Document Detail

Measurement of position acuity in strabismus and amblyopia: specificity of the vernier VEP paradigm.
MedLine Citation:
PMID:  16303949     Owner:  NLM     Status:  MEDLINE    
PURPOSE: An objective measure of positional acuity is desirable in the nonverbal clinical population. This study was conducted to investigate the specificity of the vernier VEP as a measure of positional acuity, evaluating the potential confound of asymmetric motion responses that may be present in some groups of patients. These motion responses could masquerade as position-specific responses, since they occur at the same response frequency as the vernier-related response. METHODS: Twelve observers with early-onset esotropia (EOE), 30 children with untreated amblyopia, and 15 control children underwent swept vernier VEP acuity testing accompanied by a swept motion control stimulus. The control condition was used to detect the presence of artifactual responses not related to position sensitivity. The patients with EOE were selected for high levels of motion asymmetry as documented with oscillating gratings presented monocularly. As a measure of motion confound (penetration), the proportion of first-harmonic responses recorded in the control condition was determined. RESULTS: The penetration rate in the vernier condition in each study group (EOE: 0.93%; amblyopes: 4.26%; normal subjects: 2.40%) and the entire group (2.85%) was acceptably low. The level of penetration was not significantly influenced by the presence of amblyopia. CONCLUSIONS: The vernier VEP paradigm, when applied in the manner described, can be interpreted as a measure of position sensitivity. The presence of motion asymmetry or untreated amblyopia does not affect the validity of vernier measurements made.
Sean I Chen; Anthony M Norcia; Mark W Pettet; Arvind Chandna
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Investigative ophthalmology & visual science     Volume:  46     ISSN:  0146-0404     ISO Abbreviation:  Invest. Ophthalmol. Vis. Sci.     Publication Date:  2005 Dec 
Date Detail:
Created Date:  2005-11-23     Completed Date:  2006-01-11     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  7703701     Medline TA:  Invest Ophthalmol Vis Sci     Country:  United States    
Other Details:
Languages:  eng     Pagination:  4563-70     Citation Subset:  IM    
Smith-Kettlewell Eye Research Institute, San Francisco, California, USA.
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MeSH Terms
Amblyopia / physiopathology*
Child, Preschool
Esotropia / physiopathology*
Evoked Potentials, Visual / physiology*
Motion Perception
Visual Acuity / physiology*

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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