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H. Liu, L.N. Thibos, C.G. Begley, K. Haggerty, M. Christensen; Visual Performance And Optical Quality Among Contact Lens Wearers . Invest. Ophthalmol. Vis. Sci. 2006;47(13):2383.
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© ARVO (1962-2015); The Authors (2016-present)
Previous studies in our laboratory indicate that micro wavefront aberrations due to light scatter increase between blinks, and, at the same time, vision deteriorates rapidly among soft contact lens wearers. This exposes the roughened lens surface and scatters light. Conventional wavefront aberrometry does not capture these small–scale aberrations and it does not correlate well with subjective visual performance. Therefore, the purpose of this study was to develop a new method for measuring micro aberrations that will correlate well with contrast sensitivity (CS).
A confocal imaging system with a range–defining aperture continuously measured light reflected through the pupil from an infrared laser beam focused on the retina. Light intensity (LI) passing through a range–defining aperture is a measure of the fraction of reflected light for which wavefront slope < 6.5 milliradians. A miniature VGA monitor displayed letter targets for which contrast sensitivity (CS) was measured continuously and simultaneously with optical measurements. CS and LI data at 0, 5, 10 seconds after a blink were extracted for analysis.
During the first study visit, subjects experienced an average decline of 28.3%±30.0% (LI) and 13.3%±12.4% (CS) in 5 sec and 53.6%±32.2% (LI) and 33.4%±24.4% (CS) in 10 sec during eye opening trials. At 10 sec, CS and LI were significantly correlated (r=0.615, p<0.05). The difference in decline between 5 and 10 sec was statistically significant (p<0.017, paired t–test) for both parameters, but there was no significant difference between study visits.
These methods allowed us to simultaneously and dynamically track the deterioration of objective optical quality of the eye and subjective visual performance. Because normal blinks occur approximately every 5 sec, these results demonstrate why contact lens wearers may experience rapid visual decline between normal blinks.
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