Document Detail

Influence of motion smear on visual acuity in simulated infantile nystagmus.
MedLine Citation:
PMID:  21200353     Owner:  NLM     Status:  MEDLINE    
PURPOSE: In persons with infantile nystagmus (IN), visual acuity correlates with the duration of the foveation period of the nystagmus waveform, i.e., when the retinal image is on or near the fovea and moves with low velocity. In this study, we asked how acuity is affected by the non-foveating phases of the nystagmus waveform, when the velocity of retinal image motion is substantially higher.
METHODS: Visual acuity was measured in three normal observers for high contrast, four-orientation single T-stimuli, presented during image motion that simulated either the whole jerk-IN waveform (whole-waveform) or only the foveation periods of the IN waveform (foveation-only). Simulated foveation durations ranged from 20 to 120 ms. For both motion waveforms, we displayed the acuity target for different number of cycles to examine whether acuity benefits from multiple presentations of the stimulus.
RESULTS: As expected, visual acuity improves with longer simulated foveation durations in both the whole-waveform and foveation-only conditions. Acuity is consistently better (by ∼0.1 logarithm of the minimum angle of resolution) in the foveation-only than the whole-waveform condition, indicating that the high-velocity image motion during the simulated IN waveform has a detrimental effect. This difference in acuity between the two waveform conditions increases with the number of cycles, apparently because summation occurs across cycles in the foveation-only condition but not in the whole-waveform condition.
CONCLUSIONS: In normal observers, visual acuity in the presence of a simulated nystagmus waveform is limited not only by the duration of the foveation periods, but also by the non-foveating phases of the waveform. However, because persons with IN report little or no motion smear in association with their nystagmus, it remains unclear whether the rapid retinal image motion during the non-foveating phases of the nystagmus waveform generates a similar degradation of visual acuity in IN.
Susana T L Chung; Martin W LaFrance; Harold E Bedell
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural    
Journal Detail:
Title:  Optometry and vision science : official publication of the American Academy of Optometry     Volume:  88     ISSN:  1538-9235     ISO Abbreviation:  Optom Vis Sci     Publication Date:  2011 Feb 
Date Detail:
Created Date:  2011-01-26     Completed Date:  2011-05-31     Revised Date:  2014-09-15    
Medline Journal Info:
Nlm Unique ID:  8904931     Medline TA:  Optom Vis Sci     Country:  United States    
Other Details:
Languages:  eng     Pagination:  200-7     Citation Subset:  IM    
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MeSH Terms
Eye Movements*
Fovea Centralis / physiopathology*
Models, Biological
Nystagmus, Pathologic / congenital*,  physiopathology*
Time Factors
Visual Acuity*
Grant Support
P30-EY07551/EY/NEI NIH HHS; R01 EY012810/EY/NEI NIH HHS; R01 EY012810-12/EY/NEI NIH HHS; R01-EY012810/EY/NEI NIH HHS; R01-EY05068/EY/NEI NIH HHS; T35-EY07088/EY/NEI NIH HHS

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