What is a disadvantage of CR-39 lens material compared to polycarbonate?

The choice highlighting that CR-39 lens material is thicker and heavier compared to polycarbonate is accurate because CR-39, a type of plastic lens material, generally has a higher density than polycarbonate. This increased density results in CR-39 lenses being bulkier and heavier than their polycarbonate counterparts, which are specifically designed to be lightweight and impact-resistant.

Polycarbonate is also thinner than CR-39, allowing for a sleeker profile in eyewear. This is particularly beneficial for those who prefer more comfortable frame designs or require a higher prescription, as it reduces the potential for distortion that can occur with thicker lenses.

In contrast, CR-39 lenses, while offering excellent optical clarity and being more scratch-resistant than some other lens materials, do not compete with polycarbonate when it comes to weight and thickness. Thus, for individuals looking for lightweight options, especially in active or children's eyewear, polycarbonate is typically the preferred choice.