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dc.contributor.advisorCox, Michael J.
dc.contributor.advisorChisholm, Catharine M.
dc.contributor.authorSerra, Pedro M.F.N.*
dc.date.accessioned2014-05-07T14:50:35Z
dc.date.available2014-05-07T14:50:35Z
dc.date.issued2014-05-07
dc.identifier.urihttp://hdl.handle.net/10454/6331
dc.description.abstractThe main aim of this thesis is to evaluate the effect of meridional blur, using refractive induced astigmatism, on visual performance at far and close distances. Visual performance was evaluated using letter discrimination tasks at distance and near (visual acuity, VA) and a reading task at near on subjects with pharmacologically blocked (young) or absent accommodation (presbyopic and pseudophakic). The effect of astigmatism was tested using positive cylindrical lenses oriented at 180 and 90 degrees, these simulating with- (WTR) and against-the-rule (ATR) astigmatism. Other refractive status were also evaluated, namely, in-focus and spherical defocus. The visual performance data were correlated with biometric measurements (pupil size, anterior chamber depth (ACD), corneal and ocular aberrations, corneal multifocality, patient age, axial length). Further, the functionality of meridional blur was evaluated for alphabets in addition to the standard Roman alphabet using a VA task. The results confirm that myopic astigmatism contributes to a better visual performance at closer distances, with ATR astigmatism providing higher performance for reading tasks compared to other forms of astigmatism. Anatomical factors such as pupil size, corneal multifocality and ACD were significantly correlated visual performance, while other ocular characteristics were not. Ray tracing modelling using wavefront data was a moderate predictor of VA and reading acuity. The results of the effect of meridional blur orientation on alphabets other than the Roman alphabet, suggest that visual performance is dependent on the interaction between blur orientation and letter¿s spatial characteristics. In conclusion, pseudoaccommodation is a multifactorial phenomenon with pupil size being the major contributor for the improvement in visual performance. Against-the-rule shows advantages over WTR astigmatism, by providing higher reading performance, however extending the present and previous findings for clinical application will require further investigation on the effect of meridional blur in common and socio-culturally adapted tasks.en_US
dc.description.sponsorshipBradford School of Optometry and Vision Sciencesen_US
dc.language.isoenen_US
dc.rights<a rel="license" href="http://creativecommons.org/licenses/by-nc-nd/3.0/"><img alt="Creative Commons License" style="border-width:0" src="http://i.creativecommons.org/l/by-nc-nd/3.0/88x31.png" /></a><br />The University of Bradford theses are licenced under a <a rel="license" href="http://creativecommons.org/licenses/by-nc-nd/3.0/">Creative Commons Licence</a>.eng
dc.subjectOcular optical modellingen_US
dc.subjectCataracten_US
dc.subjectReading performanceen_US
dc.subjectWavefront aberrationen_US
dc.subjectCorneal topographyen_US
dc.subjectAccommodationen_US
dc.subjectVisual performanceen_US
dc.subjectAstigmatismen_US
dc.subjectPseudoaccommodationen_US
dc.subjectPseudoaphakiaen_US
dc.subjectMeridional Bluren_US
dc.titleVisual Performance in Pseudophakia. The Effect of Meridional Blur in Pseudoaccommodation.en_US
dc.type.qualificationleveldoctoralen_US
dc.publisher.institutionUniversity of Bradfordeng
dc.publisher.departmentBradford School of Optometry and Vision Sciencesen_US
dc.typeThesiseng
dc.type.qualificationnamePhDen_US
dc.date.awarded2013
refterms.dateFOA2018-07-19T13:41:33Z


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