Prismatic loupes, also referred to as Keplerian loupes, are used to provide a greater degree of magnification by using a prism to manipulate the way your eyes perceive the object, rather than a larger outer lens. This means that these loupes can provide higher magnifications whilst keeping the loupes at an acceptable weight and size.

Prismatic loupes are generally magnifications 3.5x and above. As magnification increases, a higher level of light is required to achieve visual clarity so the eye is able to focus on the object.

While prismatic loupes do not directly increase the amount of light that reaches the eye, they can improve visibility by directing more light onto the object being viewed. This can make it easier to see small details, which can be especially helpful in low-light conditions.

Additionally, it is recommended to use a light source with prismatic loupes to provide additional illumination. This can further improve visibility and make it easier to see small details.

Overall, while prismatic loupes do not increase the amount of light reaching the eye, they can improve visibility and make it easier to see small details in a variety of settings.