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S. Xu, C. Cai, J. Wang, M. Shen, F. Lu; Changes in Corneal Biomechanical Properties After Long-Term Soft Contact Lens Wear. Invest. Ophthalmol. Vis. Sci. 2008;49(13):661.
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To determine the changes in corneal hysteresis (CH), the corneal resistance factor (CRF) and central corneal thickness (CCT) after long-term soft contact lens (SCL) wear.
A total of 28 eyes of 14 normal subjects (no contact lens wear) and 36 eyes of 18 subjects wearing SCL for more than 5 years were evaluated. Sixty four eyes were divided into 3 groups: normal (control group), 26 eyes of 13 subjects were the first day after discontinuation of SCL wear and 10 eyes of 5 subjects were discontinuation of SCL wear for more than 2 weeks. The corneal biomechanical properties were measured with the Ocular Response Analyzer (ORA), the main outcome measures were CH and CRF. CCT was obtained using a custom-built real time anterior segment optical coherence tomography (OCT).
There were no differences in age and diopter in three groups. In the control group, the mean CH value was 11.17 ±1.14 mmHg and the mean CRF was 8.75±1.44 mmHg. One day after discontinuation SCL wear, CH and CRF decreased significantly and were 10.25±1.05mmHg and 7.47±1.17mmHg, respectively. In more than 2 weeks discontinuation contact lens wear group, CH and CRF were 10.01±0.83mmHg and 7.66±1.54mmHg, respectively. There were statistically significant differences in CH (t-test, P=0.003) and CRF (t-test, P=0.001) between control group and the first day group. And there were statistically significant differences in CH (t-test, P=0.006) and CRF (t-test, P<0.05) between control group and discontinuation of SCL wear more than 2 weeks group. However, there were no significant differences of CH and CRF (t-test, P>0.05) between the first day group and 2 weeks group. And there were no significant differences in CCT (P>0.05) in three groups. There were significant correlations between the CCT and CH (P<0.05) in three groups.
At the first day after contact lens removal, CH and CRF are diminished, and after discontinuation of SCL wear for more than 2 weeks, CH and CRF are still diminished, whereas CCT is constant. Long-term SCL wear leads to a change of corneal viscoelastic properties.
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