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H. S. Ginis, A. Sahanidis, S. Plainis, T. Giannakopoulou, I. Pentari, I. Pallikaris; Forward Light Scatter in Hydrogel and Silicon-Hydrogel Contact Lenses at Different Time Intervals of Use. Invest. Ophthalmol. Vis. Sci. 2009;50(13):1550.
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The purpose of this prospective study was the evaluation of forward light scatter induced by hydrogel and silicone-hydrogel contact lenses, designed to be replaced on a monthly basis, at different time intervals of use and its implication to vision.
Fifteen contact lens users were enrolled in the study. The study was divided in two parts each of which lasted 5 weeks. Each subject wore a hydrogel lens on the left eye and a silicone-hydrogel lens on the right eye (Aqualens and Air Optix respectively, both Ciba Vision, Duluth GA). Transparency of each lens was evaluated after each week of use by means of a purposely-developed optical setup. The setup involved a CCD camera, a custom contact lens mounting cell and a computer screen. In this setup, images of disks displayed on the computer screen were recorded through the contact lenses and appropriate processing allowed the calculation of forward light scatter that is likely to be caused by deposits and surface defects on the lenses. Additionally, contrast sensitivity and visual acuity of all subjects were measured on the first and the fifth week of each part of the study while wearing the lenses under investigation. Moreover, each subject recorded daily information on the contact lens use on a special questionnaire. The study was performed under institutional board approval and an informed consent was obtained from each participant.
Contact lenses exhibited scatter ratios (SR) of the order of 3% with a small (non-statistically significant) increase over weeks of use. Moreover, SR in the lenses under investigation was not statistically significantly higher that the SR of a set of identical contact lenses that underwent the same measurements to serve as control. No statistically significant difference was found in visual acuity or contrast sensitivity between the beginning and the end of each of the 5-week periods. Analysis of the questionnaires revealed a statistically significantly higher rating for comfort for the silicone-hydrogel lenses.
Both hydrogel and silicone-hydrogel lenses retained their normal transparency after normal use for five weeks. This study however pertained to the isolated contact lenses and did not address possible transparency issues associated to their fitting or their interaction with the tear film and the cornea.
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