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Peripheral Vision: Adaptive Optics and Psychophysics
KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis is about our peripheral vision. Peripheral vision is poor compared to central vision, due to both neural and optical factors. The optical factors include astigmatism, defocus and higher order aberrations consisting mainly of coma. Neurally, the density of ganglion cells decreases towards the periphery, which limits the sampling density. The questions that this thesis attempts to answer are how much and under which circumstances correction of optical errors can improve peripheral vision. For this, an adaptive optics system has been constructed with a wavefront sensor and a deformable mirror working in closed loop to perform real-time correction of optical errors. To investigate vision, psychophysical routines utilizing Bayesian methods have been evaluated and modified for peripheral vision to handle the presence of aliasing, fixation instability and rapid fatigue.

We found that correcting both refractive errors and higher order aberrations improved peripheral low-contrast resolution acuity. \\

We looked at two specific topics in peripheral vision research in particular: Central visual field loss and myopia development. Persons with central visual field loss have to rely on their remaining peripheral vision, and it is of great interest to understand whether optical correction can offer them any benefits. In a case study on a single subject, we found meaningful improvements in vision with both optimized refractive correction as well as additional benefits with aberration correction. These improvements were larger than for comparable healthy subjects with a similar magnitude of aberrations. When it comes to myopia development, an interesting hypothesis is that peripheral optics affect and guide the emmetropization process. We have found an asymmetric depth of field in the periphery for myopic subjects, caused by their higher order aberrations, and presented a model on how this asymmetry may influence the emmetropization process.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. , xiii, 72 p.
Series
Trita-FYS, ISSN 0280-316X ; 2013:08
National Category
Other Physics Topics
Identifiers
URN: urn:nbn:se:kth:diva-120077ISBN: 978-91-7501-698-6 (print)OAI: oai:DiVA.org:kth-120077DiVA: diva2:613342
Public defence
2013-04-19, Sal FD5, AlbaNova Universitetscentrum, Roslagstullsbacken 21, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

QC 20130327

Available from: 2013-03-27 Created: 2013-03-27 Last updated: 2013-04-12Bibliographically approved
List of papers
1. Influence of Optical Defocus on Peripheral Vision
Open this publication in new window or tab >>Influence of Optical Defocus on Peripheral Vision
2011 (English)In: Investigative Ophthalmology and Visual Science, ISSN 0146-0404, E-ISSN 1552-5783, Vol. 52, no 1, 318-323 p.Article in journal (Refereed) Published
Abstract [en]

PURPOSE. Peripheral optical corrections are often thought to give few visual benefits beyond improved detection acuity. However, patients with central visual field loss seem to benefit from peripheral correction, and animal studies suggest a role for peripheral vision in the development of myopia. This study was conducted to bridge this gap by systematically studying the sensitivity to optical defocus in a wide range of peripheral visual tasks. METHODS. The spatial frequency threshold for detection and resolution in high and low contrast with stationary and drifting gratings were measured off-axis (20 nasal visual field) in five subjects with a peripheral optical correction that was varied systematically +/- 4 D. RESULTS. All visual tasks, except high-contrast resolution, were sensitive to optical defocus, particularly low-contrast resolution with an increase of up to 0.227 logMAR/D. The two myopic subjects exhibited a very low sensitivity to defocus by negative lenses for low-contrast tasks, whereas all subjects were equally affected by myopic defocus. Contrary to expectations, drifting gratings made little difference overall. CONCLUSIONS. Optical defocus as low as 1 D has a large impact on most peripheral visual tasks, with high-contrast resolution being the exception. Since the everyday visual scenery consists of objects at different contrast levels, it is understandable that persons with central visual field loss are helped by correction of peripheral refractive errors. The asymmetry in sensitivity to peripheral optical defocus in low-contrast tasks that was experienced by the myopic subjects in this study merits further investigation.

Keyword
visual-acuity, refractive error, resolution acuity, eye growth, thresholds, repeatability, aberrations, myopia
National Category
Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:kth:diva-29719 (URN)10.1167/iovs.10-5623 (DOI)000285925000040 ()2-s2.0-79952221478 (Scopus ID)
Note
QC 20110214Available from: 2011-02-14 Created: 2011-02-14 Last updated: 2017-12-11Bibliographically approved
2. Symmetries in peripheral ocular aberrations
Open this publication in new window or tab >>Symmetries in peripheral ocular aberrations
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2011 (English)In: Journal of Modern Optics, ISSN 0950-0340, E-ISSN 1362-3044, Vol. 58, no 19-20, 1690-1695 p.Article in journal (Refereed) Published
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.

Keyword
peripheral visual field, off-axis wavefront aberrations, left and right eyes, mirror symmetry
National Category
Ophthalmology
Identifiers
urn:nbn:se:kth:diva-55272 (URN)10.1080/09500340.2011.564317 (DOI)000297690900003 ()2-s2.0-84856927274 (Scopus ID)
Note
QC 20120102Available from: 2012-01-02 Created: 2012-01-02 Last updated: 2017-12-08Bibliographically approved
3. Resolution of static and dynamic stimuli in the peripheral visual field
Open this publication in new window or tab >>Resolution of static and dynamic stimuli in the peripheral visual field
2011 (English)In: Vision Research, ISSN 0042-6989, E-ISSN 1878-5646, Vol. 51, no 16, 1829-1834 p.Article in journal (Refereed) Published
Abstract [en]

In a clinical setting, emphasis is given to foveal visual function, and tests generally only utilize static stimuli. In this study, we measured static (SVA) and dynamic visual acuity (DVA) in the central and peripheral visual field on healthy, young emmetropic subjects using stationary and drifting Gabor patches. There were no differences between SVA and DVA in the peripheral visual field; however, SVA was superior to DVA in the fovea for both velocities tested. In addition, there was a clear naso-temporal asymmetry for both SVA and DVA for isoeccentric locations in the visual field beyond 10 degrees eccentricity. The lack of difference in visual acuity between static and dynamic stimuli found in this study may reflect the use of drift-motion as opposed to displacement motion used in previous studies.

Keyword
Visual acuity, Resolution acuity, Dynamic visual acuity (DVA), Peripheral vision, Drifting Gabor
National Category
Neurosciences
Identifiers
urn:nbn:se:kth:diva-39514 (URN)10.1016/j.visres.2011.06.011 (DOI)000294095300005 ()2-s2.0-79961028317 (Scopus ID)
Note

QC 20160427

Available from: 2011-09-20 Created: 2011-09-12 Last updated: 2017-12-08Bibliographically approved
4. Adaptive optics for peripheral vision
Open this publication in new window or tab >>Adaptive optics for peripheral vision
2012 (English)In: Journal of Modern Optics, ISSN 0950-0340, E-ISSN 1362-3044, Vol. 59, no 12, 1064-1070 p.Article in journal (Refereed) Published
Abstract [en]

Understanding peripheral optical errors and their impact on vision is important for various applications, e.g. research on myopia development and optical correction of patients with central visual field loss. In this study, we investigated whether correction of higher order aberrations with adaptive optics (AO) improve resolution beyond what is achieved with best peripheral refractive correction. A laboratory AO system was constructed for correcting peripheral aberrations. The peripheral low contrast grating resolution acuity in the 20 nasal visual field of the right eye was evaluated for 12 subjects using three types of correction: refractive correction of sphere and cylinder, static closed loop AO correction and continuous closed loop AO correction. Running AO in continuous closed loop improved acuity compared to refractive correction for most subjects (maximum benefit 0.15logMAR). The visual improvement from aberration correction was highly correlated with the subject's initial amount of higher order aberrations (p=0.001, R 2=0.72). There was, however, no acuity improvement from static AO correction. In conclusion, correction of peripheral higher order aberrations can improve low contrast resolution, provided refractive errors are corrected and the system runs in continuous closed loop.

Keyword
adaptive optics, low contrast resolution, off-axis wavefront aberration, peripheral vision, visual acuity
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-101593 (URN)10.1080/09500340.2012.683827 (DOI)000307270500005 ()2-s2.0-84864721326 (Scopus ID)
Note

QC 20120830

Available from: 2012-08-30 Created: 2012-08-30 Last updated: 2017-12-07Bibliographically approved
5. Benefit of Adaptive Optics Aberration Correction at Preferred Retinal Locus
Open this publication in new window or tab >>Benefit of Adaptive Optics Aberration Correction at Preferred Retinal Locus
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2012 (English)In: Optometry and Vision Science, ISSN 1040-5488, E-ISSN 1538-9235, Vol. 89, no 9Article in journal (Refereed) Published
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.

National Category
Ophthalmology
Identifiers
urn:nbn:se:kth:diva-120074 (URN)2-s2.0-84865730607 (Scopus ID)
Note

QC 20130327

Available from: 2013-03-27 Created: 2013-03-27 Last updated: 2017-12-06Bibliographically approved
6. Have we misinterpreted the study of Hoogerheide et al. (1971)?
Open this publication in new window or tab >>Have we misinterpreted the study of Hoogerheide et al. (1971)?
2012 (English)In: Optometry and Vision Science, ISSN 1040-5488, E-ISSN 1538-9235, Vol. 89, no 8, 1235-1237 p.Article in journal (Refereed) Published
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.

Keyword
emmetropization, hyperopia, myopia, myopia progression, peripheral refraction, skiagrams
National Category
Ophthalmology
Identifiers
urn:nbn:se:kth:diva-101544 (URN)10.1097/OPX.0b013e318264f2d1 (DOI)000307476600019 ()2-s2.0-84864716642 (Scopus ID)
Funder
Swedish Research Council, 621-2011-4094
Note

QC 20120905

Available from: 2012-09-05 Created: 2012-08-30 Last updated: 2017-12-07Bibliographically approved
7. Evaluating the peripheral optical effect of multifocal contact lenses
Open this publication in new window or tab >>Evaluating the peripheral optical effect of multifocal contact lenses
Show others...
2012 (English)In: Ophthalmic & physiological optics, ISSN 0275-5408, E-ISSN 1475-1313, Vol. 32, no 6, 527-534 p.Article in journal (Refereed) Published
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.

Keyword
Defocus, Depth of field, Multifocal/bifocal/dual-focus contact lenses, Myopia, Peripheral wavefront aberrations
National Category
Ophthalmology
Identifiers
urn:nbn:se:kth:diva-104947 (URN)10.1111/j.1475-1313.2012.00937.x (DOI)000309747600012 ()2-s2.0-84867434065 (Scopus ID)
Funder
Vinnova, VINNMER 2008-00992
Note

QC 20121114

Available from: 2012-11-14 Created: 2012-11-14 Last updated: 2017-12-07Bibliographically approved
8. Sign-Dependent Sensitivity to Peripheral Defocus for Myopes due to Aberrations
Open this publication in new window or tab >>Sign-Dependent Sensitivity to Peripheral Defocus for Myopes due to Aberrations
2012 (English)In: Investigative Ophthalmology and Visual Science, ISSN 0146-0404, E-ISSN 1552-5783, Vol. 53, no 11, 7176-7182 p.Article in journal (Refereed) Published
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.

Keyword
Depth-Of-Field, Refractive Error, Human Eye, Optical-Quality, Monochromatic Aberrations, Visual-Field, Children, Vision, Lenses, Growth
National Category
Ophthalmology
Identifiers
urn:nbn:se:kth:diva-107103 (URN)10.1167/iovs.11-9034 (DOI)000310589900062 ()2-s2.0-84872012994 (Scopus ID)
Funder
Swedish Research Council, 621-2011-4094Vinnova, 2008-00992
Note

QC 20121206

Available from: 2012-12-06 Created: 2012-12-06 Last updated: 2017-12-07Bibliographically approved

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