Document Detail

Effect of blur and subsequent adaptation on visual acuity using letter and Landolt C charts: differences between emmetropes and myopes.
MedLine Citation:
PMID:  23297779     Owner:  NLM     Status:  Publisher    
PURPOSE: To compare the effects of defocus induced blur and blur adaptation on visual acuity and to evaluate any differences between emmetropes and myopes using letter and Landolt C logMAR charts. METHODS: The sample consisted of 26 volunteers, with a mean age of 27 ± 3 years, comprising 13 emmetropes (spherical equivalent range: -0.63 to +0.50 D) and 13 myopes (spherical equivalent range: -0.75 to -5.00 D). Monocular visual acuity (VA) was measured in each eye using letter and Landolt C logMAR charts under the following conditions: (1) with the distance refractive correction, (2) immediately after exposure to +2.00 D defocus and (3) following 60 min of binocular adaptation to +2.00 D blur. Objective refraction at the beginning and at the end of the experimental procedure was evaluated. Averaged VA data between the two eyes were used for analysis. RESULTS: Deterioration in VA with +2.00 D defocus was greater in the emmetropes compared to myopes for both charts. The mean difference between the two refractive groups was more pronounced for the Landolt-C (0.17 logMAR) compared to the letter chart (0.10 logMAR). The reduction in VA with blur was related to the amount of the refractive error. Following 60 min of adaptation, a significant improvement in VA was observed in both groups that did not differ between the two charts. The improvement in VA following adaptation using the letter chart was linearly correlated with spherical equivalent refractive correction. CONCLUSIONS: Myopes show higher tolerance to retinal defocus compared to emmetropes, which could be attributed to previous blur experience. The effect of blur on VA is more pronounced using Landolt C optotypes than with letters. Prolonged exposure to blur results in equally improved performance for both refractive groups.
Eleni Poulere; Joanna Moschandreas; George A Kontadakis; Ioannis G Pallikaris; Sotiris Plainis
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2013-1-9
Journal Detail:
Title:  Ophthalmic & physiological optics : the journal of the British College of Ophthalmic Opticians (Optometrists)     Volume:  -     ISSN:  1475-1313     ISO Abbreviation:  Ophthalmic Physiol Opt     Publication Date:  2013 Jan 
Date Detail:
Created Date:  2013-1-9     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8208839     Medline TA:  Ophthalmic Physiol Opt     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Copyright Information:
Ophthalmic & Physiological Optics © 2013 The College of Optometrists.
Institute of Vision and Optics (IVO), School of Health Sciences, University of Crete, Heraklion, Greece.
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