Contrast sensitivity of emmetropes and myopes in bright and dark circumstances

Objective To investigate the contrast sensitivity of emmetropia,low or moderate myopia and high myopia patients in bright and dark circumstances,and then evaluate its visual function.Methods Three groups were divided according to power of refraction(emmetropia,low or moderate myopia and high myopia),38 cases in each group.CGT-1000 and Mesotest Ⅱb were used to test contrast sensitivity in bright and dark circumstances.Results In bright and glare conditions,the contrast sensitivity of myopia were lower than emmetropia(P0.05);While in bright and no glare conditions,the contrast sensitivity of high myopia group was lower than both emmetropia and low or moderate myopia group(P0.05),no significant differences was found between emmetropia and low or moderate myopia(P=0.087).In dark circumstances,the contrast sensitivity of high myopia group was lower than the other two groups(P0.05).The contrast sensitivity under glare was lower than that of no glare in each group.Conclusions Both in dark and bright circumstances,the sequence of contrast sensitivity from high to low was emmetropia group,low or moderate myopia group,and high myopia group.High-order aberrations,fundus retrogressive changes and image minification may be the reason to lower contrast sensitivity in high myopia patients.