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S. Rae, D. Austin, A. Holland, S. Pardhan; Does Variability in Wavefront Aberrations in the Inter-Blink Period Increase With Contact Lens Wear or Duration of Lens Wear?. Invest. Ophthalmol. Vis. Sci. 2009;50(13):6339.
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Ocular wavefront aberrations are known to vary during the inter-blink interval 1,2 as the tear film changes. The tear film is also known to change during contact lens wear. This study aims to identify the individual aberration terms affected by the time from blink with and without contact lens wear and the effect of the time from initial lens insertion.
Total ocular wavefront aberration was assessed using the COAS-HD aberrometer (Wavefront Sciences, USA) and analysed for a 5mm pupil aperture. Three contact lens types were worn on separate days (DefinitiveTM, balafilcon A, nelfilcon A). Aberrations were measured at 2 second intervals from 2 to 10 seconds after a blink. Measurements were obtained for 10 subjects without a contact lens, with a contact lens newly inserted and after 5-6 hours of lens wear.
Mean aberrations were calculated for each lens and each condition. Variability was assessed by calculating the standard deviation of the mean aberrations across the full 10 second period. Spherical aberration increased significantly with newly inserted lenses compared to without (p = 0.013) and also after 5-6 hours of wear compared to without lenses (p=0.001). Spherical aberration changed sign from positive to negative with both newly inserted contact lens and after 5-6 hours of wear, with an increase in the absolute magnitude. There was no significant difference in the standard deviation of any aberration term with both lens wear conditions compared to without. Coma terms and 3rd order RMS showed higher standard deviations than spherical aberration and 4th order terms, for both lens wear conditions. There was no significant effect of lens type on any changes described above.
Variability in aberrations across the inter-blink period was not adversely affected by contact lens wear as may have been anticipated. However, the absolute magnitude of spherical aberration was consistently higher indicating that the control of inherent spherical aberration and the application of aspheric optics requires careful consideration.1 Montés-Micó, R, Alió, JL, Muñoz, G and Charman, WN (2004). Invest. Ophthalmol. Vis. Sci. 45: 1752-1757.2 Koh, S, Maeda, N, Hirohara, Y et al. (2006). Invest. Ophthalmol. Vis. Sci. 47: 3318-3324.
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