In modern life, polymeric optical lens has been utilized in many electronic devices, such as camera, mobile phone, tablet, and so on. Although hundred million lenses are produced annually for those devices, the quality is the key to the main suppliers. Indeed, the optical quality is affected by both the geometric features and the optical birefringence. However, how the material’s viscoelasticity influences the optical features is still not fully understood yet. In this study, we have systematically investigated the viscoelastic effects on the optical property of a lens made of Zeonex COP 480R material by the traditional injection molding, simulated with n = 0.4 and * = 217,000 Pa in the Cross model. We assumed that the rheological parameters can be modified artificially based on the White-Metzner model of viscoelasticity, in which the viscosity was of the Cross-type model. Results show that if the power-law index (n) was changed from 0.1 to 0.6, the total fringed order has no significant difference, but the fringed patterns was varying dominantly in the perpendicular direction, instead of the flow direction. This situation was matched with the distribution of the flow-induced residual stresses. Moreover, if the * in the Cross model was varied from 100,000 Pa to 300,000 Pa, the total fringed patterns were apparently changing from being dominated in the flow direction to being in the direction perpendicular to the flow. The influenced width of the fringed patterns was almost linearly increased with the increasing *. The results can be applied as some guideline for either the further material modifications or the new material developments.