Motion sickness affects roughly a third of all people. Narrowing the field of view (FOV) can help to reduce motion sickness symptoms. In this paper, we present Tunnel Vision, a type of smart glasses that can dynamically block a wearer's peripheral vision area using switchable polymer dispersed liquid crystal (PDLC) film. We evaluate the prototype in a virtual reality environment. Our experiments (n=19) suggest that Tunnel Vision statistically significantly reduces the following Simulator Sickness Questionnaire (SSQ) related motion sickness symptoms without impacting immersion: "difficulty concentrating"(F(2,35) = 4.121, p = 0.025), "head feeling heavy"(F(2,35) = 3.231, p = 0.051) and "nausea"(F(2,35) = 3.145, p = 0.055).