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MANIPULATION OF OCULAR ABERRATIONS IN MYOPES
Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences. (OPTOMETRY-VISION ENABLING)
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Myopia is a major cause of vision loss throughout the world. High myopia is associated with severe eye diseases like maculopathy, retinal detachment and glaucoma. The prevalence of myopia is increasing, and varies by country and by ethnic group. In some Asian populations the prevalence is 70%-80%. 

This thesis includes five experiments. In experiment I we investigated the effects of added positive and negative spherical aberration on accommodative response accuracy. We found that the accommodative response can be altered by modulating the spherical aberration of the eye with soft contact lenses. There was an improvement in the accommodative response slopes and a decrease in the lag of accommodation with the negative spherical aberration lenses compared to positive spherical aberration lenses. 

In experiment II we investigated whether the negative spherical aberration in contact lenses could be tolerated visually in terms of wearability and comfort. We found that all the subjects were satisfied with the contact lens comfort, distance and near vision and the stability of the vision with the lenses. The accommodative response was stable through out the treatment period.

In experiment III we investigated the efficacy of a novel dual treatment for the improvement of accommodative accuracy and dynamics in myopes. The spherical aberration of the eye was effectively altered to negative in the treatment group as predicted. In the control group as expected there was no significant change in the spherical aberration of the eye with and without contact lenses. The treatment lenses decreased the lag of accommodation and increased the accommodative response slope at 3 months.

In the experiment IV we investigated the effect of the treatment lenses used in the previous experiment on high and low contrast visual acuities after a one year treatment period. The results showed a significant improvement in both high and low contrast visual acuities after the one year period in the treatment group compared to the control group, even though it was not clinically significant.

In experiment V we investigated the intrasession repeatability of peripheral aberrations using COAS-HD VR aberrometer and also reported the distribution of higher order aberrations in a group of young emmetropes. There was no significant difference in the variance of total higher-order RMS between on- and off-axis measurements. There was a significant change in the horizontal coma, spherical aberration and higher-order RMS with off-axis angle along the horizontal visual field. We demonstrated that fast, repeatable and valid peripheral aberration measurements can be obtained with this instrument.

This thesis contributes new results in this field of myopia, aberration and accommodation.

Place, publisher, year, edition, pages
Växjö, Kalmar: Linnaeus University Press , 2010. , p. 66
Series
Linnaeus University Dissertations ; 24/2010
Keywords [en]
Myopia, Spherical aberration, Accommodation, Contact lens, Visual acuity, Peripheral aberrations
National Category
Ophthalmology
Research subject
Natural Science, Optometry
Identifiers
URN: urn:nbn:se:lnu:diva-8314ISBN: 978-91-86491-37-6 (print)OAI: oai:DiVA.org:lnu-8314DiVA, id: diva2:349998
Public defence
2010-10-13, N2007K, Smålandsgatan 26E, Kalmar, 13:00 (English)
Opponent
Supervisors
Available from: 2010-09-10 Created: 2010-09-09 Last updated: 2014-02-25Bibliographically approved
List of papers
1. Ocular Aberrations in the Peripheral Visual Field With a Commercial Open-View Aberrometer
Open this publication in new window or tab >>Ocular Aberrations in the Peripheral Visual Field With a Commercial Open-View Aberrometer
2010 (English)In: Investigative Ophthalmology and Visual Science, ISSN 0146-0404, E-ISSN 1552-5783, Vol. 51, no 5, article id 3951Article in journal, Meeting abstract (Refereed) Published
Abstract [en]

PurposeThe interest in off-axis aberrations has increased with the discovery of a possible link between myopia development and peripheral optics. The most common technology to measure the off-axis aberrations is a Shack-Hartmann wavefront aberrometer. This is the first study to report peripheral aberrations in a large sample of emmetropic population with a commercial open-view Shack-Hartmann aberrometer. MethodsThe commercial open-view Shack-Hartmann aberrometer COAS-HD VR was used to measure the aberrations in the peripheral vision. Aberrations of the right eye of 30 emmetropes (24 {+/-} 4 years) were studied. Off-axis aberrations were measured in steps of 10{degrees} out to {+/-} 30{degrees} in the horizontal visual field. The subjects turned their eye to view the off-axis fixation target (light emitting diode placed at 3 meters) during the measurement. The resulting wavefront aberrations were parameterized with Zernike coefficients for a 5 mm diameter pupil. All analyzes are reported according to optical society of America (OSA) recommended standards. ResultsAberrations from the 2nd to 6th order and the total higher-order root-mean-square (HO RMS) were analyzed using one-way ANOVA. The defocus C02 was significantly myopic in the nasal visual field (+20{degrees}, +30{degrees}) whereas there was no significant difference in the temporal visual field. Astigmatism C22 increased quadratically from {+/-}10{degrees} in the periphery and coma C13 showed a linear increase across the horizontal visual field (p < 0.05). The spherical aberration C04 and the total HO RMS showed a significant change at {+/-}30o. ConclusionsOur results showed that in young emmetropes there was a significant increase of HO RMS at {+/-}30{degrees}, which is expected. Astigmatism, horizontal coma, and spherical aberration vary systematically across the horizontal visual field in agreement with Seidel theory. The findings of our study with a large sample of emmetropic population agree with the previous studies done with laboratory built aberrometers.

Keywords
aberrations, visual fields
National Category
Ophthalmology
Research subject
Natural Science, Optometry
Identifiers
urn:nbn:se:lnu:diva-6284 (URN)
Conference
ARVO 2010 Annual Meeting
Available from: 2010-06-17 Created: 2010-06-17 Last updated: 2017-12-12Bibliographically approved
2. Low Vision Services System in Scandinavia
Open this publication in new window or tab >>Low Vision Services System in Scandinavia
2009 (English)Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
Hyderabad, India: , 2009
National Category
Medical and Health Sciences
Research subject
Natural Science, Biomedical Sciences; Natural Science, Optometry
Identifiers
urn:nbn:se:lnu:diva-5050 (URN)
Note

Nummer:

Available from: 2010-04-28 Created: 2010-04-28 Last updated: 2015-03-13Bibliographically approved

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Theagarayan, Baskar

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