To evaluate the potential effect of refractive error on visual acuity (VA) performance and contrast sensitivity function (CSF). We examined 240 eyes of the 120 participants, and they were divided into six groups (mild & moderate hyperopia, severe hyperopia, mild myopia, moderate myopia, severe myopia, and emmetropia) according to their spherical equivalent (SE).  In severe myopia there was a statistically significant reduction in the contrast sensitivity function when the spherical equivalent is more than -10 diopters. Also, we found normal contrast sensitivity in hyperopic groups, mild & moderate myopic groups, and emmetropic groups. There was a negative correlation of contrast sensitivity functions with BCVA of studied participants whose correlation coefficient was r -0.566** & (P-value 0.000), while there was a positive correlation of contrast sensitivity function with SE whose correlation coefficient was r 0.310**& (P-value 0.000). VA and CS are two different but equally important metrics for assessing visual function. The VA defines visual performance in high-contrast settings, whereas CS testing examines visual function across a range of spatial frequencies and luminance. We noticed the visual performance impairment regardless of the optimum optical correction of high myopic participants.