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Effect of Optical Defocus on Peripheral Resolution Acuity in Old Healthy Emmetropes
Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences. (Vision Enabling Lab)
Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences. (Vision Enabling Lab)ORCID iD: 0000-0002-3745-0035
Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences. (Vision Enabling Lab)ORCID iD: 0000-0002-8365-0601
Biomedical and X-Ray Physics. (Visual Optics Group)
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2011 (English)Conference paper, Published paper (Refereed)
Abstract [en]

Background:

A recent study by Rosén et al found peripheral low contrast resolution acuity, but not high contrast acuity, to be affected by defocus in young healthy eyes. Since aging causes considerable degradation in peripheral optics even in healthy subjects we wanted to see if, older subjects were also sensitive to defocus in low contrast acuity.

 

Purpose:

The aim of this study was to evaluate the effect of optical defocus on high and low contrast resolution acuity in the peripheral visual field of healthy older emmetropes.

 

Subjects:

High- and low-contrast resolution acuity was evaluated under spherical defocus in the 20° nasal visual field of four healthy older emmetropic subjects. The off-axis refractive error at the 20° nasal visual field was measured by a COAS-HD VR aberrometer and was corrected accordingly for each subject.

 

Methods:

Resolution thresholds for visual acuity (VA) were obtained using stimuli consisting of high- (100%) and low- (10%) contrast gratings that were presented on a CRT monitor situated 1.0 meter from the subject. Stimuli, 3° in diameter were presented for 300 ms using a 2AFC paradigm. Two repeated measurements, for both high and low contrast, were obtained for each point of defocus in 1.0 D steps up to ±4 D at 45mm vertex distance. The results are corrected to effective defocus at the corneal plane.

 

Results:

Defocus had no visible effect on high contrast VA, although there was a slight decrease in VA with higher amounts of positive defocus. However, defocus was found to have a significant effect on low contrast VA. Moreover, low contrast resolution was more sensitive to positive defocus than the negative defocus.

 

Conclusions:

Defocus has an impact on low contrast resolution whereas no such effect was found for high contrast resolution. These results are similar to those obtained by Rosén et al1 in young eyes. These results suggest that low contrast optotypes could possibly be used for determining subjective refraction in low vision subjects.

Place, publisher, year, edition, pages
2011.
Keywords [en]
Defocus, Periphery, Resolution, Grating Acuity
National Category
Ophthalmology
Research subject
Natural Science, Optometry
Identifiers
URN: urn:nbn:se:lnu:diva-15010OAI: oai:DiVA.org:lnu-15010DiVA, id: diva2:448784
Conference
American Academy of Optometry 2011 Boston
Available from: 2011-10-18 Created: 2011-10-18 Last updated: 2017-02-17Bibliographically approved

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Baskaran, KarthikeyanLewis, PeterGustafsson, Jörgen

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