The PhET Interactive Simulations project has begun an initiative to increase the accessibility of its suite of science simulations. In this work, we focus on use of the PhET sim Capacitor Lab: Basics by two visually impaired learners. Comparing responses to pre and posttest questions about capacitance and circuits, our results indicate that after using the simulation with new accessibility features, both learners better understood the relationship between plate separation, area, and capacitance. Additionally, while only one learner connected the charged capacitor to the light bulb in the simulation during use, both answered that the light bulb will be illuminated in posttest questions. These findings indicate that visually impaired students can master the learning goals of a PhET sim with well-designed accessibility features. Findings from this research contribute to understanding how to develop physics education resources capable of supporting diverse students, including students with disabilities.