Prism coupling refractometry, a versatile and well-characterized technique, is a valuable tool for measuring the refractive index of transparent media in film or bulk forms. It offers distinct advantages over other refractometry methods as it does not require the same level of fabrication or user modeling of optical response. Our method, presented in combination with an infrared prism coupler, further enhances this technique. It not only allows for the measurement of optical constants but also significantly reduces the standard deviation previously found in this measurement. Furthermore, it enables the refractive index of these materials to be certified to the third decimal point or more, demonstrating the value and potential of this technique.