISSN 1094-4087, Vol. 15, no 20, 12654-12661 p.Article in journal (Refereed) Published
Abstract [en]

Retinal sampling poses a fundamental limit to resolution acuity in the periphery. However, reduced image quality from optical aberrations may also influence peripheral resolution. In this study, we investigate the impact of different degrees of optical correction on acuity in the periphery. We used an adaptive optics system to measure and modify the off-axis aberrations of the right eye of six normal subjects at 20 degrees eccentricity. The system consists of a Hartmann-Shack sensor, a deformable mirror, and a channel for visual testing. Four different optical corrections were tested, ranging from foveal sphero-cylindrical correction to full correction of eccentric low- and high-order monochromatic aberrations. High-contrast visual acuity was measured in green light using a forced choice procedure with Landolt C's, viewed via the deformable mirror through a 4.8-mm artificial pupil. The Zernike terms mainly induced by eccentricity were defocus and with- and against-the-rule astigmatism and each correction condition was successfully implemented. On average, resolution decimal visual acuity improved from 0.057 to 0.061 as the total root-mean-square wavefront error changed from 1.01 mu m to 0.05 mu m. However, this small tendency of improvement in visual acuity with correction was not significant. The results suggest that for our experimental conditions and subjects, the resolution acuity in the periphery cannot be improved with optical correction.

Keyword
Aberrations; Mean square error; Optical resolving power; Optical sensors; Wavefronts; Optical correction; Resolution acuity; Resolution decimal visual acuity; Root-mean-square wavefront error; Optical variables control
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-7155 (URN)10.1364/OE.15.012654 (DOI)000250006700010 ()2-s2.0-35148840052 (Scopus ID)
Note

QC 20100809. Uppdaterad från Submitted till Published 20100809.

QC 20150727

Available from: 2007-05-20 Created: 2007-05-20 Last updated: 2015-07-27Bibliographically approved
6. Vision evaluation of eccentric refractive correction
Open this publication in new window or tab >>Vision evaluation of eccentric refractive correction
2007 (English)In: Optometry and Vision Science, ISSN 1040-5488, E-ISSN 1538-9235, Vol. 84, no 11, 1046-1052 p.Article in journal (Refereed) Published
Abstract [en]

Purpose. This study investigates the benefits of eccentric refractive correction to resolution and detection thresholds in different contrasts for seven subjects with central visual field loss (CFL) and for four healthy control subjects with normal vision.

Methods. Refractive correction in eccentric viewing angles, i.e., the preferred retinal location for the CFL subjects and 20 degrees off-axis for the control subjects, was assessed by photorefraction with the PowerRefractor instrument and by wavefront analysis using the Hartmann-Shack principle. The visual function with both eccentric and central corrections was evaluated using number identification and grating detection.

Results. For the CFL subjects, the resolution and detection thresholds varied between individuals because of different preferred retinal locations and cause of visual field loss. However, all seven CFL subjects showed improved visual function for resolution and detection tasks with eccentric correction compared with central correction. No improvements in high-contrast resolution were found for the control subjects.

Conclusions. These results imply that optical eccentric correction can improve the resolution acuity for subjects with CFL in situations where healthy eyes do not show any improvements.

Keyword
Detection threshold; Eccentric refractive correction; Low vision; Macular degeneration; Periphery; Resolution acuity; Error correction; Error detection; Optical resolving power; Photorefractive materials; Vision; Central visual field loss (CFL); Detection threshold; Eccentric refractive correction; Low vision; Macular degeneration; Optical eccentric correction; Periphery; Photorefraction; Resolution acuity; Refractive index; adult; aged; clinical article; conference paper; control group; controlled study; evaluation; eye refraction; female; human; light refraction; male; optical resolution; priority journal; retina; task performance; vision; visual acuity; visual field; visual field defect; visual impairment; Adult; Diagnostic Techniques, Ophthalmological; Female; Humans; Male; Middle Aged; Refraction, Ocular; Refractometry; Retina; Sensory Thresholds; Vision; Vision Disorders; Visual Acuity; Visual Fields
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-7156 (URN)10.1097/OPX.0b013e318159aa7a (DOI)000251040200007 ()18043424 (PubMedID)2-s2.0-36649005597 (Scopus ID)
Note
QC 20100809. Uppdaterad från Accepted till Published 20100809.Available from: 2007-05-20 Created: 2007-05-20 Last updated: 2010-08-09Bibliographically approved

Open Access in DiVA

fulltext(1898 kB)919 downloads
File information
File name FULLTEXT01.pdfFile size 1898 kBChecksum MD5
3f4f38b6286b653ed118c210023e591c256a589b615ada25b9628e9dd44e5874fe57deed
Type fulltextMimetype application/pdf

Authority records BETA

Lundström, Linda

Search in DiVA

By author/editor
Lundström, Linda
By organisation
Applied Physics
Atom and Molecular Physics and Optics

Search outside of DiVA

GoogleGoogle Scholar
Total: 919 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 767 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf