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Optimal Use of Peripheral Vision
Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences. (Vision Enabling Lab)ORCID iD: 0000-0002-3745-0035
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

People who lose their central vision have to rely on their peripheral vision for all visual tasks. The ability to resolve fine details in the periphery is reduced due to retinal limitations and the optical aberrations arising from the use of off-axis vision. The aim of this work is to improve vision by enhancing the image quality at the preferred retinal locus by means of correcting the optical errors. The focus of this thesis has been to measure and correct peripheral optical errors, as well as to evaluate their impact on resolution acuity in both normal and central visual field loss subjects.

 In order to measure peripheral optics we employed a COAS HD VR open view aberrometer which is based on the Hartmann-Shack principle. Psychophysical methods were used to evaluate peripheral grating resolution acuity. We assessed the repeatability of the wavefront sensor in measuring the peripheral ocular aberrations. The symmetry of peripheral ocular aberrations between the left and right eyes was examined. The influence of age on peripheral ocular aberrations was also investigated. We evaluated peripheral vision with sphero-cylindrical correction in healthy eyes and performed the first adaptive optics aberration correction at the preferred retinal locus of a single central visual field loss subject.

 We found that the aberrometer was repeatable and reliable in measuring peripheral ocular aberrations. There was mirror symmetry between the two eyes for most of the peripheral aberration coefficients. Age had a significant influence on peripheral ocular aberrations; there were larger amounts of higher-order aberrations in old eyes than in young eyes. Peripheral low contrast resolution acuity improved with peripheral refractive correction in subjects who had higher amounts of off-axis astigmatism. Finally, adaptive optics aberration correction improved both high and low contrast resolution acuity measured at the preferred retinal locus of the single low vision subject.

 Because of their versatility, open view aberrometers will hopefully be a standard clinical instrument at low vision clinics as they allow for measurements to be rapidly performed at any location in the visual field. The existence of off-axis astigmatism should be better communicated within the low-vision rehabilitation community. Currently, the off-axis refractive errors can be corrected with conventional methods and we hope that the higher-order aberrations can also be corrected in a more realistic ways in the future.  

 In conclusion, this thesis has shown that peripheral visual function can be improved by optical correction. The findings of this thesis have broadened the knowledge of peripheral optical errors and their influence on vision.

Place, publisher, year, edition, pages
Kalmar, Växjö: Linnaeus University Press, 2012.
Series
Linnaeus University Dissertations, 108/2012
Keyword [en]
off-axis refractive errors, peripheral aberrations, aberrometers, central visual field loss, preferred retinal locus, eccentric viewing, absolute central scotoma, adaptive optics, eccentric correction.
National Category
Ophthalmology
Research subject
Natural Science, Optometry
Identifiers
URN: urn:nbn:se:lnu:diva-22562ISBN: 978-91-86983-94-9 (print)OAI: oai:DiVA.org:lnu-22562DiVA: diva2:571048
Public defence
2012-12-20, N2007, Smålandsgatan 26E, Kalmar, 10:00 (English)
Opponent
Supervisors
Available from: 2012-11-23 Created: 2012-11-21 Last updated: 2016-04-27Bibliographically approved
List of papers
1. Repeatability of Peripheral Aberrations in Young Emmetropes
Open this publication in new window or tab >>Repeatability of Peripheral Aberrations in Young Emmetropes
2010 (English)In: Optometry and Vision Science, ISSN 1040-5488, E-ISSN 1538-9235, Vol. 87, no 10, 751-759 p.Article in journal (Refereed) Published
Abstract [en]

PURPOSE.: The purpose of this study is to assess the intrasession repeatability of ocular aberration measurements in the peripheral visual field with a commercially available Shack-Hartmann aberrometer (complete ophthalmic analysis system-high definition-vision research). The higher-order off-axis aberrations data in young healthy emmetropic eyes are also reported.

METHODS.: The aberrations of the right eye of 18 emmetropes were measured using an aberrometer with an open field of view that allows peripheral measurements. Five repeated measures of ocular aberrations were obtained and assessed in steps of 10 degrees out to +/-40 degrees in the horizontal visual field (nasal + and temporal -) and -20 degrees in the inferior visual field. The coefficient of repeatability, coefficient of variation, and the intraclass correlation coefficient were calculated as a measure of intrasession repeatability.

RESULTS.: In all eccentric angles, the repeatability of the third- and fourth-order aberrations was better than the fifth and sixth order aberrations. The coefficient of variation was <30% and the intraclass correlation coefficient was >0.90 for the third and fourth order but reduced gradually for higher orders. There was no statistical significant difference in variance of total higher-order root mean square between on- and off-axis measurements (p > 0.05). The aberration data in this group of young emmetropes showed that the horizontal coma (C13) was most positive at 40 degrees in the temporal field, decreasing linearly toward negative values with increasing off-axis angle into the nasal field, whereas all other higher-order aberrations showed little or no change.

CONCLUSIONS.: The complete ophthalmic analysis system-high definition-vision research provides fast, repeatable, and valid peripheral aberration measurements and can be used efficiently to measure off-axis aberrations in the peripheral visual field

Keyword
repeatability, off-axis wavefront aberrations, COAS-HD VR aberrometer, peripheral aberrations, visual field
National Category
Ophthalmology
Research subject
Natural Science, Optometry
Identifiers
urn:nbn:se:lnu:diva-8763 (URN)10.1097/OPX.0b013e3181f36336 (DOI)2-s2.0-78049303467 (Scopus ID)
Available from: 2010-10-04 Created: 2010-10-04 Last updated: 2017-12-12Bibliographically 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 SI, 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.

National Category
Medical and Health Sciences
Research subject
Natural Science, Optometry
Identifiers
urn:nbn:se:lnu:diva-11156 (URN)10.1080/09500340.2011.564317 (DOI)2-s2.0-84856927274 (Scopus ID)
Available from: 2011-03-17 Created: 2011-03-17 Last updated: 2017-12-11Bibliographically approved
3. Influence of age on peripheral ocular aberrations.
Open this publication in new window or tab >>Influence of age on peripheral ocular aberrations.
2011 (English)In: Optometry and Vision Science, ISSN 1040-5488, E-ISSN 1538-9235, Vol. 88, no 9, 1088-1098 p.Article in journal (Refereed) Published
Abstract [en]

PURPOSE.: To compare peripheral lower and higher order aberrations across the horizontal (±40°) and inferior (-20°) 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° steps to ±40° horizontally and -20° 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, J45, and J180). 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 (C3) and spherical aberration (C4) 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.

Keyword
peripheral aberrations; off-axis refraction; aging; COAS-HD VR
National Category
Ophthalmology
Research subject
Natural Science, Optometry
Identifiers
urn:nbn:se:lnu:diva-13993 (URN)10.1097/OPX.0b013e3182234630 (DOI)21666523 (PubMedID)2-s2.0-80052457355 (Scopus ID)
Available from: 2011-09-04 Created: 2011-09-04 Last updated: 2017-12-08Bibliographically approved
4. Clinical Impact of Objectively Determined Peripheral Refractive Error Correction on Low-Contrast Resolution Acuity
Open this publication in new window or tab >>Clinical Impact of Objectively Determined Peripheral Refractive Error Correction on Low-Contrast Resolution Acuity
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(English)Manuscript (preprint) (Other academic)
Keyword
Visual acuity; Low-contrast resolution acuity; Off-axis refractive errors; Peripheral vision; Off-axis
National Category
Ophthalmology
Research subject
Natural Science, Optometry
Identifiers
urn:nbn:se:lnu:diva-22561 (URN)
Available from: 2012-11-21 Created: 2012-11-21 Last updated: 2017-02-17Bibliographically 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 9, 1417-1423 p.Article 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 long-standing central scotoma. METHODS.: The subject was a 68-year-old women with bilateral absolute central scotoma due to Stargardt disease. She developed a single PRL located 25 degrees nasally of the damaged macula in her left eye, this being the better of the two eyes. High- (100%) and low-contrast (25 and 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 spherocylindrical correction. The latter two corrections were two versions of adaptive optics corrections of all aberrations, namely, habitual spectacle correction with aberration correction and full spherocylindrical refractive 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 spherocylindrical correction. Under the same conditions, low-contrast (25%) acuity improved from 1.30 to 1.14 logMAR. With adaptive optics aberration correction, the high-contrast resolution acuities improved to 0.89/0.92 logMAR and the low-contrast acuities improved to 1.04/1.06 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. CONCLUSIONS.: 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 long-standing absolute central scotoma

Keyword
REFRACTIVE ERROR, RESOLUTION ACUITY, VISION
National Category
Ophthalmology
Research subject
Natural Science, Optometry
Identifiers
urn:nbn:se:lnu:diva-21527 (URN)10.1097/OPX.0b013e318264f2a7 (DOI)22842306 (PubMedID)2-s2.0-84865730607 (Scopus ID)
Available from: 2012-09-05 Created: 2012-09-05 Last updated: 2017-12-07Bibliographically approved

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Baskaran, Karthikeyan

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